Association of IL-6 and autoantibody levels with the number and phenotype of infiltrating neutrophils in inflamed joints of patients with rheumatoid arthritis.

GORLINO, C; BLAS, R; DIAZ GABUTTI, MS; MUNARRIZ A; TAMASHIRO, H; PARDO HIDALGO, RA; PISTORESI, MC; DI GENARO, S

Mar del Plata

Congreso; Sociedad Argentina de Inmunologia; 2016

Sociedad Argentina de Inmunología

Aprobado para ser presentado en la reunión Anual de la Sociedad Argentina de Inmunología. Mar del Plata. Noviembre 2016.Background/Purpose. In Rheumatoid arthritis (RA), neutrophils are recruited into inflamed joints enhancing tissue injure. Accumulated evidence has demonstrated that interleukin (IL)-6 modulates neutrophil influx at sites of inflammation and promotes humoral immunity. Among the numerous autoantibodies associated with RA, anti-cyclic citrullinated peptide antibodies (ACPA) are recognized the most disease-specific. The aim of this study was to investigate the association among ACPA, neutrophil influx and IL-6 in the inflamed joints of RA patients. Methods. Synovial fluid (SF) samples were obtained from 60 RA patients. All patients gave informed consent and the study was approved by the ethic board from IBYME. Cytokine and ACPA levels were measured by ELISA and the expression of CD16, CD62L, CXCR1, and CD66b were assessed by flow cytometry. Results. We showed that in SF of ACPA-positive patients, IL-6 levels positively correlated with neutrophil counts (p=0.009) and with IL-8 (p=0.04). Moreover, in SF of patients with high ACPA levels (ACPA-high SF: ˃200 U/ml) IL-6 was significantly increased (p<0.05) and IL-8 levels and disease activity showed positive correlation (p=0.03). To determine the effect of IL-6 on neutrophil phenotype, neutrophils from healthy donors were incubated with ACPA-high SF in the presence or absence of tocilizumab (TCZ), a monoclonal antibody which blocks the IL-6 receptor. Upon stimulation, a subset of CD16highCD62Llow neutrophils increased (p=0.004) and showed a decreased expression of CXCR1 (p=0.03) and an upregulation of CD66b (p=0.002). However, treatment with TCZ reduced the percentage of CD16highCD62Llow neutrophils (p=0.008), which showed an upregulation of CXCR1 (p=0.01) and a downregulation of CD66b (p=0.02).Conclusion. We demonstrate that IL-6 levels showed a relationship among neutrophil numbers and ACPA levels in SF of RA patients. We suggest that neutrophil activity in affected joints may be modulated by blocking IL-6 signaling.