CD20+ Tumor-Infiltrating Lymphocytes Have an Atypical CD27− Memory Phenotype and Together with CD8+ T Cells Promote Favorable Prognosis in Ovarian Cancer

Abstract Purpose: Tumor-infiltrating lymphocytes (TIL), in particular CD8+ T cells and CD20+ B cells, are strongly associated with survival in ovarian cancer and other carcinomas. Although CD8+ TIL can mediate direct cytolytic activity against tumors, the role of CD20+ TIL is poorly understood. Here, we investigate the possible contributions of CD20+ TIL to humoral and cellular tumor immunity. Experimental Design: Tumor and serum specimens were obtained from patients with high-grade serous ovarian cancer. CD8+ and CD20+ TIL were analyzed by immunohistochemistry and flow cytometry. Immunoglobulin molecules were evaluated by DNA sequencing. Serum autoantibody responses to the tumor antigens p53 and NY-ESO-1 were measured by ELISA. Results: The vast majority of CD20+ TIL were antigen experienced, as evidenced by class-switching, somatic hypermutation, and oligoclonality, yet they failed to express the canonical memory marker CD27. CD20+ TIL showed no correlation with serum autoantibodies to p53 or NY-ESO-1. Instead, they colocalized with activated CD8+ TIL and expressed markers of antigen presentation, including MHC class I, MHC class II, CD40, CD80, and CD86. The presence of both CD20+ and CD8+ TIL correlated with increased patient survival compared with CD8+ TIL alone. Conclusions: In high-grade serous ovarian tumors, CD20+ TIL have an antigen–experienced but atypical CD27− memory B-cell phenotype. They are uncoupled from serum autoantibodies, express markers of antigen-presenting cells, and colocalize with CD8+ T cells. We propose that the association between CD20+ TIL and patient survival may reflect a supportive role in cytolytic immune responses. Clin Cancer Res; 18(12); 3281–92. ©2012 AACR.