Abstract
Ascites tumor cells (2 X 10(6] of a DMBA-induced rat mammary adenocarcinoma (HH9-cl 14) were injected s.c. into tumor-free syngeneic female rats and produced a continuously growing solid tumor in all animals of this group. Inoculation of 2 X 10(7) cells induced a first brief period of tumor growth, followed by complete tumor regression from the 2nd until the 5th week after injection. Both the progressive and the regressive tumors were analyzed immunohistologically at different stages with monoclonal antibodies against different T lymphocytes and macrophages. Obviously these cells appear in different quantity and quality, during the hosts immune response. Possible interactions of T lymphocytes and macrophages with tumor cells are discussed.