Directional selection for specific sheep cell antibody responses affects natural rabbit agglutinins of chickens.

Agglutination data from generations 8 through 19 indicate that bidirectional selection for specific SRBC antibody responses was successful in a line cross of ISA x Warren medium heavy layers. After 11 generations titers of the high SRBC selected line (H line) were nearly 1:32,000; those of the low SRBC selected line (L line) were less than 1:2, but titers of the randombred control line remained stable at 1:32. Directional SRBC selection also affected levels of a naturally occurring rabbit cell agglutinating antibody (RRBC), presumably the avian form of alpha-galactose antibody (anti-Gal). This indirect response was biphasic and opposite in direction to the SRBC responses through generation 14 after which anti-Gal titers of all 3 lines increased. At generation 19, line H had the highest agglutinin titers; of both types, control line was intermediate, and line L was lowest. The correlation between SRBC and RRBC titers was 0.43 (P = 0.0). Females had higher titers than males, but the difference was only significant for the SRBC antibody (P = 0.028). Qualitative changes in anti-Gal accompanied SRBC selection. Rabbit agglutinins of 4 types were recognizable: classic, granular, annular, and one negative or very weak reaction. The score type means in line L were highest, in the control line were intermediate, and in line H were lowest, suggesting avidity differences now exist among these lines. The results show integration of natural and acquired immune systems because selection for one temporarily affected the other. Given the importance of anti-Gal in primates, our results should stimulate further study of this antibody in poultry species.