NOTES: CH 43, part 2 - Immunity in Health and Disease

PRIMARY IMMUNE RESPONSE ● PRIMARY IMMUNE RESPONSE: the first reaction / response to an antigen (first exposure)  during this response, antibodies are produced for several weeks  antibodies first show up within 5-10 days  some B cells remain dormant as MEMORY CELLS

SECONDARY IMMUNE RESPONSE ● SECONDARY IMMUNE RESPONSE: the second response (exposure) to an antigen  rapid response due to memory cells produced during the first exposure  antibodies produced within a day or two

CLASSIFICATION OF IMMUNITY 1) ACTIVE IMMUNITY ● when the person produces an immune response (including memory cells) to the antigen ● a result of direct exposure to the antigen ● long-lasting (memory cells)

ACTIVE IMMUNITY…  NATURALLY ACQUIRED ACTIVE IMMUNITY: person is directly exposed to the pathogen, develops a disease, and acquires immunity  ARTIFICIALLY ACQUIRED ACTIVE IMMUNITY: person receives a vaccine

VACCINES… **A VACCINE consists of bacteria or viruses that have been weakened or killed so they a cannot cause a serious infection; or could include a toxin that has been chemically altered to destroy its toxic effects -includes antigens that stimulate a primary immune response but does not produce the severe symptoms of disease

2) PASSIVE IMMUNITY ● person receives antibodies produced by another individual ● since the person does not produce the immune response themselves, this is short- term only (as long as the antibodies remain in the blood) ● the person remains vulnerable to the antigen if exposed at a later date

PASSIVE IMMUNITY  NATURALLY ACQUIRED PASSIVE IMMUNITY: fetus acquires limited immunity from mother through placenta and/or breast milk (colostrum)  ARTIFICIALLY ACQUIRED PASSIVE IMMUNITY: person receives an injection of antiserum collected from a person who has already developed immunity against a particular disease

ALLERGIC REACTIONS ● excessive and misdirected immune responses that may damage tissue ● triggered by antigens known as ALLERGENS ● the immune system attacks a nonharmful substance, such as chocolate

ALLERGIC REACTIONS 1) Delayed-reaction allergy: results from repeated exposure of the skin to certain chemicals (e.g. household chemicals, cosmetics) ● T cells and macrophages collect and release chemicals that cause eruptions and inflammation (DERMATITIS) ● “delayed” because it takes about 48 hours to develop

ALLERGIC REACTIONS 2) Immediate-reaction allergy: an inborn ability to overproduce IgE antibodies in response to certain antigens/allergens (i.e. pollen, pet dander, etc.) ● occurs within minutes of contact with allergen

Immediate-reaction allergy  results from mast cells bursting and releasing allergy chemicals such as HISTAMINE  causes blood vessels to dilate, tissues swell, contraction of bronchial and intestinal smooth muscles, increased mucus production  the released chemicals cause allergy symptoms such as: hives, hay fever, asthma, eczema, or gastric disturbances

Extreme allergies… **severe example of immediate-reaction allergy: ANAPHYLACTIC SHOCK! ● mast cells throughout the body release histamine ● severe drop in blood pressure (could lose consciousness and possibly die) ● person must receive an injection of epinephrine (adrenaline) to restore blood pressure

TRANSPLANTATION and TISSUE REJECTION ● TISSUE REJECTION REACTION: when a transplant recipient’s immune system reacts against the donated tissue/organ

● to minimize tissue rejection:  match donor and recipient tissues  use immunosuppressive drugs (help with transplant acceptance, but may increase the recipient’s risk of infection)

AUTOIMMUNITY / AUTOIMMUNE DISORDERS: ● the immune system manufactures AUTOANTIBODIES (antibodies that attack a person’s own body tissues) ● may result from a previous viral infection, faulty T-cell development, or reaction to a nonself antigen that resembles a self antigen

Examples of Autoimmune Disorders:  Lupus erythematous  Rheumatoid arthritis  Insulin-dependent diabetes  Multiple sclerosis  Heart valve damage  Grave’s disease  Rheumatic fever

 Immunodeficiency disease: affected individual is deficient in either humoral or cell-mediated immune defenses Examples:  SCID  Hodgkin’s lymphoma  some viral infections (e.g. AIDS)  physical / emotional stress can compromise immune system

AIDS  caused by retrovirus: HIV  affected individuals are highly susceptible to opportunistic diseases, infections, cancers  two major strains: HIV-1 and HIV-2  HIV infects T H cells, which carry CD-4 receptors on other surface

*HIV-positive = tests positive for presence of HIV-antibodies *AIDS = late stage of HIV infection -defined by reduced T-cell population -appearance of secondary infections -takes average of 10 years to reach this stage -viral load also good indicator

Secondary Infections

Transmission of HIV:  transfer of body fluids: blood, semen  most commonly via unprotected sex and unsterilized needles  transmission during fetal development occurs in 25% of HIV-infected mothers  blood transfusions (decline in incidence with screening procedures)

Drug therapies include:  DNA-synthesis inhibitors  reverse transcriptase inhibitors (e.g. AZT)  protease inhibitors  drugs to fight opportunistic infections (helps ease symptoms of secondary infections)