Culture fluids from five muminesarcomas were chemotac tic for syngeneic penitoneal macnophages in vitro. Penito neal macmophages from mice infected with Mycobacterium bovis, strain Bacillus Ca!mette-Guérin,were more respon

Culture fluids from five muminesarcomas were chemotac tic for syngeneic penitoneal macnophages in vitro. Penito neal macmophages from mice infected with Mycobacterium bovis, strain Bacillus Ca!mette-Guérin,were more respon sive to the chemotactic factor in tumor cultures than were normal macnophages. Penitoneal gran ulocytes, however, did not significantly respond to this factor. The level of chemotactic activity in tumor cultures paralleled cell growth for all five tumors; maximal levels occurred during log growth. Culture medium alone on fluids from proliferating spleen cell cultures stimulated with mitogens did not have detectable chemotactic activity. Chromatography of the tu momculture fluids resulted in a single peak of chemotactic activity in the i5,000-moleculam weight mangeon Sephadex G-iOO and at about 7.5 mmho/cm specific conductance on diethylaminoethyl cellulose. By both biological and physi cochemical characteristics, the chemotactic activity in tu mon culture fluids was different from mouse lymphocyte derived chemotactic factor.