DIFFERENTIATION OF HUMAN-LAMBDA-1 VARIABLE REGIONS WITH A MONOCLONAL-ANTIBODY TO A DEFINED, GERM-LINE-ENCODED IDIOTOPE CORRELATES WITH V-LAMBDA-1A CHEMICAL-STRUCTURE

This article describes the characterization of a mouse monoclonal anti -idiotypic antibody (1H7B) prepared against a human monoclonal rheumat oid factor (RFSJ2) whose L chain utilized a Vlambda(I) subgroup gene. The mAb 1H7B reacted with 6 of the tested 12 human Vlambda(I) proteins , as well as with a newly produced lambda mAb whose Vlambda gene usage has not as yet been determined. Because six of the 1 H7B-positive mAb were heterogeneous with respect to both their V(H) gene utilization a nd antigenic specificity, and because mAb 1H7B did not react with any of the tested 43 kappa or 12 lambda proteins belonging to various subg roups other than Vlambda(I), mAb 1H7B appeared to be a V(lambda)I subg roup-specific reagent. The L chain specificity of mAb 1H7B was confirm ed by Western blotting, and the inhibition of RFSJ2 binding to human F cgamma by 1H7B provided additional evidence for the V region specifici ty of mAb 1H7B. The 11 sequenced V(lambda)I proteins used in this stud y were assigned to sub-subgroups by comparison with the previously pub lished germ-line Vlambda(Ia), Vlambda(Ib), and Vlambda(Ic) sequences. The mAb 1H7B only appeared to recognize Vlambda(Ia) proteins as it rea cted with five of the seven Vlambda(Ia), but not with three Vlambda(Ib ) or with one Vlambda(Ic) protein. Because mAb 1H7B reacted with at le ast one Vlambda(Ia) sequence in germ-line configuration, it appeared t o be a marker for Vlambda(Ia) sub-subgroup germ-line gene(s). The idio tope recognized by 1H7B was localized to the first framework region by inhibiting its binding to RFSJ2 with a synthetic peptide to the 11-24 amino acid region of Vlambda(Ia) L chains. Comparison of the Vlambda1 -24 region sequence of RFSJ2 with those of the two 1H7B-negative Vlamb da(Ia) mAb revealed a single amino acid difference at position 17, sug gesting that the idiotope recognized by 1H7B encompassed this position .