Divergent antibody responses to vaccines and divergent body weights of chicken lines selected for high and low humoral responsiveness to sheep red blood cells.

Primary and secondary antibody responses to intramuscularly administered proteins of Eschericia coli (F11), Newcastle disease virus (NCD), infectious bronchitis virus (IB), and infectious bursal disease virus (IBD), respectively, were measured at weekly intervals in two chicken lines. The latter had been divergently selected for high and low antibody responses to sheep red blood cells (SRBC), and in a random-bred control line. An oil-based adjuvant was required to induce primary and secondary antibody responses to NCD, IB, and IBD. With respect to F11, elevated antibody responses were found in birds sensitized and boosted to F11 with and without adjuvant. The humoral response to F11 and to all viral antigens was significantly higher in the high (H) line than in the low (L) line, whereas the control (C) line showed intermediate titers. At 5 and 17 weeks of age, L line birds were significantly heavier than birds of the H and the C lines. A negative phenotypic correlation within lines between body weight at 17 weeks of age and antibody titers at 1 week after sensitization was found, but no further correlations between humoral responses and body weight or growth could be established. The present results suggest that selection for enhanced humoral responsiveness to SRBC resulted in enhanced responsiveness to components of several vaccines. Mechanisms underlying the relationship between divergent selection for immune responsiveness and body weight are discussed.