Bence Jones Proteins: Nature, Metabolism, Detection and Significance MICHAEL J

ANNALS OF CLINICAL AND LABORATORY SCIENCE, Vol. 6, No. 1 Copyright @ 1976, Institute for Clinical Science Bence Jones Proteins: Nature, Metabolism, Detection and Significance MICHAEL J. DEEGAN, M.D. Clinical Immunology Laboratory, Department of Pathology, The University of Michigan Ann Arbor, MI 48104 ABSTRACT The nature of Bence Jones proteins is developed by a review of the pertinent literature. This is followed by a discussion of their metabolism and catabolism under normal and abnormal clinical conditions. Various methods for the detection of Bence Jones proteins are critically reviewed and the significance of these pro teins in various disorders is assessed. Nature more than a century after the initial descrip tion. In 1845 Henry Bence Jones, a physician The modern era of Bence Jones (BJ) pro and chemical pathologist at St. George’s tein analysis began with a report by Hospital in London, received a specimen of Edelman and Gaily16 that BJ proteins shared urine from Dr. Thomas Watson. The urine extensive antigenic cross-reactivity with was from a patient with an illness now myeloma proteins and normal gamma glob known to be multiple myeloma. Accom ulins. Putnam35 compared peptide maps of panying the specimen was a note the text of pooled human gamma globulin, seven which is reproduced here.11 purified pathologic globulins and eight BJ “The tube contains urine of very high proteins. On the basis of these studies, he specific gravity. When boiled it becomes concluded that there were two types of BJ highly opaque. On the addition of nitric acid protein and that they represented incom it effervesces, assumes a reddish hue and be plete or aberrant polypeptide chains of comes quite clear; but as it cools assumes the normal gamma globulin. Mannik and consistence and appearance which you see. Kunkel,27 using Ouchterlony immuno Heat reliquefies it. What is it?” diffusion methods, demonstrated that ap This challenge to Bence Jones resulted in proximately 60 percent of normal gamma a series of publications in which he clearly globulin molecules carried one group of an described many of the physicochemical fea tigenic determinants and 30 percent carried tures of the urinary protein which later came a second distinctive group of antigenic to bear his name. In his laboratory investi characters. Thus, the normal kappa to gation, Bence Jones placed considerable em lambda ratio of two to one for serum im phasis on the thermal properties of this uri munoglobulins was initially described. nary substance and these features were used Schwartz and Edelman39 used two-dimen- as the basis for defining the presence or sional, high-voltage electrophoresis and absence of this protein in patient’s urine for compared the tryptic hydrolysates from the 38 BENCE JONES PROTEINS 3 9 light chain of a myeloma globulin and BJ great deal of diversity. In fact, several protein from the same patient. They found subgroups of the VL portion of both kappa that the two were identical. Based on this and lambda chains have been charac and other data they suggested that BJ pro terized.37,43 They undoubtedly play an im teins were not aberrant or incomplete portant role in the antigen binding site of polypeptide chains but rather were entire which this portion of the molecule is an inte light (L) chains which had not been incor gral part. porated into the autologous myeloma protein. Further evaluation2 of the tryptic peptide Metabolism maps of a larger number of BJ proteins from The intracellular events necessary for the both antigenic groups (kappa and lambda) production and secretion of an immuno revealed that a common set of peptides exist globulin molecule are quite similar to those for each type of BJ protein, but that the required for other proteins. Heavy (H) peptides common to the kappa group of BJ chains and light chains are synthesized on proteins are completely different than the separate polyribosomes and are then joined common peptides of the lambda group. in the cisternae of the endoplasmic re These observations led Putnam36 to propose ticulum.9,40 Under normal conditions (un that each BJ protein or L chain was com associated with malignancy) one H and one posed of a constant and a variable portion as L chain form an HL intermediate that com defined by their amino acid sequence. This bines with a second HL molecule to form a proposal has subsequently been confirmed complete immunoglobulin (H2L2).9 Control and expanded through elucidation of the of some of the intermediate synthetic events primary structure of many BJ proteins by appears to be a function (at least for IgG amino acid sequence analysis. These se synthesis) of the individual H chain quence analyses have shown that a BJ pro subgroup, each of which has a characteristic tein (or a normal light chain) is composed of number and location of disulfide bonds that approximately 214 amino acid residues. The are essential