Colony-stimulating activity in cultures of human spleen and bone marrow cells.

We found that human bone marrow cells formed mononuclear phagocyte clusters and colonies in liquid culture with or without conditioned medium. In this study, we prepared media from human spleen or bone marrow cells in several different conditions and assessed their colony-stimulating activities as well as the sensitivities of human spleen or bone marrow colony-forming cells to these conditioned media. Conditioned media from human spleen cell cultures showed distinct cluster-stimulating activity to human bone marrow cells but those from human bone marrow cell cultures did not. On the other hand, conditioned media from human spleen cell cultures showed distinct colony-inhibiting rather than -stimulating activity to human spleen cells with high plating efficiency (11-350/4 X 106) compared with those from human bone marrow cell cultures. To human spleen cells with low plating efficiency (1-10/4 X106 ), conditioned media from human bone marrow cell cultures showed distinct c1usterstimulating activity compared with those from human spleen cell cultures. Running Head: Colony-stimulating activity of human spleen and bone marrow cells