The structural basis for genetic variations of normal human gamma-globulins

CLASSIFICATION OF MYELOMA PROTEINS, BENCE JONES PROTEINS, AND MACROGLOBULINS INTO TWO GROUPS ON THE BASIS OF COMMON ANTIGENIC CHARACTERS

Antisera to normal 7S γ-globulin and to Bence Jones proteins permit the grouping of myeloma proteins (gamma and beta 2A types), Bence Jones proteins, and the Waldenström type macroglobulins into two fundamental antigenic groups. The antigenic determinants responsible for this grouping are common to all these proteins which fall in the general category of immunoglobulins. Antisera to Bence Jones proteins were particularly useful for this classification since they failed to react with the proteins of the opposite group. These antisera also permit the grouping of normal 7S γ-globulin into two major types. The Bence Jones proteins from individual patients were found to correspond in antigenic group to that of the serum myeloma protein. Studies with antisera to 7S γ-globulin and to Bence Jones proteins indicated that the Bence Jones proteins were antigenically identical to a portion of the corresponding multiple myeloma protein molecules.

TWO MAJOR TYPES OF NORMAL 7S gamma-GLOBULIN

Normal 7S human gamma-globulin was found to contain two fundamental antigenic groups of molecules. The group 1 molecules of normal gammaglobulin correspond antigenically to group 1 multiple myeloma proteins and Bence Jones proteins; and group 2 molecules of normal gamma-globulin correspond antigenically to group 2 multiple myeloma proteins and Bence-Jones proteins. Among pooled human Fr II and several individual gamma-globulin preparations, approximately 60 per cent of molecules belong to group 1 and approximately 30 per cent of molecules to group 2 in this classification. The possible existence of a third minor antigenic group, constituting about 10 per cent, is discussed. Antisera to Bence Jones proteins of antigenic group 1 and group 2, in conjunction with I-131-labeled 7S gamma-globulin proved to be the most useful system for defining the antigenic groups of normal gamma-globulin. The group-specific antigenic determinants of normal 7S gamma-globulin molecules were located on the S fragments of these proteins.

The antigenic structure of the polypeptide chains of human gamma-globulin

The antigenic properties of the polypeptide chains of human 7S γ-globulin have been related to two major non-cross-reacting antigenic determinants of the whole molecule. These determinants, called S and F, were obtained by hydrolysis of γ-globulin with papain. Antisera against whole γ-globulin and against S and F fragments were used in techniques of immune diffusion. Light (L) chains of γ-globulin showed reactions of partial identity with S fragments, and thus are antigenically deficient with respect to these fragments. Antisera directed against F determinants did not react with L chains but did react with heavy (H) polypeptide chain preparations. In addition, the major component of H chain fractions did not appear to contain determinants in common with the S fragments. L chains of a γ-myeloma protein were shown to be antigenically deficient with respect to the whole myeloma molecule, and antigenically identical with the Bence-Jones protein of the same patient. Correlation of these results with those of previous investigations have led to the conclusions that the S fragment which is known to contain the combining region of antibody molecules, consists in part of L chains or portions of L chains, and that the F fragment, which mediates several other functions of the whole molecule, is composed in part of portions of H chains.

Antigenic relationships of Bence Jones proteins, myeloma globulins, and normal human gama-globulin

By means of immunodiffusion and immunoelectrophoresis study has been made of antigenic relationships of Bence Jones proteins, and the three classes of normal and pathological immunoglobulins, 7S γ, β_2A, and β_2M. All thirty-nine Bence Jones proteins studied could be classified into either one of two distinct antigenic types, A or B. Both types are related to the immunoelectrophoretically slow (S) fragment of a papain digest of normal γ-globulin; B is related more closely than A, but neither has antigenic determinants in common with the fast (F) fragment. The 7S γ myeloma globulins were either immunological type I or II. The papain digests of these proteins produced the S and F precipitin lines in immunoelectrophoresis but multiple bands in starch gel electrophoresis, especially in the F region. The S fraction of type I myeloma globulins is antigenically similar to Bence Jones protein of type B, and the S component of type II myeloma globulins has antigenic determinants in common with type A Bence Jones protein. Correspondingly, myeloma patients with type I globulins and proteinuria usually excrete type B Bence Jones proteins, whereas patients with type II excrete type A proteins. The F fragment is the part common to normal 7S γ-globulin and types I and II myeloma globulins but is absent in β_2A and β_2M pathological globulins and in both types of Bence Jones proteins. Papain digests of β_2A myeloma globulins produced a single precipitin line in immunoelectrophoresis. β_2A myeloma globulins appeared to have two antigenic units, one in common with type B Bence Jones protein and normal γ-globulin, and another specific to β_2A. The β_2A myeloma patients excreted type B Bence Jones protein. The papain digest of a macroglobulin produced two precipitin lines, the faster of which had antigenic determinants in common with type B Bence Jones protein, the slower seemed specific for the macroglobulin. Five serum micromolecular globulins proved to be either type A or B Bence Jones proteins. From the above results, an antigenic map was constructed showing which determinants are shared and which are specific for normal 7S γ-globulin, types I and II myeloma globulins, β_2A myeloma globulins, a macroglobulin, and types A and B Bence Jones proteins.

