CD4 and HIV infectious disease: Both the foreskin and the vaginal mucosa contain CD4+ T cells, which can be infected by HIV during sexual intercourse with an infected person; however, male CD4+ T cells express higher CCR5 receptors when compared to females, which implies that males are more likely to be infected in one sexual encounter with higher viral particles, thus partially explaining the higher viral loads in males in primary HIV infection [232,233].