title: Antibodies and complement enhance binding and uptake of HIV-1 by human monocytes.
abstract: OBJECTIVE
  To characterize antibody- and complement-mediated binding and uptake of HIV-1 by human monocytes.
  
  
  METHODS
  The first step in the infection of the monocyte by HIV-1 is binding of the virus to the susceptible cell. Procedures were designed to assess the influence of anti-HIV-1 antibodies and complement on this binding, and to study the process of internalization following binding.
  
  
  METHODS
  Human monocytes were incubated with fluorescein-labelled purified HTLV-IIIB virions and human sera with high-titre anti-HIV-1 antibodies and/or complement. Binding and uptake of virus by the monocytes was measured as fluorescence per cell by flow cytometry.
  
  
  RESULTS
  Binding of purified HIV-1 to monocytes was increased by complement and, to a lesser extent, by anti-HIV-1 antibodies. Uptake of HIV-1 bound to the monocyte appeared to be mediated by antibodies and was increased further by the presence of complement. Complement alone, however, resulted in the uptake of only a small part of the bound virus.
  
  
  CONCLUSIONS
  Complement significantly increases the binding of HIV-1 to human monocytes, and a combination of antibodies and complement efficiently mediates uptake of HIV-1 by monocytes.
authors.affiliation: Department of Clinical Microbiology, University Hospital Utrecht, The Netherlands.
authors.forename: L J
authors.initials: LJ
authors.lastname: Bakker
authors.forename: H S
authors.initials: HS
authors.lastname: Nottet
authors.forename: N M
authors.initials: NM
authors.lastname: de Vos
authors.forename: L
authors.initials: L
authors.lastname: de Graaf
authors.forename: J A
authors.initials: JA
authors.lastname: Van Strijp
authors.forename: M R
authors.initials: MR
authors.lastname: Visser
authors.forename: J
authors.initials: J
authors.lastname: Verhoef
mesh_terms: D000911:Antibodies, Monoclonal / Q000378:metabolism; D015704:CD4 Antigens / Q000276:immunology; D002478:Cells, Cultured; D003165:Complement System Proteins / Q000378:metabolism*; D005453:Fluorescence; D006098:Granulocytes / Q000378:metabolism / Q000382:microbiology; D015483:HIV Antibodies / Q000378:metabolism; D015497:HIV-1 / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D009000:Monocytes / Q000378:metabolism / Q000382:microbiology*
chemical_list: D000911:Antibodies, Monoclonal; D015704:CD4 Antigens; D015483:HIV Antibodies; D003165:Complement System Proteins