The influence of the swine major histocompatibility genes (SLA) on variation in serum immunoglobulin (Ig) concentration.

Variation in serum IgG and IgM concentration was determined in three homozygous SLA-defined strains of miniature swine (SLAa, SLAc and SLAd) and one recombinant strain SLAg (ABcDd) as part of a study of SLA and other genetic effects on immune response. Data were obtained from 119 8-week-old piglets from 29 litters by 12 sires and analyzed using a SAS linear model for the effects of SLA haplotype, sire, dam, litter, sex, season of birth and sow parity. SLA haplotype (P less than 0.10) and other genetic effects due to sire (P less than or equal to 0.001) and dam (P less than or equal to 0.002) contributed to the variation in serum IgG concentrations. Season of birth and sow parity also affected IgG concentration as did litter effects. Least squares mean comparisons indicated that pigs of the dd, dg and gg haplotypes had significantly higher serum IgG than did pigs of the other haplotypes. Heritability estimates for IgG, calculated by paternal half-sib correlation, ranged from 0.31 to 0.27, indicating that selection for increased serum IgG concentrations would be possible. For serum IgM concentrations, only the effect of litter was significant at P less than or equal to 0.001 and P less than or equal to 0.009 by the radial immunodiffusion test read at 24 or 48 h. Since sire variance components estimates were negative, heritabilities were not calculated for IgM and are assumed to be zero.