Expansion of intracellular IFN-γ positive lymphocytes during Mycoplasma agalactiae infection in sheep.

A method to assess the expansion of antigen-specific intracellular IFN-γ positive T cell subsets during the infection will be helpful for a better understanding of mycoplasmal infections physiopathology in the sheep. We analysed the percentage of antigen-specific lymphocytes positive for intracellular IFN-γ during the infection of sheep with Mycoplasma agalactiae by culturing peripheral blood mononuclear cells of infected or uninfected animals with irradiated M. agalactiae. The expansion of antigen-specific IFN-γ positive lymphocytes in infected sheep was initially sustained by CD4(+) T cells at day 15 after infection, when antigen specific IgG start to be detectable, followed by CD8/IFN-γ double positive cells. γδ T-cells were not expanded at any time point analysed. IFNγ(+) T cells disappear 60 days after infection, suggesting that antigen specific IFNγ(+) T cells, mainly detected in the early phase of the disease, could be useful to understand the role of cell-mediated immunity during M. agalactiae infection.