MONOCLONAL ANTI-HUMAN ALDOLASE-C ANTIBODIES THAT REACT TO THE ISOZYMEGROUP-SPECIFIC SEQUENCES AND GENERALLY CONSERVED SEQUENCES OF HUMAN ALDOLASE-C

Nine monoclonal mouse anti-human aldolase C antibodies, mAbs A4, A8, B 4, B7, B8, C1, D9, E10, and H1, were isolated and characterized. These mAbs fall substantially into four groups according to their reactivit y with antigens. (i) Human aldolase C-specific mAbs (B8, D9, and H1). (ii) Type C aldolase-specific mAbs (B4 and E10). (iii) Ubiquitous mAbs , which react with vertebrate aldolases irrespective of type of isozym e and species (A4 and B7), (iv) Sub-ubiquitous mAbs, which are closely similar to the ubiquitous mAbs but differ slightly in terms of antige nic specificity (A8 and C1). Aldolase C-specific mAbs B8, H1, B4, and E10, but not D9, have their epitopes on a region within amino acid pos itions 79-193 of antigens, where the type-C isozyme group-specific seq uence-3 (IGS-3) is situated. In contrast, ubiquitous mAbs A4 and B7 an d sub-ubiquitous mAb A8 may have their epitopes on the commonly conser ved regions of the three isozyme groups. The epitope of sub-ubiquitous mAb C1 appears to be on the IGS-2/3 but this is yet to be resolved. T hese nine mAbs can be classified into two groups based on the mode of epitope recognition, which was determined by ELISA, immunoblotting, an d immunoprecipitation assays: (i) primary sequence-epitope mAbs such a s B4, E10, and B7; and (ii) conformation-epitope mAbs (B8, D9, H1, A4, A8, and C1). Among these mAbs, aldolase C-specific mAbs H1 and E10 ap pear to be useful as probes for detection of conformational change aro und the type-C IGS-3 motif of human aldolase C because, when assessed by immunoprecipitation assay, mAb H1 reacts only with human aldolase C but not with CA250 and CA306, while mAb E10 reacts with CA250 and CA3 06 but not with aldolase C, even though these antigens have a common t ype-C IGS-3 motif. Similarly, the ubiquitous mAb B7 should serve as a probe for general use to detect vertebrate aldolases irrespective of i sozyme groups and species.