Detection, by in situ hybridization using sulphonated cDNA probe, the specific mRNA for HLA-DR alpha induced in monocyte cell lines by recombinant interferon gamma.

We adopted the nonradioactive method used for blot hybridization for the detection of inducible mRNA for HLA-DR alpha by the in situ hybridization. Unstimulated and interferon gamma stimulated MonoMac6 and U937 human monocytic cell lines were used as target cells. Sulphonation of plasmid pBR322 with HLA-DR alpha cDNA insert (2 x 700 bp, in Pstl restriction site) was performed according to the manufacturer's procedure (SulfoProbe Kit, Sigma). The hybridization signals were detected with mouse monoclonal, anti-sulphonated DNA antibody, followed by immunovisualization with anti-mouse IgG-alkaline phosphatase conjugates. Unstimulated MonoMac6 and U937 cells showed few granular reaction products only in small percentage of cells (1-5%), while in IFN gamma stimulated cells the fine granular immunoenzymatic reaction was observed in the cytoplasm of majority of cells (> 80%). This method seems to be easy and rapid to perform, making it applicable for routine diagnostic purposes in tissue sections and biopsies.