A reply to "TCR+/BCR+ dual-expressing cells and their associated public BCR clonotype are not enriched in type 1 diabetes"

We have recently identified a novel lymphocyte that is a dual expresser (DE) of TCRαβ and BCR. DEs in T1D patients are predominated by a public BCR clonotype (clone-x) that encodes a potent autoantigen that cross-activates insulin-reactive T cells. Betts and colleagues were able to detect DEs but alleged to not detect high DE frequency, clone-x, or similar clones in T1D patients. Unfortunately, the authors did not follow our methods and when they did, their flow cytometric data at two sites were conflicting. Moreover, contrary to their claim, we identified clones similar to clone-x in their data along with clones bearing the core motif (DTAMVYYFDYW). Additionally, their report of no increased usage of clone-x VH/DH genes by bulk B cells confirms rather than challenges our results. Finally, the authors failed to provide data verifying purity of their sorted DEs, making it difficult to draw reliable conclusion of their repertoire analysis. This Matters Arising Response paper addresses the Japp et al. (2021) Matters Arising paper, published concurrently in Cell.

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.