Immunoregulatory activity of cell-free peritoneal washings of mice with Ehrlich ascitic carcinoma

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Abstract
Cell-free peritoneal washings (PW) were collected from mice with Ehrlich ascitic carcinoma at various time intervals after tumor transplantation and tested on the immunosuppressive activity in vitro. Two assays were used: (1) stimulation of human peripheral blood lymphocytes by phytohemagglutinin (PHA) and (2) inhibition of human leukocyte migration with PPD. Fluids collected in the early phase of tumor growth (up to day 6) were ineffective, or weakly suppressive, and those collected in advanced and terminal stages of carcinoma development, were suppressive in both tests applied. Control cell-free peritoneal washings obtained from normal mice without the tumor exerted suppressive activity when adjusted to the same protein concentration as the PW from mice with Ehrlich carcinoma. This suggests that host's cells in tumor-bearing animals, rather than tumor cells themselves, may be responsible for the production of inhibitory substance(s). Cell-free peritoneal washings were also tested on their ability to influence the growth of Ehrlich carcinoma cells in vitro, as measured by3H-thymidine incorporation. Samples collected from mice with advanced tumors stimulated the growth of tumor cells.