THE METABOLISM OF GAMMA GLOBULINS IN MYELOMA AND ALLIED CONDITIONS

The Path to Conserved Extended Haplotypes: Megabase-Length Haplotypes at High Population Frequency

This minireview describes the history of the conceptual development of conserved extended haplotypes (CEHs): megabase-length haplotypes that exist at high (≥0.5%) population frequency. My career began in internal medicine, shifted to pediatrics, and clinical practice changed to research. My research interest was initially in hematology: on plasma proteins, their metabolism, synthesis, and function. This narrowed to a focus on proteins of the human complement system, their role in immunity and their genetics, beginning with polymorphism and deficiency of C3. My group identified genetic polymorphisms and/or inherited deficiencies of C2, C4, C6, and C8. After defining glycine-rich beta glycoprotein as factor B (Bf) in the properdin system, we found that the genes for Bf (CFB), C2, C4A, and C4B were inherited as a single haplotypic unit which we named the "complotype." Complotypes are located within the major histocompatibility complex (MHC) between HLA-B and HLA-DRB1 and are designated (in arbitrary order) by their CFB, C2, C4A, and C4B types. Pedigree analysis revealed long stretches (several megabases) of apparently fixed DNA within the MHC that we referred to as "extended haplotypes" (later as "CEHs"). About 10 to 12 common CEHs constitute at least 25 - 30% of MHC haplotypes among European Caucasian populations. These CEHs contain virtually all the most common markers of MHC-associated diseases. In the case of type 1 diabetes, we have proposed a purely genetic and epigenetic model (with a small number of Mendelian recessive disease genes) that explains all the puzzling features of the disease, including its rising incidence.

Behavior in vivo of normal and dysfunctional C1 inhibitor in normal subjects and patients with hereditary angioneurotic edema

The metabolism of normal C1 inhibitor and two dysfunctional C1 inhibitors (Ta and WeI) was studied in 10 normal subjects and 8 patients with hereditary angioneurotic edema (HANE), 4 with low antigen concentration (type 1) and 4 with dysfunctional protein (type 2). The fractional catabolic rate of the normal C1 inhibitor in normal subjects was 0.025 of the plasma pool/hour, whereas in HANE subjects it was significantly elevated at 0.035 of the plasma pool/hour. The synthesis of normal C1 inhibitor was decreased in patients with type 1 HANE (0.087 mg/ kg per h compared with 0.218 mg/kg per h). The fractional catabolic rate of dysfunctional protein WeI was similar to normal and showed a slightly accelerated catabolism in patients with HANE, whereas the dysfunctional protein Ta had a strikingly decreased fractional catabolic rate in normals and subjects with HANE. The present study is compatible with reduced C1 inhibitor synthesis in patients with type 1 HANE consistent with a single functional C1 inhibitor gene. The lower than anticipated levels of C1 inhibitor in HANE type 1 appears to result from (a) the single functional gene and (b) increased catabolism of the protein, perhaps related to activation of C1 or other proteases.

Metabolism of IgG in type II mixed essential cryoglobulinaemia--autologous cryoprecipitated and normal homologous IgG are incorporated into complexes and metabolized in vivo at similar rates

The metabolism of autologous cryoprecipitated and normal homologous IgG was studied in four patients with type II mixed essential cryoglobulinaemia. 131I-autologous IgG purified from each patient's cryoglobulin (Cryo-IgG), and 125I-pooled normal homologous IgG (N-IgG) were studied simultaneously to compare the extent of their incorporation into complexes with IgM in vitro and in vivo, and their turnover in vivo. A proportion of each preparation of IgG was incorporated into macromolecular complexes in vitro and in vivo in all patients, the Cryo-IgG only slightly more so than N-IgG. Results of the turnover studies were heterogeneous, but the common finding was the absence of any significant difference in the metabolism of Cryo-IgG and N-IgG. In two patients the fractional catabolic rates (FCR) of Cryo-IgG and N-IgG were increased and in one they were normal. The fourth patient was also hypogammaglobulinaemic (IgG 0.52 mg/ml) and it was shown that in vivo virtually all his IgG was combined with IgM; despite this the FCR of both types of IgG was reduced. These results suggest (1) that the IgG component of the cryoglobulins in these patients is unlikely to differ significantly from normal IgG and (2) that, contrary to expectation, complexed IgG is not necessarily rapidly eliminated from the circulation.

