[Effect of a factor inhibiting hematopoietic cells on the development of the immune response].

Thymus cells from syngeneic donors treated in vitro with antilymphocyte globulin release into the medium a soluble hemopoietic stem cell inhibitory factor (SCIF). It has been found that SCIF inhibits the immune response to sheep red blood cells in the adoptive immunity system. Primarily affected by SCIF are the mature progenitors of B cells whose ability cooperate with T lymphocytes seems to be impaired. The role of lymphokines in the induction of the immune response is discussed.