PRESENTED

BY

TANIYA.M.S

MSC . BIOTECHNOLOGY

Cells of the Immune System-I

1. Originated from

Bone Marrow (BM)

2. Two major lineages:

- Lymphoid

- Myeloid

3. NK cells

- Large Granular

Lymphocytes (LGL)

Cells of Adaptive immunity

1. Lymphocytes are the key players of the adaptive

immunity.

2. Lymphocytes are able to specifically recognize and

respond to diverse antigens.

=> Antigen receptors on lymphocytes

=> Specificity Diversity & Memory

3. Lymphocytes are classified into three major groups:

- B cells => Antibodies => Humoral immunity

- T cells => Multiple subtypes => Cell-mediated immunity &

Regulate other immune cells

- NK cells => Innate immunity

Lymphocytes

Specific receptores (TCR and BCR)

Based on site of differentiation and on receptors:

T cells and naturall killers T - in thymus - (TCR)

B cells – bone marrow - (BCR)

(no cell surface specific receptors – NK cells)

Classes of Lymphocytes

1. B cells => Plasma cells

=> Abs

2. T cells:

- T helper cells

- T cytotoxic cells

- T regulatory cells

-T memory cells

-T NK cells

=> suppress immune

responses

3. NK cells

4. Subtypes in each class

Thymus derived cells

T lymphocytes

Most important players of specific immunity

Direct effectors and regulators of activity of other cells

Produced in bone marrow: not mature T cell – prothymocyte

Migrates in thymus - thymocyte, where TCR are produce.

T cells and leave thymus and enter to ciruculation

Contain surface receptors TCR

CD3, CD4 or CD8

- CD4 T cell

2/3 of all T cells containging CD3

CD4 cell surface molecule

– recognise part of MHC II

molecule that is not part

of peptid binding site

Functionally – helper

- CD8 T cells

1/3 of all T cells containing CD3

CD8 cell surface molecule – recognise part of MHC I molecule that is not designated to bind peptids

Functionally : Tc cytotoxic – eliminate virus or i.c.bacteria infected cells

Ts supressor – increase and control reactions of specific immunity

Cells produced in bone marrow only

B - lymphocytes

Not all cells produced in bone marrow migrate to

thymus

Some differentiate in bone marrow further and are

precursors of cells producing immunoglobulins

B lymphocytes – B cells – synthetise

immunoglobulin, that is then situated on the cell

surface as BCR.

Differenciated mature B cell synthetises and

secretes immunoglobulines

B cells

Plasma cells

Memory cells

B1 cells

Regulatory cells

- Plasmatic cells

Derived from terminally differentiated B cells

Produce and secrete immunoglobulines

In the momente, when they start to produce and secrete Ig, they stop to use immunoglobuline molecule as BCR

They are bigger and have bigger metabolic activity

Produce large amounts of Ig

survive 30 days

NK cells – natural killers

5% - 10% periferal blood lymphocytes

do not have markers (receptors) as T cells

(CD3, TCR) and B cells (Ig)

kill cells infected by viruses and tumor cells

without previous sensibilisation

Null cells

A null cell is a large granular lymphocyte

Without surface markers or membrane-associated proteins from B lymphocytes or T lymphocytes.

Natural killer cells are usually null cells with surface marker CD 16

Attack pathogens and abnormal cells.

Members of null cells are NK cells.

In 75% of the cases of ALL, the lymphocytes are neither B nor T-cells and are called Null cells.

Innate immune cells are

classified as following:

- Monocyte/Macrophage

- Dendritic cell (DC)

- Polymorphonuclear

granulocyte (PMN;

Neutrophil, Eosinophil,

Basophil)

- Mast cell

Classes of innate immune cells

WBC’s

Five Types

Classified according to the presence or absence of granules and the staining characteristics of their cytoplasm.

Leukocytes appear brightly colored in stained preparations, they have a nuclei and are generally larger in size than RBC’s.

Type of WBC’s

Granulocytes—have large granules in their cytoplasm

Neutrophils

Eosinophils

Basophils

Polymorphonuclear Granulocytes: Neutrophils

1. Comprise over 95% of

granulocytes

2. Short-lived (2-3 days)

3. Multi-lobed nucleus

4. Kill pathogens by

phagocytosis & releasing

cytotoxic substances.

