Immunohistochemical study of mononuclear cell infiltrates in squamous cell carcinoma of oral cavity and paranasal sinus.

Serial frozen sections were prepared from 22 squamous cell carcinomas of oral cavity and paranasal sinus. Mononuclear cell infiltrates were stained by the biotin-avidin-horseradish peroxidase method using a panel of 10 mouse monoclonal antibodies to human leukocyte antigens. The degree of infiltration was graded from + + + (marked) to - (absent). The infiltration of anti-Leu-4-reactive cells (Leu-4+ cells) was grade + + or + + + in 14 of 22 cases. In 13 of 22 cases, infiltration of Leu-3a + 3b+ cells (helper/inducer T lymphocytes) was grade + + (moderate). In 5 of 20 cases, infiltration of Leu-2a+ cells (cytotoxic/suppressor T lymphocytes) was grade + +. As for B lymphocytes, infiltration of Leu-12+ cells was grade + + in only 2 of 19 cases. In conclusion, T lymphocyte infiltrates were commonly seen in squamous cell carcinoma in oral cavity and paranasal sinus and the number of patients with grade + + infiltration of helper/inducer T lymphocytes significantly predominated over that of patients with infiltration of cytotoxic/suppressor T lymphocytes grade + +.