Hyperactivation and enhanced cytotoxicity of reduced CD8⁺ gamma delta T cells in the intestine of patients with Crohn's disease correlates with disease activity

Background and aims We aimed to investigate the immune characteristics of intestinal CD8(+) gamma delta T (CD8(+) gamma delta T) cells in Crohn's disease (CD) and their correlation with disease activity. Methods The study cohorts included 21 CD patients and 21 healthy individuals. CD8(+) gamma delta T cells were isolated from human ileal mucosa for detection by flow cytometry. The activation or inhibition status of cells was detected by detecting the expression of activation marker HLA-DR and the immunosuppressive molecule PD-1 on cells. The cytotoxicity of cells was assessed by detecting the expression of cytotoxic molecules (Perforin, Granzyme B, and TRAIL) in cells. Ratios of investigated cells were calculated as prediction factors by receiver operating characteristic curve (ROC) analysis. Results The study revealed a reduction in intestinal CD8(+) gamma delta T cells among active CD patients, with a more pronounced reduction observed in moderately active patients compared to mildly active patients. Moreover, active CD patients exhibited heightened activation levels in their intestinal CD8(+) gamma delta T cells, whereas the activation was comparatively weakened in moderately active patients compared with mildly active patients. Additionally, the cytotoxicity of intestinal CD8(+) gamma delta T cells was enhanced solely in mildly active patients, while it was impaired in moderately active patients compared with mildly active patients. Furthermore, HLA-DR+ CD8(+) gamma delta T cell ratio, CD8(+) gamma delta T ratio, and CD8(+) gamma delta T count were identified as indicators in the diagnosis of active CD. Meanwhile, the ratios of Granzyme B+ CD8(+) gamma delta T cell and Perforin(+) CD8(+) gamma delta T cell were identified as indicators that distinguish mildly moderately active CD cases. Conclusions Intestinal CD8(+) gamma delta T was reduced in active CD patients, but their activation and cytotoxicity were enhanced. However, with increased disease activity, intestinal CD8(+) gamma delta T cells became dysfunctional. CD-specific perturbations observed in various phenotypic markers in CD8(+) gamma delta T cells can be used as indicators to assist in diagnosing CD patients.