Hypersensitivity

Question 1

hypersensitivity

Answer 1

over-reactions of the immune system to harmless environmental antigens. 4 types based on the location of the target antigen and whether the immune response is mediated by antibodies or immune cells.

Question 2

type 1 or immediate hypersensitivity

Answer 2

mediated by IgE. commonly called allergies or atopic disorders. normal response to multicellular parasites but directed to innocuous antigens with structural similarities. clinical manifestations depend on the route of entry of the antigen and the location of the responding cells

Question 3

hygiene hypothesis

Answer 3

excessive hygiene reduces childhood exposures to microorganisms. vaccination reduces immune system experience with natural infection. overuse of antibiotics reduces immune system experience and ability to discriminate self from foreign. immune system perception of foreign danger is affected

Question 4

characteristics of allergens

Answer 4

low weight, highly soluble and stabile proteins. contain peptides that can be presented by MHC class II. effective at activating Th2-type cytokines, especially IL-4 (stimulates IgE response)

Question 5

initial sensitization to allergen

Answer 5

first exposure to allergen has antigen activation of Th2 cells and stimulation of IgE class switching in B cells. IgE binds to the FCR1 receptors on the mast cells.

Question 6

subsequent exposures to allergens

Answer 6

mast cell degranulation. vasoactive amines, and lipid mediators give immediate hypersensitivity reaction. cytokines give late phase reaction

Question 7

effects of mast cell mediators

Answer 7

SRS-A (slow releasing substance of anaphylaxis)-mixture of leukotrienes produced during response. Serotonin-affects vascular permeability. TNF stimulates expression of adhesion molecules on endothelial cells

Question 8

what do the mediators lead to?

Answer 8

influx of inflammatory cells! reciprocally regulated. TGFB, IL-3 lead to increased basophils and decreased eosinophils, which are stimulated by IL-5 and GM-CSF.

Question 9

granulocyte response

Answer 9

promotes expulsion of parasites by peristalsis and mucus. also makes cationic granule proteins to kill parasites, and enzymes to remodel tissue.

Question 10

responses to subcutaneous allergen

Answer 10

localized swelling (urticaria). deeper swelling is angiodema. mechanism in skin testing for allergies is done through RAST assay for allergen specific IgE.

Question 11

responses to inhaled allergen

Answer 11

Allergic rhinitis. if the eyes are affected, allergic conjunctivitis

Question 12

allergic asthma

Answer 12

Th2 cells that produce IL-13. airway constriction and mucus. chronic asthma can occur in the absence of allergens: hyper-responsive to other irritants in air such as smoke

Question 13

reactions to adsorbed allergen

Answer 13

food allergies. widely disseminated causing urticaria. smooth muscle contraction induces vomiting and diarrhea.

Question 14

responses to systemic allergen

Answer 14

systemic anaphylaxis. most severe form of a type 1 reaction: antigens include drugs, serum, venom, and peanuts. treat with epinephrine. promotes tight junctions, relaxes bronchial smooth muscle, stimulates the heart

Question 15

transfer of IgE and antigen in pregnancy

Answer 15

child more rish for allergy if mother is atopic. IgE complexed with allergen in amniotic fluid could be ingested by fetus

Question 16

treatment for type 1 hypersensitivity

Answer 16

avoid allergen. treat symptoms with antihistamines, corticosteroids, etc. desensitize through controlled exposure leading to IgA and IgG blocking of IgE. vaccines, omalizumab

Question 17

type II hypersensitivity

Answer 17

mediated by IgG. antibodies bind to a cell associated antigen or cell surface receptor and fix complement. EX: drug binds to surfaces of new RBCs creating new epitopes, and RBCs are lysed. platelets can also be lysed

Question 18

when does hemolytic disease of the newborn occur?

Answer 18

every pregnancy after the first one where a RhD- mother had an RhD+ fetus. the mother now has the IgG against RhD+, and passes them to the baby

Question 19

hyperacute graft rejection

Answer 19

may occur when transplant recipients have antibodies that react with donor ABO or HLA class I antigens

Question 20

type III hypersensitivity

Answer 20

large quantities of soluble antigens and their antibodies develop and form large latticed immune complexes. isotype, valency, charge, and ability to fix complement determine IC pathogenicity. latticed immune complexes are pathologically capable of depositing systemically in any of a variety of tissue sites

Question 21

arthus reaction

Answer 21

localized. PMNs attracted to site produce lysosomal enzymes causing tissue damage.

Question 22

serum sickness

Answer 22

occurs after the development of antibody to antigen, about 7-10 days. may occur after large amounts of a foreign protein such as antisera for snake bite, mouse antibodies as therapeutics, streptokinase.

Question 23

Type IV hypersensitivity reactions

Answer 23

mediated by antigen specific effector T cells. require greater amounts of allergen than Ig-mediated hypersensitivity

Question 24

delayed type hypersensitivty

Answer 24

antigen introduced and processed by antigen presenting cells. Th1 effector cell recognizes antigen and releases cytokines which act on vascular endothelium. leads to recruitment of T cells, phagocytes, etc. in 24-72 hours

Question 25

contact hypersensitivity

Answer 25

CD4+ t cells activate other immune cells while CD8+ T cells kill chemical reacted cells that display foreign antigen.

Question 26

transplant rejection

Answer 26

when a kidney is transplanted, the recipient’s T cells attack the transplant.

Question 27

Graft versus host disease

Answer 27

when hematopoietic cells are transplanted, the T cell in the transplant attack the recipient’s tissues

Question 28

treatment of type II, III, IV hypersensitivity reactions

Answer 28

avoid antigen. reduce impact of immune response with anti-inflamm and steroids. reduce general immune response. induce regulation of response and block effector mechanisms of allergic response