The Immune System Immune System Diseases

Non-Specific Immunity A wide variety of factors that provide non- selective opposition to the invasion of the body by foreign protein-based substances “Antigens”

Examples of Non-Specific Immunity Inflammation Mechanical Barrier, ie skin Enzyme Activity Interferons (chemical released in response to ANY viral infection) pH (acid and alkaline)

Specific Immunity Response to a specific antigen

Two Types of Specific Immune Actions

Immunoglobulins = Antibodies IgG - most abundant;crosses placenta IgA – in plasma and mucus membrane secretions IgD - ? IgE – increased with allergy IgM - largest

Antigen-Antibody Complex Action Antigen is rendered harmless by one or a combination of the following Precipitation Agglutination Opsonization Neutralization

Complement A series of protein enzymes that attach to antigen-antibody complexes involving IgG and IgM Immune Complexes – may damage host cells as well as antigen

Two Ways to Acquire Immunity

Hypersensitivity Immune response that is not needed and may cause harm

Hypersensitivity: Allergy Increased amounts of IgE IgE and antigen attach to mast cell Mast cell releases histamine and other inflammatory mediators Local – asthma, hay fever, hives (urticaria), GI/food allergy Generalized – Anaphylaxis Systemic release of histamine causes low blood pressure and swollen airways Is life-threatening allergic reaction!

Hypersensitivity: Cytotoxic Complement attaches to IgG or IgM antigen- antibody complex (now called an immune complex) Individual cells are lysed (most commonly RBCs) Examples: Rh disease (Erythroblastosis Fetalis), Transfusion reactions Transfusion reaction may also cause anaphylaxis!

Hypersensitivity: Immune Complex Mediated Immune complexes, ie IgG or IgM with complement activated, cause damage to large area of host tissue Examples: Glomerulonephritis, Rheumatic Fever

Hypersensitivity: Cell Mediated T-lymphocytes attack harmless antigenic substances May take 1-2 days to develop Examples: transplant rejection, Tb skin test

Immune Deficiencies Congenital: Agammaglobinemia Acquired: Malignancies of the bone marrow and lymphatic system Chemotherapy Steroids AIDS

Acquired Immune Deficiency Syndrome

AIDS Etiology Human Immunodeficiency Virus (HIV)

HIV can be found in all body fluids of infected persons Transmission usually most common with infected blood, semen, and vaginal secretions Unprotected exposure to body fluids puts everyone at risk, eg health care workers High-risk practices: IV drug abuse Unprotected sex (includes anal sex)

High Risk Groups

AIDS Pathology Virus attaches to the CD4+ protein on T- helper cells and destroys them Decreased T-helper cell count makes the patient prone to opportunistic infections, malignancies not normally seen in patients with intact immune systems, and direct CNS destruction

AIDS Progression HIV infection – HIV+ Antibodies produced usually within 1-6 months of exposure The antibodies produced cannot control the virus! ARC – AIDS Related Complex Enlarged lymph nodes,chronic fever and fatigue, weight loss Full blown AIDS – opportunistic infections and malignancies, and CNS damage Usually occurs when T-helper cell count drops to less than 500 (usual count is )

Some Opportunistic Infections Seen in AIDS

Malignancies Seen in AIDS Kaposi’s Sarcoma Malignant nodules form on the skin and in the mouth, lymph nodes, and internal organs Squamos cell carcinomas in the mouth, rectum, and uterine cervix

AIDS Treatment Current drug regimes prevent the virus from replicating. They control the virus but do not destroy it! These drugs are very costly and have many side effects! Reverse Transcriptase Inhibitors and Nucleoside Analogs AZT (Zidovudine), DDI (Didanosine), 3TC (Lamivudine) Protease Inhibitors Fusion inhibitors Palliative Surgeries

AIDS “COCKTAIL” Truvada A combination of Tenofovir (Viread) and Emtricitabine (Emtriva) Works So well, it is being tried as a vaccine

Implications for Health Care Professionals Frequent Handwashing Barrier Protection for potential body fluid exposure Mask, gown, gloves, protective eyewear Careful technique during invasive procedures The odds are in your favor! HIV is not spread by casual contact! Handshakes, eating & drinking utensils, toilet seats, etc do not transmit HIV

Hate the disease…….. But don’t hate the sick person!

Autoimmunity antibodies form against body tissues

Autoimmune Diseases Systemic Lupus Erythematosus (SLE or “Lupus”) Rheumatoid Arthritis Multiple Sclerosis (MS) Autoimmune diseases may be inherited, caused by a drug reaction, reaction to a virus, environmental factors, or idiopathic