Hypersensitivity

Question 1

What is a Type I hypersensitivity reaction?

Answer 1

Anaphylatctic & atopic

Question 2

What happens in Type I hypersensitivity rxns?

Answer 2

Free Ag cross-links IgE on presensitized mast cells & basophils, triggering release of vasoactive amines that act at postcapillary venules

Question 3

What is the onset of a Type I hypersensitivity rxn?

Answer 3

Rxn develops rapidly after Ag exposure b/c of preformed Ab

Question 4

What is the test for Type I hypersensitivity rxn?

Answer 4

Skin test for specific IgE

Question 5

What is a Type II hypersensitivity rxn?

Answer 5

Cytotoxic (Ab mediated)

Question 6

What happens in a Type II hypersensitivity rxn?

Answer 6

IgM, IgG bind to fixed Ag on “enemy” cell l/t cellular destruction

Question 7

What are the 3 mech of Type II hypersensitivity rxns?

Answer 7

• Opsonization l/t phagocytosis or complement activation
• Complement-med lysis
• Ab-dependent cell-med cytotoxic (ADCC) usually d/t NK cells

Question 8

Ab & complement lead to ___ ____ ___.

Answer 8

Membrane attack complex

Question 9

What are the tests for Type II hypersensitivity rxns?

Answer 9

Direct & indirect Coombs’

Question 10

What are Type III hypersensitiviy rxns?

Answer 10

Immune complex

Question 11

What happens in Type III hypersensitivity rxns?

Answer 11

Ag-Ab (IgG) complexes activate complement, which attracts neutrophils

Question 12

What do neutrophils release in Type II hypersensitivity rxns?

Answer 12

Lysosomal enzymes

Question 13

What is Serum sickness?

Answer 13

An immune complex dz in which Ab’s to the foreign proteins are produced (takes 5 days). Immune complexes form & are depositied in membranes where they fix complement

Question 14

Most serum sickness is now cause by drugs acting as ____.

Answer 14

Haptens

Question 15

What are the sx of Serum sickness?

Answer 15

• Fever
• Uticaria
• Athralgia
• Proteinuria
• Lymphadenopathy

Question 16

When does serum sickness present?

Answer 16

5-10 days after Ag exposure

Question 17

Is serum sickness or Arthus rxn MC?

Answer 17

Serum sickness

Question 18

What is Arthus reaction?

Answer 18

A local subacute Ab-med hypersensitivity rxn. Intradermal injection of Ag induces Abs which form Ag-Ab complexes in skin

Question 19

What are the characteristics of Arthus rxn?

Answer 19

• Edema
• Necrosis
• Activation of complement

Question 20

What causes Arthus rxn?

Answer 20

Ag-Ab complexes

Question 21

What is the test for Arthus rxn?

Answer 21

Immunofluorescent staining

Question 22

What is Type IV hypersensitivity rxn?

Answer 22

Delayed (T-cell med) type

Question 23

What happens in Type IV hypersensitivity rxn?

Answer 23

Sensitized T lymphocytes encounter Ag & then release lymphokines (l/t macrophage activation; no Ab involved)

Question 24

What are the 4 T’s of Type IV hypersensitivty rxn?

Answer 24

• T lymphocytes
• Transplant rejections
• TB skin test
• Touching (contact dermatitis)

Question 25

What are the tests for Type IV hypersensitivity rxn?

Answer 25

Patch test & PPD

Question 26

What are some examples of Type I hypersensitivity rxn?

Answer 26

* Anaphylaxis * Allergic & atopic disorders

Question 27

What is the presentation of Type I hypersensitivity rxns?

Answer 27

Immediate, anaphylatic, atopic

Question 28

What are some examples of Type II hypersensitivity rxns?

Answer 28

* Autoimmune hemolytic anemia (AIHA) * Pernicious anemia * idiopathic thrombocytopenic purpura * Erythroblastosis fetalis * Rheumatic fever * Goodpasture's synd * Bullous pemphigoid * Pemphigous vulgaris

Question 29

What is the presentation of Type II hypersensitivity rxn?

Answer 29

Dz tends to be specific to tissue or site where Ag is found

Question 30

What are some examples of Type III hypersensitivty rxns?

Answer 30

* SLE * Polyarteritis nodosa * Poststreptococcal glomerulonephritis * Serum sickness * Arthus rxn

Question 31

How do Type III hypersensitivity rxns present?

Answer 31

Can be assoc w/ vasculitis & systemic manifestations

Question 32

What are some examples of Type IV hypersensitivity rxns?

Answer 32

* MS * Guillain-Barré synd * PPD * Contact dermatitis

Question 33

How do Type IV hypersensitivity rxns present?

Answer 33

Response is delayed & does NOT involve Abs

Question 34

What is the pathogenesis of a Blood transfusions Allergic rxn?

Answer 34

Type I hypersensitivity rxn against plasma proteins in transfused blood

Question 35

What is the clinical presentation of a blood transfusion allergic rxn?

Answer 35

* Urticaria * Pruritus * Wheezing * Fever

Question 36

What is the tx for blood transfusion allergic rxn?

Answer 36

Antihistamines

Question 37

What is the pathogenesis of blood transfusion Anaphylactic rxn?

Answer 37

Severe rxn, IgA-def individuals must receive lood products that lack IgA

Question 38

What is the clinical presentation of blood transfusion Anaphylactic rxn?

Answer 38

* Dyspnea * Bronchospasm * HOTN * Resp arrest * Shock

Question 39

What is the pathogenesis of Febrile nonhemolytic transfusion rxn (FNHTR)?

Answer 39

Type II hypersensitivity rxn Host Ab against donor HLA Ag & leukocytes

Question 40

What is the clinical presentation of FNHTR?

Answer 40

* Fever * HA * Chills * Flushing

Question 41

What is the pathogenesis of an Acute hemolytic transfusion rxn (HTR)?

Answer 41

Type II hypersensitivity rxn Intravascular or extravascular hemolysis

Question 42

What is intravascular hemolysis?

Answer 42

ABO blood group incompatibility

Question 43

What is extravascular hemolysis?

Answer 43

Host Ab rxn against foreign Ag on donor RBCs

Question 44

What is the clinical presentation of a HTR?

Answer 44

* Fever * HOTN * Tachypnea * Tachycardia * Flank pain * Hemoglobinemia * Jaundice

Question 45

What is hemoglobinemia an example of?

Answer 45

Intravascular hemolysis

Question 46

What is Jaundice an example of?

Answer 46

Extravascular hemolysis