Additionally, whereas ICAM-1 (which binds to the CR3 I-domain and can serve as a CR3 coreceptor) (91, 93, 94) incorporation into the viral envelope with budding is thought to enhance LFA-1 (integrin αLβ2, CD11a/CD18)-mediated HIV-1 infection of CD4+ T cells (100), the potential effect of ICAM-1 binding to the CR3 (integrin αMβ2, CD11b/CD18) I-domain on Pex cells is not known. Here, CD4 is linked to HIV-1 infection.