Evaluation of Monocyte Subpopulations in Patients with Systemic Sclerosis and its Association with Clinical Manifestations of the Disease: a Cross-sectional Controlled Study.

Background: Systemic sclerosis (SSc) is a chronic autoimmune disorder characterized not only by fibrosis and vasculopathy but also by inflammation. Previous studies have demonstrated monocyte involvement in SSc development, suggesting a role for immune dysfunction in SSc pathogenesis.

Objective: To investigate the relationship between SSc's clinical manifestations and altered levels of monocyte subpopulations.

Methods: Twenty-six patients meeting the ACR/EULAR SSc criteria along with twenty healthy individuals as the control group, were enrolled in the study. Peripheral blood mononuclear cells (PBMCs) were obtained from heparinized blood samples of both the SSc patients and the control group. Subpopulations of monocytes were assessed based on HLA-DR, CD14, and CD16 expression using multi-color flow cytometry. The one-way ANOVA, Student's t-test, and Mann-Whitney U test were employed for normally and non-normally distributed data. The Spearman correlation test was utilized to identify correlations between the variables.

Results: The SSc patients showed a significant increase in the number of circulating peripheral blood monocytes (p<0.001). The percentage of CD16+ monocyte subpopulations was higher in the SSc cases compared to the control group. A significant decrease in the ratio of classic to non-classic monocytes was observed in SSc cases (7.43%) compared to the control group (52.09%, p<0.001). No association was observed between monocyte subpopulations and clinical characteristics of SSC.

Conclusion: Our results showed an increase in the level of CD16+ monocytes in patients with SSc compared to healthy individuals. Further investigation is required to determine the clinical significance of this alteration.