Flavonoide Si Sist Imun

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Bioactive Foodhttp://dx.doi

The Effects of Flavonoids on theImmune SystemF.J. Pérez-Cano, À. Franch, T. Pérez-Berezo, S. Ramos-Romero, C. Castellote,M. CastellUniversitat de Barcelona, Barcelona, Spain

ABBREVIATIONSAPC Antigen-presenting cell

BCR B-cell receptor

CCL Chemokine (C–C motif) ligand

CCR Chemokine (C–C motif) receptor

CD Cluster of differentiation

Con-A Concanavalin-A

DC Dendritic cell

EGCG Epigalocatechin gallate

ERK Extracellular signal-regulated kinases

GALT Gut-associated lymphoid tissue

IFNg Interferon gIg Immunoglobulin

IL Interleukin

JNK c-Jun N-terminal kinases

MHC Major histocompatibility complex

NF-kB Nuclear factor kappa light chain enhancer of activated B cells

NK Natural killer

OVA Ovalbumin

PBMC Peripheral blood mononuclear cells

PMA Phorbol myristate acetate

SEB Staphylococcal enterotoxin B

T-bet A transcription factor from the T-box family expressed in T cells

TCR T-cell receptor

Th Helper lymphocyte

1. INTRODUCTION

The immune system has evolved to ensure protection against invading pathogens while

avoiding reactions to innocuous self- and non-self-antigens, in a fashion that promotes

immune tolerance. The function of the immune system depends on many intricate cell–

cell interactions that even today are not fully understood. A focus for many nutritionists

as Dietary Interventions for Arthritis and Related Inflammatory Diseases.org/10.1016/B978-0-12-397156-2.00011-9

# 2013 Elsevier Inc.All rights reserved. 175

http://dx.doi.org/10.1016/B978-0-12-397156-2.00011-9

176 F.J. Pérez-Cano et al.

and scientists in the immunonutrition field is the research of food compounds that may

influence the functionality of the immune system.

Flavonoids are products of the secondary metabolism of plants that are regularly

ingested in small quantities in many edible plants. Chemically, they have a polyphenolic

structure showing antioxidant activities. These properties have aroused an increasing

interest in assessing their possible beneficial role in the prevention of various diseases,

as evidenced by the large number of studies focused on the effect of flavonoids on health

over the last decade. Flavonoids can be classified into flavonols, flavones, isoflavones,

flavanones, flavanols, and anthocyanidins. Flavonols such as quercetin, kaempferol,

galangin, morin, rutin, myricetin, isorhamnetin, and isoquercetin can be found in onions,

apples, berries, kale, leeks, broccoli, blueberries, red wine, and tea. Flavones such as

glycosides of luteolin, chrysin, and apigenin are commonly found in fruit skins, parsley,

and celery. Isoflavones such as genistein, daidzein, and glycitein are exclusively present

in leguminous plants, mainly soy and soy products. Flavanones such as naringenin, erio-

dictyol, and hesperidin are exclusive to citrus fruits. Flavanols include monomers such

as epicatechin, catechin, gallocatechin, epigallocatechin, and epigallocatechin gallate

(EGCG), and also polymers called proanthocyanidins. Proanthocyanidins or condensed

tannins can appear as procyanidins (epicatechin and catechin polymers, mainly found in

cocoa), prodelphinidins (epigallocatechin or gallocatechin polymers), and propelargoni-

dins (epiafzelechin or afzelechin polymers). Anthocyanidins include pelargonidin, cyani-

din, and malvidin, whose sources are red wine and berry fruits.

This chapter focuses on the effect of flavonoids on the immune system. Specifically, as

the relationship between flavonoids and innate immune responses, including inflamma-

tion, has been extensively discussed in other chapters, the aim of this chapter is to provide

an integrated update on the action of flavonoids on the acquired immune response, in-

cluding the most recent studies related to this topic and, particularly, those using

preclinical and clinical approaches. First, we include a short summary of the specific

or acquired immune response.

2. ACQUIRED IMMUNITY: THE TAILORED RESPONSE AGAINST ANTIGEN

Acquired immunity is characterized by antigen specificity and memory. It principally

involves the function of lymphocytes. These cells remain in a resting state waiting to bind

to a specific antigen and thus become activated. Lymphocytes can be T or B cells and have

surface antigen-specific receptors called T-cell receptors (TCRs) and B-cell receptors

(BCRs), respectively. Each lymphocyte is genetically programmed to be capable of

recognizing just one particular antigen.

