Significance of Macrophage Subtypes in the Peripheral Blood of Children with Systemic Juvenile Idiopathic Arthritis

INTRODUCTION: Symptomatic juvenile idiopathic arthritis (sJIA) is an autoinflammatory disease, and monocytes/macrophages play an important role. However, which macrophage subtype plays a major role in different stages of sJIA is still unclear. This study aimed to explore macrophage subtypes in different stages of sJIA. METHODS: Twenty-two children with sJIA who were followed up at Shanghai Children’s Hospital from January 2018 to December 2020 were enrolled in this study. sJIA children were divided into an activity group (n = 12) and an inactivity group (n = 10). In the activity group, subjects with newly diagnosed sJIA and untreated were included; in the inactivity group, subjects with inactive sJIA meeting the 2011 ACR criteria for sJIA were recruited. Ten children with orthostatic proteinuria served as controls. Peripheral blood was collected. Flow cytometry was performed to detect macrophage subtypes: M1 (CD14(+)CD86(+)CD80(+)), M2a (CD14(+)CD206(+)CD301(+)), M2b (CD14(+)CD206(+)CD86(+)) and M2c (CD14(+)CD206(+)CD163(+)), and the contents of cytokines were also examined, including interleukins (IL) (IL-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10 and IL-17), interferon-α, interferon-γ, and tumor necrosis-α. RESULTS: M1 marker CD80 and M2 marker CD163, CD301 were highly expressed in children with active sJIA. The majority of macrophages were M1 and M2a in the activity group (P < 0.05). In the inactivity group, M2 tended to polarize into M2b and M2c (P < 0.05). IL-6 significantly increased in the activity group (P < 0.05), while IL-10, IL-4 and IL-17 markedly increased in the inactivity group (P < 0.05). CONCLUSIONS: In the active sJIA, M1 activation promotes inflammation, while M2a rapidly responds to inhibit inflammation; in the inactive sJIA, M2b and M2c play a major role in inhibiting inflammation.