Phenotypic characterization of porcine IFN-γ-producing lymphocytes by flow cytometry

We have developed a three-colour flow cytometric assay for phenotypic characterization of porcine IFN-γ-producing lymphocytes. Analyses of activated swine peripheral blood mononuclear cells (PBMC) showed a significant difference in the proportion of IFN-γ producing cells between young and adult animals (13.2 ± 5.8% versus 34.2 ± 5.7%). The majority of IFN-γ producing cells were αβ T lymphocytes, although there was also an important proportion of γδ T cells particularly in young animals. Within the αβ T lymphocytes, the double positive CD4+CD8lo subset, that contains memory T cells, produced high levels of IFN-γ, whereas the CD8hi T cells ranged from low to high levels of IFN-γ. Also, consistent with a higher production by memory T cells, the CD45RA- subset of both CD4+ and CD8+ cells contained higher numbers of IFN-γ producing cells than the CD45RA+ subset. Finally, no production of IFN-γ by either B cells (CD21+) or monocytes (SWC3+) was detected. This assay may be useful for the assessment of cell-mediated immunity in vaccine trials and may contribute to our understanding of the role of IFN-γ in protective immunity against important viral diseases of the pig. © 2002 Elsevier Science B.V. All rights reserved.