Concentration of immnoglobulin G in plasma varies among 6C.7 recombinant congenic strains of chickens.

Chicken Lines 63 and 72 were inbred during selection for resistance or susceptibility to viral-induced tumors. A sandwich ELISA assay was adapted to define the milligrams per milliliter of Ig-gamma (IgG) in plasma from chickens of Lines 63 and 72, as well as 19 recombinant congenic strains (RCS). Each RCS resulted from a 7(2) x 6(3) F(1) and two backcross matings using 63 as the recurrent female line. The IgG levels in the RCS were evaluated after four to seven generations of sib-matings, when each RCS was becoming inbred and fixed for a different 12.5% of the 72 genome. In three generations approximately 24-wk-old chickens of Line 72 had higher levels of plasma IgG than chickens of Line 63 (P < 0.05). None of the RCS had repeatable IgG levels comparable to Line 7(2). However, in the last two generations, two of the 18 RCS had higher IgG levels than nine with low IgG levels (P < 0.05). There was no correlation between an IgG level of a RCS and resistance to Marek's disease. It was concluded that selected RCS may be useful for identifying genes that determine differences in IgG levels, as well as for understanding the relationship between genes, IgG levels, and other traits that differ between Lines 63 and 72.