Dr Ambika Jawalkar

Architecture of Immune System

1. Mononuclear-Phagocytic System (MPS)

2. Lymphoid Component

Also called Monocyte Macrophage system Commonly known as Reticulo Endothelial

system It is second line defense system of the body Phylogenetically this system is very primitive,

no animal can live with out this system This system is very effective in host protection

even in the absence of B / T lymphocytes Embryological hematopoietic stem cells derive

from ventral mesoderm of the yolk sac First mononuclear phagocyte appear on 12day

of gestation in the liver

Hematopoietic stem cell

Committed stem cell

Monoblast

Promonocyte

Monocyte

Macrophage

GM –CSF

GM –CSFG –CSFSCFIL – 1, 3, 6

M - CSF

M - CSF

BONE MARROW

BLOOD

TISSUES

CENTRAL MONOCYTE POOL

MARGINAL MONOCYTE POOL

DIAPEDESIS

CHEMOTAXIS

FIXED MACROPHAGES MOBILE MACROPHAGES

TRANSFORMATION DIFFERENTIATION

Different sites of distribution:

- Liver [Kupffer cells]

- CNS [Microglial cells]

- Connective tissue [Histiocytes]

- Lung [Dust cells]

- Skin [Langerhan cells]

- Bone [Osteoclasts]

- Kidney [Mesangial cells]

- Spleen

- Lymph node

- viscera etc.

FUNCTIONS OF MPS

- Phagocytosis- Antigen presentation- Antimicrobial activity- Antitumor activity- Angiogenesis- proteolytic / inhibitor activity- cytokine, growth factor production- role in inflammation - role in iron metabolism- storage function

Definition - Process of engulfment and destruction of particulate material by the cells

Also called cell eating

Phagocytes - NeutrophilsMonocytesFixed tissue macrophages

STEPS1.Margination2.Diapedesis3.Chemotaxis4.Opsonisation5.Engulfment6.Degranulation7.Degradation or killing - O2 dependent

O2 independent

MARGINATION: Vasodilation- histamine, serotonin, bradykinin, NO Neutrophils get attached towards the capillary

endothelium - endothelial selectinsintegrins on neutrophilsICAM & VCAM

DIAPEDESIS: Insinuation of neutrophils through capillary walls

CHEMOTAXIS:

Neutrophils are attracted towards bacteria at the site of inflammation

Chemotactic agents are-C5aLeukotriene B4CytokinesIL-8

OPSONIZATION:

Coating of bacteria by opsonins - IgGC3b

ENGULFMENT:By forming phagocytic vesicle

DEGRANULATION:

DEGRADATION:I. O2 independent mechanism:

-through lysosomal enzymes

II. O2 dependent mechanism:NADPH + H+ + 2O2 NADP+ + 2H+ + 2O2

-

O2- + O2

- + H+ + H+ H2 O2 + O2

Cl -,Br - HOCl, HOBr

LYMPHOID ORGANS

Central / Primary :* Thymus* Bursa Equivalent

Peripheral :* Lymph nodes* Spleen* MALT

IMMUNITY

INNATE

NON-SPECIFIC

SPECIFIC

-Species

- Racial

-Individual

ACQUIRED

ACTIVE

Natural Artificial

PASSIVE

Natural Artificial