Fig. 2.
FcγR expression on AMs is regulated by levels of GM-CSF in the lungs and expression of PU.1 in AMs, and levels are increased during pulmonary infection by adenovirus.
(A) FcγR expression on primary AMs (GM+/+, GM−/−, SPC-GM+/+/GM−/−) or cultured AMs (MH-S, mAM, mAM) was quantified by FACS as described in “Materials and methods.” Shown are data for FcγRII/III-specific antibodies (shaded histogram) and isotype controls (open histogram). Differences in autofluorescence among cultured AM cell lines, due in part to the presence of the GFP marker in mAM and mAM, have been compensated. Results are representative of 4 separate determinations in AMs from mice analyzed individually. (B) The cultured AM cell line from GM−/− mice (mAM) failed to express mRNA for either activating (FcγRIA, FcγRIIIA) or inhibiting (FcγRIIB) FcRs, but expression was stimulated by PU.1 as shown in mAM cells. Total RNA was prepared from cultured AM cell lines (MH-S, mAM, mAM) and subjected to RT-PCR analysis using gene-specific primers as described in “Materials and methods.” Shown are photographs of ethidium bromide–stained RT-PCR reaction products separated on 2% agarose gels. H20 PCR controls were negative (not shown). This experiment was repeated twice with identical results. (C) Primary AMs were recovered 36 hours after pulmonary adenoviral infection of GM+/+ or GM−/− mice, and levels of FcγR expression were assessed as above. Levels of FcγR on AMs are represented as the mean fluorescence intensity as determined using the FcγRII/III-specific antibody. Data represent means ± SEM; n = 4 mice per group; AMs from each mouse were analyzed individually. Differences in FcγR expression on AMs from infected and uninfected GM+/+ mice were significant (P < .001). FcγR expression was not detected (*) on GM−/− AMs in the absence or presence of adenovirus infection. AMs recovered from GM−/− mice and exposed ex vivo to IFN-γ for 24 hours showed a marked up-regulation of cell-surface FcγRII/III expression at levels significantly different from untreated mice (P < .001).