Enhanced immunosuppressive activity associated with metastatic lymphoma cells.

Earlier reports from our laboratory showed that Abelson virus-induced, highly malignant and liver metastatic RAW117-H10 cells, but not the parental, less metastatic RAW117-P cells, inhibited both T-cell and B-cell mitogen-induced proliferation of syngeneic normal murine spleen cells. Similar inhibition was also noted when RAW117-H10 cell surface molecules extracted with butanol were used instead of whole tumor cells. In this report we describe the suppressive properties of the butanol-extracted RAW117-H10 cell surface molecules on other immune functions and the isolation/purification of a molecule from RAW117-H10 cell butanol extract which shows inhibitory activity. The immunosuppressive molecules also inhibit natural killer cell-mediated cytotoxicity, lymphokine-activated killer cell-mediated cytotoxicity, and bone marrow colony-forming unit-granulocyte-macrophage colony formation, but not colony-forming unit-fibroblast colony formation. The suppressive molecules inhibit interleukin 2 production by the T-lymphocytes. One of the molecules responsible for some of the immunosuppressive activity has been isolated and purified from butanol extracts of the metastatic RAW117-H10 cells by preparative isoelectrofocusing techniques. The suppressive molecule has an isoelectric point of 4.3 with an approximate molecular weight of 70,000. Metastatic RAW117-H10 lymphoma cells therefore express immunosuppressive molecules, which may facilitate their growth and metastasis in vivo.