When an antigen enters the body, it is captured by specialized cells called antigen-

presenting cells (APCs), mainly dendritic cells (DCs). DCs are sentinels that have the abil-

ity to integrate a wide array of incoming signals and convey them to lymphocytes. After

177The Effects of Flavonoids on the Immune System

the capture of the antigen, DCs start a maturation process that involves the enhancement

of the expression of the major histocompatibility complex class II (MHC-II) and acces-

sory molecules, and the production of cytokines and chemokines. After the antigen

processing, the DCs present it to T-helper lymphocytes (Th or CD4þ (cluster of differ-

entiation 4þ) lymphocytes), leading to a molecular DC–Th interaction called

immunological synapse (Figure 12.1). This interaction includes the binding of the pro-

cessed antigen to a specific TCR, as well as the linkage of CD4 on the Th cell with

MHC-II molecules on the APC. The APC–Th cell interaction is tightened with co-

stimulatory molecules such as CD54 and CD11a. Moreover, CD3 on Th cells forms

a complex with TCRs playing a role in the transduction of stimuli into the cell. CD3

stimulation is associated with the tyrosine phosphorylation of multiple proteins, resulting

in the activation of various signaling pathways, eventually causing T-cell proliferation

and secretion of cytokines.

Activated Th cells produce interleukin (IL)-2 and proliferate to give a progeny of

activated antigen-specific Th cells. Similarly, B cells can become activated when the

specific antigen binds to their BCR and receive the appropriate cell interaction from

Th cells. Activated B cells will proliferate and differentiate to become antibody-

producing cells or plasma cells, highly specialized in synthesizing antibodies or immuno-

globulins (Ig), such as IgG, IgM, IgA, or IgE, which specifically bind to the antigen that

has induced their synthesis.

According to the type of antigen and the environment where the cell activation

occurs, Th cells will become effector Th cells with different profiles (Figure 12.1).

Although there are other recently described types of effector Th cells, Th1 and Th2

are the most abundant. These cells produce different patterns of cytokines resulting in

different responses. Th1 response produces interferon g (IFNg) and IL-2, and enhances

macrophage, cytotoxic T-cell, and natural-killer (NK) cell functions, as well as the syn-

thesis of antibodies capable of activating the complement system. These factors enhance

cell killing by phagocytosis and cytotoxicity, both important actions in the inflammatory

process. Conversely, the activated Th2 cells produce cytokines such as IL-4, IL-5, IL-10,

IL-13, which activate mast cells, eosinophils, and the synthesis of antibodies such as IgE

and IgA, which do not activate the complement system but are involved in the defense

against parasites, allergic reactions, and the mucosal immune response, among others.

3. FLAVONOIDS IN THE IMMUNE SYSTEM

Most studies evaluating the effects of flavonoids on the immune system are performed in

vitro. These studies allow one to approach the molecular mechanisms and targets affected

by flavonoids. However, the in vivo studies can better reflect the effects of these

compounds after absorption and metabolism.

Differentiation

EffectorTh1

IFN-g IL-2

B

BNK

EosinophilMacrophage

Neutrophil

IgG

• Inflammatory response• Immune response against intracellular antigens

• Allergic response• Immune response against extracellular antigens

IgE

IgA

Mast cell

IL-4 IL-5 IL-13

EffectorTh2

Antigen presentation

Antigen

Dendritic cell(APC)

MHC-II-antigen - TCR(immunological synapse)

Antigen-specific Th cellproliferation

Th lymphocyte(antigen-specific TCR)

IL-2 secretionActivated

Th

Flavonoids

Flavonoids

FlavonoidsFlavonoids

Flavonoids

Figure 12.1 Acquired immune response. Schematic cellular and molecular events from the antigenentrance until the activation of effector Th1 and Th2 responses. The main targets of flavonoids aremarked.



3.1 In Vitro Studies of Flavonoids in the Immune SystemAs detailed above, the first events following the entrance of antigen into the body are its

uptake by APCs and its presentation to Th (CD4þ) lymphocytes. At that moment, the

cell–cell interaction between APCs and Th cells is crucial for triggering the acquired

immune response. Two studies have reported that both quercetin (flavonol) and EGCG

(flavanol) were able to inhibit the expression of MHC class II and co-stimulatory mol-

ecules, such as CD11c, CD40, CD80, CD83, and CD86, in activated DCs (Huang et al.,

2010; Yoneyama et al., 2008). Quercetin and EGCG also downregulated the antigen

loading in DCs. Moreover, quercetin reduced the DC migration induced by the

CCL21 (chemokine (C–C motif) ligand 21). The mechanism induced by quercetin

was the disruption of the extracellular signal-regulated kinases (ERK), c-Jun N-terminal

kinases (JNK), Akt, and nuclear factor kappa light chain enhancer of activated B cell (NF-

kB) pathways involved in DC activation (Huang et al., 2010).

