Specific (Adaptive) Immunity Chapter 32 Specific (Adaptive) Immunity Natura

Two types of resistance. Innate resistance and acquired resistance. Innate resistance – one is born with the resistance. All humans are resistant to certain animal diseases such as canine distemper. Distemper virus infects the nervous system of dogs. Humans can’t get the disease because humans do not have the receptor for the virus.

Acquired resistance (acquired immunity) Resistance is acquired during one’s lifetime. Immunity is a specific defense response Interaction between an antigen and the immune system. Antigen is a foreign substance. Bacteria, pollen, insect venom, transplanted tissue.

Different classes of antibodies IgG – 80% of the antibodies in the serum. Cross placenta and give passive immunity to the fetus. Protect against viruses, bacteria and toxins that are circulating in the body fluids. Activates the complement system. Enhances phagocytosis.

IgM – 5 to 10%, pentamers First antibody to show up in response to initial infection. Activates the complement system. Agglutinates antigens IgA – 10 to 15% Found in body secretions – mucus, saliva, tears. Secretory IgA is a dimer. Prevent the attachment of bacteria and viruses to the mucosal sufaces.

IgD – 0.2% of the serum antibodies Found on the surface of the B lymphocytes. Functions as an antigen receptors. IgE – 0.002% of the serum antibodies Involved in allergic reactions.

Humoral immunity – B lymphocytes Antibodies Cell mediated immunity – T lymphocytes

Cell mediated immunity T cells have receptors for antigen. Clonal selection is involved. Memory cells are made When T cells are stimulated by antigen, they do not make antibodies. They make proteins known as cytokines.

T cells do not respond to antigens floating around in the body fluids. They respond to intracellular antigens. Antigen has to be processed and presented to the T cells by an antigen presenting cell – macrophage.

Different types of T lymphocytes Helper T cells – TH Cytotoxic T cells – TC Suppressor T cells - Ts

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T independent antigens are polysaccharide antigens such as those found in the capsules of bacteria. B cells can make antibodies on their own against these antigens. They do not need any help from the T cells.

T dependent antigens – proteins such as those found in the capsids of viruses. B cells cannot make antibodies against these on their own. They have to get help from helper T cells.

Suppressor T cells Prevent the anibodies from attacking one’s own cells. Stop the immune response once the antigen has been removed from the system.

Natural killer cells Different class of lymphocytes. They come in contact with tumor cells. Produce toxins. Destruction of the tumor cells

Antibody dependent cell mediated cytotoxicity

Hypersensitivity, allergy, anaphylaxis Abnormal immune response IgE antibodies are produced against antigens – pollen, insect venom, fungal spores. First exposure – the person becomes sensitized. Subsequent exposure results in anaphylaxis.

Secondary response is stronger. Antigen binds to IgE antibodies on the mast cells. Large amount of chemical mediators such as histamine. This leads to allergic reaction (anaphylaxis). Symptoms show up within a few minutes after the exposure to the antigen.

Systemic anaphylaxis – caused by injected antigens such as insect venom. For example, some people are allergic to bee sting. The venom binds to IgE present on the surface of mast cells and basophils stimulate them to release a large amount of chemical mediators. Cause damage to the blood vessel – drop in blood pressure known as shock.Treated with epinephrine.

Localized anaphylaxis caused by inhaled antigens such as pollen and fungal spores. Mast cells lining the respiratory tract release histamine. Watery eyes, runny nose, coughing and sneezing. Antihistamine.

ELISA Enzyme liked immunosorbent assay Plastic plates with wells in them are used Direct ELISA – presence of antigen in a sample Indirect ELISA – presence of antibodies against a specific antigen in a sample. Page 879

Antibodies against HIV Secondary antibodies Against human Antibodies. Neisseria gonorrhoeae Enzyme linked antibodies Substrate – colorless Product – blue