Granulocyte-macrophage colony-stimulating factor modulates tapasin expression in human neutrophils

Differential display-polymerase chain reaction (DD-PCR) was used to evaluate changes in mRNA expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) treated human neutrophils to better understand how this cytokine affects the functions of neutrophils at the molecular level. Although a variety of cDNA fragments were identified as modulated by GM-CSF with the use of DD-PCR, one fragment in particular, NGS-17 (neutrophil GM-CSF-stimulated fragment #17), was characterized. The NGS-17 fragment hybridized to a 3.8-kh mRNA that encodes for a protein of a predicted molecular mass of 47.6 kDa. After cloning and sequencing, this gene was found to code for the recently sequenced tapasin or TAP-A protein. Immunoprecipitation and immunoblotting studies using anti-tapasin antibodies showed that tapasin is expressed in neutrophils and is associated with the MHC class I-TAP complex. Moreover, tapasin expression was found to be induced by dimethyl sulfoxide and by retinoic acid in HL-60 cells. This is the first report on the expression of tapasin in human neutrophils. It provides novel information, at the molecular level, on how GM-CSF enhances the functions of these cells.