The following phase in the acquired immune response includes the activation of

specific Th lymphocytes. In consequence, Th cells synthesize and secrete high amounts

of IL-2, which induces the specific Th-cell proliferation. Several flavonoids have dem-

onstrated their ability to control lymphocyte proliferation and modulate IL-2 secretion

(Table 12.1). Isoflavones such as genistein decreased proliferation and the secretion of

IL-2 in stimulated human peripheral blood mononuclear cells (PBMCs) and T cells

(Gredel et al., 2008). Flavonols such as quercetin also reduced IL-2 synthesis in activated

Table 12.1 In Vitro Effect of Flavonoids on the Cytokine Production of LymphocytesCytokine Effect Flavonoid Target Reference

# EGCG Concanavalin-A (Con-A)- and/or

Staphylococcal enterotoxin B (SEB)-

stimulated human PBMC; murine

splenocytes or mesenteric lymph node

cells

Watson

et al. (2005)

# Epicatechin

Catechin

Procyanidin

B2

Jurkat T cells Mackenzie

et al. (2004)

IL-2 # Epicatechin

Cocoa extract

Phorbol myristate acetate (PMA)-

stimulated EL-4.BU.OU6

lymphocytic murine cell line

Ramiro

et al. (2005)

# Genistein Con-A-stimulated human PBMC Gredel

et al. (2008)

# Quercetin Activated T-bet-deficient and T-bet

transgenic/deficient mouse Th cells

Yu et al.

(2008)

¼ Kaempferol Con-A-stimulated human

lymphocytes

Miles et al.

(2005)

Continued

Table 12.1 In Vitro Effect of Flavonoids on the Cytokine Production of Lymphocytes—cont'dCytokine Effect Flavonoid Target Reference

↑mRNA EGCG Jurkat T cells Wu et al.

(2009)

# Cocoa extract

(flavanols)

Phytohemagglutinin (PHA)-

stimulated human PBMC

Jenny et al.

(2009)

# EGCG Con-A- and/or SEB-stimulated

human PBMC; murine splenocytes or

mesenteric lymph node cells

Watson

et al., 2005

# Formononetin

Daidzein

Equol

Primary Th cells from immunized

animals and EL4 T-cell line

Park et al.

(2005)

IFNg # Kaempferol Con-A-stimulated human

lymphocytes

Miles et al.

(2005)

# Genistein Con-A-stimulated human PBMC Gredel

et al. (2008)

# Quercetin Activated T-bet-deficient and

T-bet-transgenic/deficient mouse

Th cells

Yu et al.

(2008)

#mRNA EGCG Jurkat T cells Wu et al.

(2009)

↑ Epicatechin

Cocoa extract

PMA-stimulated EL-4.BU.OU6

lymphocytic murine cell line

Ramiro

et al. (2005)

↑ Formononetin

Daidzein

Equol

Primary Th cells from immunized

animals and EL4 T-cell line

Park et al.

(2005)

IL-4 # Genistein Con-A stimulated human PBMC Gredel

et al. (2008)

¼ EGCG Con-A- and/or SEB-stimulated

human PBMC; murine splenocytes or

mesenteric lymph node cells

Watson

et al. (2005)

¼ Kaempferol Con-A-stimulated human

lymphocytes

Miles et al.

(2005)

IL-5 ↑mRNA EGCG Jurkat T cells Wu et al.

(2009)

IL-13 ↑mRNA EGCG Jurkat T cells Wu et al.

(2009)


Th cells, and this was accompanied by a lower expression of the chain a of IL-2 receptor

(IL-2Ra or CD25) (Yu et al., 2008). In the same way, when the flavanol EGCG was

added to cultures of human PBMC, murine splenocytes or mesenteric lymph node cells

abolished the immune cell proliferation and IL-2 production by mechanisms indepen-

dent of NF-kB and AP-1 (activator protein 1) DNA-binding activities (Watson et al.,


2005). The immunological synapse may be another possible target for flavonoid action.

In this sense, Kawai et al. (2003) demonstrated that EGCG bound directly to the

cell-surface CD4 molecule, without modifying the surface expression of CD3, CD54,

and CD11a. In agreement with those results, flavonoids from the same EGCG family,

such as epicatechin, catechin, and the dimeric procyanidin B2, have been reported to

inhibit IL-2 synthesis in Jurkat T cells (Mackenzie et al., 2004). In this case, the inhibition

was attributed to the entrance of these flavanols into the lymphocyte nuclei, inhibiting

NF-kB activation at both the early stages of the activation cascade (regulation of oxidant

levels, IkB kinase (IKK) activation, and subsequent IkBa phosphorylation) and at the

later stages by preventing the binding of active NF-kB to kB sites (Mackenzie et al.,

2004). In a similar vein, Ramiro et al. (2005) reported the inhibition of IL-2 secretion

and the downregulation of CD25 by epicatechin and a cocoa extract on stimulated EL-4.

BU.OU6 lymphocytic cells.

After activation and proliferation of specific Th cells, the acquired immune response

proceeds with the differentiation of Th lymphocytes to effector Th1 or Th2 cells that

secrete their typical cytokine profile (see above). IFNg is the main product of Th1 cells,

and IL-4 is the representative cytokine of Th2 cells. Consequently, increases or decreases

in the synthesis of these cytokines could reflect Th1- or Th2-promoting or -inhibiting

activities. Several flavonoids added to lymphocytes in culture have shown the ability to

modify IFNg and IL-4 production (Table 12.1).

