Reduced number of blood circulating foxp3+CD25highCD4+regulatory T cells and a decreased foxp3 expression at the single-cell level in patients with relapsing-remitting multiple sclerosis

Abstract

CD4+CD25high regulatory T cells (Tregs) of patients with relapsing-remitting (RR), but not secondary-progressive (SP) multiple sclerosis (MS), show a reduced suppressive function and FoxP3 mRNA expression. In this study we analyzed FoxP3 protein expression by means of flow cytometry in PBMC of 55 RR-MS, 15 SP-MS patients and 40 healthy controls (HC). RR-MS patients displayed a significant reduced number of CD4+CD25highFoxp3+ T cells as compared to HC and SP-MS. In addition, a significant lower Foxp3 expression per cell was detected in RR-MS patients. Interestingly, IFN-β treated RR-MS patients (n = 15) showed a higher frequency of CD4+CD25highFoxp3+ cells as compared to untreated RR-MS patients (n = 40). Furthermore, a correlation was observed between Foxp3 levels and suppressive capacity of Tregs as measured in Treg-Tresponder coculture experiments. We further phenotypically analyzed Tregs of HC and untreated MS patients by measuring the expression of adhesion molecules by flow cytometry. Whereas no differences were detected in percentage of L-selectin+ (CD62L) and hyaluronate receptor+ (CD44) cells, a significant higher percentage of integrin αE+ (CD103) and α4+ (CD49d, VLA-4) cells was observed within CD4+CD25high Foxp3+ Tregs of RR-MS as compared to HC and SP-MS. Taken together, a lower number of CD4+CD25highFoxp3+ T cells and a reduced Foxp3 expression level was detected in RR-MS patients further demonstrating Treg dysfunction in these patients. The detection of a higher percentage of CD103+ and VLA-4+ in the Treg population in RR-MS patients could reflect an increased migration capacity of Tregs towards inflammatory lesions in the central nervous system.