NOTES: CH 43, part 2 Immunity; Immune Disruptions (43.3-43.4)
Activated B & T Lymphocytes produce: CELL-MEDIATED IMMUNE RESPONSE: involves specialized T cells destroying infected host cells HUMORAL IMMUNE RESPONSE: occurs in the blood & lymph; involves activated B cells **BOTH responses are triggered by activated helper T cells!
T CELLS and the CELL-MEDIATED IMMUNE RESPONSE * T cells are activated when an antigenpresenting cell displays a foreign antigen antigen Antigen Presenting Cell (APC) T cell!
T CELLS and the CELL-MEDIATED IMMUNE RESPONSE Example: 1) a macrophage engulfs and digests a pathogen 2) the macrophage displays the antigens on its cell membrane using class II MHC.
3) the macrophage encounters a HELPER T CELL with the appropriate antigen receptor activates T cell 4) activated helper T cell stimulates B cell to produce antibodies specific for the displayed antigen
**Activated T H cells secrete CYTOKINES: -CYTOKINES = factors that stimulate other lymphocytes; -Interleukin-2 (IL-2): stimulates B cells to differentiate into antibody-secreting plasma cells (humoral response) and induces cytotoxic T cells to become active killers (cellmediated response!). -Interleukin-1 (IL-1): secreted from APCs; promotes activation of helper T cells w/same MHC-antigen receptors.
**Other T cells: CYTOTOXIC T CELLS: recognize nonself antigens on cancer cells or virus-infected cells; antigen-activated T C cells kill body cells that are infected by pathogens (or are cancerous). T C cells recognize and bind to antigen-class I MHC markers (host cells display antigens with class I MHC molecules); (T C cells have special plasma membrane proteins called CD8, which have an affinity for class I MHC molecules remember that class I MHC is found in all nucleated body cells)
Cytotoxic T Cell Response: -cytotoxic T cells then bind to the surfaces of the antigen-bearing cells, and release a protein (PERFORIN) that cuts openings in these cells, causing them to burst (LYSE)
CELL-MEDIATED IMMUNE RESPONSE:
CELL-MEDIATED IMMUNE RESPONSE:
Before....After A fully intact cancer cell surrounded by the immune systems killer t-cells. The cancer cell is surrounded and attacked by the killer T-Cells of the immune system. Scanning electron microscope pictures shows killer t-cells attacking the cancer cell. Notice the tentacles of the cancer cell. Notice how the cancer is completely flattened and totally destroyed. During the killing process, granules in a T-Cell fuse with the cell membrane and release units of the protein PERFORIN. These combine to form pores in the target cell membrane. Thereafter fluid and salts enter so that the target cell eventually bursts.
CELL-MEDIATED IMMUNE RESPONSE:
T cells *Some T cells do not respond to the antigen on the first exposure they remain as MEMORY T CELLS; upon a second exposure to the same antigen, they respond quickly
B CELLS and the HUMORAL IMMUNE RESPONSE * B cells are activated when they encounter (1) an antigen in the blood or lymph that fits its antigen receptors, & (2) an activated helper T cell that recognizes the same antigen
B CELLS and the HUMORAL IMMUNE RESPONSE Example: 1) a B cell encounters an antigen in the blood or lymph that fits its antigen receptors internalizes & displays the antigen; 2) B cell encounters a helper T cell bearing receptors for the same displayed antigen this interaction activates the B cell!
3) some activated B cells specialize into PLASMA CELLS (antibody-producing cells) *(antibodies react against the antigen that stimulated their production!) more on this later 4) some activated B cells differentiate into MEMORY B CELLS (respond to subsequent exposures)
HUMORAL IMMUNE RESPONSE:
HUMORAL IMMUNE RESPONSE:
HUMORAL IMMUNE RESPONSE:
HUMORAL & CELL-MEDIATED IMMUNE RESPONSE:
TYPES OF ANTIBODIES antibodies are soluble proteins called IMMUNOGLOBULINS (Ig) 5 major types of antibodies: IgG, IgA, IgM, IgD, and IgE.
Antibody Structure and Function: epitope: a localized region on an antigen s surface that is recognized by antibodies structure:
ANTIBODY ACTIONS antibodies work by: 1) NEUTRALIZATION: bind directly to antigens on surface of pathogen (i.e. virus) blocking its ability to bind to a host cell!
ANTIBODY ACTIONS antibodies work by: 2) OPSONIZATION: binding to antigens on surface of bacteria promotes phagocytosis by macrophages or neutrophils -cause them to clump together (AGGLUTINATION) or form insoluble masses (PRECIPITATION)
AGGLUTINATION!
ANTIBODY ACTIONS 3) activating COMPLEMENT PROTEINS -a group of proteins that work together to produce a variety of effects: attract phagocytes formation of a Membrane Attack Complex that ruptures foreign cell membranes coating the cells/viruses, making them more susceptible to phagocytosis
ANTIBODY ACTIONS 4) stimulate changes in local areas that help prevent the spread of the antigens (i.e. promote inflammation)
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 shortterm 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
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)
Disruptions in Immune System Function: Allergies Autoimmune Diseases Immunodeficiency Diseases Attack on the Immune System (HIV)
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
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)