The flavonol quercetin reduced IFNg protein and mRNA expression in TCR-

stimulated Th cells through the modulation of a transcription factor from the T-box fam-

ily expressed in T-cell (T-bet) expression (Yu et al., 2008). Similarly, Miles et al. (2005)

reported the inhibition of IFNg, but no effect on IL-2 and IL-4 secretion, by the flavonolkaempferol in stimulated human lymphocytes.

Park et al. (2005) investigated the effect of the isoflavones formononetin, daidzein,

and equol on the production of IFNg and IL-4 in primary Th cells from immunized mice

and the EL4 T-cell line. The isoflavones also decreased IFNg synthesis but enhanced IL-4production, both at transcriptional level. However, other studies revealed that the

isoflavone genistein diminished the secretion of both IFNg and IL-4 in stimulated human

PBMC (Gredel et al., 2008).

Human PBMCs or murine lymph node cells treated with the flavanol EGCG

significantly reduced IFNg production without modifying IL-4 synthesis (Watson

et al., 2005). Likewise, a cocoa extract rich in flavanols suppressed the production of

IFNg in stimulated human PBMCs (Jenny et al., 2009). On the other hand, epicatechin

and a cocoa extract were able to increase IL-4 production by stimulated EL4.BU.OU6

murine cells (Ramiro et al., 2005). Similarly, Wu et al. (2009) showed that EGCG

significantly upregulated the mRNA expression of Th1/Th2 cytokines including

IL-2, IFNg, IL-5, and IL-13 in Jurkat T cells. The mRNA upregulation of IL-2

and IL-5 was predominantly affected by ERK signaling, whereas IL-13 gene expres-

sion, the most responsive to the EGCG treatment, was dependent on neither ERK


nor JNK signaling. IFNg gene expression was partially mitigated by both inhibitors of

ERK and JNK pathways.

In summary, most of the in vitro studies of the effect of flavonoids on lymphocytes

point to an inhibitory effect of the acquired immune activation, including very early

and late phases of the immune response, as in the case of the interaction between

DCs and Th cells, IL-2 secretion, Th cell proliferation, and Th1 or Th2 effector

responses. However, a skewed effect of flavonoids favoring or inhibiting Th1 or Th2

responses is not clearly established in vitro.

3.2 The Effect of Flavonoid Intake on the Functionality of theImmune System

In vivo studies of flavonoids include both those performed with a specific flavonoid and

those carried out with extracts or foods rich in certain flavonoids. Most of the preclinical

studies focused on the acquired immune response were performed in experimental

models based on an antigen sensitization (mainly ovalbumin, OVA) followed by a chal-

lenge through different routes, searching to provoke a harmful immune response. As

reported in the following section, different types of flavonoids show the potential to

suppress these damaging responses.

3.2.1 Preclinical studies with single flavonoids administered orallyYano et al. (2007) evaluated the immune response of OVA-sensitized mice, which were

fed diets containing the flavones chrysin and apigenin. Interestingly, total IgE concen-

tration in serum decreased with these diets, whereas concentrations of IgG, IgM, and

IgA were not affected. IL-2, IL-4, IL-10, and IL-13 mRNA expression in splenocytes

were also downregulated by the flavonoid diets. In a similar manner, mice sensitized with

picryl chloride were treated with the flavone naringenin, and this resulted in the inhibi-

tion of the proliferation of activated hapten-specific T cells and polyclonal-activated T

cells, and a reduction in CD69, IL-2, and IFNg mRNA expression in activated T cells

(Fang et al., 2010).

Kogiso et al. (2006) established the effect of the isoflavone genistein in OVA-

immunized mice. The administration of genistein decreased OVA-specific proliferative

responses and IFNg production. The concentration of OVA-specific IgG1 was also re-

duced while OVA-specific IgG2a and IgG2b and IL-4 production tended to be decreased

in genistein-treated mice. Similarly, Nazir et al. (2009) established the effect of two isofla-

vones, 5,7-dihydroxy-6,40-dimethoxyisoflavone (irisolidone) and 5,40-dihydroxy-6,7-methylenedioxyisoflavone (irilone), isolated from Iris germanica (Iridaceae) and administered

to mice. Both isoflavones produced different effects on the secretion of Th1 cytokines:

The first isoflavone increased IL-2 and IFNg secretion, whereas the second isoflavone in-duced their decrease. However, both isoflavones downmodulated the secretion of Th2

cytokines (IL-4 and IL-5). Themethylated products of both isoflavones showed a drastically


decreased activity, revealing the importance of free phenolic groups on their immuno-

modulating activities. In contrast with these results, Sakai et al. (2010) investigated the

immunomodulatory effects of the isoflavones daidzein and equol in mice by evaluating

the OVA-specific T-cell and B-cell responses. Mice showed a significantly higher level

of OVA-specific IgE than control mice when treated with equol, but not with daidzein.

