Regulation of in-vivo differentiation of myeloid leukemic cells by antigen-specific helper T lymphocytes

There are clones of myeloid leukemic cells that can be induced to differentiate in vitro and in vivo by normal macrophage and granulocyte differentiation-inducing protein MGI-2 (= DF). The differentiation of these myeloid leukemic cells in vivo is regulated by a cell mediated immune response which requires T lymphocytes. We now show that differentiation of myeloid cells in vivo can be induced by antigen-specific helper T lymphocytes and that this is associated with the ability of the helper T cells to produce myeloid cell differentiation-inducing protein MGI-2. Antigen specific helper T cells can accumulate at a site that contains the antigen. It is suggested that migration in response to antigen of helper T cells producing differentiation factors may play an important role in inducing in vivo differentiation of leukemic cells.