Third Line of Defense Immune System Notes LYMPHOCYTES

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 2 nd 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 • CD 4 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 CD 4’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 • Ig. E 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 – Epi. Pen – 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