Innate (non-specific) immunity:
- Called inborn immunity.
- Always available to protect out body.
- This is called the first line of defense.
- Consists of various barriers that prevent entry of foreign agents into the body.
- If enters they are quickly killed by some other components of this system.
- Different types of barriers are as follows:
Physical barriers:
- Skin is the main barrier which prevents entry of micro-organism.
- Mucous coating of the epithelium lining of respiratory, gastrointestinal and urinogenital tracts helps in trapping microbes.
Physiological barriers:
- Acidity of the stomach kills most ingested microbes.
- Lysozyme in tears, saliva, and snot kills bacteria by digesting bacterial wall.
- Pyrogen released by WBC raise body temperature to prevents growth of microbes in out body.
- Interferon induces antiviral state in non-infected cells.
Phagocytic barrier:
- Polymorpho-nuclear leukocytes (PMNL-neutrophils), macrophages, and natural killer cells in the blood and tissues kill pathogen by phagocytosis.
Inflammatory barrier:
- When there is injury to the tissue there is release of histamine and prostaglandins by the mast cells.
- Due to vasodilation there is leakage of vascular fluid containing serum proteins with antibacterial activity.
- Further there is influx of Phagocytic cells into the affected area.
Acquired (specific) immunity:
- It is also known as adaptive immunity.
- This immunity developed after birth when encountered with pathogen.
- It supplements the immunity provided by the innate immunity.
- Acquired immunity has following unique features:
- Specificity: distinguish specific foreign molecules.
- Diversity: recognize vast variety of foreign molecules.
- Discrimination between self and non-self: it is able to recognize and respond to molecules that are foreign or non-self. It will not respond to our own cell or molecules.
- Memory: after responding to the foreign microbes and elimination, this immune system retains the memory of that encounter (primary immune response). The second encounter with the same microbe evokes a heightened immune response. (Secondary immune response)
- Acquired immunity is carried out by two special types of lymphocytes:
- B-lymphocytes.
- T-lymphocytes.
- The B-lymphocytes produce a group of proteins in response to pathogen into the blood to fight with them called antibody.
- T-lymphocytes do not produce antibody but help B-cells to produce them.
Structure of antibody:
- Each antibody has four polypeptide chains.
- Two small chains called light chains.
- Two longer chains called heavy chains.
- Antibody represented as H2L2.
- Different classes of antibody produced in out body are IgA, IgM, IgD, IgE and IgG.
AMI vs. CMI:
- Immune response by the B-cells by production of antibody is called Antibody mediated immune response or humoral immune response.
- Immune response by T-cells is by activation of cytotoxic killer cells which detects and destroys the foreign cells and also cancerous cells called cell mediated immune response.
- Rejection of organs transplants are due to T-lymphocytes.
- Tissue matching, blood group matching are essential for organ transplantation.
- Even after tissue typing immune-suppressants is required before and after transplantation.
CBSE Biology (Chapter Wise) Class XII ( By Mr. Hare Krushna Giri )
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