Granuloctyes

Neutrophils

Stain light purple with neutral dyes

Granules are small and numerous—course appearance

Several lobes in nucleus

65% of WBC count

Highly mobile/very active

Diapedesis—Can leave blood vessels and enter tissue space

Phagocytosis (eater), contain several lysosomes (janitor)

Neutrophils are a type of phagocyte.

During the beginning phase of inflammation, the first-responders of inflammatory cells to migrate towards the site of inflammation.

They migrate through the blood vessels, then through interstitial tissue,

following chemical signals such as Interleukin-8 (IL-8), Leukotriene B4 in a process called chemotaxis.

They are the predominant cells in pus, accounting for its whitish/yellowish appearance

Granulocytes

Eosinophils

Large, numerous granules

Nuclei with two lobes

2-5% of WBC count

Found in lining of respiratory and digestive tracts

Important functions involve protections against

infections caused by parasitic worms and

involvement in allergic reactions

Secrete anti-inflammatory substances in allergic

reactions

Eosinophils play a crucial part in the killing of

parasites (e.g., enteric nematodes) because their

granules contain a unique, toxic basic protein and

cationic protein

Granulocytes

Basophils

Least numerous--.5-1%

Diapedesis—Can leave blood vessels and

enter tissue space

Contain histamine—inflammatory chemical

Basophils are one of the least abundant

cells in bone marrow and blood(occurring

at less than two percent of all cells).

Like neutrophils and eosinophils, they have

lobed nuclei; however, they have only two

lobes, and the chromatin filaments that

connect them are not very visible.

Agranulocytes,

mononuclear leukocytes,

with a one-lobed nucleus.

They are characterised by the absence of

granules

2 types of agranulocytes in the blood

circulation are lymphocytes and monocytes.

A third type of agranulocyte, the

macrophage is formed monocytes leave the

circulation and differentiate into

macrophages.

Agranulocytes

Lymphocytes

Smallest WBC

Large nuclei/small amount of cytoplasm

Account for 25% of WBC count

Two types—T lymphocytes—attack an infect

or cancerous cell, B lymphocytes—produce

antibodies against specific antigens (foreign

body)

Agranulocytes

Monocytes

Largest of WBCs

Dark kidney bean shaped nuclei

Highly phagocytic

ROLES

Replenishing resident macrophages under normal states,

In response to inflammation signals, monocytes can move to sites of infection in the tissues and divide/differentiate into macrophages and dendritic cells to elicit an immune response.

Half of them are stored in the spleen

Monocytes are usually identified in stained smears by their large kidney shaped or notched nucleus.

These change into macrophages after entering into the tissue spaces.

Macrophages

Big eaters “( MΦ)

That engulf and digest cellular debris, foreign substances, microbes and cancer cells in a process called phagocytosis .

Beyond increasing inflammation and stimulating the immune system,

macrophages also play an important anti-inflammatory role and can decrease immune reactions through the release of cytokines.

Macrophages that encourage inflammation are called M1 macrophages, whereas those that decrease inflammation and encourage tissue repair are called M2 macrophages

Phagocytosis

Dendritic cells (DCs)

Accessory cells

Dendritic cells were first described by Paul

Langerhans in the late 19th century.

Antigen-presenting cells of the mammalian

immune system.

Main function -process antigenmaterial

and present it on the cell surface to the t cells.

Act as messengers between the innate and

the adaptive immune systems .

Dendritic cells are present in those tissues that are in contact with the external environment,

Eg. skin and the inner lining of the nose, lungs, stomachand intestines.

also be found in an immature state in the blood.

Once activated, they migrate to the lymph nodes where they interact with T cells and B cells to initiate and shape the adaptive immune response.

At certain development stages they grow branched projections, the dendrite that give the cell its name .

Immature dendritic cells are also called veiled cells, as they possess large cytoplasmic 'veils' rather than dendrites

REFERENCE

Campbell, Neil A., Reece Jane B., Biology(6th edition), Pearson Education, Inc., 2002

Delves, P.J., Martin, S. J., Burton, D. R. and Roit I.M. Roitt's Essential Immunology(11th edition), Blackwell Publishing, 2006,

Ernst J. D. and Stendahl O., (editors), Phagocytosis of Bacteria and Bacterial Pathogenicity, Cambridge University Press, 2006,

Hoffbrand, A.V., Pettit, J.E. and Moss, P.A.H., Essential Haematology (4th edition), Blackwell Science, 2005

Thank you