EPO down-regulates proliferation of MOG-specific T cells and suppresses T cell cytokine production.

<p>a) Single cell suspensions of hyperimmune EAE spleen were prepared 7 days post MOG peptide immunization and quantified by flow cytometry for CD8 and MOG_44–54/H-2Db dimer double positive binding. In normal mice, 0.42% of splenic CD8 cells bound to the MOG_44–54/H-2Db dimer (left side), whereas an 8-fold increase in MOG_44–54/H-2Db dimer positive staining occurred in CD8 T cells obtained from MOG_35–55 immunized EAE animals (middle). In contrast, when a non-specific control peptide was tested, only 0.6% of CD8 cells exhibited non-specific binding to the NP_366–374 dimer (right). b & c) MOG-EAE antigen specific T cells were enriched by exposure to antigen in long term tissue culture, and then exposed to EPO (1 or 10 U/ml) for 72 hrs. Supernatants were collected from the cultured MOG-T cells for cytokine profile analysis and the remaining cells were quantified for number of CD8 and MOG_44–54/H-2Db dimer double binding cells after exposure to EPO or control treatment. EPO induced a marked decrease in pro-inflammatory cytokine production (black bars) when compared to controls (white bars). EPO at 1 U/ml induced a substantial decline in the MOG-specific CD8 T cell population (c-middle panel). Some of the MOG_44–54-peptide/H-2Db dimer positive, non-CD8 T cell (including portion of CD11c positive cells) populations were also reduced by EPO treatment (c-middle panel). Each data point is the mean±SEM of three experiments performed in triplicate. *, p<0.005.