Effect of Anti - lL - 3 Antibody on TC - 1 CM Stimulated

We reported previously that a cell line (TC-1 ) derived from adherent marrow cells produced colony-stimulating factor 1 (CSF-1 ) and a separate activity that acts synergistically with CSF-1 to stimulate giant macrophage colonies. We now report that an activity in TC-1 conditioned media (CM) separate from CSF-1 also synergizes multilineage colony formation by pure interleukin 3 (IL 3) and a crude source of granulocyte-macrophage colony-stimulating activity (GMCSA) (murine lung-conditioned media). IL 3-induced megakaryocyte colony formation is also synergized. The CSF-1 -dependent synergistic activity is not blocked by antibodies to IL 3 and is characterized as a nondialyzable (mol wt cutoff 3.000). heat-stable (56 ‘C. 30’) activity that binds to DE-52 cellulose under conditions in which IL 3 does