Furthermore, at day 21 of infection, the memory T cell population was comprised of an increased proportion of TEM (CD62L-CD127+) when Elf1 expression was knocked down and an increased frequency TCM (CD62L+CD127+) and a decreased frequency of t-TEM (CD62L-CD127-) when Prdm9 was knocked down (Fig 6B and 6C). This evidence concerns the gene PRDM9 and infection.