Preliminary chemical and biologic characterization of (Fc)TRF: an Fc fragment-induced T cell-replacing factor

Fc fragment stimulation of Lyt-1+2- T lymphocytes triggers release of a T cell-replacing factor, here called (Fc)TRF. Chemical and biologic characterization of (Fc)TRF has been undertaken to provide information for its comparison with other T cell factors. Preliminary chemical characterization by column chromatography and isoelectric focusing suggest (Fc)TRF activity resides in a class of acidic molecules that fall into two size classes of 58-60,000 daltons and 35-40,000 daltons. This factor is distinct from Interleukin 2 (IL 2) as it has no T cell growth-promoting or costimulator activity, although it can also be generated by Con A activation of murine spleen cells. By these results (Fc)TRF has been defined as a unique T cell-replacing activity that promotes differentiation of B lymphocytes to antibody-secreting cells.