In the study presented here, we selected three representative pathogenic PV mAbs cloned from 3 different PV patients: F706, an anti-Dsg3 IgG4 isolated by heterohybridoma, F779, an anti-Dsg3 IgG1 isolated by heterohybridoma, and Px43, an anti-Dsg3/Dsg1 monovalent IgG antibody of unknown subclass isolated by phage display, and generated pairs of recombinant IgG1 and IgG4 antibodies expressing the identical variable region in order to assess the effects of the constant region on antibody function. Here, DSG1 is linked to acquired polycythemia vera.