Some studies have shown that both the long (p45) and the short (p33) TCF-1 isoform are expressed by CD8 T cells that will give rise to stem-like CD8 T cells during viral infection, and it has been shown that the long isoform of TCF-1 is capable of promoting stem-like CD8 T cell formation during viral infection by regulating genes like CD127, CXCR5, and cMyb [15]. This evidence concerns the gene CXCR5 and viral infectious disease.