Subset-specific alterations in frequencies and functional signatures of γδ T cells in systemic sclerosis patients

Abstract

Objective and design: Here, we evaluated the distribution and functional profile of circulating CD27⁺ and CD27^- γδ T-cell subsets in systemic sclerosis (SSc) patients to assess their potential role in this disorder.

Materials and methods: Peripheral blood from 39 SSc patients and 20 healthy individuals was used in this study. The TCR-γδ repertoire, cytokine production and cytotoxic signatures of circulating γδ T-cell subsets were assessed by flow cytometry. Gene expression of EOMES, NKG2D and GZMA was evaluated by quantitative RT-PCR in both purified γδ T-cell subsets.

Results: Absolute numbers of γδ T-cell subsets were significantly decreased in SSc groups, likely reflecting their mobilization to the inflamed skin. Both γδ T-cell subsets preserved their relative proportions and Th1-type cytokine responses. However, cytotoxic properties showed significant disease-associated and subset-specific changes. SSc patients exhibited increased percentages of CD27⁺ γδ T cells expressing granzyme B or perforin and upregulated GZMA expression in diffuse cutaneous SSc. Conversely, EOMES and NKG2D were downregulated in both SSc γδ T-cell subsets vs. normal controls. Interestingly, patients with pulmonary fibrosis showed a biased TCR repertoire, with a selected expansion of effector Vγ9⁺ γδ T cells associated with increased frequency of cells expressing granzyme B, but decreased IFN-γ production.

Conclusions: Significant alterations on circulating γδ T-cell subsets suggest a deregulated (increased) cytotoxic activity and thus enhanced pathogenic potential of CD27⁺ γδ T cells in SSc.

Keywords: CD27; Cytotoxicity; Gamma–delta T cells; Systemic sclerosis; Th1-type cytokine.