Rapamycin improves Graves' orbitopathy by suppressing CD4+ cytotoxic T lymphocytes.

Abstract

CD4+ cytotoxic T lymphocytes (CTLs) were recently implicated in immune-mediated inflammation and fibrosis progression of Graves' orbitopathy (GO). However, little is known about therapeutic targeting CD4+ CTLs. Herein, we studied the effect of rapamycin, an approved mTORC1 inhibitor, in GO mouse model, in vitro and in refractory GO patients. In the adenovirus-induced model, rapamycin significantly decreased the incidence of orbitopathy. This was accompanied by reduction of CD4+ CTLs, and improvement of inflammation, adipogenesis and fibrosis in orbits. CD4+CTLs from active GO patients showed upregulation of mTOR pathway, while rapamycin decreased their proportions and cytotoxic function. Low-dose rapamycin treatment substantially improved diplopia and clinical activity score in steroid-refractory GO patients. Single-cell RNA sequencing revealed that eye motility improvement was closely related to suppression of inflammation and chemotaxis in CD4+ CTLs. In conclusion, rapamycin is a promising treatment for CD4+ CTL-mediated inflammation and fibrosis in GO.