Cutaneous lymphocyte antigen is expressed on memory/effector B cells in the peripheral blood and monocytoid B cells in the lymphoid tissues

Cutaneous lymphocyte antigen (CLA) is expressed on a subpopulation of human memory T cells and is involved in the primary step of their skin homing. T cells and some B cells in the peripheral blood express CLA, but the pathop hysiologic roles of CLA(+) B cells have not yet been clarified. We examined the relationships among CLA expression in B cells and immunoglobulin heavy chain subtype, the localization of CLA(+) B cells in the peripheral lympho id tissues, and their functional binding to E-selectin. CLA was expressed o n class-switched, memory B cells in the peripheral blood and tonsils as rev ealed by how cytometry. Immunohistochemical staining of the lymph nodes wit h various types of inflammation or reactive hyperplasia showed CLA on the m onocytoid B cells, which correspond to memory cells. The functional study r evealed that CLA on B cells bound to E-selectin transfectants. E-selectin w as detected on some of the high endothelial venules in the monocytoid B-cel l-rich lymph nodes. These findings suggest that CLA is also expressed on a subset of memory/effector B cells, in addition to a subset of memory T cell s. Such B cells were located in the lymph nodes or tonsils and rarely in ch ronic dermatitis. Therefore, CLA seems to be related to memory/effector B-c ell trafficking to the lymph nodes or tonsils. According to the multistep t heory, mechanisms involved in the second or third step might be different b etween CLA(+) B and T cells. (C) 1999 Academic Press.