To examine the effects of 1α,25-dihydroxyvitamin D3 on effector function and immune checkpoint regulation in human peripheral blood T cells, particularly focusing on CD8+ T cells.
Approach:
Cell Culture: Peripheral blood mononuclear cells (PBMCs) from healthy donors were cultured for five days with or without 1,25(OH)2 vitamin D (10 or 100 nM).
Assays: IFN-γ production was assessed by ELISpot assay, IC-related gene expression was evaluated by RT-qPCR, and flow cytometry was used to assess expression of IC, degranulation, and activation markers.
Quantification: FluoroSpot assays were performed to quantify interleukin secretion.
Key Findings:
1,25(OH)2 vitamin D reduced IFN-γ expression and secretion independently of baseline circulating levels.
Dose-specific modulation of immune checkpoint genes was observed, with increased PDCD1 and CTLA4 mRNA expression.
Increased PD-1 expression was noted in CD8+ T cells at 10 nM and increased CTLA-4 expression at 100 nM.
Decreased degranulation and activation markers were observed in CD8+ T cells.
No significant changes in TIM-3 or TIGIT expression were detected, and IL-22 secretion was reduced in CD4+ T cells.
Interpretation:
The study supports an immunomodulatory effect of 1,25(OH)2 vitamin D on human CD8+ T cells, indicating modulation of effector-associated responses and immune checkpoint pathways in vitro.
Limitations:
The study was conducted in vitro, and the functional implications in vivo remain to be investigated.
The sample size and diversity of healthy donors may limit the generalizability of the findings.
Conclusion:
Vitamin D may contribute to the regulation of inflammatory T-cell responses under controlled culture conditions.
by Lisa Isdraele Romano, Ilenia Aversa, Antonio Abatino, Costanza Maria Cristiani, Giulio Cesare Antico, Debora Gentile, Caterina Giordano, Emilio Straface, Michael Marrano, Elvira Angotti, Camillo Palmieri, Raffaella Gallo, Giuseppe Fiume
