Two edged sword: Vital to survival, Harmful when excess.

immunity- Immunodeficiency- render Humans easy prey to

infections and possibly tumors;

immunity- Hypersensitivity; fatal allergic reaction to sting bite.

Autoimmune rn: Reaction against one’s own tissues and cells.

BASIC CONCEPTS OF IMMUNITY

1. INNATE IMMUNITY (NATURAL/ NATIVE):

Defense mechanisms that are present even before infection.

First line of defense; Not specific to any microbe

2. ADAPTIVE IMMUNITY (ACQUIRED/ SPECIFIC):

Mechanisms that are stimulated by microbes and are capable

of also recognizing non-microbial substances (antigens).

Develops later after infection

More specific and more powerful.

First line defense: it is always ready to prevent and eradicate

infections.

Components:

1. Epithelial cells

2. Phagocytic cells

3. NK –natural killer cells

4. Plasma proteins and complement system

Body defense mechanisms

Develops later after exposure to microbes

Even more powerful in combating infections.

Consists of Lymphocytes and their products

(antibodies).

Generated from immature precursors in the thymus

Found in :

1. BLOOD- 60-70% of lymphocytes

2. LN- Paracortical areas

3. SPLEEN- Periarteriolar lymphoid sheath (PALS).

Contains T Cell Receptor (TCR)

T LYMPHOCYTES

CD 4

60%

CD 8

40%

MHC

CLASS II

HELPER CYTOTOXIC

TH 1 CELLS: IL-2, IFN

TH 2 CELLS: IL-4,5,13

IL-2, IFN gamma.

MHC

CLASS I

MHC

ANTIGEN

PRESENTATION

COMPONENTS OF

COMPLIMENTS

CLASS IIICLASS IICLASS I

(ALL NUCLEATED

CELLS)

(MACROPHAGES,

DC, EC’S)

HLA

A,B,C

HLA-D

ALPHA & BETA

DP

DQ

DR

CD-8 T

CELLSCD-4 T CELLS

Master regulator / Conductor of Symphony Orchestra

T cells secrete cytokines

CD 4 TH-1 cell secretes IL-2 & IFN .

CD 4 TH-2 cell secretes IL-4, 5, 13.

The cytokines influence T cells, B cells, Macrophages & NK cells

CD4 T cell is crippled in HIV infection

Short acting soluble mediators.

Paracrine, Autocrine, Endocrine effects.

Recombinant cytokines Immunotherapy in cancers

Develop from Immature precursors in BM

10 -20% of peripheral blood lymphocytes

Superficial cortex, follicles of lymph node & White pulp of

spleen

After antigenic stimulation, B cells form Plasma cells that

secrete Immunoglobulins

B - LYMPHOCYTE

ANTIGENS

(PROTEINS AND NON-PROTEIN SUBSTANCES)

B-LYMPHOCYTE

ACTIVATION

DIFFERENTIATION

PLASMA

CELLS IMMUNOGLOBULINSImmunoglobulinsG.A.M.D.E.

5% -15% of peripheral blood lymphocytes

Larger than small lymphocytes, azurophilic granules

Large Granular Lymphocytes

Innate immunity: Kill tumor cells, Virally infected cells.

NK cells are CD 16, CD 56 positive .

Part of Mononuclear Phagocyte system

Induction of Cell mediated immunity

They ingest protein antigens, process & present the peptide

fragments to T cells

Important role in Type IV hypersensitivity, activated by IFN

secreted by CD 4 TH-1

Can phagocytose opsonized or Ig coated microbes

Blood: Monocytes

Brain: Microglial cells

Lung: Alveolar macrophages/ Dust cells/ Heart failure cells

Liver: Kupffer cells

Spleen: Splenic sinusoidal macrophages

Kidney: Mesangial Cells

Lymph node: Sinus Histiocytes

Skin: Interdigitating Dendritic Cells

Bone: Osteoclastic giant cells

Joint: Synoviocytes

APC’s.

LPS TOLL LIKE

RECEPTORS ON

MACROPHAGES

NUCLEAR FACTOR

ACTIVATION

CYTOKINE PRODUCTIONS

HYDROLYTIC ENZYMES, REACTIVE OXYGEN SPECIES

P H A G O C Y T O S I S

Innate Immunity --vs.-- Acquired Immunity