Immune System Innate Immunity Innate immunity preprogrammed defense

Immune System

Innate Immunity • Innate immunity – pre-programmed defense responses.

Barrier Defenses • Skin and mucus • Oil, sweat (low skin p. H)

Internal Defense • Macrophages – engulf pathogens • Interferons – proteins secreted by infected cells that signal neighboring cells to defend themselves.

Internal Defense • Inflammatory Response – pain and swelling that occur upon injury or infection. • Mast cells – hold histamines that cause blood vessels to dilate, bringing extra blood which causes swelling in the tissues. • This attracts phagocytes to come and help deal with the infection.

Internal Defense • Natural killer cells – destroy infected or cancerous cells

Acquired Immunity • Acquired immunity – a defense response that is enhanced by previous exposure to the pathogen.

Lymphocytes • • Lymphocytes – white blood cells B – cells mature in the bone marrow T- cells mature in the thymus White blood cells fight infection, but each has a specific job

Recognition • Antigen – a foreign molecule that is recognized and gets a response from lymphocytes. • Antigen receptors – receptors found on lymphocytes that recognizes the epitopes of antigens • -antibody / immunoglobulin (Ig) – a soluble form of the antigen receptor that can be secreted by the B-cell.

Recognition • Major histocompatibility complex (MHC) – an infected cell protein that displays a fragment of the antigen for white blood cells to recognize. • Class I – found in most cells, and calls cytotoxic Tcells that use toxins to kill the infected cell • Class II – found in dendritic cells and macrophages, which are called antigen presenting cells. They use Class II MHC’s to call helper T- cells that assist other lymphocytes.

Clonal Selection • Clonal selction – cloning of lymphocytes in response to a binding an antigen • When exposed to an antigen a B or T cell will divide rapidly making effector cells to attack and memory cells to store incase of future invasion.

Primary Immune response • The clonal selection is the primary immune response it peaks about 10 to 17 days after infection.

Secondary immune response • Upon another exposure to the same antigen, the reserved memory cells are called upon in greater numbers. The response peaks 2 -7 days after exposure and last longer.

Lymphocyte Types • B – cells – secrete antibodies to bind to antigens in the blood or lymph. • Cytotoxic T-cells – secrete proteins that kill infected cells. They must be signaled by helper T- cells and/ or MHC molecules • Helper T cells – activated by antigen presenting cells (class II MHC) and release cytokines to call upon B and T cells to act.

Humoral Response • Humoral response – clonal selection of B cells. Usually fights pathogens not in cells yet. ** • The antibodies secreted can neutralize pathogens or make them targets for phagocytes.

Cell Mediated Response • Cell mediated response – cytotoxic T-cells destroy infected cells. **

Helper T-Cells • Can call for B-cells and T-cells to act. **

5 antibody classes

Antibody Affects **

Immunization • Active immunity – secondary response • Passive immunity – antibodies passive from mother to fetus can cause a secondary like response the first time a fetus is exposed to infection. (Passed across the placenta(Ig. G) and breast milk (ig. A)) • Vaccination – introducing an antigen into the body to elicit clonal selection.

Allergies • Allergies – exaggerated responses to antigens. Can trigger mast cell to elicit a an inflammatory response.

Autoimmune disease • Sometimes the immune system turns against certain molecules naturally in the body. • Lupus- against DNA histones in breaking down cells. • Rheumatoid Arthritis – against cartilage