Ten genetically modified Maackia amurensis hemagglutinin (MAH) clones at the carbohydrate-recognition loop were found to bind glycophorin A and a mucin mimetic with NeuAcalpha2-3Galbeta1-3GalNAcalpha (monosialyl-T antigen) in different relative intensity. Binding profiles of these lectins to human serum IgA1 from healthy individuals and from IgA nephropathy patients were subjected to the cluster analysis. Two large groups, one with only healthy individuals and another with all IgA nephropathy patients, were generated. The results strongly suggest that the library of genetically modified MAH is a useful tool for serum diagnosis of IgA nephropathy.