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Lymphocytes from 90 mature pigs and 548 growing pigs from 65 litters were screened with cytotoxic antibodies against swine lymphocyte antigens. Pigs included in the survey were from the Chester White, Duroc, Hampshire, Landrace and Yorkshire breeds. Significant differences between breeds were found in the frequency of the three haplotypes tested. Such differences may provide the genetic variability needed to determine associations between disease susceptibility and the pig's major histocompatibility gene complex.

Two phenomena appear to distinguish the D region class I genes from those in the K region in the murine MHC: (a) haplotype disparity in the number of expressed D region class I molecules has been observed; and (b) clines of closely related D region class I molecules among and within mice of different H-2 haplotypes can be defined. Both of these observations have been based on serological and peptide mapping analyses of these molecules. Recent reports using molecular biological approaches have corroborated these findings. Since the mouse strain B10.AKM expresses multiple D region class I antigens, all of which are closely related to the prototypic Ld molecule, we investigated the Dq region of B10.AKM using molecular approaches. Three D region class I genes were isolated from genomic B10.AKM bacteriophage and cosmid libraries. Based on alignment of those genes with the BALB/c D region class I genes by analogous restriction endonuclease sites and by hybridization of one of those genes with a D4d gene-derived oligonucleotide probe, we have designated these genes as Dq, Lq, and D4q. As determined by DNA-mediated gene transfer to mouse L cells followed by serological analyses, the Dq and Lq genes encode previously characterized Dq region class I antigens. The nucleic acid sequence comparisons of the Dq and Lq genes demonstrated a higher level of homology with the Ld and Db genes than with other D region class I genes. In addition, CTL stimulated with a Dq, Lq, or Ld gene transfectant showed strong crossreactions with the other transfectants as targets, suggesting that the products of these genes are also functionally related. Thus, these studies suggest that the L molecule represents a prototypic structure shared by several D region gene products, and furthermore, the duplication of an Ld-like progenitor gene resulted in two Dq region class I genes, Dq and Lq. Unexpectedly, the sequences determined for the Dq and Lq genes are nearly identical to the sequences of two genes, A166 and A149, respectively, which were reported to encode the tumor-specific antigens; these novel class I genes were isolated from an H-2k fibrosarcoma, 1591. This raises the distinct possibility that these purported tumor-specific class I genes were introduced into this tumor by contamination.

Three miniature swine lines, inbred for swine leukocyte antigen (SLA) haplotypes, a, c, and d, and a recombinant line, haplotype g, were analyzed for possible restriction fragment length polymorphisms (RFLP) by Southern blot hybridization with human C2, factor B (Bf), and C4 specific probes. The search for RFLP by using a human C2 probe failed to reveal any variants. However, a Taq I polymorphism was identified with the human Bf probe and Bam HI and Pvu II polymorphisms were identified with the human C4 probe. Overlapping restriction fragments were found with the C2 and Bf probes, which strongly suggests close linkage of C2 and Bf genes in swine. Segregation analyses of the Bf and C4 polymorphisms indicated that the polymorphic fragments followed a Mendelian pattern of inheritance. The recombinant haplotype g, which expresses class I genes of haplotype c and class II genes of haplotype d, was shown to produce an identical RFLP pattern, by using the Bf and C4 probes, as haplotype d, but different from that of haplotype c. This indicates that there is a close association of [C4-Bf-C2] and class II genes in miniature swine. Although these data do not show conclusively the location of the [C4-Bf-C2] genes, it is hypothesized that swine [C4-Bf-C2] genes are located between the class II and class I genes, as has been demonstrated in mouse and man.

Genetic differences in immune response to B. bronchiseptica after vaccination with a commercial B. bronchiseptica bacterin were investigated in 1,069 8-wk-old pigs. These pigs were from 65 litters born in the spring and 66 litters born in the fall of 1982 and were purebreds from the Chester White (n = 128), Duroc (n = 281), Hampshire (n = 143), Landrace (n = 309) and Yorkshire (n = 208) breeds. Each litter was raised separately. Individual pigs were vaccinated im at 4 and 6 wk of age with 2 ml of B. bronchiseptica bacterin. At 8 wk of age, 8 ml of blood were collected from each animal and serum prepared to determine agglutinating antibody titers against B. bronchiseptica bacterin by a bacterial agglutination method. In addition, lymphocytes were separated from 1 ml of heparinized blood and used to determine Swine Lymphocyte Antigen (SLA) haplotypes by using cytotoxic antibodies against the SLA complex. Antisera for 3 SLA haplotypes were made available by the National Institutes of Health. Results indicated that breed of pig (P less than .01) and dam of pig (P less than .01) affected the immune response of the pig after B. bronchiseptica vaccination. Higher immune response was also associated (P less than .05) with one of the SLA haplotypes tested. Heritability estimates for immune response following vaccination were .10 +/- .12 (half-sib) and .42 +/- .19 (full-sib). Results suggest that the relationship of the SLA complex to immune response in the pig and nonadditive genetic and maternal effects on immune response should be further investigated.