A HUMAN CD4(-CELL LINE EXPRESSES FUNCTIONAL CD64 (FC-GAMMA-RI), CD32 (FC-GAMMA-RII), AND CD16 (FC-GAMMA-RIII) RECEPTORS BUT THESE DO NOT ENHANCE THE INFECTIVITY OF HIV-1-IGG COMPLEXES() T)

T cells do not generally express Fc receptors (FcRs). However, we repo rt here that C8166 cells, a human CD4(+) T lymphoblastoid cell line, w idely used in research into the human immunodeficiency virus type 1 (H IV-1), expressed CD64 (Fc gamma RI), CD32 (Fc gamma RII), and CD16 (Fc gamma RIII) on the plasma membrane as shown by immunostaining with sp ecific monoclonal antibody fragments. Another human CD4(+) T lymphobla stoid cell line, H9, expressed none of these FcRs. C8166 cells bound m onomeric normal rat serum IgG in a dose-dependent manner, and when sat urated bound heat-complexed immunoglobulin G (IgG) also dose dependent ly. These observations are consistent with the presence on the C8166 T -cell line of both high- and low-affinity Fc gamma Rs. Fc gamma Rs are putative receptors for virus-IgG complexes, but in this study did not enhance infectivity of HIV-1 complexed with a human neutralizing mAb or three rat neutralizing mAbs. Virus complexed with a non-neutralizin g mouse mAb was unable to infect cells using Fc gamma Rs as receptors after CD4 was blocked with a specific anti-CD4 mAb.