CALR and myeloproliferative disorder: However, this approach may be limited by several factors: (a) MHC-1 having a high affinity for these neo-epitopes is under-represented in MPN patients128; (b) huge levels of soluble mutated CALR are present that inhibit the phagocytosis of dying cancer cells by dendritic cells and suppress the effects of PD-1 blockade129; and (c) CALR is implicated in the peptide loading on MHC-1130.