Genetic characters of human gamma-globulins in myeloma proteins

The genetic factors Gm(a), Gm(b), Gm(x), and Inv(a), Inv(b) described for normal human γ-globulin were all found in different myeloma proteins. A single myeloma protein never contained more than one product of alternate alleles even in heterozygous individuals. However, factors determined by the two different loci were often found in the same myeloma protein. The Gm(a) character of the myeloma protein parallelled that of the normal γ-globulin of the same serum in most cases. In contrast, the Gm(b) character was usually absent in the myeloma protein when it was directly demonstrable in the normal γ-globulin. The myeloma proteins from six Negroes were Gm(a+b-), whereas the normal γ-globulin was Gm(a+b+). This indicates that the effect of gene Gm^b is similar in Negroes and whites, even though its relation to gene Gm^a is different in the two races. Gm factors were found only in the 7S γ-globulin type myelomas and not in other products of plasma cell tumors. Inv characters were, however, present in all four types of proteins studied, namely 7S and 19S γ-globulins, β_2A-globulins, and Bence Jones proteins. In two instances, genetic heterogeneity of the protein products was demonstrated suggesting the proliferation of more than one clone of plasma cells in some multiple myeloma patients. The accumulated evidence obtained in this study strongly suggested that the presence and absence of genetic characters was compatible with the concept that myeloma proteins were closely analogous to individual moieties in the spectrum of normal γ-globulins rather than truly abnormal proteins. Their study offered evidence of a heterogeneity of genetic characters among the normal γ-globulins in a given individual. It also appears probable that in normal individuals single plasma cells have a restricted capacity to express genetic information in their protein product.

STUDIES ON HUMAN ANTIBODIES. II. DISTRIBUTION OF GENETIC FACTORS

Human antibodies against dextran, teichoic acid, blood group A substance, levan, tetanus toxoid, and nuclei were isolated and analyzed for their content of Gm(a), Gm(b), and Inv(a) γ-globulin genetic factors. The majority of these antibodies contained all the genetic factors determined in the donor's whole γ-globulin, but in many antibodies at very different concentrations. In a few instances specific factors could not be detected despite their presence in the individual's whole γ-globulin. Different antibodies isolated from the serum of the same individual showed different relative concentrations of genetic factors. The distribution of genetic factors seen in certain isolated human antibodies appeared to approach the selective occurrence of these factors in myeloma proteins.

THE IMMUNOGLOBULINS OF MICE. I. FOUR MAJOR CLASSES OF IMMUNOGLOBULINS: 7S GAMMA-2-, 7S GAMMA-1-, GAMMA-1A (BETA-2A)-, AND 18S GAMMA-1M-GLOBULINS

Two classes of 7S γ-globulins are identified in normal mouse serum and are designated 7S γ₂-globulins and 7S γ₁-globulins. These two immunoglobulin classes are similar in size. They differ in range of electrophoretic mobility, in specific antigenic determinants, and in genetically determined isoantigens. Four classes of immunoglobulins in mouse serum, i.e. 7S γ₂-, 7S γ₁-, γ_1A (β_2A), and γ_M-globulins, were shown to have antibody activity. Each class was characterized and shown to have distinctive immunochemical and physicochemical properties. The genetically determined isoantigens, Iga-1 and Iga-2, were shown to be present only on 7S γ₂-globulin molecules.

IMMUNOGLOBULIN ISOANTIGENS (ALLOTYPES) IN THE MOUSE. I. GENETICS AND CROSS-REACTIONS OF THE 7S GAMMA-2A-ISOANTIGENS CONTROLLED BY ALLELES AT THE IG-1 LOCUS

Eight antigens of 7S γ₂-immunoglobulins controlled by alleles at a single locus Ig-1, have been identified in mice. This locus has previously been shown to determine antigenic specificities on the F fragments of 7S γ_2a-globulins. The reactions of these antigens with various isoantisera have shown that the antigens all cross react with one another. New methods for the analysis of antigenic specificities of soluble proteins are presented in detail. A sensitive method for detecting in the order of 0.01 µg of these isoantigens has been developed, based on the quantitative inhibition of precipitation of I¹²⁵-labeled antigen. Cross-reactions of the antigens were analysed in inhibition assays and the data is compatible with the existence of a minimum of eight antigenic specificities. Each of the antigens is composed of different combinations of these specificities, with only one antigen having a specificity not present in any other. Sixty-eight mouse strains have been tested with specific isoantisera, and on the basis of the results, have been placed into the eight allele groups. Evidence for close genetic linkage of the Ig-1 locus and 11 chromosome markers has been sought and not found.

