Infiltrating mononuclear cells in human breast carcinoma: Predominance of T4+ monocytic cells in the tumor stroma

Frozen sections of 52 breast carcinomas were examined for the presence and nature of a leukocytic infiltrate. The number of “common leukocyte (T200‐) antigen”‐bearing cells was remarkably high in the stromal compartment of the carcinomas, whereas the tumor foci themselves were usually infiltrated only sparsely. Approximately 80% of these T200+ stromal cells carried the myelomonocyte lineage‐associated antigens M‐M522 and 63D3 and exhibited “non‐specific esterase” activity. More than 2/3 of the stromal monocytic cells expressed the T4 antigen as verified by monoclonal antibodies (MAbs) directed against different T4‐associated epitopes. A T‐cell analysis showed that T4+ cells clearly outweighed the total number of T cells as defined by anti‐T3 and anti‐TII antibodies. In addition, a correlation became apparent between the HLA‐DR phenotype and the T lymphocyte content of tumor cell areas in the sense that densely infiltrated tumor areas were invariably HLA‐DR+.