Final answer:
The statement that most Type IV Hypersensitivity reactions are orchestrated by cytokines released by TH1 cells in response to antigen is a. true.
Step-by-step explanation:
Most Type IV Hypersensitivity reactions are orchestrated by the cytokines released by TH1 cells in response to antigen. This statement is true. Type IV hypersensitivity, also known as delayed hypersensitivity, is mediated by T cells, particularly TH1 cells. The process begins with sensitization, where antigens are presented by antigen presenting cells (APCs) which then activate helper T cells.
This leads to clonal proliferation and differentiation into memory TH1 cells. Upon re-exposure to the antigen, these sensitized memory TH1 cells release cytokines that activate macrophages. These activated macrophages are principally involved in tissue damage seen in type IV hypersensitivity reactions such as the Mantoux skin test for tuberculosis and contact dermatitis from latex allergies. Type IV hypersensitivities are indeed T-cell-mediated immune responses that differ from other types of hypersensitivity which are mostly antibody-mediated.