POSTTRANSCRIPTIONAL REGULATION OF INTERFERON-ALPHA-4 SUBTYPE PRODUCTION BY LYMPHOBLASTOID-CELLS

The constitutive production of interferon-alpha (IFN-alpha) subtypes b y the lymphoblastoid cell lines, Namalwa, Daudi and Raji, was investig ated using sensitive and semi-quantitative flow cytometric techniques. Further, we sought to determine whether the previously described fail ure of these cell lines to produce IFN-alpha-4 was a result of the del etion of the IFN A4 gene. Cytoplasmic production of IFN-alpha-2 and IF N-alpha-4 was assessed using IFN-alpha subtype-specific antipeptide an tibodies and FITC-labelled secondary antibodies in indirect immunofluo rescence-flow cytometry studies. The constitutive production of IFN-al pha-2 was detected in all three cell lines. Significant increases in f luorescence representing increased production of IFN-alpha-2 and possi bly other IFN-alpha subtypes were detected after induction by Sendai v irus. Approximately 100 per cent of cells in the Namalwa, Daudi and Ra ji cell populations contained IFN-alpha-2 before and after induction. However, no cells from the same cell populations contained the IFN-alp ha-4 subtype. Analysis of genomic DNA isolated from the lymphoblastoid cells using the Polymerase Chain Reaction (PCR) and oligonucleotide p rimers specific for IFN A2 or IFN A4 confirmed the presence of the gen es encoding both IFN-alpha subtypes. Furthermore, using reverse transc riptase-PCR amplification, mRNAs for both IFN-alpha-2 and IFN-alpha-4 were detected. Therefore, in contrast to some leukaemias and derived c ell lines where IFN A genes have been deleted, these cell lines of B c ell lineage exhibit selective expression of IFN A genes, as a result o f altered transcriptional/translational control of IFN-alpha expressio n.