Abstract 5596: TNFα production by myeloid DCs in response to rituximab induces monocyte and NK cell proliferation and survival

Abstract

Abstract Background: Rituximab is a central component of chemoimmunotherapy for B cell lymphomas. With over two decades in clinical use, new insights into its mechanisms of action continue to emerge. Rituximab infusion into patients results in elevated levels of TNFα in patient sera. However, our understanding of the mechanism of TNFα production in the context of rituximab and its role in anti-tumor immunity remain limited. In our study, we sought to determine the major producers of TNFα following rituximab treatment and the effect of rituximab-induced TNFα on anti-tumor effector cells. Methods: Peripheral blood mononuclear cells (PBMCs) from normal donors were cocultured in vitro with CD20-expressing Raji cells for 1 to 7 days. The coculture was treated with rituximab or non-specific antibody trastuzumab. Recombinant TNFα or TNFα blocking antibody infliximab were used to test the effect of TNFα in the rituximab- or trastuzumab-treated coculture system. ELISA was used to evaluate TNFα production in culture supernatant. Multicolor flow cytometry was used to evaluate for phenotypic and functional changes with TNFα treatment or blockade in various immune cell populations. Results: TNFα was robustly produced by PBMCs when treated with rituximab. This production was mediated by the Fc portion of rituximab antibody, as rituximab Fab elicited very little if any TNFα response from PBMCs. Myeloid dendritic cells (HLA-DR+CD123-CD11c+) were the key producers of TNFα in response to rituximab. In the absence of antibody therapy, recombinant TNFα treatment induced proliferation and survival of two major effector cells in the peripheral blood: monocytes and NK cells as determined by cell count and percent of Ki67+ cells. TNFα blockade using infliximab inhibited monocyte and NK cell proliferation and survival. TNFα blockade also protected Raji cells from rituximab-mediated killing. Conclusions: Rituximab-induced TNFα production promotes the proliferation and survival of monocytes and NK cells. Myeloid dendritic cells are necessary for TNFα production in this context. These results highlight the complexity of the immune response to rituximab treatment. Additional studies are ongoing exploring the role TNFa plays in the therapeutic response to rituximab. Citation Format: Nanmeng Yu, George J. Weiner. TNFα production by myeloid DCs in response to rituximab induces monocyte and NK cell proliferation and survival [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5596.