Both untreated and neuraminidase-treated L 1210 cells stimu-lated proliferative activity of thymic lymphocytes in the BDF1 host. This T-cell activity was followed by the production of immunoglobulins by B-cells. While neuraminidase-treated cells did not grow in the normal host, they did cause progressive tumor growth in the immunosuppressed hosts. In addition, the humoral response to either untreated or neuraminidase-treated tumor cells was inhibited when mice were immunosuppressed with rabbit anti-mouse thymocyte serum. Immunosuppressed mice were not able to respond to a T-dependent antigen, sheep red blood cells, but were able to respond to lipopolysaccharide, a T-independent antigen. Neuraminidase-treated cells retained viability and redeposited sialic acid quickly after treatment with neuraminidase. The evi-dence indicates that competent T-cells were necessary for a humoral response to either untreated or VCN-treated tumor cells and that recognition of VCN-treated cells necessary for the production of a cytotoxic response occured within 4 to 5 hours after cells were injected
