IMMUNOGLOBULIN ISOANTIGENS (ALLOTYPES) IN THE MOUSE : II. ALLOTYPIC ANALYSIS OF THREEγG(2)-MYELOMA PROTEINS FROM (NZB x BALB/C)F(1) HYBRIDS AND OF NORMALγG(2)-GLOBULINS

Further analysis of the isoantigens (allotypes) of 2 classes of normal mouse immunoglobulins, γG(2a) and γG(2b), has shown a minimum of 10 specificities for the Ig-1 locus (controlling γG(2a)-antigens) and 3 specificities for the Ig-3 locus (controlling γG(2b)-antigens). Three γG(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 γG(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 γG(2b)-globulin, carries only one of the Ig-3 specificities normally associated with γG(2b)-globulins of NZB. Most remarkably it also carries one Ig-1 specificity normally associated with γG(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.