chapter 19 microbiology
Describe the basis of the ABO and Rh blood group systems.
-Human blood may be grouped into four principal types, designated A, B, AB, and O. -Approximately 85% of the human population possesses another blood group antigen, designated the Rh antigen; these individuals are designated Rh+.
Describe the mechanism of immune complex reactions.
-Immune complex diseases occur when IgG antibodies and soluble antigen form small complexes that lodge in the basement membranes of cells. -Subsequent complement fixation results in inflammation.
Explain the relationship among blood groups, blood, transfusions, and hemolytic disease of the newborn.
-Naturally occurring antibodies are present in serum against the opposite AB antigen. - Incompatible blood transfusions lead to the complement-mediated lysis of the donor red blood cells. -Subsequent pregnancies involving Rh incompatibility may result in hemolytic disease of the newborn (erythroblastosis).
Compare and contrast systemic and localized anaphylaxis.
-Systemic anaphylaxis may develop in minutes after injection or ingestion of the antigen; this may result in circulatory collapse and death. -Localized anaphylaxis is exemplified by hives, hay fever, and asthma.
Describe the mechanism of delayed cell-mediated reactions, and name two examples.
. Delayed cell-mediated hypersensitivity reactions are due primarily to TD cell proliferation. 30. Sensitized T cells secrete cytokines in response to the appropriate antigen. 31. Cytokines attract and activate macrophages and initiate tissue damage. 32. The tuberculin skin test and allergic contact dermatitis are examples of delayed hypersensitivities. Examples: poison ivy, poison oak, dermatitis
Define autograft, isograft, allograft, and xenotransplant.
: autografts=use one's own tissue, isografts= use of identical twins tissue, allografts= use of tissue from another person, and xenotransplants=use of nonhuman tissue (animal).
Describe the mechanism of anaphylaxis.
Anaphylactic reactions involve the production of IgE antibodies that bind to mast cells and basophils to sensitize the host. (can cause air way to close) (less than 30 minutes) mast cells and basophils undergo degranulation
What is blocking antibody.
Desensitization to an antigen can be achieved by repeated injections of the antigen, which leads to the formation of blocking (IgG) antibodies.
Define HLA complex, and explain its importance in disease susceptibility and tissue transplants.
HLA: MHC genes in humans - To prevent the rejection of transplants, HLA and ABO blood group antigens of the donor and recipient are matched as closely as possible.
Describe a mechanism for self-tolerance
Self-tolerance occurs during fetal development; T cells that will target host cells are eliminated (clonal deletion) or inactivated.
Explain how rejection of a transplant is prevented.
To prevent the rejection of transplants, HLA and ABO blood group antigens of the donor and recipient are matched as closely as possible
Describe the mechanism of cytotoxic reactions
Type II reactions are mediated by IgG or IgM antibodies and complement. (complement activation causes cell lysis or damage by macrophages) 11. The antibodies are directed toward foreign cells or host cells. Complement fixation may result in cell lysis. Macrophages and other cells may also damage the antibody-coated cells. -hemorrhaging could result
priveleged sites
an area of the body that does not elicit an immune response
Explain how graft-versus-host disease occurs.
can result from transplanted bone marrow that contains immunocompetent cells
Give an example of immune complex, cytotoxic, and cell-mediated autoimmune diseases.
immune: Systemic lupus erythematosus and rheumatoid arthritis Cytotoxic: Graves' disease and myasthenia gravis Cell-mediated: Multiple sclerosis, insulin-dependent diabetes (type 1) mellitus, and psoriasis
Describe how the immune system responds to cancer and how cells evade immune responses.
immunotherapy and immunotoxins specifically target and kill cells of a tumor
Are all immune responses beneficial?
no
Define hypersensitivity
represent immunological responses to an antigen (allergen) that lead to tissue damage rather than immunity.