Characterization of dextran-activated T-cell factors.

Dextran given to mice caused splenic T cells to elaborate factors in vitro which heightened normal splenic B- and T-cell responses to the mitogens LPS and Con A, respectively. Chromatographic separation of dextran-triggered spleen cell supernatants revealed two T cell-derived enhancing factors which affect T cells (TDEF-TI and TDEF-TII) and two that alter B cells (TDEF-BI and TDEF-BII). All appear to be proteinaceous because exposure to trypsin destroyed their activities. Furthermore, their presence was found to be dependent upon protein synthesis since cycloheximide treatment of the cells inhibited synthesis whereas mitomycin C treatment did not. Based on absorption studies, receptors for TDEF-TI and TII were detected on thymic cells as well as on O-deficient bone marrow cells, whereas receptors for TDEF-BI and BII were on bone marrow cells but not thymic cells.