CCR5 and HIV infectious disease: To understand associations between polyfunctional Th17 and Tc17 subsets and the phenotype of memory CD4 T (CD4+ CD45RO+) cells in the rectum, which comprise the majority of CD4+ cells in the rectal mucosa, we measured the expression of CD38+ (indicator of activation status), Ki67+ (indicator of proliferation status), CCR5+ (co-receptor for HIV) and α4β7+Ki67+ (gut homing potential and ability to facilitate HIV infection) on unstimulated rectal mucosal memory CD4 T cells from HIV negative study participants.