third line of defense

• The adaptive immune system has specific responses and memory; recognizes and destroys specific pathogens or foreign molecules
• The adaptive immune response has important characteristics: specificity (directed at a specific pathogen) and memory(remember the pathogen and attacks it so quickly that illness does not result upon second exposure)
• The major histocompatibility complex (MHC) markers are used by the immune system to distinguish cells of your body from foreign invaders (to distinguishing self from nonself)
• The antigen is a nonself substance or organism that triggers an immune response
• Antigens are usually large molecules such as proteins, polysaccharides, or nucleic acids; often found on the surface of the invader
• Lymphocytes are responsible for the specificity and memory of the adaptive immune response
• B lymphocytes (B cells): form and mature in bone marrow
• T lymphocytes (T cells): form in bone marrow and mature in thymus gland
• Lymphocytes recognize MHC self markers; programmed to recognize one particular type of antigen
• Lymphocytes divide repeatedly, forming two cell lines: effector cells (short-lived that attack the invader) and memory cells(long-lived cells that remember the invader and mount a quick response when that invader is next encountered)
• An antibody-mediated immune responses defend against antigens that are free in body fluids, including toxins or extracellular pathogens; effector B cells (plasma cells) use antibodies (Y-shaped proteins) to neutralize the antigen
• Cell-mediated immune responses protect against cancer cells and body cells that have become infected with viruses or other pathogens; cytotoxic T cells cause cancer cells and infected body cells to burst
• Active immunity: the body produces memory B cells and T cells following exposure to an antigen; occurs when a person gets an infection or through vaccination
• Passive immunity: results when a person receives antibodies that were produced by another person; short-lived because the recipient's body was not stimulated to produce memory cells
• The problem of the immune system is autoimmune disorders- occur when the immune system fails to distinguish between self and nonself and attacks tissues or organs of the body
• Organ-specific usually caused by problematic T cells (ex: Hashimoto's thyroiditis)
• Non-organ-specific usually caused by problematic B cells (ex: systemic lupus erythematosus)
• Celiac disease is an error in antigen presentation
• Gluten is a protein from wheat, barley, or rye (also called gliadin)
• Symptoms are diarrhea, failure to thrive, IBS (Irritable bowel syndrome)
• Allergies is overreaction by the immune system to an antigen
• First exposure of allergic reaction: allergens cause plasma cells to release class IgE antibodies; IgE antibodies bind to mast cells
• Subsequent exposure of allergic reaction: allergen combines with IgE attached to mast cells and causes release of histamine
• Anaphylactic shock: extreme allergic reaction that can be fatal (can be life threatened situation)
• Common triggers of anaphylactic shock: insect stings; medications including penicillin; food such as shellfish, peanuts
• Treatments: antihistamines; epinephrine; allergy shots
• Antihistamines: block the effects of histamine
• Epinephrine: constricts blood vessels and prevents blood pressure from dropping
• Allergy shots: inject increasing amounts of a known allergen in an effort to desensitize the person to the offending allergen