Chapter 17 Immune response

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