[Refractoriness of mouse spleen rosette-forming cells to thymus hormones during the period of early postnatal ontogeny].

The content of thymic serum factor in mice during the early postnatal ontogenesis is at the level characteristic of immunologically mature animals. Their spleen rosette-forming cells are, however, much less sensitive to antilymphocytic serum than those of adult animals. The sensitivity to the latter did not increase after incubation of splenocytes with thymosin or upon its multiple introduction to the neonatal mice. The results obtained suggest the refractoriness of the spleen rosette-forming cells to the thymic hormones during early postnatal ontogenesis.