The long-lasting clinical response by lymphoma patients to anti-CD20 therapy has been attributed to the induction of an anti-tumor adaptive immunity. We previously demonstrated that a CD4-dependent mechanism is responsible for the long-term protection of CD20(+) tumor-bearing mice by anti-CD20 treatment. Here, we compare tumor immunity in tumor-bearing animals that did or did not receive anti-CD20 treatment. Splenic CD4(+)FoxP3(+) regulatory T cells (Tregs) expanded substantially in untreated mice that exhibited then a reduced survival, whereas Tregs depletion led to long-term survival of the animals, suggesting the establishment of a Treg-dependent immunosuppressive environment after tumor injection. Strikingly, anti-CD20 therapy reversed the initial expansion of Tregs, and was accompanied by a marked increase in the number of Th1 cells, with no detectable change in Th2 and Th17 cell numbers. Interleukin-12 serum level was also increased by the anti-CD20 treatment, and activated myeloid dendritic cells producing interleukin-12 could be detected in lymph nodes of treated animals, while interferon-γ blockade strongly reduced survival. Also, CD4(+) effector memory T cells were evidenced in surviving animals, and the transfer of CD4(+) T cells induced long-term protection. Thus, anti-CD20 therapy promotes strong anti-tumor adaptive immunity, opposes Treg expansion and inhibits tumor cells from maintaining an immunosuppressive environment.
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Adaptive Immunity, Animals, Antibodies, Monoclonal, Murine-Derived, Antineoplastic Agents, CD4 Antigens, Cell Proliferation, Female, Forkhead Transcription Factors, Gene Expression Regulation, Leukemic, Immunologic Memory, Interferon-gamma, Interleukin-12, Lymph Nodes, Lymphoma, B-Cell, Mice, Mice, Inbred C57BL, Rituximab, Signal Transduction, Survival Analysis, T-Lymphocytes, Regulatory, Th1 Cells, Th17 Cells, Th2 Cells