Immunohistologic characterization of major histocompatibility antigens and inflammatory cellular infiltrate in human breast cancer.

The presence of major histocompatibility antigens [HLA-A,B,C; beta 2 microglobulin (beta 2)m; la-like] on tumor cells and the nature and distribution of mononuclear cellular infiltrates in benign and malignant human breast tumors were studied by the use of monoclonal antibodies and immunoperoxidase techniques on frozen tissue sections. Although all benign tumors expressed HLA-A,B,C or beta 2m, 20 of 53 primary breast cancers did not react with anti-HLA-A,B,C or anti-beta 2m antibodies. Expression of la-like antigens was rarely encountered on tumor cells. The intensity of the inflammatory mononuclear cellular response did not correlate with the expression of HLA-A,B,C or beta 2m by the tumor cells. Most of the mononuclear cells were identified as T-cells. T-cells with a cytotoxic-suppressor phenotype (T8+) were generally the predominant cell type among those found as single cells in the tumor stroma or invading tumor nests. However, infiltration of tumor nests by lymphocytes was infrequently seen and was usually limited to the periphery of the tumor. In contrast, lymphocytes with a helper-inducer phenotype (T4+, Leu-3a+) predominated in the lymphoid aggregates. Anti-Leu-7 (HNK-1) antibody, which reacts with natural killer cells, stained only a few mononuclear cells in the cellular infiltrate in most cases of breast cancer.