Effect of Transcription Factor GATA-2 on Phagocytic Activity of Alveolar Macrophages fromPneumocystis carinii-Infected Hosts

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Abstract
Alveolar macrophages fromPneumocystis carinii-infected hosts are defective in phagocytosis (W. Chen, J. W. Mills, and A. G. Harmsen, Int. J. Exp. Pathol. 73:709-720, 1992; H. Koziel et al., J. Clin. Investig. 102:1332-1344, 1998). Experiments were performed to determine whether this defect is specific forP. cariniiorganisms. The results showed that these macrophages were unable to phagocytose bothP. cariniiorganisms and fluorescein isothiocyanate (FITC)-conjugated latex beads, indicating that alveolar macrophages fromP. carinii-infected hosts have a general defect in phagocytosis. To determine whether this defect correlates with the recently discovered down-regulation of the GATA-2 transcription factor gene duringP. cariniiinfection, alveolar macrophages from dexamethasone-suppressed or healthy rats were treated with anti-GATA-2 oligonucleotides and then assayed for phagocytosis. Aliquots of the alveolar macrophages were also treated with the sense oligonucleotides as the control. Cells treated with the antisense oligonucleotides were found to have a 46% reduction in phagocytosis ofP. cariniiorganisms and a 65% reduction in phagocytosis of FITC-latex beads compared to those treated with the sense oligonucleotides. To determine whether the defect in phagocytosis in alveolar macrophages fromP. carinii-infected hosts can be corrected by overexpression of GATA-2, a plasmid containing the rat GATA-2 gene in the sense orientation driven by the cytomegalovirus (CMV) promoter was introduced into alveolar macrophages fromP. carinii-infected rats. Aliquots of the same cells transfected with a plasmid containing GATA-2 in the antisense orientation relative to the CMV promoter served as the control. Alveolar macrophages treated with the sense GATA-2 expression construct were found to increase their phagocytic activity by 66% in phagocytosis ofP. cariniiorganisms and by 280% in phagocytosis of FITC-latex beads compared to those that received the antisense GATA-2 construct. The results of this study indicate that GATA-2 plays an important role in the regulation of phagocytosis in alveolar macrophages duringP. cariniiinfection.