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Types of immunity

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  1. 1. IMMUNITY AGA 207 Animal Physiology 1 Written by Dr Chikwanda Uploaded byWaiton Sherekte
  2. 2. Body defense and the immune system  Body defense: Is protection against injury  Immunity: Is the protection against foreign micro- organisms or the harmful effect of antigenic substances (antigens)  Antigens: are molecules that can stimulate immune response directed at the specific molecule.  Most cases antigens are components of foreign cells or secretions from microorganisms  Non specific defense: General defense that do not need to recognise specific antigens to be effective protect the body against injury.
  3. 3.  Foreign: Refers to cells or substances that are not self  Self: Cells or substances that are normal components of an animal’s body & that do not normally elicit an immune response  The ability to distinguish between self and foreign is critical to the immune system  Auto-immune disorder: occurs when the immune system erroneously identifies self tissues or antigens as foreign & mounts an inappropriate immune response
  4. 4.  The immune system should also identify self cells that have changed so that they can be harmful.  Identification and destruction of changed cells is important in protecting against cancer
  5. 5. Immune System  Def: Refers to all structures and cells involved in providing immune protection  Cells of this system can be found throughout the body in many tissues  Lymphocytes are the primary cell type involved in an immune response and their wide distribution throughout the body provides them ready access to invading microorganisms
  6. 6.  Lymphocytes are not a uniform group of cells but in general  Primary response of lymphocytes are:  production of circulating antibodies (humoral response)  Generation of lymphocytes capable of removing the potential harmful cell (cellular response) or both
  7. 7.  Inflammation: is the response of tissues to injury characterised by:  Swelling  Pain,  Heat and redness  The above are produced in response of tissues to injury  Desired outcome to injury is complete repair and restoration of tissues to original state
  8. 8.  Effects of injury produce local changes that initiate inflammatory response  Cells attracted to the site of injury leukocytes and macrophages also participate in inflammatory response
  9. 9. Non specific defenses  Include:  Epithelia that covers surfaces exposed to the external environment confers a protective barrier that prevent entry of injurious agents  Protective barrier enhanced by epithelial secretions such as HCl in the stomach and non specific antimicrobial agents in saliva e.g. lysozyme  Physical damage to the epithelial barrier may provide entry point for harmful agents to reach body fluids and spread
  10. 10. Non-specific or innate response  Damage to the epithelial barrier by microbes or injurious agents initiate a response and inflammation  Initial phases of the inflammation response are immediate and similar regardless of the type and identity of the microbe or pathogen  Referred to as non-specific or innate responses
  11. 11.  Local tissue phagocytes (microphages) are among the first cells to respond in non specific response  They engulf and destroy any foreign microbe or substance  Neutrophils are also attracted to the cite of injury as part of the non specific response  Cytokine: Is a term applied to all chemical messengers (mainly proteins) that regulate cells involved in any immune response
  12. 12. Specific or acquired immune response  Def: Is the identification of the specific microbe or agent and development of a response directed to that specific agent  Important characteristic of acquired immunity is:  Specificity &  memory
  13. 13.  The two characteristics of specificity and memory are the basis of vaccination  Vaccination: is the deliberate induction of a specific immune response and immunologic memory by planned exposure to an antigen in a manner that does not cause disease
  14. 14.  Lymphocytes: are the important leukocytes that develop a specific immune response. Their functions in this response are to: 1. Antigen recognition 2. Antibody production 3. Cytotoxic attack on infected cells 4. Immunologic memory 5. Regulation of the specific immune response  This function is not done by a single cell but subpopulations are responsible for different aspects of the specific immune response
  15. 15. B Lymphocyte s  B Lymphocytes (B cells): are lymphocyte subtype responsible for the production of antibody or the humoral component of a specific immune response  Steps of their immune response: 1. Recognition of antigen by B cells. Antigen binds to specific membrane receptor on B Cells and causes them to proliferate (clonal selection) 2. Cells then differentiate into plasma cells that produce antibodies specific to the antigen. Each plasma cell produces only one antibody
  16. 16. 3. Other B cells develop into memory cells  These remain in the body for extended periods of time sometimes for a lifetime  Any second infection later n life the immune system will be ready and the immune response will be accelerated and amplified (For further reading: Frandson 7th edition page 274- 275)
  17. 17. Immunoglob ulins  Immunoglobin is a term that is given for a protein that can bind to an antigen  Includes both antibodies (circulating immunoglobins), &  Those found on the cell membranes of B Cells  Immunoglobins fall into five major classes based o their chemical and functional characteristics (see Table 16- 1 Frandson 7th edition)
  18. 18. T Cells and Cell Mediated Immunity  T Cells are a type of lymphocytes associated with the component of an immune response known as cell mediated immunity  It is different from humoral response involved with antibodies that have their effects at distant sites from their site of production in that  In Cell mediated immune response, the responding T Cell need to be in contact with the cells bearing the foreign antigen
  19. 19. Passive Immunity  Def: PI is a state of temporal immunity achieved by the transfer of immunoglobins or T Cells from an animal to another that has not encountered the antigen involved  Passive immunity is a temporal state because the immunoglobins and or T Cells are degraded or destroyed over tie  E.g. Mother to foetus transfer; mother to child through colostrum, antidote in snake venom treatment
  20. 20. ACTIVE IMMUNITY  Def: Is a state of immunity to a specific antigen achieved by the response of one’s own immune system  Active immunity involves both humoral and cell mediated responses
  21. 21. Further reading  Further reading. See handout on the lymphatic system covering: i. Lymphatic vessels ii. Lymph nodes iii. Spleen iv. Thymus v. Tonsils