Immunohistologic study of mononuclear cell infiltrates in oral squamous cell carcinomas.

Intensity of mononuclear cell infiltrates in 50 oral cancer tissues was evaluated by immunohistochemical stainings. The intensity of the infiltrates was graded into four degrees from marked ( ) to absent (-); and the degree of each infiltrated lymphocyte subpopulation including Leu-3a3b/Leu-2a ratio was matched against clinical and histopathologic features. The vast majority of the infiltrated lymphocytes had antigens which were reactive with anti-T cell antibodies. In T cell subsets, Leu-3a3b+ cells infiltrated clearly (grade ++ or ) in 44 cases, and infiltration greater than grade ++ of Leu-2a+ cells was found in nearly half of the cases (26 of 50). In contrast, B cells (Leu-14+ cells) were obviously detectable in only a few cases, and moderate or marked infiltration of the natural killer (NK) population (Leu-11b+ cells) was not observed. Regarding correlation of T cell infiltrates with clinicopathologic features of the tumors, the degrees of Leu-4+ cell and Leu-2a+ cell infiltration became weak with advancing T stage. Leu-2a+ cells also infiltrated weakly into diffusely invading tumors. Out of 28 cases with no metastasis, 22 cases (78.6%) showed grade ++ approximately of Leu-2a+ cells, and only 4 (18.2%) of 22 cases with lymph node metastasis were clearly positive for Leu-2a+ cells (p less than 0.001). However, Leu-3a3b+ cell infiltration was only slightly related to T stage, metastasis, and to mode of invasion. Therefore, the Leu-3a3b/Leu-2a ratio increased significantly in advanced (T3 + T4) tumors, metastasized cases, or diffuse invasion type.