Multiple M-Components in a Single Individual

Clustering of extensive somatic mutations in the variable region of an immunoglobulin heavy chain gene from a human B cell lymphoma

Following treatment of a human B cell lymphoma with an anti-idiotype antibody, a subpopulation of tumor cells remained that had lost the tumor-specific heavy chain idiotypic determinant. Nucleotide sequence analyses of eight independent heavy chain variable region isolates showed extensive point mutations, so that no two sequences were identical. Comparison of pretreatment and posttreatment sequences implicated an amino acid in CDR2 as being involved in the idiotypic determinant. Apparently the malignant B cells escaped the therapeutic effects of the anti-idiotype antibody through an ongoing process of somatic mutation in their immunoglobulin genes. Non-random clustering of amino acid replacements in CDR2 suggested that growth of the tumor may have been influenced by endogenous selective forces interacting with the tumor cell-surface immunoglobulin.

Structural studies of three IgG kappa proteins from a patient with multiple myeloma

Three distinct IgG proteins of similar concentration and the same light-chain type were demonstrated in a myeloma serum. The bonds between the heavy and light chains were split, and the isolated gamma- and kappa-chains were characterized by crossed immunoelectrophoresis, subgroup determination and N-terminal amino acid sequence. The studies showed that the IgG heterogeneity was due to differences in the primary structure of the variable parts of the kappa-chains. Two of the kappa-chains belonged to subgroup V kappa I, and one chain, the most anodic one, belonged to V kappa III The gamma-chains were homogeneous and belonged to subgroup VHIII.

Two IgM paraproteins differing in carbohydrate content in a patient with Waldenström's macroglobulinemia

Two IgM paraproteins of different electrophoretic mobility were detected in the serum of a patient with Waldenstrom's disease. Both were type kappa, existed as high molecular weight polymers, and contained J-chain. The faster-moving protein contained a greater amount of carbohydrate, in both H and L chains.

Studies on IgA and IgA monoclonal proteins derived from a single patient. Evidence for identical light chains and variable regions of the heavy chain

Two immunoglobulins, IgA(K) and IgG(K), were isolated from the serum of a single patient with two monoclonal components (biclonal proteins). After chain separation, the light chains from each molecule were found to be identical by the following criteria: electrophoretic mobilities under various pH and dissociating conditions, amino acid compositon, fingerprint analysis of tryptic peptides and of 14C-succinylated chymotryptic peptides, and amino acid sequence of the N-terminal 40 residues. The heavy chains were indistinguishable for the N-terminal 45 amino acid residues. These data are consistent with the hypothesis that a single heavy chain variable (VH) region may be associated with two different heavy chain constant (CH) genes.