Immunological and structural properties of human monoclonal IgG cryoglobulins

Abstract

Structural and immunological properties were determined for sixteen IgG and one Bence-Jones, human monoclonal cryoglobulins. The heavy chain subclass percentages were 47% IgG1, 14% IgG2 and 29% IgG3, and were different from previously reported distributions of myeloma proteins. In addition, 69% (eleven out of fifteen) of the cryoglobulins and 100% (seven out of seven) of the IgG1 cryos contained type lambda light chains. Electrofocussing of the cryoproteins by analytical liquid gradient column showed the isoelectric points to be included in the range of pH 6.3--8.9. The pI of six light chains and five out of six heavy chains were at acidic and slightly basic pH, respectively. The pI of the intact cryoglobulins were thus close to those of their constituent heavy chains. Six out of seven of the heavy chains were subjected to automated Edman degradation and were classified as containing vH-i or vH-ii variable region subgroups on the basis of their blocked amino termini. One type lambda light chain was unusual in that it contained an amino terminal sequence initially described in an amyloid fibril protein and is the first instance in which light chains with this sequence have been isolated from IgG. The data support the notion that the cryoglobulins are IgGs with unique structural and immunological properties which separate them from non-cryoprecipitable IgGs.