Presence of the Fc-Fragment Allotypic Determinant, A15, on IgG from an Allotype-Suppressed Aa2 Homozygous Rabbit Lacking the Aa2 Determinants of the Fd Fragment

摘要

Approximately 10% to 30% of normal rabbit IgG molecules lack the allotypic specificities, Aa1, Aa2 or Aa3, of the Aa heavy chain locus (1, 2). Suppression of the Aa locus determinants has been observed in Aa locus homozygous rabbits following exposure to anti-allotype antisera in utero and neonatally (3, 4). Approximately 95% of the IgG obtained from an Aa 2 Aa 2 homozygous suppressed rabbit lacked the Aa2 allotypic specificity (5). Recent data (5) on these Aa-negative molecules have shown that: a) Aa-negative IgG molecules carry a “new” set of allotypic determinants, A31, which are present on the Fab portion of the molecule; b) by peptide mapping, the Fab portion of Aa-negative molecules differs from the Fab portion of Aa-positive molecules; and c) by peptide mapping, the Fc portion of Aa-negative molecules is indistinguishable from the Fc portion of Aa-positive molecules.