Human immunoglobulin allotypes: previously unrecognized determinants and alleles defined with monoclonal antibodies.

Abstract

The highly polymorphic system of serologically defined genetic markers on human IgG heavy chains (Gm allotypes) is second only to the HLA complex in terms of the large number of determinants, alleles, and haplotypes that can be used for analyses of disease associations and other genetic studies. However, present typing methods are based on the use of antiGm antisera that are derived mainly from fortuitously immunized human donors, often requiring processing before use, and must be used in a hemagglutination-inhibition assay that cannot be used in typing for isoallotypic determinants (currently termed "nonmarkers"). In studies presented here, we describe an allotyping system that utilizes monoclonal antibodies in a "sandwich" modification of the solid-phase radioimmunoassay, which is capable of reliable quantitative typing of allotypic, isoallotypic, and isotypic immunoglobulin determinants. We show that these highly reproducible, easily disseminated, and essentially inexhaustible reagents can be used for rapid, sensitive, and quantitative Gm typing. Using this system we define two previously unrecognized Gm determinants, one of which, found to date only in Caucasians, is different from all known Gm markers and thus defines previously unrecognized alleles and haplotypes. The other determinant cosegregates with the conventional G3m(bl) marker but is distinct from that marker on serological grounds. The successful preparation of mouse monoclonal antibodies that detect human Gm allotypic differences and the development of an assay system capable of typing isoallotypic as well as allotypic determinants opens the way to further dissection and application of this rich genetic system.

Human Gm, Km, and Am Allotypes: WHO/IMGT Nomenclature and IMGT Unique Numbering for Immunoinformatics and Therapeutical Antibodies

“…To compensate for the rarity of some reagents, attempts were made to obtain monoclonal antibodies; however, the main difficulty resides in the characterization of their specificity [117,123]. Molecular biology was first used for the determination of A2m2 by RFLP [85], and this method is particularly interesting given the rarity of the reagents and was the first protocol to determine allotypes in the absence of serum (e.g., from cell lines).…”

Immunoglobulin G genetic variation can confound assessment of antibody levels via altered binding to detection reagents

“…These Ig polymorphisms were initially termed ‘allotypes’ following identification in 1956 via rabbit anti‐sera produced by animals inoculated with serum from an immunogenetically distinct counterpart 4 . Almost three decades later, monoclonal anti‐allotype antibody detectors were developed 5 . Given the immunogenic nature of allotypes, it is not surprising that these alleles underlie variable interactions between immunoglobulins and their respective anti‐isotype detection reagents.…”

“… 4 Almost three decades later, monoclonal anti‐allotype antibody detectors were developed. 5 Given the immunogenic nature of allotypes, it is not surprising that these alleles underlie variable interactions between immunoglobulins and their respective anti‐isotype detection reagents. Although individual allotypic markers are typically defined by only one or two amino acid substitutions, these substitutions may alter protein–protein interactions by mutating the epitope recognised by the detection antibody, interfering with binding via steric hindrance, or by inducing conformational changes at the binding site of the detection antibody, even if this epitope is distant from the position of the substituted amino acids.…”