Rheumatoid arthritis (RA) is a chronic and genetically complex inflammatory disorder that leads to erosive destruction of peripheral joints. The use of animal models mimicking RA, such as pristane-induced arthritis (PIA) in rats, should facilitate its genetic analysis. Pristane is a non-immunogenic synthetic oil that, after a single subcutaneous injection into DA rats, induces arthritis restricted to peripheral joints with a chronic relapsing disease course. To identify genes involved in the control of chronic arthritis, we made crosses between susceptible DA rats and resistant E3 rats and analysed the progeny with microsatellite markers covering the entire rat genome. Our results show that different arthritis phenotypes are associated with different chromosomal loci. Loci on chromosomes 4 and 6 (Pia2 and Pia3) influence arthritis onset, whereas a locus on chromosome 12 (Pia4) is associated with severity and joint erosion. We found that chronicity is associated with a different set of loci, one on chromosome 4 and the other on chromosome 14 (Pia5, Pia6). These findings demonstrate for the first time that different phases of a chronic self-perpetuative disease which mimics RA are associated with distinct sets of genes.

B10.RIII mice develop chronic and relapsing experimental autoimmune encephalomyelitis (EAE) after immunization with the myelin basic protein (MBP) peptide 89-101. The disease is associated with the major histocompatibility complex (MHC) (eae1). We have now investigated the importance of non-MHC regions for the EAE susceptibility in a cross between RIIIS/J and B10.RIII mice which share the MHC region but differ in disease susceptibility. Linkage analysis using microsatellite markers spanning the genome identified a region (eae2) on chromosome 15 which showed linkage to disease (P = 0.0002). Our data also suggest linkage to a second region (eae3) on chromosome 3 (P = 0.0024), and provide evidence for locus interactions between eae2 and eae3. These results provide clues to the genetic basis of multiple sclerosis.

Multiple sclerosis (MS) is a chronic inflammatory disorder characterized by multifocal damage of myelin in the central nervous system (CNS). The prevalence of this putative autoimmune disease is 0.1% in individuals of northern European origin. Family, adoption and twin studies implicate genetic factors in the aetiology. MS is widely speculated to be a multifactorial disorder with a complex mode of inheritance. Despite many studies of candidate genes, only an association with HLA-DR2-DQ6 has been generally detected, and the number of susceptibility genes remains unknown. The chronic variant of experimental allergic encephalomyelitis (EAE), a T-cell mediated autoimmune disease in rodents, represents a relevant animal model for MS given the chronic relapsing disease course and inflammatory changes of CNS observed in these demyelinating disorders. Susceptibility to EAE is also influenced by the major histocompatibility complex (MHC). Human syntenic regions to murine loci predisposing to EAE were tested as candidate regions for genetic susceptibility of MS. Three chromosomal regions (1p22-q23, 5p14-p12 and Xq13.2-q22) were screened in 21 Finnish multiplex MS families most originating from a high risk region in western Finland. Several markers yielded positive lod scores on 5p14-p12, syntenic to the murine locus Eae2. Our data provide evidence for a predisposing locus for MS on 5p14-p12.

Although familial PNE probably arises from polygenic inheritance, analysis of a large number of families may enable the identification of major susceptibility loci. Recently, linkage analysis with polymorphic markers identified a locus predisposing to PNE, assigned ENUR1, in a proportion of Danish families.'4The gene resides in a 4 cM interval flanked by markers D13S263 and D13S291 on chromosome 13q.In a clinical and genetic study we examined two aspects of PNE. First, we investigated the genetic predisposition to PNE in 392 cases by recording family history of enuresis. Second, we performed linkage analysis in 16 families segregating for dominant PNE. Materials and methods PATIENTSIn a continuing Swedish multicentre study," 392 children (291 boys and 101 girls) older than 6 years were identified. All showed a severe form of PNE including .10 wet nights out of 28 and absence of a dry period >3 months. Concomitant neurological or urological dysfunction associated with PNE was excluded. Evaluation of each patient included physical examination and urine analysis.A detailed family history was recorded in each case in order to determine the presence of familial PNE as defined by any close relative with PNE beyond the age of 6 years. The parents of affected probands underwent a structured interview with specific questions regarding the onset, frequency, and cessation of bedwetting. Direct contact was made with the relatives when the information from the parents indicated a positive family history for PNE. The diagnosis among second and third degree relatives was ascertained, or excluded, with the same criteria as for the proband. Fam-ily members under the age of 7 years were not included.

The loci encoding the class II cell surface antigens HLA-DR, -DQ, and -DP exhibit a remarkable degree of aflelic polymorphism. Most of the class I allelic diversity is localized to the second exon, which encodes a fl-pleated sheet followed by an a-helical domain. Here, phylogenetic analysis of 39 human DR8I alleles and 21 DRBI alleles obtained by polymerase chain reaction (PCR) amplification from a set of closely related primates reveals that sequences encoding the fl-pleated sheet and those encoding the a-helix of the second domain have different evolutionary histories. The polymorphisms in the fpleated sheet have been conserved between species and appear to reflect the ancestral relationships among haplotypes, whereas polymorphic segments encoding the a-helical domain appear to have been inserted by interallelic sequence exchange into the framework of different ancestral DRBI sequences. Allelic polymorphism at the DRBl locus may thus have been generated in part by combining different variants of the two structural domains.Loci in the major histocompatibility complex (MHC) class II region encode cell surface antigens that consist of highly polymorphic a and fl glycoprotein chains (1-5). The T-cell receptor recognizes antigen peptide fragments bound to the class II molecule on the surface of antigen-presenting cells (6,7). Most of the polymorphism in the class II molecule is located in the NH2-terminal domain, which forms the putative sites for binding foreign antigen peptides and is encoded by the second exon of the a-and f-chain loci (8).Recently, alleles at primate MHC loci have been shown to predate the divergence of hominoids, and in some cases even that of Old World monkeys, indicating that the polymorphism has been conserved by selection over long evolutionary periods (9)(10)(11)(12). The patchwork ofallelic sequence diversity at some ofthe human class II loci has been taken to indicate that allelic diversity is generated by recombination or segmental transfer. For instance, the similarity between DRB1 and DRB5 sequences on the DR2 haplotype was postulated to be due to a reciprocal exchange (13), and, similarly, sequences from the second exon of DRB3 on a DRw6 haplotype were suggested to have been donated by gene conversion to the DRBI locus (14). However, the presence of shared polymorphism between alleles could, in principle, be due to either common ancestry, convergent evolution, or sequence exchanges between members of different allelic lineages. § MATERIALS AND METHODSThe second exon ofHLA-DRBI was enzymatically amplified by 30 cycles ofPCR (15, 16) using the oligonucleotide primers GH46 and GH50 (17) and 1 ug of genomic DNA from 13 chimpanzees (Pan troglodytes), 4 pygmy chimpanzees (Pan paniscus), 6 gorillas (Gorilla gorilla), 2 rhesus monkeys (Macaca mulatta), and 2 baboons (Papio leucophaeus). Amplified DNA fragments were ligated into phage M13 mp18 and sequenced by the chain-termination method (18). The amino acid sequence of each allele was inferred from the nucleotide sequence of at le...