A 24-year-old man is diagnosed with disseminated histoplasmosis after developing symptoms of fever, lymphadenopathy, hepatosplenomegaly and pancytopenia. Which of the following is the body's major immunologic defense against histoplasmosis?
immunoglobulin G (IgG) antibodies
mononuclear leukocytes
complement
immunoglobulin M (IgM) antibody
The major reaction to fungal infections such as histoplasmosis is delayed-type hypersensitivity. This is a reaction of T cells, which have been stimulated by antigen to react against infectious agents, grafts, and tumors. A classic example is the response to the tuberculin skin test in a person previously exposed to Mycobacterium tuberculosis organisms which occurs between 48 and 72 hours after antigen exposure.
Immunology and Rheumatology