Rituximab and Immune Molecule Modulation in Burkitt’s Lymphoma Cell Lines

Objectives: Burkitt’s lymphoma is an aggressive B cell malignancy that is associated with EBV infection. The monoclonal antibody rituximab is used to treat many B cell malignancies, including Burkitt’s lymphoma. Studying immune molecule modulation in Burkitt’s lymphoma allows insight on developing new or refining existing immunotherapy agents for refractory or chemotherapy-resistant patients. The main purpose of this study was to explore rituximab’s impact on expression of immune molecules associated with immune activation or immune inhibition. Methods: Burkitt’s lymphoma cell lines Raji, Ramos, Bjab, and an EBV-transformed B cell line, COX, were cultured and treated with an optimally-determined concentration of rituximab or human IgG for 24 hours. Immune modulation was determined by flow cytometric analysis of HLA-I, HLA-DR, PD-L1, and CD40. Three experiments were conducted for Raji, Ramos, Bjab, while 2 experiments were conducted for COX. Results: Treatment of cells with rituximab, 10 µg/ml, completed downregulated CD20 expression and modulated expression of immune molecules. Compared to human IgG control, rituximab treatment decreased HLA-1, HLA-DR and CD40 expression on all cell lines, but significantly only for HLA-I on Bjab. Interestingly, the immune inhibitor PD-L1 was decreased on EBV-positive COX and Raji, but increased on EBV-negative Ramos and Bjab. Conclusion: Downregulation of HLA-I could contribute to an immune escape mechanism. As this was a small study, there is limited transferability of the results to the clinical setting and further experiments are needed.