[Immunological evaluation of splenectomy in tumor-bearing mice]

The effect of splenectomy upon neoplastic outgrowth was examined after inoculation of methylcholanthrene-induced C3H/He murine tumors. Three days or 20 days after tumor inoculation, splenectomy resulted in significant retardation of tumor growth when compared with sham operation, while splenectomy 6, 9, 15 days after tumor inoculation did not alter the tumor outgrowth. These results suggest that spleen might have immunologically negative element in early or late stage of tumor burden. In fact, spleen cells from mice bearing MCA-F tumors for 3 days or 30 days nonspecifically facilitated the tumor outgrowth in Winn assay. The non-specific tumor-enhancing cells were radioresistant (700 rads), capable of phagocytizing carbonyl-iron and adherent to plastic dish suggesting those were tumor enhancing macrophages. On the other hand, spleen cells from tumor-bearing mice for 9 to 15 days specifically reduced the tumor growth in Winn assay, and those cytotoxic cells were radio-sensitive (700 rads) T cell population.