Hypersensitivity

Question 1

Type I

Answer 1

Anaphylatic or atopic
Free antigen crosslinks IgG on mast cells and basophils
Histamines act at poscapillary venules.
Rapid reaction because of preformed Ab

Test: skin test for specific IgG

Question 2

Type II

Answer 2

Cytotoxic (antibody mediated)
IgM, IgG bind to fixed antigen on enemy cell, leading to cellular destruction.

1) optonization: leading to phago or complement
2) complement mediated lysis
3) ADCC, via NK cells

Test: direct and indirect Coombs

Question 3

Type III

Answer 3

Immune complex: antigen antibody (IgG) complexes activate complement, which attracts neutrophils, neutrophils release lysosomal enzymes.
“Type III: three things are attacking; antigen, antibody, complement”

Serum sickness: most caused by drugs acting as haptens. Fever, rash, arthralgias, proteinuria, LAD 5-10 days after antigen exposure. Immune complex fix complement and lead to tissue damage

Arthus reaction: local subacute AB hypersensitivity (type III) intradermal injection, which forms complex in the skin. Characterized by edema, necrosis, and activation of complement. Test with IFA

Question 4

Type IV

Answer 4

Delayed, the only T cell mediated
Sensitized T cells encounter antigens and release lymphokines, leading to MP activation. No Ab involved.

4T: T lymphocyte, Transplant rejection, TB skin test, Touching (contact dermatitis)

SJOGREN IS TYPE IV TOO

Question 5

Disease of Type I

Answer 5

Anaphylaxis, allergic and atopic disorder

Question 6

Disease of Type II

Answer 6

Autommine hemolytic anemia (AIHA)
Pernicious anemia
idiopathic throbocytopenia purpura
Erythroblastosis fetalis
Acute hemolytic transfusion reaction
Rheumatic fever
Goodpasture's syndrome
Bullous pemphigoid
Pemphigus vulgaris

Disease tends to be specific tissue or site where antigen is found

Question 7

Disease of Type III

Answer 7

SLE
Polyarthritis nodosa
Post streptococcal glomerulonephritis
Serum sickness
Arthus reaction (swelling, inflamm after tetanus vaccine)

Can be associated with vasculitis and systemic manifestations

Question 8

Disease of Type IV

Answer 8

Multiple sclerosis
Guillan-Barre syndrome
GVHD
PPD
Contact dermatitis
SJOGREN

Response is delayed and does NOT involve Abs.

Question 9

Blood transfusion reaction: allergic reaction

Answer 9

Type I hypersensitivty against plasma protein in transfused blood

Rash, pruritus, wheezing, fever, treat with antihistimine

Question 10

Anaphylactic reaction

Answer 10

Severe reaction

IgA-deficient individuals must receive blood products that lack IgA

Dyspnea, bronchospasm, hypotension, respiratory arrest, shock.

Question 11

Febrile nonhemolytic transfusion reaction

Answer 11

Type II reaction

Host antibodies against donor HLA antigens and leukocytes.

Fever, headaches, chills, flushing

Question 12

Acute hemolytic transfusion reaction

Answer 12

Type II reaction

Intracellular hemolysis (ABO blood group incompatibility) or extravascular hemolysis (host antibody reaction against foreign antigen or donor RBC)

Fever, hypotension, tachypnea, tachycardia, flank pain, hemoglobinemia (intravascular), jaundice (extracellular hemolysis)