PROTECTIVE IMMUNITY TO MICROBES
Basic structure 3 layers of defense system
- Barrier immunity : skin ( antimicrobial proteins)
- Innate immunity
- Acquired immunity
Innate immune cells
- Fight immediately: Neutrophil, Macrophage and dendritic cells etc.
- Some Macrophage secrete chemokine
- More immune cells comes at site of infection
- Dendritic cell engulf microbes and their endosome fuse with lysosome
- Debris displayed on dendritic cell cell surface
- On class 2 MHC molecules present these antigen to T helper cells.
- Lymph nodes : Army base camp
- Dendritic cell mobilize towards lymph nodes
- Paracortex region : T cells area
- Germinal center : B cells area
Depending upon microbes
Some directly activate B cell endotoxin
T cell activated by dendritic cell and now activate
B cell
Activity of B cells
Once B cell activated : they become plasma cell
Produce
antibodies
For long term defense : B cell would proliferate
inside GC
Finally differentiate into plasma cell
Activation of B cell
Either by T cell dependent or by T cell independent Antibodies
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Many bacteria are endotoxin so B cell directly
activated
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Ultimate goal of activated cell B cell is to Proliferate and get experience
⬇
Eventually secrete different isotypes of AB
AB coat the microbes and neutralize it
⬇
Afterwards, difficult to microbes affect other cell
Antibody
Dependent Cellular Toxicity (ADCT)
Many immune cells NK cells , Macrophage,
Neutrophil and dendritic cells Has
receptors against fc portion of AB
Immune cells now bind with AB and engulf pathogen
Complement mediated lysis
Body produce complement proteins
Coat bacteria and neutralize them
Membrane attack complex lead fluid leakage
Complement proteins also work like Anaphylatoxins.
Disbalance and bursting of microbes
Soluble molecules as chemo attractant evoke
inflammation
Help in extravasation
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