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

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.

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.

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.

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.