Depletion of Ift88 in thymic epithelial cells affects thymic synapse and T-cell differentiation in aged mice

Primary cilia are ubiquitous hair-like organelles, usually projecting from the cell surface. They are essential for the organogenesis and homeostasis of various physiological functions, and their dysfunction leads to a plethora of human diseases. However, there are few reports on the role of primary cilia in the immune system; therefore, we focused on their role in the thymus that nurtures immature lymphocytes to full-fledged T cells. We detected primary cilia on the thymic epithelial cell (TEC) expressing transforming growth factor beta (TGF-beta) receptor in the basal body, and established a line of an intraflagellar transport protein 88 (Ift88) knockout mice lacking primary cilia in TECs (Ift88-TEC null mutant) to clarify their precise role in thymic organogenesis and T-cell differentiation. The Ift88-TEC null mutant mice showed stunted cilia or lack of cilia in TECs. The intercellular contact between T cells and the thymic synapse of medullary TECs was slightly disorganized in Ift88-TEC null mutants. Notably, the CD4- and CD8-single positive thymocyte subsets increased significantly. The absence or disorganization of thymic cilia downregulated the TGF-beta signaling cascade, increasing the number of single positive thymocytes. To our knowledge, this is the first study reporting the physiological role of primary cilia and Ift88 in regulating the differentiation of the thymus and T cells.

Automated summary

Primary cilia play a crucial role in organogenesis, homeostasis, and immune system function. This study focuses on primary cilia in the thymus, where immature lymphocytes develop into T cells. By studying knockout mice lacking primary cilia in thymic epithelial cells (TECs), the researchers found that the absence or disorganization of thymic cilia leads to an increase in CD4- and CD8-single positive thymocytes. This is the first study to report the physiological role of primary cilia and Ift88 in thymus and T cell differentiation.