Hypersensitivity

Question 1

Type 1 Hypersensitivity

Answer 1

Immediate
Mechanism: IgE
Main player: Antibodies
Mechanism of injury: Mast cells and their mediators

Question 2

Type 2 Hypersensitivity

Answer 2

Antibody mediated
Mechanism: IgM, IgG. Against cell surface or ECM antigens
Main player: Antibodies
Mechanism of injury: Opsonization and phagocytosis, complement

Question 3

Type 3 Hypersensitivity

Answer 3

Immune complex mediated
Mechanism: IgM or IgG + antigen
Main player: Antibodies
Mechanism of injury: Complement

Question 4

Type 4 Hypersensitivity

Answer 4

T cell mediated
Mechanism: CD4+ T cells (cytokine-mediated inflammation)
CD8+ T cells (T cell mediated cytolysis)
Main player: T cells
Mechanism of injury: Recruitment and activation of leukocytes

Question 5

Mast cells activated by cross-linking of ____

Answer 5

Fc-epsilon-RI molecules

Question 6

Lipid mediators of type 1 hypersensitivity

Causes:

Answer 6

Prostaglandin D2, Leukotrienes C4, D4, E4

Vasodilation, increased vascular permeability, bronchoconstriction, mucus secretion

Question 7

Cytokine mediators of type 1 hypersensitivity

Causes:

Answer 7

IL-4, IL-5, IL-13

Inflammation/late-phase reaction, IgE production, Eosinophil production/activation

Question 8

Autoimmune hemolytic anemia

Answer 8

IgG against protein antigens on surface of RBCs

Question 9

Acute Rheumatic Fever

Answer 9

Type 2 hypersensitivity
Molecular mimicry
Occurs 2-4 weeks after group A streptococcus pharyngitits

Question 10

Post-streptococcal glomerulonephritis

Answer 10

Type 3 hypersensitivity
Immune complexes in glomeruli trigger inflammation
Occurs after skin or throat infection w/ group A streptococci
Very low serum C3

Question 11

TH1 produce ____ which leads to ____

Answer 11

IFN-gamma

activate macrophages

Question 12

TH17 produce ____ which leads to ____

Answer 12

IL-17

Recruit neutrophils

Question 13

Poison ivy dermatitis

Answer 13

Type 4 hypersensitivity

Question 14

AIRE gene mutations

Answer 14

Failure to delete autoreactive T cells

Question 15

APECED

Answer 15

AIRE gene mutations
Autoimmune PolyEndocrinopathy, Candidiasis, Ectodermal Dystrophy
Hypoparathyroidism, adrenal insufficiency, hypogonadism

Question 16

FAS gene mutations

Answer 16

Impaired apoptosis

Question 17

ALPS

Answer 17

FAS gene mutations
Autoimmune LymphoProliferative Syndrome
Hemolytic anemia, thrombocytopenia (low platlets), neutropenia (low neutrophils)
Increased risk of lymphoma

Question 18

FOXP3 gene mutations

Answer 18

Impaired regulatory T cells

Question 19

IPEX

Answer 19

FOXP3 gene mutations
Immune dysregulation, Polyendocrinopathy, Enteropathy, X-linked
Chronic life-threatening diarrhea due to enteropathy, dermatitis

Question 20

Systemic Lupus Erythematosus

Answer 20

Type 3 Hypersensitivity

IC deposition

Question 21

Rheumatoid Arthritis

Cytokines:

Answer 21

Type 4 Hypersensitivity
T cell and Abs –> joint inflammation
Innate immune response in synovium
Proinflammatory cytokines: IL-17, TNF, IL-1

Question 22

Diabetes Mellitus Type 1

Inflammation mediated by:

Answer 22

Type 4 Hypersensitivity
Immune-mediated destruction of pancreatic beta cells of islets of Langerhans –> insulin deficiency
Mediated by CD4 TH1 cells

Question 23

Myasthenia Gravis

Answer 23

Type 2 Hypersensitivity

Abs against acetylcholine receptors at postsynaptic membrane of neuromuscular junction

Question 24

Graves’ Disease

Answer 24

Type 2 Hypersensitivity
Hyperthyroidism
Simulated by immune response

Question 25

Hashimoto’s Thyroiditits

Answer 25

Hypothyroidism

Autoimmune destruction of thyroid gland