Tumour metastasis in mice with reduced immune reactivity. I. Studies with two MCA‐induced sarcomas in radiation and thymectomized radiation C57BL/6J chimeras

Spontaneous metastasis formation from two MCA‐induced sarcomas with different degrees of antigenicity was studied in radiation and thymectomized radiation C57BL/6J chimeras. The immune reactivity of the thymectomized chimeras was tested with one of the tumours and it disclosed no specific immune response. Tumour growth was decreased in the chimeras. Spontaneous metastasis formation was not influenced in either of the tumours by the immune suppressive treatment. The results could mean that immune factors have no influence on metastasis formation in the two systems tested, or that the immune suppressive treatment might not have influenced an interplay between presumed facilitating and inhibiting immune factors.