Abstract

Abnormalities in CD4+CD25+ regulatory T cells (Treg) may contribute to type 1 diabetes (T1D) development. First-degree relatives of T1D patients are at increased risk especially when they carry certain HLA II haplotypes. Using two novel markers of CD4+CD25+ Treg (CD127- and FoxP3+ respectively), we evaluated number and function of Treg after specific stimulation with diabetogeneic autoantigens in 11 high-risk (according to HLA-linked risk) relatives of T1D patients and 14 age-matched healthy controls using a cytokine secretion assay based on interferon-gamma (IFN-gamma) production. High-risk relatives of T1D patients had significantly lower pre- and post-stimulatory number of CD127- Treg than that of healthy controls (P < 0.05). Labelling Treg with FoxP3+ demonstrated similar trend but did not reach statistical significance. Although the stimulation with diabetogenic autoantigens did not lead to a significant change in number of Treg in both groups, the defective function of Treg was performed by significantly higher activation of diabetogeneic T cells in high-risk relatives of T1D patients compared to healthy controls (P < or = 0.02). Individuals at increased HLA-associated genetic risk for T1D showed defects in Treg.