During chronic viral infection, PSGL-1 engagement promotes effector T cell exhaustion (42). While the intracellular signals that direct this PSGL-1 driven enhancement of T cell exhaustion are not known, it has been shown that ligation of PSGL-1 on exhausted CD8+ T cells resulted in diminished ERK and AKT signaling (42). This evidence concerns the gene SELPLG and viral infectious disease.