Proposed model of TCR-CXCR4–mediated stabilization of cytokine mRNA transcripts. Ligation of TCR induces the TCR to associate with and transactivate CXCR4 on S339 which leads to stabilization of IL-2, IL-4, and IL-10 mRNA transcripts via activation of a PREX1-Rac1–signaling pathway. CDS, coding sequence.