Specific for human MUC1 glycoprotein (peptide tandem repeat in MUC1 core). Affinity > 1 x 108 for all MAbs.Binds with high efficiency with region of GVTSAPDTRPAPGSTAPPAHGVTSA synthetic peptide spanning the one repeat of VNTR extracellular portion of MUC1 molecule; reacts with VNTR5 and VNTR20 recombinant unglycosylated fragments of MUC1 protein and underglycosylated MUC1 prepared from tumor fluids or as a result of chemical treatment of human milk MUC1. Does not recognize natural MUC1 protein isolated from human milk by affinity purification on carbohydrate epitope specific MAbs and belong to MAb cluster 1-4 according to ISOMB TD-4 classification. No cross-reactivity with egg white avidin. Can be used for construction of highly effective ELISA tests for detection and measurements of unglycosylated and underglycosylated tumor-associated MUC1 mucins in human serum; as solid-phase reagents for MUC1 isoforms capture (a) in conjunction with the same MAbs enzyme-conjugated vertions (detection of unglycosylated MUC1), or (b) with enzyme-conjugated MAbs M2C5, M2E10 or M3A10 specific to carbohydrate portions of MUC1 (detection of underglycosylated MUC1).