Genetic associations of body weight and immune response with the major histocompatibility complex in White Leghorn chicks.

Survival, body weight, and humoral immune response to sheep red blood cells (SRBC) were measured in 256 chicks of the Iowa State University S1 Leghorn line. The chicks were produced from breeders selected for serological Ea-B blood type (B1 or B19), high or low humoral immune response to the amino acid polymer, glutamic acid-alanine-tyrosine (Ir-GAT), and response to Rous sarcoma virus-induced (RSV) tumors (progression or regression). Chicks were hatched from sublines representing all eight triple homozygous genotypes. Survival was significantly (P less than .01) associated with Ir-GAT, but not with Ea-B or RSV response. Body weight was affected by Ea-B, Ir-GAT, and the interaction between Ea-B and Ir-GAT, but not by interaction with RSV response. The SRBC antibody titer was affected by the interaction of Ea-B and Ir-GAT. The SRBC antibody titer was also lowest in the B19 low group. There were positive significant correlations (.21 to .31) between SRBC antibody titer and body weights at all ages except hatch in the Ir-GAT low group, but there were no significant correlations between SRBC antibody titer and body weights in the Ir-GAT high group. In this population of White Leghorn chicks, the heritabilities of body weight ranged from .43 to .27 for weights at 2 to 6 wk of age, and the heritability of SRBC antibody titer at 4 wk was .34 +/- .25.