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Immunoglobulin isoantigens (allotypes) in the mouse. II. Allotypic analysis of three gammaG2-myeloma proteins from (NZB x BALB/c)F1 hybrids and of normal gammaG2-globulins.

Further analysis of the isoantigens (allotypes) of 2 classes of normal mouse immunoglobulins, gammaG(2a) and gammaG(2b), has shown a minimum of 10 specificities for the Ig-1 locus (controlling gammaG(2a)-antigens) and 3 specificities for the Ig-3 locus (controlling gammaG(2b)-antigens). Three gammaG(2)-myeloma proteins of plasma cell tumors induced in (NZB x BALB/c)F(1) mice have been analyzed for the isoantigens they carry. NZB mice are genotypically Ig-1(e) Ig-3(e), while BALB/c are Ig-1(a) Ig-3(a). Two of the myeloma proteins are gammaG(2a)-globulins. One of these, GPC-7, carries all the isoantigenic specificities of the Ig-1(e) allele while the other, GPC-8, carries all the isoantigenic specificities of the Ig-1(a) allele. Thus only one of the parental alleles of the mouse in which the tumor arose is expressed in each of these myeloma proteins. The third myeloma protein GPC-5, also carries the antigens of only one parental strain (NZB). However GPC-5, a gammaG(2b)-globulin, carries only one of the Ig-3 specificities normally associated with gammaG(2b)-globulins of NZB. Most remarkably it also carries one Ig-1 specificity normally associated with gammaG(2a)-globulins of NZB. This is the first analyzed mouse myeloma shown (a) to express some but not all the antigenic specificities normally associated with an allele and (b) to carry antigenic specificities controlled by two distinct immunoglobulin loci. The implications of these findings are discussed in relation to the genetic control of immunoglobulins.

Animals↗

In vitro studies on allotype suppression. II. Regulation of antibody synthesis by anti-allotype serum.

The regulatory effects of rabbit antibodies specific for light chain determinants (b locus) on the formation of rabbit serum immunoglobulins have been studied in an in vitro system which measures of the response of unprimed rabbit spleen cells to solubilized T2 phage antigen. Treatment of spleen cells from b4b4 rabbits with anti-b4 serum, which was either incorporated into the culture medium or employed in appropriate pulse treatment of the cells before culture, prevented the formation of T2 neutralizing antibodies by such cells. Spleen cells of heterozygous (b4b5) rabbits formed anti-T2 antibodies which could be shown to be divided between the b4 and b5 specificities. Incorporation of anti-b4 or anti-b5 serum into the culture medium suppressed the specific anti-T2 response and, except in the instances noted in the text, did not significantly change the level of T2 neutralizing antibodies marked with the alternate allelic determinant. These findings are discussed in the light of the compensatory formation of an alternate immunoglobulin type which occurs during allotype suppression in vivo.

Animals↗

DNA sequences specific for Caucasian G3m(b) and (g) allotypes: allotyping at the genomic level.

Assignment of the G3m(g) and (b) correlative amino acid residues was performed at the genomic level by direct sequencing of DNA from nine Caucasian individuals. Two oligonucleotide primers were used for subclass-specific enzymatic amplification of a DNA segment comprising a major portion of the second and third constant region domains (CH2 and CH3) of the human IgG3 heavy chain gene. Comparison of the sequences of amplified DNA from individuals serologically typed as homozygous for G3m(b) or G3m(g) or as heterozygous, G3m(b,g), revealed differences in the codons for the amino acid residues 291, 296, and 384. Proline, phenylalanine, and serine at these positions corresponded to G3m(b), and leucine, tyrosine, and asparagine to G3m(g). Heterozygotic individuals, typed G3m(b,g), displayed both the G3m(b) and G3m(g) codons at these three positions. The polymorphism at each of these three codons could be identified either as the appearance, or the loss, of recognition sites for the two restriction endonucleases, Nsp BII and Rsa I. This allowed the development of a polymerase chain reaction (PCR)-based assay permitting the distinction of G3mb and G3mg alleles by analyzing the electrophoretical mobility of the DNA fragments generated by digestion of the PCR-products with Nsp BII and Rsa I.

Amino Acid Sequence↗