Tumor induction and immunity to
tumors were studied following the injection of Moloney sarcoma virus (MSV) into mice whose B-lymphocyte functions had been suppressed by the chronic administration of
anti-IgM antibodies. Two preparations of MSV were used; one which gives rise to
tumors which uniformly regress in normal adult mice, and another which elicits progressively growing
tumors in the majority of recipients. The
tumor incidence, mean
tumor size, and
tempo of regression were not modified by treatment with
anti-IgM. However, whereas
tumors induced by the regressor virus were all rejected in 19 NRG-treated and 29 untreated recipients, continued growth was obtained in 2 of 23 B-lymphocyte-deprived mice. Furthermore, in 9 additional mice from this group, apparent rejection was followed by
tumor recurrence at the site of the initial
tumor. Continued growth was accompanied by widespread
metastasis. These
tumors were freely transplantable to normal syngeneic recipients.
Metastasis and transplantability were also detected in 7 of 24
anti-IgM-treated mice given progressor virus, but were not seen in the control animals. Recurrence and
metastasis was obtained despite the presence of high levels of specific cytotoxic T lymphocytes in the spleen. It is concluded that B lymphocytes or their products play an essential role in host protection against MSV-induced
tumors.