Specificity of anti-light-chain MoAbs for free light chains. Inhibition by κ Bence Jones protein (BJP) of anti-free-κ MoAb Fκ-C8 (a) and by λ BJP of anti-free-λ MoAb Fλ-G9 (b) using ELISA and polyclonal IgG, IgM and IgA proteins and κ and λ type BJP. OD, Optical density. ▪, BJP κ; ▴, BJP λ; ▵, IgA; ○, IgM; □, IgG.