Sr. Lewin et al., SURFACE CD4 IS CRITICAL TO IN-VITRO HIV-INFECTION OF HUMAN ALVEOLAR MACROPHAGES, AIDS research and human retroviruses, 12(10), 1996, pp. 877-883
The CD4 glycoprotein is the major cellular receptor for HIV. CD4 surfa
ce expression of monocytes decreases with time in culture while their
susceptibility to HIV-1 increases. Our aim was to investigate whether
this phenomenon occurs in macrophages that have differentiated in vivo
by investigating CD4 expression and HIV-1 infection of human alveolar
macrophages (AMs). Using flow cytometry to detect CD4 expression by L
eu-3a labeled indirectly with fluorescein isothiocyanate or allophycoc
yanin, we found that CD4 was expressed at low but detectable levels, d
espite the high background autofluorescence well described in AMs, Thi
s finding was supported by the detection of CD4 mRNA in AMs using RT-P
CR, T cell contamination of mRNA extracts of AMs was excluded by ampli
fying in parallel with primers to the constant region of the T cell re
ceptor, Despite this low level of surface CD4, recomibinant soluble CD
4 and anti-CD4 antibody completely inhibited HIV-1 infection of AMs. W
e conclude that CD4, although expressed at low levels on the surface o
f AMs, appears to be critical to HIV-1 infection of these cells.