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ADAPTIVE IMMUNITY

ADAPTIVE IMMUNITY. *To adapt means to become suitable, and adaptive immunity can become “suitable” for and respond to almost any foreign antigen. *Adaptive immunity is: -specific -and is carried out by lymphocytes and macrophages. *The majority of lymphocytes are -T cells and

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ADAPTIVE IMMUNITY

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  1. ADAPTIVE IMMUNITY *To adapt means to become suitable, and adaptive immunity can become “suitable” for and respond to almost any foreign antigen. *Adaptive immunity is: -specific -and is carried out by lymphocytes and macrophages. *The majority of lymphocytes are -T cells and -B cells.

  2. T Cells • In the embryo, T cells are produced in the bone marrow and thymus. • They must pass through the thymus, where the thymic hormones bring about their maturation. • The T cells then migrate to the spleen, lymph nodes, and lymph nodules, where they are found after birth.

  3. B Cells • Produced in the embryonic bone marrow, then migrate directly to the spleen and lymph nodes and nodules. * When activated some B cells will divide many times and become plasma cells that produce antibodies to a specific antigen. *The mechanisms of immunity that involve T cells and B cells are specific

  4. macrophage . A macrophage has receptor sites for foreign chemicals such as those of bacterial cell walls or flagella, and may phagocytize just about any foreign material it comes across

  5. steps of destruction of a pathogen • 1- recognition of its antigens as foreign. • The foreign antigen is first phagocytized by a macrophage, and parts of it are “presented” on the macrophage’s cell membrane. • If a specialized group of T lymphocytes ( called helper T cells )encounters this macrophage, it become sensitized to that antigen and initiates both mechanisms of adaptive immunity

  6. Mechanisms of adaptive immunity 1-cell-mediated immunity which involves: -T cells -and macrophages 2-antibody-mediated immunity (or humoral immunity), which involves: - T cells, - B cells, -and macrophages

  7. Cell-Mediated Immunity • No antibodies, • effective against intracellular pathogens (such as viruses), fungi, malignant cells, and grafts of foreign tissue. • After recognition of the foreign antigen by macrophages and helper T cells, these activated T cells, which are antigen specific, divide many times to form • memory T cellsand • Cytotoxic (killer) T cells

  8. Cell-Mediated Immunity (cont.) • The memory T cells will remember the specific foreign antigen and rapidly become active if it enters the body again. • Cytotoxic T cells are able to : 1- chemically destroy foreign antigens by disrupting cell membranes as destruction of cells infected with viruses 2- produce cytokines, which are chemicals that attract macrophages to the area to phagocytize the foreign antigen and cellular debris. 3-produce(with helper T) feedback chemicals to limit the immune response once the foreign antigen has been destroyed ( T suppressor).

  9. Antibody-Mediated Immunity • First step is recognition of the foreign antigen, this time by B cells as well as by macrophages and helper T cells. The sensitized helper T cell presents the foreign antigen to B cells, which divide many times, and two types of cells are formed: 1- memory B cells, which will remember the specific antigen 2-plasma cellthat produce antibodies specific for this one foreign antigen.

  10. Antibodies, immune globulins (Ig) orgamma globulins, *are proteins shaped somewhat likethe letter Y. * Antibodies do not themselves destroy foreignantigens, but rather become attached to such antigensto “label” them for destruction. *Each antibody produced is specific for only one antigen forming antigen antibody complex labelled for phagocytosis or fixation by complement *millions of different antigen-specific antibodies can be produced.

  11. CLASSES OF ANTIBODIES

  12. Cell-mediated

  13. Antibody-mediated

  14. Antibody Responses and Functions • 1. On the first exposure to a foreign antigen, antibodies are produced slowly and in small amounts, and the person may develop clinical disease. • 2. On the second exposure, the memory cells initiate rapid production of large amounts of antibodies, and a second case of the disease may be prevented. • This is the basis for the protection given by vaccines, which take the place of the first exposure.

  15. 3. Antibodies cause agglutination (clumping) of bacterial cells; clumped cells are easier for macrophages to phagocytize • 4. Antibodies neutralize viruses by bonding to them and preventing their entry into cells. • 5. Antibodies neutralize bacterial toxins by bonding to them and changing their shape so become not harmful and easily phagocytized

  16. TYPES OF IMMUNITY • Genetic immunity is conferred by our DNA, and • acquired immunity is developed or acquired by • - natural or • - artificial means.

  17. Genetic immunity • Genetic immunity does not involve antibodies or the immune system; it is the result of our genetic makeup. • some pathogens cause disease in certain host species but not in others. • Dogs and cats, for example, have genetic immunity to the measles virus, which is a pathogen only for people

  18. Acquired immunity • Acquired immunity does involve antibodies. • 1-Passive immunity means that the antibodies are from another source, • 2-active immunity means that the individual produces his or her own antibodies

  19. naturally acquired passive immunity • 1-placental transmission of antibodies (IgG) from maternal blood to fetal circulation. The baby will then be born temporarily immune to the diseases the mother is immune to. • 2-breast-feeding, breast milk also contains maternal antibodies (IgA).

  20. Artificially acquired passive immunity -the injection of immune globulins (gamma globulins or preformed antibodies) after presumed exposure to a particular pathogen. Such immune globulins are available for German measles, hepatitis A and B ,tetanus and botulism (anti-toxins), and rabies -it is only for weeks or months • is obtained

  21. Active immunity • Active immunity is the production of one’s own antibodies and may be stimulated by natural or artificial means. -Naturally acquired active immunity means that a person has recovered from a disease and now has antibodies and memory cells specific for that pathogen. -Artificially acquired active immunity is the result of a vaccine that has stimulated production of antibodies and memory cells

  22. TYPES OF IMMUNITY

  23. VACCINES The purpose of vaccines is to prevent disease. A vaccine contains an antigen that the immune system will respond to, just as it would to the actual pathogen. - The types of vaccine antigens are a killed or weakened (attenuated) pathogen, part of a pathogen such as a bacterial capsule, or an inactivated bacterial toxin called a toxoid -

  24. allergy • An allergy is a hypersensitivity to a particular foreign antigen, called an allergen. -Allergens include plant pollens, foods, chemicals in cosmetics, antibiotics such as penicillin, dust, and mold spores. -Such allergens are themselves harmless as most people, for example, can inhale pollen, eat peanuts, or take penicillin with no ill effects.

  25. AGING AND THELYMPHATIC SYSTEM • Elderly people are more likely than younger ones to develop: -infections as influenza and to what are called secondary infections, such as pneumonia -Autoimmune disorders as rheumatoid arthritis -cancer is also higher

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