PWM-induced generation of immunoglobulin-secreting cells in patients with multiple myeloma

The pokeweed-mitogen-induced transformation of B-lymphocytes into immunoglobulin-secreting cells was studied in vitro in 25 patients with multiple myeloma using a reverse hemolytic plaque assay. Fifteen patients showed a good response in generating immunoglobulin-secreting cells, whereas 10 patients showed a decreased B cell reactivity which was not due to intermittent melphalan/steroid therapy administered to 15 patients. Experiments with lymphocyte subpopulations demonstrated that the inability of some multiple-myeloma patients to generate immunoglobulin-secreting cells was always based on a defect in the B-cell subset. Co-culture experiments with lymphocytes from normal individuals and patients revealed a cell-mediated suppression in one case, whereas humoral suppressive factors in the patients' serum could not be observed using the reverse hemolytic plaque assay. Patients were classified into three groups: (a) patients with a normal B-cell function, (b) patients with a reversible, tumor-dependent suppression of B-cell reactivity and (c) patients in whom the normal B-cell population was replaced by non-reactive cells.

Visual loss caused by corneal crystals in myeloma: rapid improvement and plasma exchange and chemotherapy

Recognition of needle-like crystals in the cornea of a patient with deteriorating visual acuity initiated laboratory studies which demonstrated underlying multiple myeloma. Crystal deposition in the cornea occurs only rarely in multiple myeloma, and evidently reflects an unusual tendency for certain paraproteins to form numerous small aggregates which are deposited particularly within, and between, corneal epithelial cells. Treatment with chemotherapy, plus repeated plasma exchange with a normal plasma protein product resulted in significant depletion of crystals, and improvement in visual acuity over a period of three weeks. Accelerated clearance of paraprotein by plasmapheresis appeared to contribute materially to the rapidity of recovery, since recovery was considerably faster than in reported cases where treatment was with chemotherapy alone.

Metabolism of autologous and homologous IgG in rheumatoid arthritis

The metabolism of radioiodinated IgG was studied in 20 patients with rheumatoid arthritis and 11 normal controls using autologous IgG and homologous IgG pooled from normal donors. Fractional catabolic rates in the controls were 4.44% of the autologous- and 4.29% of the homologous-labeled protein per day. The corresponding rates in the rheumatoid patients were 9.67% of the autologous- and 8.64% of the homologous-labeled protein per day. Extravascular catabolism occurred only in the rheumatoid group and accounted essentially for the entire increased catabolism of IgG observed in these patients. 10 patients were especially hypercatabolic, with fractional catabolic rates for autologous IgG greater than 10%. Moreover, they catabolized their autologous IgG significantly faster than the homologous IgG (12.6 vs. 9.9%). The increment of catabolism of autologous over homologous IgG also occurred in the extravascular compartment. These highly hypercatabolic patients had a significantly increased number of manifestations of extra-articular disease. The hypercatabolism of IgG could not be correlated with age, weight, sex, duration of disease, joint erosions, corticosteroid therapy, erythrocyte sedimentation rate, rheumatoid factor titer, serum IgG concentration, or circulating immune complexes as measured by the Raji cell radioimmunoassay. Conceivable sites of extravascular catabolism and possible causes of faster catabolism of autologous (rheumatoid) than of homologous (normal) IgG are discussed.

The plasma and tissue turnover and distribution of two radio-iodine-labelled pig plasma low density lipoproteins

Two classes of pig plasma low density lipoprotein (LDL1 and LDL2) with different densities and molecular sizes were isolated by zonal ultracentrifugation and were further purified by flotation. The peptide component was iodinated with 125I, and the labelled lipoprotein was injected intravenously. 125I-LDL1 turnover studies were performed on 22 3-4 month old female Large White pigs, and 125I-LDL2 turnover studies on 4 similar pigs. A biological screening experiment confirmed that the shape of the plasma activity curve was not a function of protein denaturation. The pattern of radioactivity decline in plasma was not affected by the degree of LDL iodination. 125I-LDL1 turnover: The curve of plasma radioactivity plotted against time over the first 5 days after injection could be resolved into two exponentials. The plasma biological half-life (T 1/2) was calculated from the slower exponential predominant from the second day. The mean T 1/2 over 2-5 days was 22.9 hr (range 17.2-28.5 hr). Multicompartmental analysis of the plasma decay curve using an open mammillary model gave a mean fractional catabolic rate per day for LDL1 of 1.4 (range 0.9-1.9). The mean T 1/2 was 0.26-0.31 times and the fractional catabolic rate 3.0-3.9 times those values found in two studies on adult humans. The tissue distribution of 125I was analysed in a series of 20 animals killed from 1.0 to 33.8 days after 125I-LDL1 injection. Most tissue 125I (86-89%) was protein bound. An appropriate correction was made to the 125I counts for retained plasma in liver and spleen (using 131I-albumin); retained plasma in other tissues was negligible. Highest 125I tissue levels were found in the liver, supporting other evidence that the liver may be the major site of LDL1 catabolism. After 2.06 and 4.06 days the livers in two animals contained 1.6% and 0.7% respectively of the total injected 125I, equal to 33% and 54% of the total plasma 125I at those times. The skin contained about one-third to one-ninth the 125I in the liver at various times. Distribution in other organs was quantitatively minimal. Higher levels of radioactivity were found in the intima and inner media of the aorta than in the outer media. These results suggest that plasma LDL in the pig diffuses through the endothelial surface into the arterial wall. These findings are confirmed by autoradiography. 125I-LDL2 turnover: Parallel studies of plasma 125I-LDL2 turnover and tissue distribution were performed. The plasma biological decay curve was multi-exponential, suggesting that LDL2 metabolism is complex, and possibly more rapid than that of LDL1 (LDL2 is smaller and denser than LDL1). The tissue distribution of 125I-LDL2 in these pigs was very similar to that of 125I-LDL1. As LDL1 and LDL2 differ in the amount of lipid they contain, they may have different roles to play in lipid transport, and there may be interconversion of one into the other at different sites. This hypothesis remains conjectural.

