Production and Immunodiagnostic Applications of Antihuman Light Chain Monoclonal Antibodies

Hybridomas producing antihuman light chain monoclonal antibodies (MoAbs) were derived from fusion of SP2/O mouse myeloma cells with splenic lymphocytes from mice repeatedly immunized with purified Kand κ -type Bence Jones proteins representative of the major V κ , (V κ I, V κ II, V κ III, V κ IV) and Vλ (VλI, VλII/V, VλIII, VλIV, VλVI,) subgroups or gene families. Monoclonal antibodies were obtained that had specificity for constant-region (CI) determinants common to all κ or λ light chains (C κ and Cλ, respectively) as well as for variable-region (VL) epitopes unique to each of the V κ or Vλ subgroups. The capability of these reagents to recognize CI and VL determinants on monoclonal immunoglobulin (Ig) molecules was demonstrated in fluid-phase antigen-capturing enzymelinked immunosorbent assay (ELISA), solid-phase ELISA, and immunoblotting. In addition, these antilight chain MoAbs were used to establish immunocytochemically the κ or λ type and VL-subgroup nature of light chains expressed by the cytoplasmic Ig of monoclonal plasma cell and surface Ig of B-lymphocyte populations, respectively. These antibodies facilitated the immunohistochemical detection and characterization of light-chain-associatcd amyloid (AL amyloid) and other types of light-chain-related tissue deposits. Furthermore, the unti-CL-specific MoAbs were used to measure serum and urinary Ig κ and Igλ concentrations. Quantification of Bence Jones protein excretion, even in the presence of other urinary proteins, was possible using the highly sensitive anti-C κ and anti-Cλ MoAbs reactive only with free light chains. The ability to identify and characterize, through the use of these antihuman light chain MoAbs, light-chain-related epitopes at the protein, cellular, and tissue level has clinical importance in the diagnosis and treatment of patients with monoclonal plasma cell and related B-cell immunoproliferative diseases.