Contact dermatitis is a delayed-type hypersensitivity reaction.
A type II hypersensitivity reaction occurs when red blood cells are lysed after an incompatible blood transfusion.
Dramatic hypotension sometimes accompanies type I hypersensitivity reactions because A) massive histamine release from mast cells leads to vasodilation. B) toxins released into the blood interfere with cardiac function. C) anaphylaxis results in large volume losses secondary to sweating. D) hypoxia due to bronchoconstriction impairs cardiac function.
Autoimmune diseases A) are due to increased T suppressor cell activity associated with aging. B) occur only when lymphocytes are in close contact with body cells during embryogenesis. C) result from failure of the immune system to differentiate self and nonself molecules. D) are often communicable to others by direct contact.