- Innate immunity
- Acquired immunity
- Physical barriers:Skin and Mucous membranes lining different body openings.How?All the epithelia that are exposed to the external environment like skin and mucous membranes of oral cavity ,urethra and vagina have tight junctions in between there cells which do not let the micro organisms(residing as the normal flora on the skin and mucous membranes of the body) and any other harmful material to pass.
- Body secretions:HCL of stomach, lysozyme present in tears and saliva.HCL of stomach:Intense low pH of stomach can not be favorable to any living organism so when any microorganism enters GIT ,its digested n no more harmful.Lysozome:A hydrolytic enzyme present in saliva n tears, that attacks cell wall of the bacteria leaving it non-pathogenic.
- After passing through these barriers, if a bacteria is strong enough to enter the body tissues through broken skin part or mucosa, macrophages are there to engulf him and kill him.(Macrophages are actually monocytes which when enter the tissues from blood become mature, enlarge in size in ready to engulf bacteria and kill them.)
- Then if bacteria survives tissue macrophages, it enters the tissue fluid and then lymphatics.Once they have entered lymphatics they must have to pass through lymph nodes (lymph filtering organs),where must b killed.
- If survived it enters the blood where different WBCs like neutrophils and eosinophils are ready to attack rendering it non-pathogenic,blood also pass through spleen that is a blood filtering organ lined by macrophages.
- Also the bacteria entering via GIT first enter liver through hepatic portal system where liver macrophages are waiting to engulf and kill them.
- Cell mediated immunity.(supplied by T cells)
- Humoral immunity. (by B cells)
It functions by following mechanism:
Whenever any bacterium enters the body it is phagocytosed and the antigen is sent to the T cells which form some memory cells for the future use n some activated T cells against that particular antigen.
Provided by B-cells( these cells are called so because first these where discored for a bird gland called bursa of fabricious was found to have a role in immunity)
This type of immunity is called so because no whole cell is involved but the activated cell produce antibodies that fight against the invader.
Constant zones are for maintaining structure where as variable zones r for producing variety in types.
- Active immunity.
- Passive immunity.