Medical Laboratory Scientist ASCP Practice Exam 2025 – Complete Study Guide

T lymphocytes play a crucial role in mediating contact dermatitis, which is a type of delayed-type hypersensitivity reaction. This condition occurs when the skin comes into contact with an allergen, triggering an immune response. Specifically, it is the CD4+ T helper 1 (Th1) cells and CD8+ cytotoxic T lymphocytes (CTLs) that are primarily involved in this process.

When an allergen penetrates the skin, it is processed by professional antigen-presenting cells (APCs), such as dendritic cells. These APCs then present the allergenic peptides to naive T lymphocytes in the lymph nodes, leading to their activation and differentiation into effector T cells. The activated T cells then migrate to the site of exposure, where they release cytokines that recruit other immune cells and contribute to the inflammatory response, ultimately resulting in the clinical manifestations of contact dermatitis, such as redness, swelling, and vesicle formation.

The other cell types listed do not play a direct role in this particular immune response. B lymphocytes are primarily involved in antibody production rather than T cell-mediated responses. Natural killer cells are part of the innate immune system and are involved in the surveillance against tumors and virally infected cells. Monocytes,