The document summarizes the architecture of the immune system. It describes the mononuclear-phagocytic system (MPS), also known as the monocyte macrophage system or reticuloendothelial system, as the second line of defense that is phylogenetically primitive but effective in host protection even without B and T lymphocytes. It also describes the lymphoid component, which includes primary organs like the thymus and peripheral organs like lymph nodes and spleen. The MPS originates from hematopoietic stem cells in the bone marrow and differentiates into monocytes and tissue-based macrophages that carry out phagocytosis and antigen presentation.

1. Dr Ambika Jawalkar

2. Architecture of Immune System
1. Mononuclear-Phagocytic System
(MPS)
2. Lymphoid Component

3.  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

4. Hematopoietic stem cell
Committed stem cell
Monoblast
Promonocyte
Monocyte
Macrophage
GM – CSF
G – CSF
SCF
IL – 1, 3, 6
GM – CSF
M - CSF
M - CSF
BONE MARROW
BLOOD
TISSUES

5. CENTRAL MONOCYTE POOL
MARGINAL MONOCYTE POOL
DIAPEDESIS
CHEMOTAXIS
TRANSFORMATION
DIFFERENTIATION
FIXED MACROPHAGES MOBILE MACROPHAGES

7. 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.

8. 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

9.  Definition - Process of engulfment and
destruction of particulate material by the
cells
 Also called cell eating
 Phagocytes - Neutrophils
Monocytes
Fixed tissue macrophages

10. STEPS
1.Margination
2.Diapedesis
3.Chemotaxis
4.Opsonisation
5.Engulfment
6.Degranulation
7.Degradation or killing - O2 dependent
O2 independent

11.  MARGINATION:
 Vasodilation- histamine, serotonin, bradykinin, NO
 Neutrophils get attached towards the capillary
endothelium - endothelial selectins
integrins on neutrophils
ICAM & VCAM
 DIAPEDESIS:
 Insinuation of neutrophils through capillary walls

13. CHEMOTAXIS:
 Neutrophils are attracted towards bacteria at the
site of inflammation
 Chemotactic agents are-
C5a
Leukotriene B4
Cytokines
IL-8

15. OPSONIZATION:
 Coating of bacteria by opsonins - IgG
C3b
ENGULFMENT:
By forming phagocytic vesicle
DEGRANULATION:

17. DEGRADATION:
I. O2 independent mechanism:
-through lysosomal enzymes
II. O2 dependent mechanism:
NADPH + H+ + 2O2 NADP+ + 2H+ + 2O2
-
O2
- + O2
- + H+ + H+ H2O2 + O2
Cl -,Br - HOCl, HOBr

18. LYMPHOID
ORGANS
Central / Primary :
* Thymus
* Bursa Equivalent
Peripheral :
* Lymph nodes
* Spleen
* MALT

20. IMMUNITY
INNATE
NON-SPECIFIC
SPECIFIC
-Species
- Racial
-Individual
ACQUIRED
ACTIVE
Natural Artificial
PASSIVE
Natural Artificial