Figure 2.

Pathways that could produce the in vivo hyperproliferation of lpr T cells. Left: Fas-deficient T cells that fail to undergo apoptosis might acquire an indirect increased capacity for proliferation, enhanced by inflammatory cytokines that create a feedback loop and result in hyperproliferating lpr T cells. p21 overexpression inhibits hyperproliferation of these cells, which reduces lymphadenopathy. Right: Fas-deficient T cells show a hyperproliferative phenotype due to lack of Fas, which after interacting with Fas ligand (FasL), has a direct regulatory effect on activation/proliferation. These hyperactivated lpr T cells accumulate in lymph nodes. p21 overexpression reduces hyperactivation/proliferation of lpr T cells, and lymphadenopathy development is minimal.