Tumor neutralization by immune in vitro-sensitized splenocytes depends on an interaction with bone-marrow-derived...

In a Winn assay, the inhibition of methylcholantherene-induced sarcoma growth by tumor-immune, secondarily in vitro-sensitized splenocytes was augmented by normal unsensitized bone-marrow cells. Bone-marrow cells augmented the effect of a fixed number of sensitized splenocytes in a dose-dependent manner, yet had no tumor-neutralizing capacity by themselves. The marrow's capacity to enhance tumor neutralization was not shared by normal splenocytes, thymocytes or lymph node cells. When two non-cross-reacting tumors were used, marrow cells were capable of augmenting tumor neutralization only if admixed with sensitized splenocytes and the sensitizing neoplasm. Equal numbers of bone-marrow cells administered intravenously to recipients of an admixture of sensitized splenocytes and tumour were unable to augment neutralization, suggesting a direct interaction between sensitized lymphocytes and normal bone-marrow cells in the inhibition of tumor growth.