STUDIES ON HUMAN ANTIBODIES. 3. AMINO ACID COMPOSITION OF FOUR ANTIBODIES FROM ONE INDIVIDUAL

Antilevan, antidextran, antiteichoic acid, anti-"A" and normal γG, all isolated from a single human, as well as pooled γG and γM, were analyzed for amino acid content. Differences ranging from 7 to 32 residues were found among these antibodies in glycine, valine, leucine, tyrosine, arginine, lysine, and threonine content. These conspicuous differences in amino acid composition were not correlated with the Gm type of these antibodies. Hydroxylysine was found in two of the four antibodies, antidextran and antiteichoic acid, and in γM- immunoglobulin. No hydroxylysine was found in γG- globulins. These findings probably account for discrepancies in the literature concerning the occurrence of this residue in antibody protein.

PROPERTIES OF VARIOUS ANTI-GAMMA-GLOBULIN FACTORS IN HUMAN SERA

The serological and physicochemical properties of the following three forms of human anti-γ-globulin factors were compared: (a) rheumatoid factors; (b) Milgrom type anti-γ-globulin factors; and (c) factors directed against an antigen in human γG-globulin that is hidden in the intact molecule and revealed by enzymatic digestion at low pH. The property common to these factors is ability to interact with human γG-globulin; they are distinguishable because they react with different antigenic groups on this molecule. In all of five sera, the Milgrom type anti-γ-globulin factors were γM-globulins. They reacted with various human γG-globulin antibodies but failed to interact with γM-globulin type antibodies in agglutination and absorption experiments. When isolated from other anti-γ-globulin factors, they agglutinated red cells coated with intact anti-Rh antibodies, but failed to react with cells cells coated with pepsin-digested anti-Rh antibody. These observations indicate that the agglutinator reacts with the crystallizable, inert fragment of γG-globulin. Anti-γ-globulin activity directed against an antigen in human γG-globulin revealed by pepsin digestion was demonstrated in γG-, γA-, and γM-globulins. This anti-γ-globulin factor could be absorbed by antigen-antibody precipitates containing human antibody, which shows that the hidden antigen in human γG-globulin is revealed not only by enzymatic digestion at low pH, but also when γG-globulin is present as antibody in an antigen-antibody precipitate. Rheumatoid factors and Milgrom type anti-γ-globulin factors were also absorbed by antigen-antibody precipitates containing human antibody. The results indicate that the three distinct forms of antiγ-globulin factors may all be produced as a result of antigenic stimulation by autologous antigen-antibody complexes.

RHEUMATOID FACTOR PROPERTIES OF HYPERIMMUNE RABBIT SERA

The rheumatoid factor-like substance (RFLS) induced by hyperimmunization of rabbits with bacteria was consistently and exclusively associated with the macroglobulin fraction of the sera studied. The RFLS is separable from the bulk of serum proteins by zone centrifugation, DEAE cellulose chromatography, and gel filtration. Partially purified preparations of the RFLS were studied by immunoelectrophoretic analysis and analytical ultracentrifugation. Certain RFLS sera demonstrated selective reactivity with one or more rabbit isohemagglutinin antibodies. Pepsin treatment of rabbit γ-globulin removed or greatly diminishes its capacity to react with the RFLS.

Inv(1) allotype: effect of immunoglobulin G heavy chain subtype on its expression

More protein is required to detect the Inv(1) antigen carried in the light chain of immunoglobulin G molecules when the light chain is combined with a gamma2 heavy chain than when it is combined with a gamma1 or gamma3 heavy chain. One of the four gamma2 heavy chains used in the experiment, however, was as efficient as the gamma1 and gamma3 chains, indicating that there may be two subtypes of gamma2. Inv(1) was more easily detected in one of the two light chains used in the experiment. This difference may be associated with the subtypes of the kappa chain derived from studies of the variable portion of the chain.

