SEROLOGICAL AND CHEMICAL SPECIFICITIES OF 12 MONOCLONAL ANTI-LEA AND ANTI-LEB ANTIBODIES

The serological specificities of twelve hybridomas were compared as to their chemical reactivity as determined using direct binding to synthetic carbohydrate structures. All anti-Le(a) cross-react with type-1-precursor structures and three different variants of anti-Le(a) could be defined by their binding to type-3-precursor chains. sialylated compounds and the monosaccharide D-galactose. Three major reactivity patterns were also identified among anti-Le(b) reagents. Anti-Le(bL) cross-react with Le(a) and do not significantly bind to H-related structures. Anti-Le(bH,L) had both anti-Le(bL)-like activity (cross-reaction with Le(a)) and anti-Le(bH)-like activity (cross-reaction with H). Finally, anti-Le(bH) cross-reacts strongly with H compounds and do not bind to Le(a). The binding pattern of anti-Le(bL) suggests that these antibodies have lower affinity for ALe(b) and BLe(b) pentasaccharides than anti-Le(bH). All these specificities are not absolute, but rather are expressed as members of a quantitative progressive varying series, suggesting the existence of a whole range of antibody specificities gradually changing from Le(a) --> Le(a,b) --> Le(bL) --> Le(bH,L) --> Le(bH). The results suggest that anti-Le(bL) will always cross-react with Le(a) and that anti-Le(bH) will always cross-react with H related structures. However, under certain well-defined conditions these cross-reactions may not be apparent and antibodies might behave as specific anti-Le(a) or anti-Le(b) in certain tests.