CD103 was initially reported to be necessary for retention, but not for accumulation, of CD8+ T cells in the SI epithelial layer [42]; however, a later report suggested that CD103 confers an initial advantage in terms of recruitment to the epithelium, but is not required for later maintenance, as co‐transfer of WT and CD103 deficient T cells upon infection produced an uneven ratio of cells lodging in the epithelium, which however remained constant at later time points [22]. This evidence concerns the gene CD8A and infection.