Selection for high immune response: an alternative approach to animal health maintenance?

To test the hypothesis that variation in ability to respond immunologically correlates with health, Yorkshire pigs were bred for high (HIR) and low (LIR) antibody (Ab) and cell-mediated immune response (CMI). Selection was based on standardized measures of Ab (secondary response to hen egg white lysozyme, serum IgG concentration) and CMI (cutaneous delayed-type hypersenstivity to purified protein derivative of tuberculin after immunization with bacillus Calmette-Guérin and in vitro lymphocyte response to Con-A). Differences in Ab and CMI by line were not restricted to the antigens used in the selection. Antibody response to vaccines was highest in HIR and non-responders were restricted to LIR pigs. The HIR pigs had the best rate of weight gain. After infection with Mycoplasma hyorhinis, HIR developed more severe arthritis and less polyserositis. Differences were associated with variation in cytokine message in joint-related cells. Following exposure to attenuated transmissible gastroenteritis virus, natural killer cells of the LIR pigs but not of HIR or control lines, were unresponsive. Genetic selection for Ab and CMI may provide health and productivity advantages and complement traditional health-maintenance methods.