IgA cold agglutinins recognize Pr and Sa antigens expressed on glycophorins

Three cases of IgA kappa cold agglutinins (CAs) were studied. One had anti-Pr1 specificity, one had anti-Pra, and one had anti-Sa. The CAs recognize O-glycans of glycophorins. The findings supplement previous data on anti-Pr1 specificities of four IgA kappa CAs. Because all IgA kappa CAs described recognize O-glycans of glycophorins, a close association between the CA IgA isotype and specificities for O-glycans becomes apparent. It is unlikely, however, that the striking association reflects interrelations between IgA CA structure and specificity, because anti-Sa specificity and all anti-Pr subspecificities were originally defined with IgM CAs.