Thymosin-induced differentiation of murine thymocytes in allogeneic mixed lymphocyte cultures.

Calf thymosin is shown to enhance the one-way MLR of CBA thymocytes cultured with allogeneic mitomycin-C- treated C57BL/J6 spleen cells. Thymosin does not enhance the one-way MLR of CBA thymocytes cultured with syngeneic mitomucin-C-treated spleen cells. Based on this finding we present a relatively simple, rapid and quantitative in vitro microculture hioassay for inducers of T-cell differentiation and propose that thymosin treatment, when accompanied by antigen presentation, induces the two-step maturational sequence of pre-T yields T1 yields T2.