[Distribution and function of gp90MEL-14 positive and negative T lymphocytes]

The expression of gp90MEL-14 molecules on lymphocytes in vitro was extremely unstable. Even in the course of usual procedures for preparing single cell suspension, the amount of gp90MEL-14 was down-or up-regulated depending on the condition. Addition of NaN3 in the medium for preparing cell suspension stabilized the level of gp90MEL-14 and enabled to quantify the precise amount of gp90MEL-14 on various lymphoid cells, which appeared to reflect the expression pattern of gp90MEL-14 in vivo. By using this simple method, it was clearly demonstrated that the proportion of gp90MEL-14 positive cells and amount of gp90MEL-14 on the cells were associated with the anatomical and functional distance from endothelial cells of high endothelial venule in peripheral lymph nodes. Furthermore, the expression of gp90MEL-14 showed the reverse association with that of Pgp-1. When immunological functions were compared between gp90MEL-14 positive T cells and gp90MEL-14 negative T cells, the latter gp90MEL-14 negative T cells generated higher responses than gp90MEL-14 positive cells in mixed lymphocyte reaction. Furthermore, upon stimulation with concanavalin A (Con A), phytohaemaggultinin or immobilized anti-CD3 antibodies, gp90MEL-14 negative CD8+T cells showed significantly higher proliferative responses and generated extremely higher amounts of IL-2 and IFN-gamma than gp90MEL-14 positive CD8+ T cells did. By contrast, among the CD4+ T cell subpopulations no difference in the Con A response was observed and only slightly higher IL-2 secretion was detected in gp90MEL-14 negative CD4+ T cells than in gp90MEL-14 positive cells. The present findings demonstrate that gp90MEL-14 negative CD8+ and in some case CD4+ T cells, which make up a minor T cell subpopulation in peripheral lymphoid tissues are in functionally active state in vivo and may play a different role from major gp90MEL-14 positive T cells.