BREEDING AND GENETICS The Effect of Genetic Origin, Source of Antigen, and Dose of Antigen on

ABSTRACT The total agglutinin antibody titers and the 2-mercaptoethanol resistant antibody titers were determined in cockerels of three genetic origins, i.e., White Plymouth Rock (WPR), White Leghorn (WL), and a medium heavy breed cross (Warren). At 34 days of age the chicks were injected i.m. with 1.0 ml of either 100, 10, or 1 % suspension of packed sheep red blood cells (SRBC) in phosphate buffered saline. Antibody titers were determined on days 0, 3, 7, and 14 postinfection. The response to phytohemagglutinin (PHA) was measured at 49 days of age after intradermal injections of the antigen into the wingweb of the birds that had received the 100% suspension of SRBC. Differences among genetic groups resulted in significant differences for total antibody titers. The ranking of groups of different origin varied with day postinjection. The highest antigen dose yielded the highest antibody titers and there were no significant genetic origin-dose interactions. The WPR cockerels showed the greatest swelling in the PHA test, followed by the Warren and WL in that order, with differences being significant (P<.05). There was no correlation between anti-body titers to SRBC measured on day 3, 7, and 14 postinjection and PHA response, either overall or within groups of different genetic origin. We tentatively conclude that selection for general immune responsiveness may mean combining parameters of antibody and cell-mediated immune responses. The WPR cockerels were significantly (P<;005) heavier than the Warren cockerels, which in turn were significantly heavier (P<.005) than the WL. Statistical analyses suggest that the antibody response may be independent of body weight differences within genetically similar groups. (Key words: sheep red blood cells, hemagglutinin antibody titer, genetic stock X dose interaction, phytohemagglutinin skin response