CD69 prevents PLZFhi innate precursors from prematurely exiting the thymus and aborting NKT2 cell differentiation

Abstract

While CD69 may regulate thymocyte egress by inhibiting S1P1 expression, CD69 expression is not thought to be required for normal thymocyte development. Here we show that CD69 is in fact specifically required for the differentiation of mature NKT2 cells, which do not themselves express CD69. Mechanistically, CD69 expression is required on CD24+ PLZFhi innate precursors for their retention in the thymus and completion of their differentiation into mature NKT2 cells. By contrast, CD69-deficient CD24+ PLZFhi innate precursors express S1P1 and prematurely exit the thymus, while S1P1 inhibitor treatment of CD69-deficient mice retains CD24+ PLZFhi innate precursors in the thymus and restores NKT2 cell differentiation. Thus, CD69 prevents S1P1 expression on CD24+ PLZFhi innate precursor cells from aborting NKT2 differentiation in the thymus. This study reveals the importance of CD69 to prolong the thymic residency time of developing immature precursors for proper differentiation of a T cell subset.

A focus on natural killer T‐cell subset characterization and developmental stages

“…This result confirms our original study, where we reported the NKT cell proportion among NKT cells to vary between 0.2% and 0.5% in 2‐ to 5‐week‐old C57BL/6 mice 34 . However, numerous studies investigating NKT cell development report a higher proportion, varying from 3% to 17% . The unusually high proportion of HSA high NKT cells reported in these studies may be a result of the absence of enrichment strategies or inefficient application of such strategies, resulting in contamination of the HSA high NKT cell with conventional T cells or cortical thymocytes.…”

“…Although these cells did not bind unloaded CD1d tetramers, they have not been checked for Vβ8 or CD69 expression. A more recent study analyzed the phenotype of HSA high NKT cells obtained without using an enrichment strategy, and found that stage 0 NKT cells consisted of CD44 low and CD44 high subpopulations, named stage 0a and stage 0b, respectively 38 . Both subsets express CD4 and CD8 and are thus HSA high DP thymocytes.…”

High Dimensional Single-Cell Analysis Reveals iNKT Cell Developmental Trajectories and Effector Fate Decision

“…Conversely, iNKT0 expressed CD69, while iNKT2b and iNKT1a/b subsets expressed Cxcr3 (Figure 4A), two genes encoding for proteins involved in thymic retention (Drennan et al, 2009;Weinreich and Hogquist, 2008). To test these observations in vivo, we attempted to block iNKT thymocyte egress by means of FTY720 (Kimura et al, 2018), a selective sphingosine 1-phosphate receptor agonist that induces its internalization (Mandala et al, 2002). Prolonged FTY720 treatment led to a significant increase in iNKT thymocytes (Figure 4B).…”

Epigenetic and Transcriptional Regulation in the Induction, Maintenance, Heterogeneity, and Recall-Response of Effector and Memory Th2 Cells

“…TCR stimulation increases H3K4 methylation at the Cd69 gene in naïve CD4 T cells, suggesting that the expression of CD69 is epigenetically regulated (94). More recently, CD69 has been found to be crucial for maturation of NKT2 cells in the thymus, where CD69 prevents immature precursors from exiting by suppressing the sphingosine-1-phosphate receptor 1 (S1P 1 ) expression (95). A number of studies have reported roles of CD69 in murine models of inflammatory diseases, including arthritis, airway inflammation, and dextran sulfate sodium (DSS)-induced colitis (96–98).…”