A THYMIC NURSE CELL-SPECIFIC MONOCLONAL-ANTIBODY

A thymic epithelial cell line (tsTNC-1) that maintains the ability to selectively bind and internalize immature alpha beta TCR(lo)CD4(+)CD8( +) thymocytes in vitro was used in the development of a monoclonal ant ibody that is specific to the cell surface of thymic nurse cells (TNCs ) in the thymus. The rat monoclonal antibody ph91 showed specificity t o cells of the subcapsular region of the thymic cortex. Upon mechanica l dispersion of the thymus in vitro, ph91 recognized cells displaying the multicellular morphology unique to TNCs. Ph91 staining was not det ected on fresh thymocytes, stromal cells of the inner thymic cortex, t hymic medullary cells, B cells or fibroblasts. Ph91 recognized a 43-kD a protein on the surface of TNCs. Exposure of tsTNC-1 cells to ph91 in tissue culture significantly reduced the percentage of binding of the alpha beta TCR(lo)CD4(+)CD8(+) thymocyte subset previously shown to t arget TNCs. In organ culture, ph91 reduced the viability of developing thymocytes by 70%. The largest reduction was found in the alpha beta TCR(lo)CD4(+)CD8(+) thymocyte subset. These results represent the firs t report of a TNC-specific monoclonal antibody. Further, the antigen t o which ph91 binds may play a role in the process of thymocyte binding and their subsequent internalization which is unique to TNCs and impo rtant to the T cell developmental process. (C) 1998 Academic Press.