CD4 and HIV infectious disease: For example, experiments done in vitro indicate that CD4+ Th17 cells, which express high levels of CCR5 as well as the chemokine receptor CCR6 and the integrin α4β7, are preferentially targeted during early infection, and analysis of samples from female sex workers who are infected with HIV indicate that CD4+ Th17 cells are selectively depleted from the cervix during HIV infection [25], [56]–[58].