Immunity Nonspecific Defenses –Surface barriers: skin, mucous membranes(lysozyme) –Phagocytic cells: WBC’s –Natural killer cells: perforins –Resident bacteria and fungi –Defensive proteins: interferons & complement –Fever –Inflammation: Redness, swelling, heat, pain

–Redness and heat from increased blood to area –Swelling from extra leaky capillaries –Pain from chemicals released by cells –Phagocytic cells arrive: clean up debris, bacteria

Specific Defenses - 2 parts –Antibody immunity –Cell-mediated immunity –Antibody immunity involves 2 active components: 1. the antigen and 2. the antibody Types of antigens – The antibody – protein secreted by B lymphocytes Structure of an antibody molecule/classes – IgG,IgM, etc. Clonal selection – B cells –Cell-mediated immunity – T cells – mature in thymus Macrophages (monocytes) engulf pathogen, digest it Parts of proteins “displayed” Presented to helper T cells with matching receptor – T cells will form cytotoxic T cells or helper T cells.

Action of antibody when encounters antigen: –Neutralization – viruses coated –Agglutination – blood group antigens Immune response turned off by the release of chemicals by suppressor T cells; memory cells remain

Immunity and Vaccination Primary response takes time Secondary response quicker and stronger Vaccines artificially produce primary response – killed or inactivated pathogens Immunity can last a few years, or decades – “booster” shots

When things go wrong Autoimmune disorders – failure to recognize “self” markers –Lupus, multiple sclerosis, rheumatoid arthritis, Type 1 diabetes, etc. Allergies –Overreaction to pollen, food, insect stings –Mast cells & basophils release histamine Anaphylactic shock – allergen has entered the blood stream

Acquired Immune Deficiency Syndrome Caused by HIV infection (human immunodeficiency virus) Targets helper T cells Cripples entire immune system Death from opportunistic infections Thought to have originated in Africa Virus structure –RNA genome (retrovirus)

–Protein coat –Phospholipid envelope –Glycoprotein spikes – gp120 –Reverse transcriptase enzyme Life Cycle –gp120 binds to CD4 receptors –Viral envelope fuses with cell membrane –Reverse transcriptase copies RNA to DNA –DNA inserts into cell chromosome (latency) –Later, activation produces viral RNA and protein

Transmission –Sexual contact without latex condom –Intravenous drug use – Blood transfusion –Mother to fetus – crosses placenta Testing –Typically look for antibodies in blood (HIV +) –Can also look for viral proteins or RNA

Stages of Infection –Initial infection (flu like symptoms) –Asymptomatic stage: multiplies in lymph nodes –Eventually, AIDS Low helper T count (under 200/cc) Opportunistic infections occur Loss of 10% body weight Dementia Death results as body weakens and infections accumulate

Opportunistic infections –Fungal: thrush, Pneumocyctis carinii in lungs, others –Protozoa, bacteria –Cytomegalovirus –Cancers: Kaposi’s sarcoma, lymphoma Treatments –Drugs: reverse transcriptase inhibitors (AZT), protease inhibitors, “cocktail” combination

–Side effects, viral resistance –Vaccine???? – High mutation rate of HIV; latent infections