To characterize, by flow cytometry, myeloid, B and T cells in a cohort of patients with a recent diagnosis of Relapsing Remitting Multiple Sclerosis (RRMS) naïve to Disease-Modifying Therapies (DMTs).

The characterization of immune cells when patients are naïve to any treatment has not been fully investigated. Scarce data are available about changes in immune cell subsets in peripheral blood mononuclear cells as surrogate biomarkers of activity to monitor treatment response in MS.

This is a prospective-case-control study from the MS centre of Catania, Italy. Demographic/clinical data and peripheral blood samples were collected from 52 naïve patients  with a recent diagnosis of RRMS and sex- and age-matched healthy controls (HCs), with a 2:1 ratio. Flow cytometry of isolated peripheral blood mononuclear cells was performed to assess differences in immune cell subsets between RRMS patients and HCs. The biomarker potential of the investigated cellular subsets was explored with receiver operating characteristic (ROC) curves and relative areas under the curves (AUC). A logistic regression was built to analyse association between cellular subsets and disease activity at last clinical and neuroradiological follow up.

Monocytic myeloid derived suppressors cells (Mo-MDSCs, CD14+/HLADR^-/low) and inflammatory monocytes (CD14+CD16+) had higher frequencies in RRMS patients compared with HCs (for all, p<.05). A lower percentage of B-unswitched memory cells was observed in RRMS than HCs (p=.026). The T-cells revealed a higher frequency of the T-Helper CD4+cells and their subset CD4+CD161+ in RRMS than in HCs (for all, p<.001). The ROC analyses revealed an AUC >70% for Mo-MDSCs (CD14+/HLADR^-/low) and inflammatory monocytes (CD14+CD16+), T-Helper (CD4+) and T-subset (CD4+CD161+). The logistic regression analysis did not reveal any association with clinical and radiological activity at last follow up.

Patients with recent RRMS diagnosis and naïve to DMTs showed peculiar immunophenotype for myeloid as well as for B and T cells.