GENETIC ANALYSES OF AN IMMUNODEFICIENCY IN HEREDITARY MUSCULAR DYSTROPHIC CHICKENS

The F1 and F2 progeny of the Storrs strain of muscular strophic chickens were analyzed for the modes of inheritance of two immunodeficiencies, reduced IgG levels and a suppressed Con A response, and the relationship the immunodeficiencies have to the muscular dystrophic phenotype. The F1 hybrids derived from normal x muscular dystrophic chicken crosses were normal for the muscular dystrophy phenotype and the two immunodeficiency traits. The reduced IgG levels were not observed in the F2 progeny (F1 x F1) so the factors influencing reduced IgG levels in the Storrs strain of muscular dystrophic chickens remain undetermined. F2 data indicated that the suppressed Con A response is inherited as an autosomal recessive trait. In the F2 progeny, chickens expressing the muscular dystrophy phenotype occurred in significantly reduced numbers (50 percent of the expected). F2 digenic analyses of the muscular dystrophy trait and the suppressed Con A trait revealed a significantly decreased number of chickens in the muscular dystrophy- normal Con A trait category. Selective mortality of these chickens was ruled out, and it is postulated that the muscular dystrophy-normal Con A chickens may have been classified as normal for both traits. It is possible that the locus coding for Con A responsiveness or perhaps other genes contributed by the gene pool in the progeny crosses have ameliorated the expression of the muscular dystrophy phenotype in segregating F2 progeny. Resolution of any relationship between normal immune Con A responsiveness and reduced severity of the muscular dystrophy phenotype awaits the establishment of a critical muscle pathological index and analyses of testcross or advanced generations. Independent assortment of the suppressed Con A trait and the muscular dystrophy phenotype does not support the generalized membrane defect theory and emphasizes the importance of genetic studies in discerning the relationship between potential common membrane abnormalities and myopathic conditions. © 1979 American genetic association.