Culture supernatants of a stimulated T-cell line have helper activity that acts synergistically with interleukin 2 in the response of B cells to antigen.

Abstract

Culture supernatants of an antigen-stimulated long-term alloreactive [mouse] T cell line, C.C3.11.75, contain a T cell-replacing factor (TRF) activity for the B cell response to antigen. These same supernatants show little activity in the T cell growth assay or the costimulator assay. TRF activity was assayed by using spleen cells that were rigorously depleted of T cells and macrophages. In this assay, preparations containing interleukin 2 and supernatants from stimulated C.C3.11.75 cells are relatively inactive if added alone but show marked synergy when added together. The C.C3.11.75 TRF activity apparently is not due to interleukin 1 or to interleukin 2 but to a 3rd factor provisionally designated as (DL)TRF. This activity may be equivalent to the (late-acting) TRF described by Schimpl and Wecker. The helper activity (DL)TRF is probably a product of the T cell line.