Moreover, IFNg and IL-4 production were not modified in mice receiving equol, but

IL-13 production was significantly higher than that in control mice.

As well as from the preclinical studies in healthy sensitized animals, models of induced

hypersensitivity were used to establish the possible effects of flavonoids. Amurine model of

airway hyperreactivity can be induced by OVA sensitization and posterior challenge with

OVA inhalation. In this context, OVA-sensitized mice that received a daily inhalation of

OVA from day 19 to day 23 were administered daily with the flavone luteolin during the

sensitization or after challenge (from day 26) (Das et al., 2003). The flavonoid reduced

OVA-specific IgE concentration in serum and increased IFNg and decreased IL-4 and

IL-5 secretions in the bronchoalveolar lavage fluid, which significantly attenuated

OVA-induced airway bronchoconstriction and bronchial hyperreactivity (Das et al.,

2003). Similarly, the flavanone naringenin was administered during allergic airway inflam-

mation in mice. Serum total IgE and OVA-specific IgG1, IgG2a, and IgM were not mod-

ified, but IL-4, IL-5, and IL-13 from stimulated splenocytes decreased with naringenin

administration. Moreover, there was an attenuation of airway hyperreactivity and eosino-

philic infiltration in the bronchioalveolar lavage fluid in flavonoid-treated mice (Iwamura

et al., 2010). Similar promising effects were reported for the flavone apigenin. Yano et al.

(2009) examined the effect of dietary apigenin on a mice model of atopic dermatitis. The

apigenin diet decreased serum IgG1 and IgE concentrations, ameliorated the development

of skin lesions, and reduced IFNg secretion (but not IL-4) in spleen cells.

3.2.2 Preclinical studies using food extracts rich in flavonoidsRegarding the effects of diets with high flavonoid content, we have demonstrated that

a cocoa-enriched diet containing flavanols such as epicatechin and procyanidins is ca-

pable of modifying the composition and functionality of several lymphoid tissues, in-

cluding the gut-associated lymphoid tissue (GALT) in young healthy rats. In

particular, a continuous cocoa intake by young rats reduced the proportion of Th cells

in the spleen, Peyer’s patches (PP), and mesenteric lymph nodes, although neither the

proliferative response nor IL-2 secretion in these tissues was modified by the diet

(Ramiro-Puig et al., 2007, 2008). Rats fed a cocoa diet showed lower serum IgG,

IgM, and IgA concentrations (Ramiro-Puig et al., 2007) and a reduced ex vivo IL-4

secretion by splenocytes than reference animals (Ramiro-Puig et al., 2007, 2008).

In addition, the effect of a cocoa diet on an OVA-specific immune response in rats

was established (Perez-Berezo et al., 2009). The diet attenuated OVA-specific IgG1

(the main subclass associated with the Th2 immune response in rats), IgG2a, IgG2c,


and IgM concentrations but led to higher amounts of anti-OVA, IgG2b (subclass

linked to the Th1 response). This effect was accompanied by decreased IL-4 and in-

creased IFNg secretions (Perez-Berezo et al., 2009). Similarly, a cocoa diet was able to

attenuate the specific antibody response in a model of chronic inflammation (Ramos-

Romero et al., 2011). Moreover, in the GALT, a cocoa-enriched diet decreased IgA

secretion into the gut, and this was accompanied by a reduction in the gene expression

of several molecules involved in IgA-secreting cell activation (IL-6, CD40), gut hom-

ing (RARa (retinoic acid receptor a), CCR9 (chemokine (C–C motif) receptor-9),

CCL28), and IgA synthesis (transforming growth factor b (TGFb)) (Perez-Berezoet al., 2011a, b). Likewise, cocoa-fed animals showed a modified toll-like receptors

(TLR) expression pattern in gut tissues, which may reflect a change in the crosstalk

between microbiota and body cells induced by a cocoa diet (Perez-Berezo et al.,

2011a,b). Nevertheless, the effect of cocoa-enriched diets could also be attributed

to compounds other than flavonoids present in cocoa, such as fiber.

On the other hand, Cruz et al. (2008) reported the immunosuppressive action of

an aqueous extract of Kalanchoe pinnata (Crassulaceae) containing quercetin 3-O-a-L-arabinopyranosyl (1!2) a-L-rhamnopyranoside, quercitrin, and kaempferol 3-O-a-L-arabinopyranosyl (1!2) a-L-rhamnopyranoside. Mice treated daily with this extract

during OVA-sensitization were protected against death when challenged with OVA

and showed a reduced production of OVA-specific IgE antibodies and impaired pro-

duction of the IL-5 and IL-10 cytokines. Similarly, Akiyama et al. (2005) demon-

strated that the intake of apple-condensed tannins inhibited the development of

oral OVA sensitization in mice. This diet produced a decreased serum OVA-specific

