T cells from autoimmune "IL 2-defective" MRL-lpr/lpr mice continue to grow in vitro and produce IL 2 constitutively.

MRL-lpr/lpr mice and other autoimmune strains that bear the lpr gene develop a profound lymphadenopathy characterized by an expansion of a unique dull Lyt-1+2- T cell population. Because fresh splenic and lymph node T cells from such mice stimulated Con A in vitro are extremely defective in IL 2 production and proliferation, T cell lines derived from MRL-lpr/lpr spleens were established and maintained for several months, and were analyzed for their factor production to define their growth requirements. The results indicate that cultivation in vitro leads to constitutive production of IL 2 and the capacity to respond to growth factors, thereby facilitating the continuous proliferation of T cells bearing the dull Lyt-1+2- phenotype in vitro in the absence of exogenous antigen or mitogen. These studies indicate that MRL-lpr/lpr T cells have the ability to produce IL 2 and to respond to IL 2 with long-term proliferation. In addition, the impaired responsiveness to Con A of fresh MRL-lpr/lpr lymph node T cells was found to be quite transitory, because even short-term culture allowed MRL lpr/lpr T cells to respond normally.