Structural studies of human gamma-G-myeloma proteins of different antigenic subgroups and genetic specificities

1. Peptide maps of Fc fragments or heavy chains of 36 G myeloma proteins and two "heavy chain disease" proteins belonging to the four gamma-chain subgroups revealed very striking similarities between them. However differences in a few peptides were noted. This was most pronounced for the Ge(gamma(2)d) subgroup which lacked three peptides characteristic of the other three subgroups. While Fc fragments from different proteins belonging to the same subgroup appeared very similar, minor differences in addition to those based on currently recognized Gm factors were occasionally noted. 2. Fc fragments from Gm(a+) We(gamma(2)b) proteins had a peptide previously shown to be characteristic of normal Gm(a+) gammaG-globulins. Fc fragments from Gm(a-) molecules belonging to the We(gamma(2)b), Vi(gamma(2)c), or Ne(gamma(2)a) subgroups, whether Gm(b+), Gm(f+), or Gm(-), had the peptide previously identified in Gm(b+f+) normal gammaG-globulin. This "non-a" peptide was absent in peptide maps from Gm(-) molecules of the Ge(gamma(2)d) subgroup which contained instead another peptide with the same electrophoretic mobility but migrating slightly further on chromatography. 3. Both the "a" and "non-a" peptides were pentapeptides having three amino acids in common, and differing in the other two. The "a" peptide contained one residue of lysine, aspartic acid, threonine, leucine, and glutamic acid. The "non-a" peptides prepared from Gm(b+), Gm(f+), and Gm(-) proteins were identical and contained one residue of lysine, threonine, and methionine sulfone, and two residues of glutamic acid. 4. Several possible mechanisms for the origin of these differences, and their possible role in serologic specificity are discussed.

Allelic antigenic factor Inv(a) of the light chains of human immunoglobulins: chemical basis

Twenty-seven Bence Jones proteins of immunological type K show a common set of peptides. One 6f the commnon peptides differs in three of the proteins which are the only ones classified by a serological test as Iav(a+). The difference in the peptide analyzed is caused by a valine-leucine interchange; Inv(a+) proteins have leucine, whereas Inv(a-) proteins have valine in position 189.

Antibodies against gamma-globulin after repeated blood transfusions in man

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Genetic factors and polypeptide chain subclasses of human immunoglobulin G detected in chimpanzee serums

The Gm and Inv genetic factors, characteristic antigens of human immunoglobulin G, were detected in chimpanzee serums. All animals tested were Gm(a+, x-, b(l)-, b(2)-, b(3)+, b(4)+). Polymorphism was demonstrated for factors Gm(c), Inv(l), and Inv(b). Three of the subclasses of heavy polypeptide chains and both types of light polypeptide chains that are present in human immunoglobulin G were identified in chimpanzee serums.

GM and INV factors in subclasses of human IgG

Human G myeloma (7S gamma(2)-myeloma) proteins were investigated for relationships between Gm and Inv genetic factors and the different antigenic types of heavy polypeptide chains (gamma-chains) and light polypeptide chains. Myeloma proteins were isolated from the sera of 1 Chinese, 60 white and 28 Negro individuals. These 89 proteins were tested for eight Gm factors [Gm(a), Gm(x), Gm(b(2)), Gm(f), Gm(b(1)), Gm(b(3)), Gm(b(4)), and Gm(c)], and two Inv factors [Inv(l) and Inv(b)]. Results of the tests were correlated with the four gamma-chain subclasses (gamma(2a), gamma(2b), gamma(2c) and gamma(2d)) and the two types of light polypeptide chains, kappa-chains (type K or I) and lambda-chains (type L or II) found in human IgG molecules. 1. Gm factors were limited to myeloma proteins with heavy polypeptide chains of the gamma(2b)- and gamma(2c)-subclasses. No Gm factors were detected on gamma(2a)- and gamma(2d)-myeloma proteins or on a "heavy-chain" disease protein of subclass gamma(2d). 2. gamma(2b)-Proteins were positive for at least one Gm factor and were either Gm(a+), Gm(a + x+), or Gm(b(2)+ f+). 3. gamma(2c)-Myeloma proteins, and one gamma(2c)-"heavy-chain" disease protein, were positive for at least one Gm factor and contained various combinations of factors Gm(b(1)), (b(2)), (b(4)), and (c). Myeloma proteins from 3 Negroes were included in this group. 4. Inv factors (l) and (b) were limited to myeloma proteins with kappa-light polypeptide chains. These Inv factors were not detected on proteins with lambda-light polypeptide chains. 5. Most (70 per cent) of the gamma(2b)- and gamma(2c)-proteins with kappa-chains were Inv(l+) or Inv(b+). None of the gamma(2a)- or gamma(2d)-proteins with kappa-chains, however, contained these Inv factors.

A circulating anticoagulant in gamma-1A-multiple myeloma: its modification by penicillin

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