IgE and IgG1 synthesis in sensitized mice, which was accompanied by a higher pro-

portion of gut intraepithelial gd T cells and inhibited the reduction of body temper-

ature or the increase of serum histamine concentration associated with antigen

stimulation. Similarly, Medeiros et al. (2008) evaluated the properties of plant extract

collected by Apis mellifera bee, rich in myricetin, tricetin, quercetin, and luteolin, on a

murine model of OVA-induced allergy. The extract produced inhibition of OVA-

specific IgE and IgG1 concentrations and, in addition, decreased leukocyte migration

to the bronchoalveolar lavage, thereby protecting against the anaphylactic shock

reaction induced by OVA. Zuercher et al. (2010) evaluated the effect of a polyphe-

nol-enriched apple extract on a similar model. In this case, mice fed with the apple

extract did not show modified OVA-specific IgE, IgG1, or IgG2b concentrations,

and the apple extract also inhibited the release of mast cell protease and reduced symp-

toms of allergy upon challenge.

In conclusion, most of these studies suggested that diets containing flavonoids, regard-

less of their class, produce a certain immunosuppressant effect that might be desirable in

IgE allergic reactions. Moreover, it may be useful to explore this effect on oral tolerance

and antibody-mediated diseases such as autoimmune pathologies.


3.2.3 Clinical studies using food or extracts rich in flavonoidsAlthough there are many in vitro and experimental preclinical studies on the modulatory

effect of flavonoids on acquired immune responses, there are currently a limited number

of trials evaluating this effect in humans. There are evident and ethical obstacles to

evaluating the functionality of the immune system in people. Therefore, the blood com-

partment, as a noninvasive approach, is widely used to evaluate lymphocyte function by

means of cytokine secretion. However, such products are scarce or undetectable in serum

in most conditions. For this reason, in order to study the Th1/Th2 effector immune

responses’ modulation by flavonoids, an ex vivo approach after a dietary intervention is

usually designed.

Chen et al. (2005) reported the effects of purple sweet potato leaves, which were rich

in carotenoids and flavonoids, on a randomized crossover study involving 16 healthy

nonsmoking adults. In contrast to most preclinical studies, this diet increased the

proliferative response of PBMCs and enhanced the secretion of IL-2 and IL-4. Karlsen

et al. (2007) assessed the effect of anthocyanins isolated from bilberries and blackcurrants

(Medox capsules for 3 weeks) on a parallel-designed, placebo-controlled clinical trial.

The Medox group showed decreased serum IL-4 and IL-13 concentrations (Th2

cytokines) and also a reduction in pro-inflammatory chemokines such as IL-8, regulated

upon activation, normal T-cell expressed, and secreted (RANTES), and IFNa. Interest-ingly, Ryan-Borchers et al. (2006) evaluated the effects of soy isoflavones, both in

soymilk and in a supplement form, on the immune system of postmenopausal women.

This 16-week double-blind, placebo-controlled trial included three groups: (1) control,

706 mL cow milk/day plus a placebo supplement; (2) soymilk, 71.6 mg isoflavones

derived from 706 mL soymilk/day plus a placebo supplement; and (3) supplement,

70 mg isoflavones in a supplement plus 706 mL cow milk/day. Isoflavone intervention

in postmenopausal women resulted in a higher proportion of the B-cell population but

did not significantly influence plasma concentrations of IFNg and IL-2.

In conclusion, further preclinical studies and clinical trials should be performed in

order to better delimit the effects of flavonoids on acquired immune response and to

investigate the mechanisms involved in this process.

4. CONCLUDING REMARKS

Flavonoids comprise a myriad of vegetal products that are included in diets containing

fruits and vegetables, and also wine, tea, and cocoa. Although structurally different, most

of the flavonoids assessed in in vitro and preclinical studies showed similar activities in

terms of lymphocyte function and acquired immune response. The effects induced by

flavonoids are referred to as an attenuation of the immune functionality, a fact that implies

their putative beneficial role on immune hypersensitivity status. However, the few trials


performed to date do not seem to support this hypothesis. In any case, more preclinical

models and protocols closer to human responses should be conducted in order to better

establish the immune consequences of these dietary compounds.

GLOSSARY

Acquired immune response Immunity mediated by lymphocytes and characterized by antigen-

specificity and memory.

Antibody Also known as immunoglobulin, this is a glycoprotein of the g-globulins family produced by B

lineage cells in order to neutralize foreign molecules from bacteria, viruses, and parasites and provide

immune defense.

Antigen Any foreign (pathogen or not) or own molecule capable of being specifically recognized by an

antibody or T-cell receptor.

Antigen-presenting cells Cells that present a processed antigen through the MHC class II molecules to

the T-cell receptor of CD4þ T cells. This event is essential for initiating the acquired immune response.

Chemokine Family of structurally related cytokines which selectively direct movements to certain body

environment (chemotaxis) and activation of leukocytes.

Cytokine Soluble and low-molecular-weight proteins that stimulate or inhibit the differentiation,

proliferation, or function of immune cells. The family of cytokine includes, among others,

interleukins (IL) such as IL-2, IL-4, etc.

