CD4 and infection: In view of the importance and the controversial nature of the issue of HIV-1 binding to erythrocytes, we examined the binding of HIV-1 both to human erythrocytes and to highly purified erythrocytic ghosts in order to ascertain the degree, if any, that infectious HIV-1 virions bind to erythrocytes in the absence of antibodies or complement, and to shed light on possible implications of such binding for concepts of HIV-1 pathogenesis and mechanisms of transmission for uptake and infection of CD4(+) cells.