To evaluate the involvement of the various Siglec receptors in HIV-1 infection, GM-CSF– and M-CSF–derived MDMs from 2 donors (donors 130 and 132) were preincubated with purified mAbs to block Siglec-1, -3, -5, or -9 and then infected with HIV-1 (US-1, subtype B). The gene discussed is CSF1; the disease is HIV-1 infection.