REFERENCESAkiyama, H., Sato, Y.,Watanabe, T., et al., 2005. Dietary unripe apple polyphenol inhibits the development

of food allergies in murine models. FEBS Letters 579, 4485–4491.Chen, C.M., Li, S.C., Lin, Y.L., et al., 2005. Consumption of purple sweet potato leaves modulates human

immune response: T-lymphocyte functions, lytic activity of natural killer cell and antibody production.World Journal of Gastroenterology 11, 5777–5781.

Cruz, E.A., Da-Silva, S.A., Muzitano, M.F., et al., 2008. Immunomodulatory pretreatment with Kalanchoepinnata extract and its quercitrin flavonoid effectively protects mice against fatal anaphylactic shock. In-ternational Immunopharmacology 8, 1616–1621.

Das, M., Ram, A., Ghosh, B., 2003. Luteolin alleviates bronchoconstriction and airway hyperreactivity inovalbumin sensitized mice. Inflammation Research 52, 101–106.

Fang, F., Tang, Y., Gao, Z., Xu, Q., 2010. A novel regulatory mechanism of naringenin through inhibitionof T lymphocyte function in contact hypersensitivity suppression. Biochemical and BiophysicalResearch Communications 397, 163–169.

Gredel, S., Grad, C., Rechkemmer, G., Watzl, B., 2008. Phytoestrogens and phytoestrogen metabolites dif-ferentially modulate immune parameters in human leukocytes. Food and Chemical Toxicology46, 3691–3696.

Huang, R.-Y., Yu, Y.-L., Cheng, W.-C., et al., 2010. Immunosuppressive effect of quercetin on dendriticcell activation and function. Journal of Immunology 184, 6815–6821.

Iwamura, C., Shinoda, K., Yoshimura, M., et al., 2010. Naringenin chalcone suppresses allergic asthma byinhibiting the type-2 function of CD4 T cells. Allergology International 59, 67–73.

Jenny, M., Santer, E., Klein, A., et al., 2009. Cacao extracts suppress tryptophan degradation of mitogen-stimulated peripheral blood mononuclear cells. Journal of Ethnopharmacology 122, 261–267.

Karlsen, A., Retterst�l, L., Laake, P., et al., 2007. Anthocyanins inhibit nuclear factor-kB activation inmonocytes and reduce plasma concentrations of pro-inflammatory mediators in healthy adults. Journalof Nutrition 137, 1951–1954.


Kawai, K., Tsuno, N.H., Kitayama, J., et al., 2003. Epigallocatechin gallate, the main component of tea poly-phenol, binds to CD4 and interferes with gp120 binding. The Journal of Allergy and Clinical Immu-nology 112, 951–957.

Kogiso, M., Sakai, T., Mitsuya, K., Komatsu, T., Yamamoto, S., 2006. Genistein suppresses antigen-specificimmune responses through competition with 17b-estradiol for estrogen receptors in ovalbuminimmunized BALB/c mice. Nutrition 22, 802–809.

Mackenzie, G.G., Carrasquedo, F., Delfino, J.M., et al., 2004. Epicatechin, catechin, and dimericprocyanidins inhibit PMA-induced NF-kB activation at multiple steps in Jurkat T cells. The FASEBJournal 18, 167–169.

Medeiros, K.C.P., Figueiredo, C.A.V., Figueredo, T.B., et al., 2008. Anti-allergic effect of bee pollenphenolic extract and myricetin in ovalbumin-sensitized mice. Journal of Ethnopharmacology119, 41–46.

Miles, E.A., Zoubouli, P., Calder, P.C., 2005. Effects of polyphenols on human Th1 and Th2 cytokineproduction. Clinical Nutrition 24, 780–784.

Nazir, N., Koul, S., Qurishi, M.A., et al., 2009. Immunomodulatory activity of isoflavones isolated from Irisgermanica (Iridaceae) on T-lymphocytes and cytokines. Phytotherapy Research 23, 428–433.

Park, J., Kim, S.H., Cho, D., Kim, T.S., 2005. Formononetin, a phyto-oestrogen, and its metabolitesup-regulate interleukin-4 production in activated T cells via increased AP-1 DNA binding activity.Immunology 116, 71–81.

Perez-Berezo, T., Ramiro-Puig, E., Perez-Cano, F.J., et al., 2009. Influence of a cocoa-enriched diet onspecific immune response in ovalbumin-sensitized rats. Molecular Nutrition and Food Research53, 389–397.

Perez-Berezo, T., Franch, A., Ramos-Romero, S., et al., 2011a. Cocoa-enriched diets modulate intestinaland systemic humoral immune response in young adult rats. Molecular Nutrition and Food Research55, S56–S66.

