HUMAN HYBRIDOMA-DERIVED SUPPRESSOR FACTOR-160 AND TRANSFORMING GROWTH-FACTOR-BETA ARE DIFFERENT MOLECULES

We have previously identified a suppressor factor (SF), designated 160 constitutively produced by human T-T-cell hybridomas generated by fus ing Con A-activated human peripheral blood lymphocytes from a normal d onor with cells of the Jurkat tumor T-cell line (Hybridoma 8:127-151, 1989). The 160 SF inhibited in vitro proliferative responses to polycl onal activators and allogeneic cells, and immunoglobulin synthesis and secretion of human and mouse lymphocytes. We investigated whether the hybridoma-derived 160 SF and transforming growth factor-beta (TGF-bet a) are distinct molecules. TGF-beta has been shown to inhibit a number of lymphocyte responses. In agreement with our previous findings, the 160 SF abrogated the proliferative responses of human peripheral bloo d mononuclear cells (PBMC) to mitogens and allogeneic cells in mixed l ymphocyte culture. In contrast, TGF-beta, added to the PBMC cultures a t the same time with the mitogen or the stimulating allogeneic cells, had no effect on the proliferative response. Acid treatment of the 160 SF completely abolished the 160 SF activity. In contrast, this treatm ent results in activation of the latent TGF-beta form to the active fo rm, and acidification does not affect the function of existing active TGF-beta. A polyclonal anti-TGF-beta antibody did not detect TGF-beta by Western blotting in concentrated (10x) 160 SF preparations. In addi tion, the 160 SF did not induce the anchorage-independent growth of NR K fibroblasts in the presence of EGF.TGF-beta at concentrations as low as 1 ng/ml, in the presence of EGF, induced the anchorage-independent growth of the anchorage-dependent indicator NRK cells. These methods of detection of TGF-beta are sufficiently sensitive to detect less tha n 1 ng/ml of TGF-beta. These results demonstrate that the 160 SF and T GF-beta are clearly different molecules with different structural and functional properties.