Metabolism of properdin in normal subjects and patients with renal disease

Properdin deposition has been recognized in glomeruli of patients with acute and chronic nephritis and lupus nephritis, and low serum properdin levels have been found in these disorders. These findings suggest that properdin may be involved in the production of glomerular damage and that low properdin levels may be due to hypercatabolism. The study was designed to examine the metabolism of properdin in normal subjects and to look for an abnormality in five patients with systemic lupus erythematosus with renal involvement and in six patients with membranoproliferative glomerulonephritis or dense deposit disease (MPGN). Highly purified human properdin was prepared by elution from zymosan, followed by DEAE-cellulose and carboxymethyl-Sephadex chromatography, and labeled with 125I by the iodine monochloride method. Parameters of metabolism were determined by monitoring plasma and urinary radioactivity at frequent intervals after the intravenous injection of 1-2 muCi of labeled material. The fractional catabolic rate (FCR) of properdin in normal subjects was found to have a very narrow range of 0.78-1.0,% of the plasma pool per hour (mean 0.95%). In systemic lupus erythematosus, the FCR was regularly elevated with a range of 1.21-2.30% (mean 1.70%). In MPGN, FCR was elevated in three patients (1.22, 1.94, and 2.08%) and within or below the normal range in three (0.78, 1.00, and 1.00%). Properdin levels were reduced in two patients who had the highest FCR's noted in the study. Properdin synthetic rates in normals varied from 4.1 to 14.3 mug/kg per h (mean 9.1) and was not found to be reduced in any patient. Properdin catabolism was found to be normal in a patient deficient in the C3b inactivator. These studies show that properdin is hypercatabolized in patients with renal disease and that decreased properdin levels when they occur in these patients can be entirely explained on the basis of this hypercatabolism.

Metabolism of radio-iodinated IgG in patients with abnormal serum IgG levels. II. Hypogamma-globulinaemia

The metabolism of radio-iodinated IgG was studied in seven patients with IgG deficiency (<600 mg/100 ml). The group comprised two patients with primary hypogamma-globulinaemia, one with primary hypogamma-globulinaemia and nodular lymphoid hyperplasia, and one each with chronic lymphatic leukaemia (CLL), γG multiple myeloma, renal homotransplantation and the nephrotic syndrome.

All patients had markedly reduced plasma and total body pools of normal IgG with normal distribution (intravascular and extravascular pools). An increase in the initial urinary excretion of free isotope in one patient was attributed to a degree of protein denaturation. Compared to the normal range of 20–60 mg/kg/day for IgG synthesis, the patients with primary deficiency and the patient with CLL all had markedly reduced synthesis of normal IgG (2, 5, 4 and 7 mg/kg/day respectively). These patients also had a prolonged or normal plasma T½ and a normal or decreased fractional turnover rate (FTR).

The patients with deficiency of normal IgG secondary to multiple myeloma, renal homotransplant or nephrotic syndrome all had an IgG synthesis rate at the lower limit of the normal range with values of 19, 21 and 19 mg/kg/day respectively. They had increased catabolism with a short plasma T½ and increased FTR.

An assessment of the factors controlling the metabolism of normal IgG is important in the individual patient as regards the management of their recurrent infections with therapeutic human γ-globulin.

Metabolism of radio-iodinated IgG in patients with abnormal IgG levels. I. Hypergamma-globulinaemia

Metabolic turnover studies were performed with radio-iodinated IgG in twelve patients with a serum IgG level greater than 1600 mg/100 ml (six with monoclonal gammopathy and six with a polyclonal increase in IgG associated with liver disease). The six patients with an IgG monoclonal protein comprised four multiple myeloma, one benign monoclonal gammopathy and one biclonal gammopathy presenting as Waldenström's macroglobulinaemia. The six patients with liver disease comprised two patients with cirrhosis, two with infective hepatitis and two with chronic active hepatitis. The injected IgG was either autologous normal IgG (five cases), autologous monoclonal IgG (five cases), homologous normal IgG (one case) or therapeutic intravenous HGG (two cases).

