Inhibition of hyaluronan synthesis restores immune tolerance during autoimmune insulitis (THER5P.919)

We recently reported that abundant deposits of the extracellular matrix polysaccharide hyaluronan (HA) characterize autoimmune insulitis in human type 1 diabetes (T1D) but the significance of these deposits was unclear. Here, we demonstrate that HA is critical for the pathogenesis of autoimmune diabetes. Using the DO11.10xRIPmOVA (DORmO) mouse model of T1D, we show that HA deposits are temporally and anatomically associated with the development of insulitis. Moreover, treatment with an inhibitor of HA synthesis, 4‑methylumbelliferone (4-MU), halted progression to diabetes even after the onset of insulitis. 4-MU reduced HA accumulation, constrained effector T-cells to non-destructive insulitis, and increased numbers of intra-islet Foxp3+ regulatory T-cells (Treg). Consistent with this, Treg differentiation was inhibited by HA and anti-CD44 antibodies and rescued by 4-MU in an ERK1/2-dependent manner. These data may explain how peripheral immune tolerance is impaired in tissues under autoimmune attack, including islets in T1D. We propose that 4-MU, already an approved drug used to treat biliary spasm, could be repurposed to prevent, and possibly treat, T1D in at-risk individuals.

HLA class II tetramers: tools for direct analysis of antigen-specific CD4+ T cells

Immunotherapies for human autoimmune and immune-mediated diseases are proliferating rapidly, and with these changes comes the opportunity to monitor patients for immune responses to therapy based on early surrogate markers for clinical responses. Class II tetramers have the potential to serve as these sorts of markers for immune monitoring, and thereby assist with patient management, therapy selection, and improved outcomes. However, important issues of TCR avidity require resolution, because much is still unknown regarding location, quantitation, and characterization of the human T cell response. Opportunities for application of tetramer technologies in the near future will enable both clinical progress and the development of new insights into human CD4+ T cell biology in vivo.