Hypersensitivities

Question 1

allergic contact dermatitis, e.g., due to contact with urushiol-containing plants such as poison oak, poison ivy, or poison sumac

Answer 1

(type IV hypersensitivity reaction)

Antigens penetrating the skin are phagocytosed by Langerhans cells, which subsequently migrate to the lymph nodes and there induce the formation of sensitized T lymphocytes. On a subsequent exposure, these presensitized T lymphocytes secrete lymphokines (e.g., interferon-γ) that induce macrophage-mediated tissue inflammation as seen in this patient.

Question 2

An overreaction of the immune system that accounts for many glomerulonephritides and vasculitides, serum sickness, and the Arthus reaction

Answer 2

Type III hypersensitivity reaction

Question 3

It is caused by immune complex deposition, which leads to complement activation and release of lysosomal enzymes from neutrophils, which subsequently results in cell death and inflammation.

Answer 3

Type III hypersensitivity reaction

Question 4

Many rheumatologic diseases involve type_____hypersensitivity reactions, including rheumatoid arthritis, systemic lupus erythematosus, and Henoch-Schonlein purpura, all of which can manifest with skin lesions.

Answer 4

III

Question 5

Mast cells provoke IgE-mediated immediate immune responses in type____hypersensitivity reactions.

Answer 5

I

Question 6

Rashes due to type____hypersensitivity reaction are classically disseminated and diffuse, rather than localized to the area of likely exposure, as seen in this patient. Moreover, type ___hypersensitivity reactions classically occur within minutes of antigen exposure.

Answer 6

I

Question 7

Eosinophil infiltration is a hallmark of type ___ hypersensitivity reactions.

Answer 7

I