Purification and characterisation of ovine C4: evidence for two molecular forms in ovine plasma

Class I major histocompatibility complex antigens and C4 concentrations in sheep plasma

Data are presented demonstrating that high concentrations of complement protein C4 in sheep plasma are associated with a particular class I OLA specificity. By way of contrast, a similar association could not be demonstrated between C3 plasma concentrations and OLA specificities. These data support the hypothesis that gene(s) determining C4 plasma concentrations are linked to the ovine MHC.

The immunogenetics of resistance to Trichostrongylus colubriformis and Haemonchus contortus parasites in sheep

Three possible immunogenetic markers for resistance to intestinal parasites in sheep have been studied. Allotypes of the major histocompatibility complex (MHC) of the sheep have been investigated as markers, using serological typing or gene probes, for associations between allotypes and resistance to parasites in selected high responder and low responder lines of sheep. Only the serologically-determined class I ovine leucocyte antigen (OLA) types SY 1a and SY 1b have been found to be consistently associated with increased resistance to Trichostrongylus colubriformis, but this association has not extended to the immunologically distinct Haemonchus contortus parasite. Gene probes of the sheep DRB, DQB and DQA MHC class II loci have detected animals with increased susceptibility to T. colubriformis. Eosinophilia was investigated as a marker and found to be associated with increased resistance to parasites in lines of Australian Merinos and New Zealand Romneys selected for resistance on the basis of low faecal egg count. Blood eosinophilia was distinct from eosinophil infiltration of the gut which was poorly associated with resistance. The mechanism of parasite resistance appeared to involve the release of vasoactive amines and leukotrienes into intestinal mucus, since the selected high responder sheep to T. colubriformis and H. contortus had significantly increased amounts of these agents in their gut mucus, compared with selected low responder or random-bred sheep. Antibodies to T. colubriformis and H. contortus have also been used as markers to select high responder sire groups of lambs in contact with the parasites, for the first time, at weaning. This assay had the advantage of detecting distinct antigens for the two parasites, which would allow resistance to the species of parasite to be selected in the lambs. Vaccines have been developed against H. contortus using 'novel' gut antigens from the parasite, but variable responsiveness of the host sheep seemed to result in varying degrees of protection which were stimulated by these vaccines.

Analysis of the C4 genes in baleen whales using a human cDNA probe

We have used a human C4 cDNA probe to investigate the complement component C4 gene in four members of the family Balaenopteridae: fin whale (Balaenoptera physalus), sei whale (B. borealis), minke whale (B. acutorostrata), and bryde's whale (B. edeni). Restriction mapping of genomic DNA from the first three species suggests the presence of only one locus in these species, and also shows that the C4 genes in the three species are very similar. We have used 14 restriction endonucleases to investigate the restriction fragment length polymorphism (RFLP) of fin whales, 13 enzymes for sei whales, and 8 enzymes for the minke whale. No polymorphism was seen in DNA from the five minke whale samples, but Rsa I and Taq I restriction enzymes gave polymorphism in fin and sei whales whereas Hind III and Msp I restriction enzymes showed polymorphism in sei whales only. Only one bryde's whale sample was available for investigation. The study of DNA available from mother-fetus pairs from the two polymorphic species demonstrated a simple, two-allele transmission of RFLP alleles.

The complement component C4 of mammals

Human complement component C4 is coded by tandem genes located in the HLA class III region. The products of the two genes, C4A and C4B, are different in their activity. This difference is due to a degree of 'substrate' specificity in the covalent binding reactions of the two isotypes. Mouse also has a duplicated locus, but only one gene produces active C4, while the other codes for the closely related sex-limited protein (Slp). In order to gain some insight into the evolutionary history of the duplicated C4 locus, we have purified C4 from a number of other mammalian species, and tested their binding specificities. Like man, chimpanzee and rhesus monkey appear to produce two C4 types with reactivities similar to C4A and C4B. Rat, guinea pig, whale, rabbit, dog and pig each expresses C4 with a single binding specificity, which is C4B-like. Sheep and cattle express two C4 types, one C4B-like, the other C4A-like, in their binding properties. These results suggest that more than one locus may be present in these species. If this is so, then the duplication of the C4 locus is either very ancient, having occurred before the divergence of the modern mammals, or there have been three separate duplication events in the lines leading to the primates, rodents and ungulates.