Antigen receptor on a new lymphocyte represents a key immune player in autoimmune diseases

Abstract

Abstract PURPOSE: We have recently identified a previously unknown lymphocyte that is a dual expresser (DE) of productively rearranged and surface-expressed TCRαβ and BCR (surface immunoglobulin, Ig) (Ahmed et al, Cell, 2019: 177:11583). Importantly, a single immunoglobulin heavy-chain, IGHV clonotype (clone-x) predominates DEs that encodes a potent autoantigen (x-autoantigen) in its CDR3 region. The x-autoantigen (as a soluble intact x-mAb) cross-activate autoreactive T cells. The goal of this study is to investigate the properties of x-mAb reactive T cells and examining the mechanisms of how x-mAb recognizes and activates the tolerant autoreactive T cells in autoimmune diseases particularly in T1D. METHODS: We used EBV immortalized DE clone as a source of x-mAb and FACS-based protocols to identify x-mAb-responsive autoreactive T cells and their functional properties. ImmunoSEQ assay used to characterize TCR repertoires. RESULTS: Preliminary data show that x-mAb potentially binds and activates a subset of autoreactive T cells in T1D compared to HC subjects. Additionally, x-mAb-reactive T cells exhibits an activated and antigen experienced phenotype, including expression of CD45RO, CD44, and CD69. TCRVβ repertoire analysis shows that x-mAb reactive T cells are enriched for public clonally expanded TCRs in T1D patients. Further, x-mAb activates the autoreactive T cell through by crosslinking directly to their T cell receptor (TCR). CONCLUSIONS: DE cells in T1D patients secretes a public x-mAb that binds and activate specific subset of autoreactive T cells predominated by few clonotypes that express public TCRs. Our results are revealing previously unknown mechanism that appears to be a play critical role in pathogenesis of T1D.