T cell-intrinsic lymphoproliferation as a key driver of intestinal autoimmunity in acquired generalized lipodystrophy

Acquired generalized lipodystrophy (AGL) is a rare metabolic disorder frequently associated with autoimmunity. Its etiology is incompletely understood and the impact of adipose tissue loss on autoimmunity and intestinal inflammation in AGL remains unclear. Using mass cytometry and single-cell RNA sequencing, we observed an oligoclonal expansion of T cells in the periphery and inflamed intestine in a patient with AGL and Crohn’s disease (AGLCD). To explore if loss of adipose tissue triggers lymphoproliferation, we studied lipodystrophic mice as a model for AGL. Unexpectedly, lipodystrophic mice did not show T-cell expansion, were protected from colitis and displayed a defect in the development of pro-inflammatory T cells, which could be reversed by allogeneic fat transplantations, indicating that clonal T-cell expansion is not primarily caused by lipodystrophy. Instead, gene sequencing revealed a T cell-intrinsic de-novo NRAS mutation, pointing towards somatic mosaicism as a driver of clonal T-cell expansion and systemic autoimmunity in AGLCD.