Possible involvement of IL-6-producing tissue-resident macrophages in early-onset pericardial effusion pathogenesis after hematopoietic stem cell transplantation.

PURPOSE: Pericardial effusion (PE) is a potentially life-threatening complication following hematopoietic stem cell transplantation (HCT). A higher incidence of early-onset PE, unrelated to graft-versus-host disease, before day 100 after HCT has been reported in pediatric patients, but the pathogenic mechanism is poorly understood. Aiming to determine the pathogenesis of early-onset PE in pediatric patients, we analyzed the cytokine concentration and cell population in the pericardial fluid of four pediatric patients with PE. METHODS: Between January 2009 and December 2015, four patients requiring pericardiocentesis for clinically significant PE were identified in 60 patients. We evaluated the interleukin-6 (IL-6), interferon-γ, IL-1ß, and tumor necrosis factor-α levels in PE. Two patients were available for analysis with intracellular cytokine flow cytometry and a chimerism assay. RESULTS: All patients showed the accumulation of pericardial macrophages and high concentrations of IL-6 in PE. Notably, the accumulated pericardial macrophages were CD163+ CD15+ CD14+ cells of host origin that produced IL-6. CONCLUSION: These IL-6-producing tissue-resident macrophages may be key players in the pathogenesis of early-onset PE.