Allotype suppression in the chicken. V. Abnormal isotype ratios of chronically suppressed IgM and IgG allotypes

Chronic allotype suppression was generated in M-1 (C mu), G-1 (C gamma) heterozygous B14 line chickens either by embryonal injection or by maternal transfer of anti-M-1b allotype antibodies. Using a sensitive radioimmunoassay to detect the suppressed IgM-1b, a striking disparity was observed between the degree of suppression of the IgM-1b allotype and that of the genetically linked IgG-1i allotype. The amount of suppressed IgM-1b ranged between 0.2 and 3% of total serum IgM in chronically suppressed birds. The levels of the genetically linked IgG-1i, however, comprised 5 to 25% of total serum IgG in such birds. The allotypes measured in suppressed chickens were qualitatively identical to those in normal, nonsuppressed birds by serological criteria. These results are discussed within the context of isotype regulation in the chicken.