Perez-Berezo, T., Franch, A., Castellote, C., Castell, M., Perez-Cano, F.J., 2011b. Mechanisms involvedin down-regulation of intestinal IgA in rats by high cocoa intake. The Journal of Nutritional Biochem-istry. doi:http://dx.doi.org/10.1016/j.jnutbio.2011.04.008.

Ramiro, E., Franch, A., Castellote, C., et al., 2005. Effect of Theobroma cacao flavonoids on immuneactivation of a lymphoid cell line. British Journal of Nutrition 93, 859–866.

Ramiro-Puig, E., Perez-Cano, F.J., Ramırez-Santana, C., et al., 2007. Spleen lymphocyte function mod-ulated by a cocoa-enriched diet. Clinical and Experimental Immunology 149, 535–542.

Ramiro-Puig, E., Perez-Cano, F.J., Ramos-Romero, S., et al., 2008. Intestinal immune system of young ratsinfluenced by cocoa-enriched diet. The Journal of Nutritional Biochemistry 19, 555–565.

Ramos-Romero, S., Perez-Cano, F.J., Castellote, C., Castell, M., Franch, A., 2011. Effect of cocoa-enriched diets on lymphocytes involved in adjuvant arthritis in rats. British Journal of Nutrition107, 378–387.

Ryan-Borchers, T.A., Park, J.S., Chew, B.P., et al., 2006. Soy isoflavones modulate immune function inhealthy postmenopausal women. The American Journal of Clinical Nutrition 83, 1118–1125.

Sakai, T., Furoku, S., Nakamoto, M., et al., 2010. The soy isoflavone equol enhances antigen-specific IgEproduction in ovalbumin-immunized BALB/c mice. Journal of Nutritional Sciences and Vitaminology56, 72–76 (Tokyo).

Watson, J.L., Vicario, M., Wang, A., Moreto, M., McKay, D.M., 2005. Immune cell activation and sub-sequent epithelial dysfunction by Staphylococcus enterotoxin B is attenuated by the green tea polyphenol(-)-epigallocatechin gallate. Cellular Immunology 237, 7–16.

Wu, H., Zhu, B., Shimoishi, Y., Murata, Y., Nakamura, Y., 2009. (-)-Epigallocatechin-3-gallate inducesup-regulation of Th1 and Th2 cytokine genes in Jurkat T cells. Archives of Biochemistry and Biophysics483, 99–105.

Yano, S., Umeda, D., Yamashita, T., et al., 2007. Dietary flavones suppresses IgE and Th2 cytokines inOVA-immunized BALB/c mice. European Journal of Nutrition 46, 257–263.

Yano, S., Umeda, D., Yamashita, S., Yamada, K., Tachibana, H., 2009. Dietary apigenin attenuates thedevelopment of atopic dermatitis-like skin lesions in NC/Nga mice. The Journal of NutritionalBiochemistry 20, 876–881.


Yoneyama, S., Kawai, K., Tsuno, N.H., et al., 2008. Epigallocatechin gallate affects human dendritic celldifferentiation and maturation. The Journal of Allergy and Clinical Immunology 121, 209–214.

Yu, E.S., Min, H.J., An, S.Y., et al., 2008. Regulatory mechanisms of IL-2 and IFNg suppression byquercetin in T helper cells. Biochemical Pharmacology 76, 70–78.

Zuercher, A.W., Holvoet, S.,Weiss, M.,Mercenier, A., 2010. Polyphenol-enriched apple extract attenuatesfood allergy in mice. Clinical and Experimental Allergy 40, 942–950.

FURTHER READINGComalada, M., Xaus, J., Galvez, J., 2011. Flavonoids and immunomodulation. In: Bioactive Foods and

Chronic Disease States. Elsevier, Amsterdam.Gomes, A., Fernandes, E., Lima, J.L.F.C., Mira, L., Corvo, M.L., 2008. Molecular mechanisms of anti-

inflammatory activity mediated by flavonoids. Current Medicinal Chemistry 15, 1586–1605.Gonzalez-Gallego, J., Garcıa-Mediavilla, M.V., Sanchez-Campos, S., Tunon, M.J., 2010. Fruit polyphe-

nols, immunity and inflammation. British Journal of Nutrition 104, S15–S27.Hamer, M., 2007. The beneficial effects of tea on immune function and inflammation: a review of evidence

from in vitro, animal, and human research. Nutrition Research 27, 373–379.Kawai, M., Hirano, T., Higa, S., et al., 2007. Flavonoids and related compounds as anti-allergic substances.

Allergology International 56, 113–123.Middleton, E., Kandaswami, C., Theoharides, T.C., 2000. The effects of plant flavonoids on mammalian

cells: implications for inflammation, heart disease, and cancer. Pharmacological Reviews 52, 673–751.Ramiro-Puig, E., Castell, M., 2009. Cocoa: antioxidant and immunomodulator. British Journal of Nutrition

101, 931–940.Sakai, T., Kogiso, M., 2008. Soy isoflavones and immunity. The Journal of Medical Investigation

55, 167–173.

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