Immune System - Gill Vince PDF

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Lecture notes on the immune system...

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The GI Tract: - In the lamina propria is MALT and GALT. Some areas up to 50% lymphoid tissue. - IgA is important to these surfaces - large surface area of GI tract. - Tolerates 500 species of bacteria but mounts appropriate response to pathogens. - Lymph nodes contained in the mesentery - deep to the lamina propria. - Chronic inflammation of the gut - IBD (crohn’s and ulcerative colitis) The spleen: - White pulp - B cells organised into primary areas where they are unstimulated and secondary areas where they are antigen stimulated (germinal centre). - Splenectomy - without a spleen people are more susceptible to infection by encapsulated bacteria. Therefore strict prophylaxis taxes place - this includes vaccines and lifelong antibiotics. Lymph Nodes: - Filter antigens - Same structure of B cells to that of the spleen ^ - In the paracortex you can find T cells, APC cells - these can come from the skin in which case they are Langerhans cells, otherwise they are dendritic cells. Complement System: - Deficiencies: - Mannan binding lectin associated with infection in children - Alternative pathway and c3 associated with bacterial infection - Terminal pathway predisposes to gram -ve bacteria - C1 inhibitor leads to hereditary angioedema - angioedema is an area of

swelling of the lower layer of skin and tissue just under the skin or mucous membranes. The swelling may occur in the face, tongue, larynx, abdomen, or arms and legs Primary Deficiencies: ● Antibody deficiency causes recurrent pyogenic infections by encapsulated bacteria ○ X linked agammaglobulinaemia ■ Low or undetectable serum Ig which leads to reduced or absent B cells. Treated with injections of antibody. ○ Selective IgA deficiency (normal IgM and IgG so has a variable presentation ● Combined immunodeficiency - broad susceptibility ● Phagocytic cell disorder ○ Neutrophils - prone to bacteria and fungal infections ● Hypersensitivity disorders ○ Has five types (I-V) ■ I - IgE (think allergy) response to soluble antigen ● Mast cells and basophils and is an overreaction ● Associated with hayfever, asthma etc ● Mast cells release histamine which causes the response ■ II - Antibody dependent, mediated by antibodies binding to specific cells. Involves all antibodies. ● Damages tissues ● Examples include blood transfusion reactions and rhesus

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disease. ● IgG and IgM recognise antigens III - Involve immune complexes (antibody antigen complex made of lots of antigens and antibodies) which is normally removed is no longer removed. Instead these immune complex can build up - eg on membranes and in blood vessels. ● This can cause a complement cascade to be formed which eventually forms membrane attack complexes which destroy host cells. ● Causes widespread inflammation in the body such as in lupus. IV - T-cell mediated. ● TB and leprosy are examples of type IV hypersensitivity, as well as transplantation rejection. ● Sometimes called a delayed hypersensitivity V - Stimulatory - antibody reacts with receptor and switches on the cell. ● Associated with hyperthyroidism...