Lymphocyte infiltrates have been observed in the microenvironment of oral cancer; however, little is known about whether the immune response of the lymphocyte infiltrate affects tumor biology. For a deeper understanding of the role of the infiltrating-lymphocytes in oral squamous cell carcinoma (OSCC), we characterized the lymphocyte infiltrate repertoires and defined their features. Immunohistochemistry revealed considerable T and B cell infiltrates and lymphoid follicles with germinal center-like structures within the tumor microenvironment. Flow cytometry demonstrated that populations of antigen-experienced CD4+ and CD8+ cells were present, as well as an enrichment of regulatory T cells; and T cells expressing programmed death-1 (PD-1) and T cell Ig and mucin protein-3 (Tim-3), indicative of exhaustion, within the tumor microenvironment. Characterization of tumor-infiltrating B cells revealed clear evidence of antigen exposure, in that the cardinal features of an antigen-driven B cell response were present, including somatic mutation, clonal expansion, intraclonal variation and isotype switching. Collectively, our results point to an adaptive immune response occurring within the OSCC microenvironment, which may be sustained by the expression of specific antigens in the tumor.What's new?
In many cancers, the types and ratios of T cells and B cells within a tumor correlate with prognosis. They may also affect potential immunotherapies. Some tumor-infiltrating lymphocytes (TILs) can suppress the anti-tumor response, while others enhance it. In this study, the authors extensively analyzed TILs in oral squamous cell carcinoma (OSCC) tumors. They found evidence of a tumor-specific immune response among both the T and B cells within these tumors. These results may help researchers develop immune-related therapies for oral cancers.