Enhancement of murine erythroid colony formation in the presence of activated T lymphocytes.

Erythroid colony formation was enhanced by treatment of mouse bone marrow cells with PHA prior to culture in diffusion chambers implanted into intact mice. Addition of PHA-pretreated thymocytes, lymph node lymphocytes, and spleen cells to untreated bone marrow cells also resulted in increased numbers of erythroid colonies in diffusion chambers but had no effect on myeloid colonies. PHA did not augment erythroid colony formation when bone marrow was depleted of Thy 1-bearing cells, although cells capable of erythroid differentiation were still present as judged by the response to erythropoietin. Furthermore, mixing of bone marrow depleted of Thy 1 + cells with PHA-treated thymocytes restored augmented erythroid colony formation. Lack of responsiveness of bone marrow cells to concanavalin A and pokeweed mitogen may indicate that a specific T cell subpopulation reacting with PHA is able to stimulate erythropoiesis. Note that addition of untreated thymocytes, lymph node lymphocytes, and spleen cells into cultures had no effect.