A patient develops an oral ulcer approximately one week after starting a new medication (drug-induced stomatitis). Which cell type is primarily responsible for the tissue destruction in this type of reaction?

Drug-induced oral ulcers (lichenoid drug reactions, fixed drug eruptions, or aphthous-like ulcers) developing over 1–2 weeks represent a delayed-type (Type IV) hypersensitivity reaction mediated primarily by CD8+ cytotoxic T-lymphocytes. The drug or its metabolites act as haptens, binding to keratinocyte proteins and triggering T-cell recognition and immune-mediated cytotoxicity. The histopathology shows a band-like subepithelial infiltrate of lymphocytes with basal cell vacuolization and apoptotic keratinocytes (civatte bodies), similar to lichen planus. Neutrophils predominate in acute bacterial/ulcerative processes; mast cells and basophils are involved in Type I (immediate) hypersensitivity reactions.