Constitutive and virus induced interferon production by peripheral blood leukocytes

The production of interferon-α (IFN-α) by normal human peripheral blood mononuclear cells (PBMNC) was studied using polyclonal antipeptide antibodies designed to react either with all IFN-α subtypes or with individual subtypes IFN-α2 or IFN-α4. In this study, we demonstrate the detection of intracellular IFN-α in PBMNC using immunofluorescence staining and flow-cytometric analysis. Virtually all cells of the PBMNC population were shown to produce IFN-α reactive with all three antisera after stimulation with Sendai virus. The immunofluorescence studies also demonstrated that IFN-α is produced by PBMNC in the absence of known viral stimulation but is not secreted in detectable levels. Double-labeling with specific monoclonal antibodies to T and B lymphocytes confirmed that the entire populations of these two cell types produce IFN-α, both constitutively and after virus induction. Polymorphonuclear cells (PMNC) isolated from Ficoll-Paque pellets were also shown to contain intracellular IFN-α, both before and after virus induction. The finding that all PBMNC produce IFN-α constitutively suggests that IFN-α may have important regulatory functions in situations other than during overt viral infections.