[Immunohistochemical study on the MHC class I antigen expression on squamous cell carcinoma of the uterine cervix]

Immunohistological analysis was performed to detect MHC Class I antigen expression on uterine cervical squamous cell carcinomas of 23 patients using a monoclonal antibody (W6/32) to recognize a monomorphic determinant of HLA-ABC and an antibody (MA2.2) to react only with cells typed as HLA-A2. The results were as follows. 1. In 2 of 23 cases examined, cancer cells lacked reactivity with W6/32, although normal epithelial cells and connective stromal cells surrounding cancer nests were clearly positive for the antibody in all cases. 2. Of the remaining 21 cases, fourteen cases were judged to be HLA-A2 positive, based on the obvious staining of the stromal cells with MA2.2. Of these 14 only 5 carcinomas were positive for HLA-A2, and the cancer cells in the other 9 cases failed to bind MA2.2. These data suggest that in most clinically diagnosed patients, cancer cells do not have their own MHC Class I products on their cell surfaces phenotypically, and this unique property may be related to the biological characteristic that permits cancer cells to survive and proliferate unrestrictedly in vivo, mainly escaping from the immune-surveillance system under cytotoxic T lymphocytes (CTLs), which need to recognize not only cancer-specific (associated) antigen(s) but also the self-MHC Class I products to kill the cancer cells efficiently.