8Lymphocytes develop in lymph nodes (after they are formed in the bone marrow)T cells develop in the thymus and then enterthe circulationMacrophages and dendritic cells “present”antigen in the lymph nodesWhat are the major organs/tissues of thelymphatic system?How do the cells get there?
13B and T lymphocytes confer “specific immunity” Body also has “non-specific” responses toinfectionBarriers- skin, mucosa, chemical barriersInflammationredness, swelling, heat, painPhagocytesFever
14Cells of inflammationNeutrophils- leave blood and enter site ofinjury- kill and phagocytose microbesMacrophages- also phagocytesMast cells- release inflammatory substancesComplement proteins- contribute toinflammationLymphocytes may be activated, too
15What about specific immunity? Arises when barriers (first line of defense)and inflammation (second line) do notcontrol the infectionIs directed against specific antigensWhat is an antigen?
16What are the cells of specific immunity? B lymphocytes (produce antibodies)T lymphocytes (helper, cytotoxic)Helper T cells regulate the immune responseCytotoxic T cells kill altered cellsinfected with virusestumor cells
17What do these cells do, when exposed to antigen?Proliferate (divide rapidly)Produce “effector molecules”B cells- antibodieshelper T cells- cytokinescytotoxic T cells- cytotoxic granulesMacrophages, dendritic cells- present antigento T cells
19What do antibodies do? (five classes) Ig (immunoglobulin) G- active in blood againstbacteria and viruseshelps activate complementhelps phagocytes eliminate antigensmost common antibody in the bloodIgM- reacts with certain antigens, usually onfirst exposureIgA- most common in mucosa
20IgD and IgE are rare in blood IgE is involved in allergic reactionssticks to mast cells, which releaseinflammatory substancesIgD is usually found on B cells (not released)may be involved in B cell activation
21When the body is exposed to an antigen for the first time, antibody production is slow andat low levels. Usually IgMIf exposed to the same antigen again, theantibody response is much more rapidand intense (IgG)(Most antibody in the blood stream is IgG)
23Vaccination Exposure to antigen will produce an immune response Repeated exposure will produce memoryVaccine-produce the memory response without getting the diseaseWhy are vaccine produced to protect against some diseases but not others?
24Immune system protects against infection, but also against other antigensBlood group antigensTissue antigens (i.e., graft rejection)For successful organ graft, immune systemmust be suppressedTransplanted tissue must be cleared of immunecells, too
25What if there is an immune response against the “wrong” antigens?Allergies- antigen that is otherwise harmless(hypersensitivity)Immediate type is mediated by IgEDelayed-type is caused by T cells
26AutoimmunityNormally immune system does NOT react to“self” antigensAutoimmunity occurs when it doesdisease can be localized (to kidneys,joints, thyroid, etc.) or can be systemic(lupus)Treatment usually requires some form ofimmunosuppression
27Immune deficiencyPrimary- lack of development of all or part ofthe immune systemSCID- severe combined immune deficiencyDiGeorge syndrome- lack of a thymus, etc.Secondary- due to diseaseAIDScan also be temporary
28SummaryThe lymphatic system helps maintain homeostasisof fluids, and also helps remove antigen fromthe bodyThe immune system consists of barriers (physicaland chemical) and specific and nonspecificmechanisms to eliminate antigen“Immune cells” are blood cells. Some circulate inthe blood and can then migrate into tissuesat site of injury. These include neutrophilsand macrophages.
29All blood cells arise in the bone marrow. B lymphocytes initially develop in the bonemarrow and then migrate to lymphoidtissues (esp. lymph nodes and spleen)T lymphocytes develop in the thymus.B cells produce antibodies, which interact withantigen to help eliminate it.Helper T cells regulate the immune response;cytotoxic T cells kill virus-infected cellsand probably tumor cells. (They also areresponsible for transplant rejection.)
30B and T cell response is antigen-specific and has “memory” (second response is fasterand stronger than the first)Immune system can be overly responsive toantigens (hypersensitivity/allergy) or canmistakenly be directed against self antigen(autoimmunity)Immune deficiencies leave people vulnerableto infection