The thymus X factor

Abstract

Immunology The thymus is an organ that facilitates the maturation of thymocytes into T cells and is notable for its variable size and composition. It is largest during early life, then it shrinks with age and in response to injury and infection. Thymic development also affects T cell output but remains poorly understood. Chan et al. report that liver X receptors (LXRs), nuclear receptors important for immunity and metabolism, play an important role in thymus dynamics. In mice, thymic epithelial cells use LXRαβ for self-renewal and thymic regeneration. Meanwhile, LXRαβ makes thymocytes more resistant to negative selection, thereby boosting the production of autoreactive T cells. This work therefore cautions that LXR-focused thymic regeneration therapies may need to be cell specific to prevent unwanted autoimmunity. J. Exp. Med. 217 , e20200318 (2020).