CD5-expressing CD8+ T-cell subsets differ between children with type 1 diabetes and controls.

Different lymphocyte subsets are involved in autoimmune pathogenesis of type 1 diabetes (T1D). Previous studies suggested a role of CD5-expressing T and B cells including rare unconventional lymphocytes with combined T- and B-cell features [dual expressing (DE) cells]. We performed algorithm-supported multiparameter flow cytometry and quantitative PCR to investigate immune cell subsets and DE cells in children with T1D (n = 20) and matched controls (n = 20). Comparisons of conventional immune cells detected increased proportions of CD3+ T cells in T1D patients, whereas CD19+ B-cell proportions were comparable to controls. Self-organizing maps for flow cytometry analyses (FlowSOM) showed highly similar CD5-expressing B-cell subsets and no differences for DE cells were detected between the study groups by flow cytometry or specific quantitative PCR. Notably, differences in CD8+ T cells were indicated by FlowSOM and similarity-based t-distributed stochastic neighbor embedding (tSNE) analyses. Study group comparisons confirmed significantly reduced CD8+ T-cell proportions with moderate or low CD5 expression in T1D patients. Finally, in vitro experiments showed stable CD5 expression differences of CD8+ T cells after T-cell activation, cytokine stimulation and culture. We observed differences of T-cell coreceptor CD5 expression in T1D patients with potential relevance for immune regulation of CD8+ T-cell activation.