IPR T-CELLS HAVE LOWER ABILITY TO MAINTAIN BCL-2 EXPRESSION EX-VIVO

Autoimmune-prone lpr mice develop lymphoproliferative disorders, where as their lymphocytes show accelerated apoptosis in culture. To elucida te whether the bcl-2 protein, a repressor of apoptosis, is critical to the discrepancy between in vivo and in vitro survival, we examined bc l-2 expression in T cells from +/+ and lpr mice during culture. The ex pression levels of bcl-2 in cultured T cells from lpr mice were signif icantly down-modulated compared to those from +/+ mice and freshly obt ained T cells. Besides, the reduction of bcl-2 protein levels was inhi bited in T cells cultured in the presence of T cell receptor (TCR) sig nalling. These results suggest that lpr T cells might be susceptible t o apoptosis in vitro due to down-modulation of bcl-2 by withdrawal of TCR signalling.