Low Memory T Cells Blood Counts and High Naïve Regulatory T Cells Percentage at Relapsing Remitting Multiple Sclerosis Diagnosis.

Objective: The aim of this study is to assess the peripheral immune system of newly diagnosed patients with relapsing remitting multiple sclerosis (RRMS) and compare it to healthy controls (HC).
Methods: This cross-sectional study involves 30 treatment-naïve newly diagnosed patients with RRMS and 33 sex- and age-matched HC. Peripheral blood mononuclear cells were analyzed regarding: i) thymic function surrogates [T cell receptor excision circles (TRECs) and recent thymic emigrants (RTEs)]; ii) naïve and memory CD4 ⁺ and CD8 ⁺ T cells subsets; iii) T helper (Th) phenotype and chemokine receptors expression on CD8 ⁺ T cells subsets; iv) regulatory T cell (Tregs) phenotype; and exclude expression of activating/inhibitory receptors by natural killer (NK) and NKT cells. Analyses were controlled for age, sex, and human cytomegalovirus (HCMV) IgG seroprevalence.
Results: Newly diagnosed patients with RRMS and HC have equivalent thymic function as determined by similar numbers of RTEs and levels of sjTRECs, DJβTRECs, and sj/DJβTREC ratio. In the CD8 ⁺ T cells compartment, patients with RRMS have a higher naive to memory ratio and lower memory cell counts in blood, specifically of effector memory and TemRA CD8 ⁺ T cells. Interestingly, higher numbers and percentages of central memory CD8 ⁺ T cells are associated with increasing time from the relapse. Among CD4 ⁺ T cells, lower blood counts of effector memory cells are found in patients upon controlling for sex, age, and anti-HCMV IgG seroprevalence. Higher numbers of CD4 ⁺ T cells (both naïve and memory) and of Th2 cells are associated with increasing time from the relapse; lower numbers of Th17 cells are associated with higher MS severity scores (MSSS). Patients with RRMS have a higher percentage of naïve Tregs compared with HC, and lower percentages of these cells are associated with higher MSSS. Percentages of immature CD56 ^bright NK cells expressing the inhibitory receptor KLRG1 and of mature CD56 ^dim CD57 ⁺ NK cells expressing NKp30 are higher in patients. No major alterations are observed on NKT cells.
Conclusion: Characterization of the peripheral immune system of treatment-naïve newly diagnosed patients with RRMS unveiled immune features present at clinical onset including lower memory T cells blood counts, particularly among CD8 ⁺ T cells, higher percentage of naïve Tregs and altered percentages of NK cells subsets expressing inhibitory or activating receptors. These findings might set the basis to better understand disease pathogenesis.
Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
(Copyright © 2022 Canto-Gomes, Silva, Rb-Silva, Boleixa, da Silva, Cheynier, Costa, González-Suárez, Correia-Neves, Cerqueira and Nobrega.)