HLTH module 3: hypersensitivity and transplants Flashcards
hypersensitivity meaning
aka allergic reactions; can be unusual and harmful immune responses to normally harmless substances; reactions stimulate an inflammatory response
what are the most common transplants?
skin, cornea, bone, kidneys, lungs, hearts, and bone marrow
organ rejection
primarily involves a type IV cell-mediated hypersensitivity reaction (and small humoral response); this causes inflammation and tissue necrosis, eventually destroying the organ
what organs are less rejection associated with?
corneas and cartilage because they lack a blood supply
why do better transplants occur in young infants?
because their immune system in not yet mature and does not respond to the foreign tissue
two types of rejection
host-verus graft disease and graft-verus host disease
host-verus-graft disease
occurs when the host’s immune system rejects the graft
graft-versus-host disease
occurs when the graft tissue contains T cells that attack the host cells; common in bone marrow transplants
hyperacute rejection
rejection occurs immediately as circulation to the site is reestablished
acute rejection
occurs after several weeks when unmatched antibodies cause a reactionc
chronic or late rejection
occurs after months or years, with gradual degeneration of the blood vessels
how can rejection be treated?
immunosuppression techniques that reduce the immune response; involves drugs such as cyclosporine, Imuran, and a glucocorticoid
concern with treatment of rejection
immunosuppression increases the risk of infection because the normal body defences are now limited
allergen
the antigen causing the allergic reaction; can be a food, drug, plant, pollen, or chemical
atopic hypersensitivity reaction
tendency for allergic conditions to be inherited, and this is the manifestation name
what antibodies are associated with a type I hypersensitivity?
IgE antibodies from B lymphocytes; these attach to mast cells, creating a sensitized mast cell
where are mast cells abundnat?
mucosa of the respiratory and digestive tracts
what occurs in a type I hypersensitivity reaction?
the allergen attaches to the IgE antibody on the mast cell, stimulating the release of chemical mediators such as histamine; this causes vasodilation and increased capillary permeability at the site, resulting in swelling and redness, and sometimes itching
what are other chemical mediators involved in type I hypersensitivity reactions?
prostaglandins and leukotrienes; these are released at the second phase of the reaction
when are hay fever signs present?
when the antigen-antibody reactions occurs in the nasal mucosa
what does the first exposure to an antigen do?
does not cause a reaction but causes the formation of antibodies and sensitized mast cells
hay fever
an allergic reaction in the nasal mucosa that causes frequent sneezing, water secretions from the nose, and itching; causes red eyes as well; usually associated with plant pollens
common signs of a food reaction
nausea, vomiting, diarrhea, and rash/hives
eczema other name
atopic dermatitis
eczema
often genetic and common in young children; forms a skin rash on the face, trunk, or extremities and is often associated with foods, irritating fabrics, and a dry atmosphere
anaphylaxis
a severe, life-threatening hypersensitivity reaction resulting in airway obstruction, decreased BP, and hypoxia
what is anaphylaxis commonly caused by?
latex materials, insect stings, nuts, shellfish, penicillin, or local anesthesia
signs of anaphylaxis
itching, tingling, coughing, and difficulty breathing initially, then weakness, dizziness, or fainting; edema may also occur around the eyes, lips, tongue, hands or feet, as well as hives; low BP and airway obstruction also occur
why does itching occur in allergic reactions?
histamine and chemical mediators irritate sensory nerves
treatment of anaphylaxis
epinephrine injection; antihistamine drugs or chlorpheniramine may be useful in the early stages as they block histamine release
type II hypersensitivity other name
cytotoxic hypersensitivity
type II hypersensitivity
occurs when the antigen is present on the cell membrane, reacting with circulating IgG antibodies which cause destruction of the cell by phagocytosis or releasing cytolytic enzymes
example of a type II hypersensitivity
a incompatible blood transfusion; ex. type A blood has A antigen and anti-B antibodies in the blood, and type B blood will cause a reaction due to anti-A antibodies
another name for type III hypersensitivity
immune complex hypersensitivity
type III hypersensitivity
occurs when the antigen combines with the antibody, forming a complex that is deposited in tissue, often vessel walls, activating complement which causes inflammation and tissue destruction
what diseases are believed to be caused by type III hypersensitivties?
glomerulonephritis and rheumatoid arthritis
serum sickness
refers to the systemic reaction that occurs when the immune complex is deposited in many tissues
type IV hypersensitivity other name
cell-mediated or delayed hypersensitivity
type IV hypersensitivity
is a delayed response by sensitized T lymphocytes to antigens, resulting in the release of lymphokines or other chemical mediators that cause an inflammatory response and destruction of the antigen
what is type IV hypersensitivity associated with?
organ transplants
test for checking of prior exposure of the organism causing tuberculosis
tuberculin test
contact dermatitis
is an allergic skin reaction and is caused by a type IV reaction often by cosmetics, dyes, soaps, metals, or poison ivy
signs of a type IV hypersensitivity reaction
often skin reactions that damage the mucous membranes; signs can be asthma, hives, anaphylaxis, as well as red and itchy skin
