One cell–one immunoglobin. Origin of limited heterogeneity of myeloma proteins

Abstract

Plasma-cell tumour 5563 forms a single molecular species of immunoglobulin IgG(2)a, i.e. one variant of heavy chain and one variant of light chain. The molecules formed are labile and undergo alterations in charge properties, which rapidly lead to heterogeneity of the myeloma protein after synthesis. The single immunoglobulin species originally formed is found only after the shortest time-intervals tested, i.e. 10min incubation. Two types of changes in charge properties take place: (1) The originally formed protein (component o) is converted via an intermediate o' into the most basic form of 5563 myeloma protein found in serum (component a). Charge differences between these components are suppressed at pH8.9, but can be studied by chromatography at pH6.5 or by analysis of isoelectric points by isoelectric focusing in polyacrylamide gel. The conversion of components o and o' into component a apparently commences soon after assembly of the molecules and proceeds to completion extracellularly. (2) The second type of charge difference that distinguishes components a, b, c and d is exhibited over the pH range 6.0-8.9, but not at acid pH, and has been studied by electrophoresis at pH8.9, by chromatography and by isoelectric focusing. Conversion of component a into components b, c, d and e is only partial so that all five components can be found at decreasing concentrations in serum. Both types of charge alteration can be effected in vitro in the presence of serum, with optimum pH8.0. None of the charge differences could be attributed to the secretion process, since a component with the same isoelectric point as component o was found in secreted myeloma protein (1h). We have found no evidence to support the idea that the first type of change from component o to component a is due to ring formation of N-terminal [(14)C]glutamine into pyrrolid-2-one-5-carboxylic acid; however, our findings do not exclude this process happening very rapidly to a precursor of component o, possibly the polypeptide chain during or immediately after synthesis. In studying this point we noted that not only the heavy chains but also the kappa-type light chain of mouse 5563 myeloma protein have a blocked N-terminus.

Determination of the Primary Structure of a Mouse IgG2a Immunoglobulin

“…It could not be established whether these deamidations took place in the course of purification or whether they reflected a process in vivo [26]. There was complete agreement between the amino acid composition of peptides and the sequence data, with the exception of peptides C10, TC3, and P9, which contained a Val-Val dipeptide that led to an underestimation of the valine content as found after a 24-h hydrolysis.…”

Distinct functions of monoclonal IgG antibody depend on antigen-site specificities.

“…When, however, patterns were visualized by binding of I~II-Av-CHO (Fig. 1 B) according to Keck et al (18) very complex spectrotype patterns emerged with up to 75 bands, corresponding to 20-30 clonotypes (31). T h e d o m i n a t i n g clonotypes were no longer identified as such but replaced by other bands (Fig.…”

Dr Brigitte Askonas (1923‐2012)

“…She applied her biochemical knowledge to the process of antibody syntheses, elucidating the processes required for syntheses of immunoglobulin molecules within B cells. This resulted in several seminal discoveries especially in respect to the biochemical basis of antibody heterogeneity and a demonstration that a single antibodyforming cell produces a single type of antibody [6][7][8][9]. It was for her work on B-cell clonality that she was elected to the Fellowship of the Royal Society in 1973.…”