Constitutive and inducible expression of PDGF in the human basophilic cell line, KU 812

The human basophilic cell line KU 812, that also has some mast cell characteristics, was found to express the PDGF-A gene and secrete PDGF-A like activity. After treatment with IL-6+ TNF-alpha, the PDGF-A mRNA expression increased as did cytoplasmic immunostaining with anti-PDGF antibodies. Secretion of PDGF-A was visualized by immunoprecipitation. An augmentation of non-secreted PDGF-like activity after IL-6+ TNF-alpha treatment was not accompanied by induction of the long splice variant of the PDGF-A-chain mRNA. Treatment with TPA caused an increase in PDGF-A expression and in addition, an induction of PDGF-B transcripts were seen. Staining of cytospin preparations with anti-PDGF antibodies visualized a substantial increase in immunostaining of the TPA treated cells and both intracellular and secreted PDGF-AA-like activity was substantially increased as compared to untreated control cultures. There was a concomitant induction of exon 6 specific mRNA, corresponding to a cellular retention signal after TPA treatment. Our results show that PDGF can be produced by a cell line of the basophilic/mast cell lineage, i.e. cells involved in allergic disorders and inflammation.