Identification of plasmacytoid T cells in lymphoid hyperplasia of the skin

Abstract

Well-defined clusters of plasmacytoid T cells were identified in two cases of lymphoid hyperplasia of the skin. With the use of paraffin-embedded and frozen sections and 46 different antibodies, the antigenic profile of plasmacytoid T cells was obtained. Corresponding to plasmacytoid T cells in reactive and neoplastic lymph node conditions, plasmacytoid T cells of the skin were devoid of most T-cell-restricted differentiation antigens CD2, CD3, CD5, and CD8 while expressing monocyte/macrophage-related antigens recognized by Ki-M6 and Ki-M7. In addition, plasmacytoid T cells were positive for CD4, CD45, HLA class II antigens (HLA-DR, Leu-10, MB3, LN2, LN3) and the transferrin receptor. Furthermore, they reacted with anti-Leu-8, MB1, Ki-B3 (CD45R), and MT1. Thus plasma-cytoid T cells are considered to be mononuclear cells with monocyte/macrophage differentiation rather than T lymphocytes. In addition, our findings substantiate the concept that plasmacytoid T cells may function as a hitherto unrecognized subgroup of antigen-presenting cells in the skin.