Additionally, studies examining the longevity and phenotypic and functional changes that might occur in Trm CD8 T cells over time following infection will be complicated due to a lack of phenotypic markers that definitively identify Trm cells, as CD103 and CD69, markers used to identify Trm cells, are not expressed on all Trm cells [7,58,59]. The gene discussed is ITGAE; the disease is infection.