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

We examined the ontogeny of IFN-alpha Secreting Cells (IFN-alpha SC) in different hematopoietic organs and blood of porcine fetuses at different stages of gestation. Cells were induced to produce IFN-alpha by incubation with the coronavirus TGEV and IFN-alpha SC were detected by ELISPOT. A striking finding was that IFN-alpha 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-alpha 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-alpha 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-alpha SC were found to be associated with hematopoietic organs, which argues for their hematopoietic lineage.