Memory CD4+ T cells lacking expression of CCR7 promote pro-inflammatory cytokine production in patients with diffuse cutaneous systemic sclerosis

Background: Systemic sclerosis (SSc) is a predominantly T-cell-mediated autoimmune disorder with a characteristic sequence of Th1 and Th2 inflammation resulting in fibrosis. The contribution of differentiated memory T-cell subpopulations and methylation of CpG regions of Th1-or Th2-specific transcription factor genes on the inflammatory cytokine signature in SSc is not well understood. Objectives: The study aimed to investigate phenotypic differentiation, the cytokine signature, sensitivity of memory T cells to in vitro suppression by autologous regulatory T cells (Tregs), and methylation of Th1- and Th2-specific transcription factor genes in patients with limited (lcSSc) and diffuse cutaneous SSc (dcSSc) compared to healthy donors (HD). Materials and methods: Phenotype/intracellular cytokine production and methylation of Th1-and Th2-specific transcription factor genes were determined by flow cytometry and epigenetic analysis, respectively, and compared between patients with lcSSc, dcSSc and HD. Results: Discrimination of CD4+ T cells that lack CCR7 expression revealed that CCR7- CD4+ memory T cells and effectors are producers of intracellular TNFα, IL-13 and IL-4, particularly in dcSSc. A proportional increase in CCR7- memory T cells was demonstrated by SSc-derived CD4+ T-cells after insufficient suppression by Tregs. A higher level of methylation of GATA3 or STAT4 (Th2- and Th1-specific transcription factor genes, respectively) was observed in dcSSc. Conclusion: An abundance of specific CD4+ memory T-cell subpopulations strongly contributes to the production of pro-inflammatory cytokines in dcSSc. Our results suggest that therapeutic concepts should focus more intensively on the memory phenotype to control T cell-mediated inflammation in SSc patients.