Myeloid-derived suppressor cells and monocytes are biomarkers of the clinical phenotype and activity of psoriatic disease

Objectives To assess the relation between the proportion of myeloid-derived suppressor cells (MDSCs), monocyte subsets, and the clinical phenotypes and disease activity of psoriatic disease (PsD), including psoriasis (PsO) and psoriatic arthritis (PsA). Methods We carried out a cross-sectional study including 47 patients with PsD and 10 age and sex-paired healthy controls. Using multiparametric flow cytometry, we evaluated the granulocytic (G) and monocytic (M) MDSCs, classical, intermediate and non-classical monocytes in peripheral blood. We compared these cell populations according to the clinical features, phenotype of PsD, and treatment groups. We evaluated their capability to predict disease activity measured by Psoriasis Area and Severity Index (PASI) and Disease Activity in Psoriatic Arthritis (DAPSA) by multivariate logistic and linear regressions. Results In comparison to healthy donors, PsD patients displayed lower mature G-MDSCs (5.88% vs 60.97%), increased M-MDSCs (0.62% vs 0.02%), decreased expression of arginase-1 and PDL1, and expansion of non-classical monocytes (12.2% vs 4.68%). Increased mature G-MDSCs and decreased arginase-1 expression were seen in patients with cutaneous features. G-MDSCs were associated with cutaneous disease activity (PASI (β 5.05, p= 0.05)), whilst non-classical monocytes were related to active PsA (DAPSA (β 0.68, p= 0.004)), highlighting their potential as disease activity biomarkers. Conclusion In PsD, G-MDSCs relate to cutaneous disease activity, whereas non-classical monocytes correlate with musculoskeletal features, highlighting their role as potential biomarkers of disease activity in PsD. Further prospective studies addressing the function of these cell subtypes would confirm their relationship with PsD activity status.