Third Line of Defense Immune System Notes

LYMPHOCYTES Are the key cells of the immune system Two types: B and T Both produced in the bone marrow B matures in the bone marrow T matures in the thymus

Immunocompetency B and T lymphocytes must recognize “self.” “self” is determined by glycoproteins (proteins with carbohydrate side chains) on cell surface Group of glycoproteins is called Major Histocompatibility Complex - MHC Genetically determined – only identical twins have perfect match Transplants require similar matches for success (along w/antirejection drugs)

Immunocompetency Failure Results in autoimmune diseases – examples MS multiple sclerosis – myelin sheath of axons Graves’ disease – TSH receptors –hyperthyroidism: anxiety, weight loss, etc. Type I Diabetes – beta insulin secreting cells of the pancreas RA rheumatoid arthritis – tissue in joints

ANTIGENS B and T cells have specific antigen receptors on their plasma membranes Antigen (def) – foreign (nonself) molecule (usually a protein) that elicits an immune response Virus, bacteria, parasitic worm, fungus Pollen, transplanted tissue, RBC’s, shellfish, peanuts, bee stings, snake/spider bites

Primary vs Secondary Immune Response Secondary response is quicker and greater magnitude because of memory cells.

Third Line of Defense: Immune Response Humoral B lymphocytes respond to free antigens in blood Body fluids including blood are called HUMORS; thus the name Helper T cells stimulate both humoral and cellular Cellular T lymphocytes respond to antigens from cancer and virus- infected cells Cytotoxic T cells kill/lyse Helper T cells – orchestrate the immune system’s various responses

HUMORAL IMMUNITY CATEGORIES ACTIVE The body makes antibodies in response to antigens PASSIVE Immunity is passed from person to person

CLONAL SELECTION Produces plasma cells that produce antibodies. Produces memory cells that activate secondary immune response.

ACTIVE IMMUNITY NATURAL Acquired to exposure to antigens in daily life. Encounters with infectious diseases like measles, chicken pox, etc. Both form Memory Cells so 2nd response is quicker and greater magnitude ARTIFICIAL Acquired by vaccination Vaccines include dead, weakened, inactivated viruses, bacteria, etc. that can’t cause disease but can elicit an immune response

PASSIVE IMMUNITY NATURAL Antibodies received through the placenta and after birth through breast milk Only lasts a few months until baby begins developing own immunity ARTIFICIAL Antivenoms to snake, spider bites Hepatitis A virus Rabies virus Injecting an antibody from someone who is already immune from a previous exposure. Short term, but immediate protection Treats what the body CANNOT respond to

AIDS Caused by HIV – Human Immunodeficiency Virus CD4 cell surface protein on Helper T cells assist in cell-antigen-presenting-cell interactions; but are also the Main receptor for HIV HIV positive – body has produced antibodies AIDS – Number of CD4’s is too low; immune system is too compromised; person dies of pneumonia, certain cancers (Kaposi’s sarcoma)

ALLERGIES Hypersensitive (exaggerated) response to an environmental antigens called ALLERGENS IgE antibodies stimulate the release of HISTAMINES from MAST CELLS results in dilation of the blood vessels, lowering blood pressure leaking of fluid from blood vessels leading to hives and swelling, especially around the face and throat. asthmatic reaction -- that is, causing the lung's airways to constrict, thus making breathing very difficult

ANAPHYLACTIC SHOCK Occurs when the allergic reaction goes systemic Most common causes: food allergies (peanuts and shellfish, bee/wasp stings, medications, latex Immediate treatment – EpiPen Injection of the hormone epinephrine (adrenaline) which reverses the symptoms by Constricting blood vessels, opening airways Results in increase of blood pressure, heart rate and breathing rate