Monoclonal proliferation of CD4+ large granular lymphocytes with cytolytic activity

Abstract
A rare case of monoclonal proliferation of CD3+4+8- T-cell receptor-alpha beta+ large granular lymphocytes (LGL) is presented. CD4+ LGL in the present case showed spontaneous cytotoxicity against herpes simplex virus-infected cells and antibody- and lectin-dependent cytotoxicity. Perforin, which is one of the important cytolytic mediators of cytotoxic T cells (CTL) and natural killer cells, was abundantly expressed in CD4+ LGL of this case. The present case suggests that perforin-positive CD4+ CTL, which have recently been shown in the in vitro studies, certainly exist in vivo.