Reduced Circulating Regulatory T Cells in Autoimmune and Chronic Idiopathic Neutropenia of Childhood: An Observational Study of Clinical and Laboratory Associations.

OBJECTIVES: To investigate circulating regulatory T cells (Tregs) in children with autoimmune neutropenia (AIN) and chronic idiopathic neutropenia (CIN) and evaluate their associations with clinical and laboratory features of neutropenia. METHODS: Plasma and Peripheral Blood Mononuclear Cells (PBMCs) were collected from 69 participants. Anti-neutrophil antibody testing included flow cytometry Granulocyte Immunofluorescence Testing (fGIFT) and Granulocyte Agglutination Testing (GAT). Subjects were classified as AIN upon positive assays (n = 40), CIN upon negative assays (n = 19), and controls healthy children (n = 10). Personal history, infection susceptibility, and laboratory tests were recorded. Tregs were measured through flow cytometry, while FOXP3 expression was measured through Western blot. RESULTS: Tregs percentages (Tregs%) and absolute values were significantly lower among AIN and CIN than controls (Tregs%: p < 0.01 for AIN CIN, Tregs: p < 0.01 for AIN, p = 0.01 for CIN- Mann- Whitney U test). FOXP3 expression was maintained. Tregs were analogous with white blood cells (ρ = 0.43, p < 0.01 Spearman's) and lymphocytes (ρ = 0.42, p < 0.01) among children with AIN, while Tregs levels were associated infection severity among children with CIN. CONCLUSIONS: Children with AIN and CIN exhibit reduced circulating Tregs, while these values are associated with clinical and laboratory aberrations, suggesting a potential contribution in the immunopathogenesis of neutropenia.