RNA-binding proteins Zfp36l1 and Zfp36l2 protect against premature thymic involution.

The thymus is a primary lymphoid organ in which diverse and self-tolerant T cells are produced from bone marrow-derived hematopoietic progenitors. Progressive, age-associated thymic involution reduces T-cell output and impairs adaptive immunity; however, the molecular mechanisms underlying this process remain elusive. Here, we report that the conditional deletion of the RNA-binding proteins Zfp36l1 and Zfp36l2 in thymic epithelial cells (TECs) leads to a pronounced reduction in the number of TECs during the embryonic stage and early neonatal stage, despite a largely preserved thymus size. Postnatally, these mice exhibit excessive medullary TEC (mTEC) expansion, elevated intrathymic proinflammatory cytokine production, FOXN1 downregulation, and premature thymic involution. These findings reveal a protective role for Zfp36 Tristetraprolin (TTP) family proteins in regulating cytokine levels within the thymic microenvironment and preventing premature thymic involution. Moreover, our results suggest a previously unappreciated connection between central tolerance induction and the onset of age-associated thymic involution.