Factors regulating yolk sac hematopoiesis in diffusion chambers: various types of sera, cyclophosphamide, irradiation and long-term culture.

A series of studies were conducted using suspensions of murine 10 1/2 day yolk sac cells, cultured in diffusion chambers (DC), to evaluate the effects of several variables on cell growth and differentiation. The variables evaluated were: treatment of chamber recipients with cyclophosphamide (Cy) or sublethal total body irradiation (TBI), culture medium supplementation with different sera, and long-term culture. The growth of cells in Cy- and TBI-groups was parallel to that of the control group (C) until day 7 of culture. Thereafter, cells in the chambers of each group proliferated at a different rate. Whereas, cell growth in Cy-hosts was significantly greater than in C-hosts, growth of TBI-hosts was less than that in C-hosts. Horse serum supported chamber cellularity better than syngeneic mouse serum or fetal calf serum. Long-term cultures showed an increase in cell numbers until day 56, followed by a steady decrease to day 70, reaching a new level that was maintained until day 98. By day 14 of culture, and throughout the long-term culture study, there was no difference in the pattern of differentiation of DC cultured yolk sac cells. Regardless of the type of host treatment or culture medium the cells harvested were macrophages, plasma cells and lymphocytes.