QUANTITATIVE STUDIES ON THE HEMAGGLUTINATION INHIBITION REACTION FOR DETERMINATION OF THE Gm TYPES

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.

Immunogenetic markers as probes for polymorphism, gene regulation and gene transfer in man--the Gm system in perspective

The genetic markers of immunoglobulins (Ig) demonstrable by immunological methods have shown their usefulness as genetic probes. The study of these allotypes originally proved that Ig production is under conventional genetic control and also established that allelic exclusion is valid for the key molecules of the immune response. The codons responsible for the G1m(a) marker and their position in the human genome are precisely known. This knowledge implies that Gm typing may be used as a convenient and reliable means of following the fate of IgG constant gene segments. Anti-Gm's are common in rheumatoid arthritis. They appear early in the disease and may persist throughout life. The stimulus for their appearance has not yet been established. The anti-Gm's in the allegedly autoimmune disease rheumatoid arthritis are commonly and apparently paradoxically specific for Gm gene products of other persons. Another apparent paradox brought to light by Ig allotype research is the occasional appearance of non-nominal allotypes in contradiction to Mendelian laws. It is proposed that a plausible explanation for these two paradoxes is Ig gene transfer between individuals with viral vectors. Reasons for this proposal and some possible consequences of gene transfer in a polymorphic species are delineated. Immunogenetics and DNA technology in combination provide powerful tools to elucidate the fate of genes. A method allowing the assignment of G1m(a+) and G1m(a-) at the gene level by polymerase chain reaction analysis has recently been established and is briefly described.

The Gm system. Anti-Gm's: characteristics in rheumatoid arthritis; experimental induction without resort to allotype; frequent occurrence in mononucleosis

Gm system: Some RFs specifically detect Mendelian markers of human Ig, originally proving that Ig production is gene controlled. The genetic marker systems of human Ig with 17 Gm, 2 Am, 3 Km and 1 Em markers are briefly described. Examples of the usefulness of the Gm system in medicine, immunology and molecular biology are mentioned.

CONCLUSIONS

1. Some RFs have been essential tools in elucidating genetic control mechanisms in Ig production. 2. Knowledge of the Gm system is extensive. Anti-Gm's: High-titered anti-Gm's are common in R.A. The anti-allotypes in R.A. are markedly restricted as to their specificity. They are usually not directed against the individuals own Gm markers. Anti-human-immunoglobulins were observed in 12 of 18 sera from patients with mononucleosis. The majority of these anti-immunoglobulins were inhibitable by native human Ig and showed restricted specificity.

CONCLUSIONS

1. There is a strong stimulus for production of particular anti-Gm's in a majority of R.A. cases. 2. Notions of an autoimmune origin for many anti-Gm's in R.A. are not in obvious agreement with experimental observations. 3. Anti-human-Ig's with restricted specificity are commonly induced in mononucleosis.

Biological activity of the cleavage product of human immunoglobulin G with cyanogen bromide

Treatment of human IgG with cyanogen bromide in 0.05 M HCl under specified conditions resulted in the cleavage of about half of its methionyl peptide bonds. A major fragment of about 5S was isolated from the reaction mixture by gel filtration in quantitative yield. The CNBr fragment reacted fully with goat antiserum against human light chain, but its reaction with anti-heavy chain was markedly decreased. The treatment with CNBr caused a drastic decrease in the following biological activities of IgG: complement fixing, skin binding, reaction with antiglobulin factors, and reaction with specific anti-Gm(12) serum. On the other hand, the reaction with serum of anti-Gm(1) or anti-Gm(4) specificity was not impaired and antibody activity, namely antistreptolysin and isohemagglutinin, was retained after the treatment with CNBr. It is concluded that the CNBr cleaves preferentially the methionyl bonds in the Fc portion of IgG, and that the major fragment obtained, denoted F(ab'')(2), has still the combining properties of a divalent antibody. The possible therapeutic uses of F(ab'')(2) are discussed.