The plasma volume was increased in six patients; the plasma IgG pool in nine; and the total body IgG pool in seven. The plasma T½ was normal in one patient with monoclonal and one patient with polyclonal gammopathy but shortened in the other ten studies with mean values of 11·3 and 11·0 days in monoclonal and polyclonal gammopathy respectively. The fractional turnover rate was normal in two studies in polyclonal gammopathy and increased in the other ten with mean values of 13·6% per day in both groups of patients. The IgG synthesis rate was significantly increased in all studies except for a reduced synthesis of normal IgG in one patient with multiple myeloma. The mean synthesis rates in monoclonal and polyclonal gammopathy were respectively 6·7 and 4·1 times the mean synthesis rate in normal controls.

The pattern of increased synthesis and increased catabolism in such patients confirms published reports in some diseases and demonstrates a similar pattern in chronic active hepatitis. The findings are consistent with the `concentration-catabolism' effect.

Immunoglobulin synthesis and total body tumor cell number in IgG multiple myeloma

Studies of synthesis of IgG paraproteins were performed in 10 patients who had IgG myeloma in order to quantitate cellular immunosynthetic functions and derive estimates of the number of tumor cells present in such patients. Serial in vitro studies demonstrated constancy in the cellular rate of IgG paraprotein secretion for up to 8 months. Average molecular synthesis rates in different patients ranged from 12,500 to 85,000 molecules of IgG per minute per myeloma cell. Estimated total body tumor cell number ranged from 0.5 x 10(12) to 3.1 x 10(12) myeloma cells, and could be correlated with the degree of skeletal damage observed on roentgenograms (P = <0.01). Serial measurements of tumor cell number may prove useful in characterizing the growth rate and natural history of multiple myeloma. Myeloma is the first metastatic human malignancy in which quantitative measurements of the body's burden of malignant cells have been obtained.

Red cells coated with immunoglobulin G: binding and sphering by mononuclear cells in man

Human monocytes, macrophages, and certain lymphocytes bind firmly to red cells coated with immunoglobulin G, whether or not it is acting as antibody. Monocyte binding is specific for cells coated with immunoglobulin G and is inhibited specifically by this immunoglobulin or its Fc-fragment in solution. Although not involving serum complement and not usually a prelude to erythrophagocytosis, this binding causes rapid morphological injury to red cells, as manifested by their sphering, increased osmotic fragility, deformation, and fragmentation. It is inferred that mononuclear cells have specific surface receptors for immunoglobulin G and that these provide a critical phase of the mechanism in vivo, whereby red cells or other particles coated with antibody are apprehended and destroyed.

Alper CA, Rosen FS: Studies of the in vivo behavior of human C'3 in normal subjects and patients

The metabolic behavior of C'3 labeled with radioactive iodine was investigated in 10 normal subjects and in 20 patients with diseases in which complement is thought to play a pathophysiological role. The mean fractional catabolic rate of C'3 in normal subjects was 2.3 +/- 1.0% of the plasma pool per hr, whereas the fractional catabolic rate of C'3(i), the inactive conversion product of C'3 produced by complement activation, was at least five times as great. Increased catabolic rates were found in some patients with acute glomerulonephritis, systemic lupus erythematosus, idiopathic nephrotic syndrome of childhood, and progressive glomerulonephritis. Depressed synthesis was found in each of four studies of patients with progressive glomerulonephritis and seemed to be the major factor in the lowering of plasma C'3 concentrations regularly observed in patients with this disease. Of three patients with acute glomerulonephritis, synthesis rates of C'3 were markedly depressed in one subject, at the lower limit of normal in another, and entirely normal in the third. Increased extravascular: plasma pool ratios were observed in the studies of C'3(i) metabolism in a normal subject, and of C'3 metabolism in two of three patients with acute glomerulonephritis, in one of four patients with systemic lupus erythematosus, and in one patient with idiopathic nephrotic syndrome. The increased pool ratios are possibly compatible with tissue attachment of part of the injected C'3 or its conversion products. No important abnormalities of metabolism were found in patients with acquired hemolytic anemia, paroxysmal nocturnal hemoglobinuria, hereditary angioneurotic edema, or rheumatoid arthritis.By means of antigen-antibody crossed electrophoresis, C'3(i) could be demonstrated in the fresh plasma of three of eight patients who had acute glomerulonephritis. This finding was used as evidence for in vivo complement activation in this disease. Since C'3(i) was demonstrated only in plasma from patients with very low plasma concentrations whose onset of symptoms was very recent, there may be two phases in the metabolism of C'3: early complement activation with resultant increased catabolism and later depressed synthesis, both of which lead to lowered serum concentrations.