RESUMO
Translation products in Xenopus laevis of mRNA from human peripheral blood mononuclear cells were tested for their capacity to replace T cells in the anti-SRBC response of nude spleen cells. When the starting material came from PHA or FCS-stimulated lymphocytes, the translated lymphokines, displaying such a B cell helper activity were found to be encoded by mRNA sedimenting at 6-7S and 13S on a sucrose density gradient. 6-7S mRNA from control, non-stimulated lymphocytes was also able to code for B cell helper activity. Thorough T-cell depletion of mouse responder cell populations left unchanged the activity of 6-7S mRNA products while preventing that of 13S products. The latter were found to contain IL-2, which suggests that their action on B cells was indirect, mediated by T-cell stimulation.