Expression of T cell suppressor activity in the immune response of newborn mice to a T-independent synthetic polypeptide.

One and two day old mice responded to the T-independent synthetic polypeptide poly (DTyr,DGlu)-poly(DPro)--poly(DLys) with high antibody production, whereas a dramatic decrease was observed in the immune response of 3 day old injected animals. The presence and expression of suppressor T cells in the 3 day old newborn mice spleens was demonstrated by transferring spleens of 3 day old mice into either thymectomized, irradiated recipients together with bone-marrow cells, or into 1--2 day old newborn recipients. In both cases a significantly lower antibody response was observed in recipients of the 3 day old newborn spleen cells as compared to recipients of the same number of adult spleen cells. No decrease in the antibody levels was detected following inoculation of 3 day old spleen cells after anti-theta-treatment, while enriched T cell populations obtained from nylon wool columns had the same suppressive effect as the whole spleen cell preparations. Thus, the cell expressing the suppressor activity in the newborn spleen is a T cell.