CD8A and myeloproliferative disorder: While we could readily detect virus-specific multimer+ CD8+ T cell populations in PBMCs from 5 of the 7 MPN patients, putative mCALR multimer+ CD8+ T cell populations were undetectable in all patients, suggesting that these putative mCALR multimer+ CD8+ T cell populations are not, or very weakly, immunogenic (Fig. 1).