(A) Bone marrow–derived macrophages (BMDMs) were incubated with B cells and/or neutrophils, or alone in the presence of 100 ng/mL LPS for 12 hours and 1 μg/mL monensin, a Golgi blocker, for the last 4 hours. Intracellular IL-10 and TNF-α of F4/80⁺ macrophages were detected by flow cytometry. NS, normal saline. (B) Freshly isolated neutrophils were labeled with CMFDA and cultured with B cells or alone for 12 hours. Efferocytosis assay was conducted by adding CMFDA-labeled neutrophils cocultured with or without B cells to BMDMs for 60 minutes, as described in the Methods. The percentage of BMDMs phagocytosing CMFDA-labeled neutrophils was quantified using flow cytometric analysis. (C) Confocal microscopy images show Alexa Fluor 563–conjugated phalloidin–labeled macrophages phagocytosing CMFDA-labeled neutrophils (n = 4 per group). Scale bars: 5 μm. (D) Freshly isolated neutrophils were cocultured for 12 hours with B cells or alone. In 1 group, B cells were also cocultured in Transwells. During coculture, cells were treated with 100 ng/mL LPS or vehicle. The percentage of apoptotic CD19^–Ly6G⁺ neutrophils was determined by flow cytometry. (E) Representative images of immunofluorescent staining show the interaction between Ly6G⁺ neutrophils and CD19⁺ B cells in heart sections of mice 3 days after myocardial I/R (n = 5). Scale bar: 50 μm. (F) The neutrophils from the heart of B cell–depleted and control mice subjected to myocardial I/R were analyzed for annexin V and PI staining. The percentage of annexin V⁺ neutrophils was quantified. The experiments were independently replicated twice. Data are presented as mean ± SEM. *P < 0.05; **P < 0.01; ****P < 0.0001 by 1-way ANOVA test followed by Tukey’s post hoc test (A, B, and D); differences between 2 groups were compared by unpaired, 2-tailed t test (F). BD, B cell depletion; FMO, fluorescence minus one; I/R, ischemia and reperfusion.