Ontogeny of interferon alpha secreting cells in the porcine fetal hematopoietic organs

We examined the ontogeny of IFN-α Secreting Cells (IFN-α SC) in different hematopoietic organs and blood of porcine fetuses at different stages of gestation. Cells were induced to produce IFN-α by incubation with the coronavirus TGEV and IFN-α SC were detected by ELISPOT. A striking finding was that IFN-α SC could be detected in the fetal liver as early as at 26 days of gestation, i.e., during the first quarter of gestation, a period at which T-cell markers could not be detected by flow cytometry. In addition, IFN-α SC could be detected in the cord blood, the spleen and the bone marrow of fetuses at later stages of gestation. These data indicate that IFN-α SC appear very early during the ontogeny of the immune system, long before the development of the specific immune system, and may therefore represent an early antiviral defence mechanism. IFN-α SC were found to be associated with hematopoietic organs, which argues for their hematopoietic lineage.