A new T cell subset expressing B220 and CD4 in lpr mice: defects in the response to mitogens and in the production of IL-2.

Autoimmune-prone mice homozygous for the lpr gene develop prominent lymphadenopathy composed mainly of Thy-1+ CD8- CD4- B220+ cells. Expression patterns of B220 vs CD4 on lymph node cells from lpr mice were analysed using two-colour flow microfluorometry. B220+CD4+ cells, which were hardly seen in lymph nodes of B6-+/+ mice, increased significantly in B6-lpr mice with ageing. Functional analysis of purified B220+ CD4+ cells from lpr mice revealed that these cells scarcely responded to T cell mitogens with or without rIL-2. Furthermore, B220+ CD4+ cells were defective in IL-2 production when cultured with Con A. On the other hand, B220-CD4+ cells from B6-lpr mice showed an ability to respond to T cell mitogens similar to that of B220- CD4+ cells from B6-+/+ mice. These results indicate that an unusual T cell subset expressing both B220 and CD4 in lpr mice is functionally defective, but the intrinsic ability of B220-CD4+ cells is almost intact as compared with the counterpart in normal mice.