METHODS: BALB/c mice were orally sensitized to peanut and treated with EPIT for 8 weeks or left untreated (Sham). Splenic dendritic cell subsets were characterized and activation of expression markers were analyzed by flow cytometry [MFI (median of fluorescence) for IDO, CD86, CD80 and MHC-II] immediately following treatment and 8 weeks after the end of the treatment.
RESULTS: Total splenic dendritic cells (CD11c+MHC-II+) exhibited higher MFI for IDO, MHC-II and CD80 following EPIT treatment compared to Sham (respectively 4632 vs 3565, 12978 vs 9447 (p˂0.05), 236.5 vs 212 (p˂0.01)). More specifically, only the resident CD11c+MHC-II+CD11b+CD8- subset demonstrated over-expression of those molecules compared to Sham (IDO: 4548 vs 3543, CD80: 370.5 vs 353, MHC-II: 13881 vs 9624 (p˂0.05)). Increases in IDO and MHC-II expressions (p˂0.01) was sustained 8 weeks after the end of treatment in CD11c+MHC-II+ and CD11c+MHC-II+CD11b+CD8-subsets (IDO MFI p˂0.01).
CONCLUSIONS: EPIT upregulated expression of IDO, CD80 and MHC-II in total splenic dendritic cells and resident CD11b+CD8-, IDO over-expression being sustained for 8 weeks off treatment in both populations. EPIT seems to specifically modify the CD11b+ CD8- subset, which might inhibit CD4+ proliferation by co-expression of IDO and MHC-II, and promote a tolerogenic environment.