Plasma cell infiltrate of the primary tumor as a source of early systemic protection against metastases in mice.

Histologic examination of sc implants of the syngeneic C3H/He mammary carcinoma MC2 showed that the accumulation of a large number of lymphoid cells in the stroma around the implants in C3H/He mice was a constant feature of the early primary host response. This stromal reaction had two main components, the first composed of small lymphocytes and the second composed of larger blast cells with a high proportion of plasma cells. The surgical removal of a 6-day-old tumor implant with its surrounding stromal reaction, if performed 4 days before systemic dissemination of MC2 cells via injection into the left ventricle, resulted in a more frequent growth of the disseminated cells as compared to the frequency of growth in mice carrying their tumor implants. This increased frequency of growth in surgically cured mice could be reduced by repeated transfusions of plasma from MC2-bearing hosts. Repeated ip injections of antigen, in the form of 2 X 10(5) inactivated tumor cells after tumor excision, did not support the development of strong systemic resistance against metastases. When sublethal whole-body radiation was given before the sc tumor implant, the stromal reaction was much reduced, and the surgical removal of sc tumor implants from irradiated mice resulted in only a minor increase in the growth of tumor cells injected into the circulation compared to the growth of tumor cells injected into irradiated mice carrying their tumor implants. It appears that a strong, local primary immune reaction may act as a temporary accessory lymphoid organ, constituting an early and potent source of systemic immune protective factors.