Blister fluid T lymphocytes during toxic epidermal necrolysis are functional cytotoxic cells which express human natural killer (NK) inhibitory receptors

Toxic epidermal necrolysis (TEN) is a rare life-threatening adverse drug re action characterized by a massive destruction of the epidermis. Immunohisto logical studies of skin biopsies of TEN showed infiltrates of predominantly CD8(+) T lymphocytes even though other authors reported a prominent involv ement of cells of the monocyte-macrophage lineage. The aim of this study wa s to characterize phenotypically and functionally the cells present in the cutaneous blister fluid of four patients with TEN. We first determined that lymphocytes were predominant in blister fluid obtained early, while monocy tes/macrophages later became the most important population. We then showed that this lymphocyte population, mainly CD3(+)CD8(+), corresponded to a pec uliar cell subset as they expressed cutaneous leucocyte antigen, killer inh ibitory receptors KIR/KAR and failed to express CD28 molecule. Functionally , we determined that blister T lymphocytes had a cytotoxic T lymphocyte (CT L)- and NK-like cytotoxicity. The role of this cytotoxic lymphocyte populat ion present at the site of lesions during TEN remains to be understood.