The role of L3T4+ cells in the pathogenesis of lupus in lpr-bearing mice. I. Defects in the production of interleukins 2 and 3.

Mice which bear the lpr gene spontaneously develop autoimmune syndromes characterized by massive expansion of an unusual T cell subset which is phenotypically Thy-1+, L3T4-, Lyt-2-, B220+. The mutant T cells are refractory to stimulation with mitogenic lectins and, by implication, are thought to be solely responsible for the defects in lymphokine production manifested by lpr mice. The contribution of the remaining L3T4+ T cell subset to the latter derangements has not been previously examined and is the focus of this study. We found that abnormalities in concanavalin A-induced interleukin 2 and 3 production in the spleens of MRL-lpr/lpr and C57BL/6.lpr mice occurred in the presence of limited infiltration with B220+, L3T4- T cells. Mixing experiments indicated that B220+ T cells were not suppressive. Furthermore, lpr spleen cells enriched for L3T4+ cells and depleted of sIg+, B220+ and Lyt-2+ cells demonstrated reductions in lymphokine production which were comparable to those seen in unfractionated preparations. Spleen cells from C57BL/6.lpr mice, enriched for L3T4+ cells, were also markedly impaired in a mixed leukocyte reaction in response to stimulator cells from the class II major histocompatibility complex mutant bm12. The results indicate that the aberrations in lymphokine production and proliferation in the spleen cells of lpr mice involve not only B220+ T cells but also L3T4+ cells and suggest a potential role for the L3T4+ subset in the pathogenesis of lupus in lpr-bearing mice.