Immunologic aspects of fibrosis in mouse mammary carcinomas

The nature of the fibrosis associated with mammary carcinomas MC2 and MC3 was investigated in syngeneic C3H mice. Accelerated and enhanced peri-tumor cellular and fibrotic responses and retarded tumor growth were observed in actively immunized and in adoptively immunized mice, and in mice treated with IL-2. T lymphocytes and, particularly, macrophages were closely associated with collagen deposition at the tumors. The collagen deposition frequently resulted in the encapsulation and regression of the less invasive tumor MC2. A cellular fibrous response was not observed at tumors implanted into athymic C3Hnu/nu mice. The results suggest that tumor fibrosis may in some circumstances be promoted by an immune response.