<prompt> Which of the following principally mediates delayed type hypersensitivity?Cytotoxic T cells, TH1 cells, and macrophagesIgE, basophils, and mast cellsIgG and complementIgG, IgM, neutrophils, and macrophages  <response>: Cytotoxic T lymphocytes, helper T1 lymphocytes, and macrophages mediate the delayed-type hypersensitivity reaction, which develops in response to viral, fungal, and intracellular bacterial antigens. Antibodies do not play a significant role in this type of response. IgE, basophils, and mast cells are involved in the production of type I hypersensitivity. IgG and complement is a mechanism of toxicity in type II cytotoxic hypersensitivity. IgG, IgM, neutrophils, and macrophages may be involved in types II or III hypersensitivities. Ref: Levinson W. 2012. Chapter 65. Hypersensitivity Allergy. In W. Levinson Ed, Review of Medical Microbiology Immunology, 12e. 