DUOX1 regulates primary B cell function under the influence of IL-4 through BCR-mediated generation of hydrogen peroxide

Engagement of the BCR with Ags triggers signaling pathways for commitment of B lymphocyte responses that can be regulated, in part, by reactive oxygen species. To investigate the functional relevance of reactive oxygen species produced in primary B cells, we focused on the role of the hydrogen peroxide generator Duox1 in stimulated splenic B cells under the influence of the T _H 2 cytokine IL-4. We found that H ₂ O ₂ production in wild type (WT) and Nox2-deficient CD19 ⁺ B cells was boosted concomitantly with enhanced expression of Duox1 following costimulation with BCR agonists together with IL-4, whereas stimulated Duox1 ² / ² cells showed attenuated H ₂ O ₂ release. We examined whether Duox1-derived H ₂ O ₂ contributes to proliferative activity and Ig isotype production in CD19 ⁺ cells upon BCR stimulation. Duox1 ² / ² CD19 ⁺ B cells showed normal responses of Ig production but a higher rate of proliferation than WT or Nox2-deficient cells. Furthermore, we demonstrated that the H ₂ O ₂ scavenger catalase mimics the effect of Duox1 deficiency by enhancing proliferation of WT CD19 ⁺ B cells in vitro. Results from immunized mice reflected the in vitro observations: T cell–independent Ag induced increased B cell expansion in germinal centers from Duox1 ² / ² mice relative to WT and Nox2 ² / ² mice, whereas immunization with T cell–dependent or –independent Ag elicited normal Ig isotype secretion in the Duox1 mutant mice. These observations, obtained both by in vitro and in vivo approaches, strongly suggest that Duox1-derived hydrogen peroxide negatively regulates proliferative activity but not Ig isotype production in primary splenic CD19 ⁺ B cells. The Journal of Immunology, 2019, 202: 428–440.