Hapten-sandwich labeling. IV. Improved procedures and non-cross-reacting hapten reagents for double-labeling cell surface antigens.

New procedures are presented for preparation of hapten-antibody conjugates with the bifunctional amidinating reagent methyl-p-hydroxybenzimidate (HB). Conjugates with improved solubility are effective for hapten-sandwich labeling of cell surface antigens with high sensitivity and specificity. Several non-cross-reacting hapten-antihapten antibody systems are described which are well-suited for simultaneous labeling of different surface antigens.