Expression of blood group H antigen by normal, benign, and carcinoma cells of the oral epithelium: immunohistochemical study using monoclonal antibody RS13.

The H antigen was investigated by an indirect immunoperoxidase method in sections of 65 surgical specimens from the oral mucosa. These comprised 29 squamous cell carcinomas, 28 benign lesions, and 8 specimens of clinically healthy mucosa. A monoclonal antibody (RS13) was used to identify the H antigen. The peroxidase stain was positive at high dilutions of the antibody in the epithelium of normal mucosa, and the titers were significantly higher than those within benign lesions (p less than 0.001) and carcinomas (p less than 0.001). However, the titers in the benign lesions varied considerably, with two specimens recorded as negative. In contrast, the reaction for the H antigen was negative in 19 specimens (66%) of the malignant lesions and the endpoint titers of the H positive carcinomas indicated marked loss of the antigen. This loss was significant when compared to the benign lesions (p less than 0.001). The results show that the loss of the H antigen on malignant epithelial cells may be a valuable marker for primary squamous cell carcinoma.