Type I interferon subtypes produced by human peripheral mononuclear cells from one normal donor stimulated by viral and non-viral inducing factors.

Through the activation of Toll-like receptors (TLRs) or cytosolic RNA helicases, a large number of pathogenic or synthetic components can induce the transcription of genes coding for type I interferons (IFNs). This family of related cytokines includes notably, a single IFN-beta protein and 13 different IFN-alpha subtypes, whose biological activities are probably not the same. The aim of this study was to characterize the type I IFN subtypes produced in vitro by human peripheral blood mononuclear cells (PBMCs) in response to specific inducers. Thus, PBMCs obtained from a single donor, were exposed to various agents including Sendai virus, Herpes simplex virus-1 (HSV-1), poliovirus-IgG complexes and serum from a patient with systemic lupus erythematosus (SLE). Six hours later, mRNA was extracted and amplified by RT-PCR using primers which recognize IFN-B mRNA and the different IFN-A mRNA subtypes. IFN-A subtypes were identified by cloning and sequencing the amplification product. Antiviral activity was assayed in supernatant at 18 hours. Human PBMCs were found to express constitutively type I IFNs mRNA. Antiviral activity and expression of IFN-A and IFN-B mRNA increased with each inducing agent. Although almost all the IFN-A subtypes were detected, their relative abundance appeared to be dependent upon the inducing agent. Incubation of PBMCs with a neutralizing monoclonal antibody directed against the type I IFN receptor (IFNAR) did not affect the level of antiviral activity in the supernatant of induced PBMCs. Our results suggest that the level of IFN-alpha expressed by PBMCs cells is independent of IFNAR feedback signalling and that the nature of the inducing agent modifies the pattern of IFN-A subtypes preferentially expressed by these cells.