to interchain linkage.9 initial one-half (residues 1 to 107) or amino Initial investigations suggested that the terminal end represents the variable portion formation of immunoglobulin molecules was of the molecule (VL). The carboxy terminal characterized by the production of an excess portion (residues 108 to 214) corresponds to of light chains41 and this was considered the the constant portion of the polypeptide source of the small amount of L chains pres chain (CL). Thus the C L portion of a par ent in normal serum and urine. Other ticular kappa type BJ protein is essentially workers, however, have shown that balanced identical to the CL region of all other type synthesis of H and L chains is most charac kappa BJ proteins and normal immunoglob teristic of nonmalignant immunoglobulin ulins containing kappa light chains, but production.1 These investigators also dem differs considerably from the CL region of all onstrated the existence of a small, rapidly type lambda proteins. An exception to this utilized intracellular pool of free light chains constancy is the occurrence of the genetic that may be important in controlling the marker Inv at position 191 on the kappa assembly of immunoglobulins.1 Their results chain.3 Various amino acids substituted in did not exclude the possibility that a small this position account for the different Inv amount of light chain might appear in the allotypes.48 In contrast to the constant por circulation as a result of cell death, cyto tion of the BJ protein or light chain is the plasmic shedding or unbalanced synthesis by variable region where there appears to be a a limited number of cells. 4 0 DEEGAN In malignant plasma cells of human and maleate or in clinical disorders such as the animal origin, a wide spectrum of synthetic Fanconi syndrome, Wilson’s disease and events has been shown to occur. Zolla and chronic cadmium poisoning.30 In these con coworkers55 demonstrated three basic pat ditions the processes of protein uptake and terns of immunoglobulin synthesis by ma catabolism diminish and increasing amounts lignant plasma cells: (1) production of only of small molecular weight proteins appear in L chains, (2) balanced synthesis where H the urine. In conditions characterized by a and L chains are made in equal amounts and selective proximal tubular disease, there is (3) an unbalanced synthesis in which intact usually little or no decrease in the immunoglobulin molecules and excess L glomerular filtration rate. However, when chains are made and secreted. It was also renal damage is more severe and involves the demonstrated that the formation of an HL glomeruli and tubules, there is a decrease of intermediate was common in the synthesis of the glomerular filtration rate. This results in a complete IgG myeloma protein and that less protein being filtered and presented to dimerization of L chains occurred intracellu- the tubular epithelium; therefore, ca larly.55 Excretion of the monoclonal L chain tabolism and excretion are diminished. In (i.e., BJ protein) into the urine as a monomer addition, many small proteins (e.g., L or a dimer was usually the same as the state chains) that would have undergone ca of polymerization when secreted by the ma tabolism or been excreted by the kidneys lignant plasma cell. However, in a number remain in the circulation and have a of cases where free light chains were clearly significantly prolonged half-life. demonstrated to be secreted by the cells, Individuals with normal renal function they were not detected in the urine. This remove labelled BJ proteins at a rate of 10 to suggests that the presence or absence of BJ 42 percent of the intravascular pool each protein in the urine is dependent on the rate hour; the half-life of a BJ protein or L in the and amount of free light chain synthesized circulation is approximately four hours.29,42 and the patient’s renal status (vida infra). Miettinen and Kekki29 injected 131I-labelled The investigations of Solomon,42 Woch- BJ protein into normal subjects and found ner51 and Miettinen29 and their collaborators that only 3.6 percent of the labelled protein have all contributed to establishing the was recovered intact in the urine. The bulk kidney as the major organ responsible for of the injected BJ protein was degraded the catabolism of normal light chains and within the body. The kidney was clearly BJ proteins. In a normal individual, the demonstrated to be the site of this degra- glomerular filtration apparatus effectively dative process in the studies of Wochner and controls the amount and type of protein that others.51 They showed that the survival time enters the tubular lumen usually allowing of human BJ protein was quite short in both only trace amounts of albumin to be ex unoperated and ureterligated mice; but in creted while significantly larger amounts nephrectomized animals it was markedly of proteins with molecular weights less than prolonged.

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