IGHA1 and plasma cell myeloma: Takahashi et al. reported that the galactose-deficient form of O-glycan at Thr233 is more frequently observed than that at Thr225 in serum IgA1 isolated from healthy control and IgA1 myeloma protein,(13) which implies that serum Gd-IgA1 detected by KM55 ELISA predominantly contains P231ST(GalNAc)PP235 sequence rather than P223ST(GalNAc)PP227.