Major histocompatibility complex class II polymorphisms in humans and chimpanzees

Allelic variation at the MhcPatr-DR and -DQ loci was studied by molecular biological techniques and compared to available HLA data. With regard to the number of allelic lineages, the chimpanzee shows a condensation of its major histocompatibility complex (MHC) class II repertoire as compared to humans. This does not have an impact on the overall degree of MHC class II polymorphism in the chimpanzee since a few lineages that are oligomorphic in humans display an extensive degree of polymorphism in the chimpanzee.

Mhc-DRB diversity of the chimpanzee (Pan troglodytes)

Fifty-four chimpanzee Patr-DRB and five human HLA-DRB second exons were cloned and sequenced from thirty-five chimpanzees and four human B-cell lines and compared with known Mhc-DRB sequences of these two species. Equivalents of the HLA-DRB1*02, -DRB1*03, -DRB1*07 allelic lineages and the HLA-DRB3, -DRB4, -DRB5, -DRB6, and -DRB7 loci were all found in the chimpanzee. In addition, two chimpanzee Patr-DRB lineages (Patr-DRBX and -DRBY) were found for which no human counterparts have been described. None of the Patr-DRB sequences is identical to known HLA-DRB sequences. The Patr-DRB1*0702 and HLA-DRB1*0701 alleles are the most similar sequences in a comparison between the two species and differ by only two nucleotides out of 246 sequenced. Equivalents of the HLA-DRB1*01, -DRB1*04, and -DRB1*09 alleles were not found in our sample of chimpanzees. A per locus comparison of the number of Patr-DRB alleles with the HLA-DRB alleles shows that the Patr-DRB3, -DRB4, -DRB5, and -DRB6 locus are, thus far, more polymorphic than their human homologs. The polymorphism of the Patr-DRB1 locus seems to be less extensive than that reported for the HLA-DRB1 locus. Nevertheless, the Patr-DRB1 locus seems to be the most polymorphic of the Patr-DRB loci. Phylogenetic analyses indicate that the HLA-DRB1*09 allele may have originated from a recombination between a Mhc-DRB5 allele and the DRB1 allele of a Mhc-DR7 haplotype. Although recombination seems to increase the diversity of the Patr-DRB alleles, its contribution to the generation of Patr-DRB variation is probably low. Hence, most Patr-DRB diversity presumably accumulated via recurrent point mutations. Finally, two distinct Patr-DRB haplotypes are deduced, one of which (the chimpanzee equivalent of the HLA-DR7 haplotype) is probably older than 6-8 million years.

Evolutionary stability of transspecies major histocompatibility complex class II DRB lineages in humans and rhesus monkeys

Sequence analysis of rhesus monkey (Macaca mulatta) polymorphic second exon of major histocompatibility complex class II DRB subregion genes demonstrates the existence of at least 34 alleles. Some of these rhesus monkey alleles are very similar (or nearly identical) to HLA-DRB alleles. These data demonstrate that members of the lineages for Mhc-DRB1*03, -DRB1*04, -DRB1*10, and the loci of Mhc-DRB3, -DRB4, -DRB5, and -DRB6 predate speciation of man and rhesus monkey and were already present 25 million years ago. Calculation of evolutionary rates suggests that the various allele lineages have differential stabilities. Furthermore, the data indicate that distinct species may not have inherited or lost transspecies Mhc-DRB lineages in evolution, because several allele lineages in rhesus monkeys appear to be absent in humans and vice versa.

Mhc-DQB repertoire variation in hominoid and Old World primate species

Comparison of 87 distinct Mhc-DQB sequences, obtained from 13 primate species, demonstrates that five out of eight trans-species Mhc-DQB allele lineages are at least 30 million years old and predate divergence of hominoid and Old World primate species. One lineage may be much older because its members are not only traced back in higher primates, but also are present in a New World primate species. Comparing Mhc-DQB repertoire variation in distinct species, allows one to pinpoint when certain polymorphisms were lost or gained in primate evolution. Heterogeneity observed among members of trans-species Mhc-DQB allele lineages can be explained in major part by point mutations, whereas intraexonic crossing-over is a potent mechanism in generating new allele lineages. The stability of Mhc-DQB polymorphisms is influenced by selective forces because distinct allele lineages appear to have accumulated nucleotide substitutions and amino acid replacements at different rates.

Mhc-DQB repertoire variation in hominoid and Old World primate species

Comparison of 87 distinct Mhc-DQB sequences, obtained from 13 primate species, demonstrates that five out of eight trans-species Mhc-DQB allele lineages are at least 30 million years old and predate divergence of hominoid and Old World primate species. One lineage may be much older because its members are not only traced back in higher primates, but also are present in a New World primate species. Comparing Mhc-DQB repertoire variation in distinct species, allows one to pinpoint when certain polymorphisms were lost or gained in primate evolution. Heterogeneity observed among members of trans-species Mhc-DQB allele lineages can be explained in major part by point mutations, whereas intraexonic crossing-over is a potent mechanism in generating new allele lineages. The stability of Mhc-DQB polymorphisms is influenced by selective forces because distinct allele lineages appear to have accumulated nucleotide substitutions and amino acid replacements at different rates.

Evolutionary relationships among the primate Mhc-DQA1 and DQA2 alleles

The variation of the Mhc-DQA1 and DQA2 loci of ten different primate species (hominoids and Old World monkeys) was studied in order to obtain an insight in the processes that generate polymorphism of major histocompatibility complex (Mhc) class II genes and to establish the evolutionary relationships of their alleles. To that end nucleotide sequences of 36 Mhc class II DQA1 and seven DQA2 second exons were determined and phylogenetic trees that illustrate their evolutionary relationships were constructed. We demonstrate the existence of four primate Mhc-DQA1 allele lineages, two of which probably existed before the separation of the ancestors of the hominoids and Old World monkeys (approximately 22-28 million years ago). Mhc-DQA2 sequences were found only in the hominoid species and showed little diversity. We found no evidence for a major contribution of recombinational events to the generation of allelic diversity of the primate Mhc-DQA1 locus. Instead, our data suggest that the primate Mhc-DQA1 and DQA2 loci are relatively stable entities that mutated primarily as a result of point mutations.

Resistance to collagen-induced arthritis in a nonhuman primate species maps to the major histocompatibility complex class I region

Type II collagen-induced arthritis (CIA) is an experimentally inducible autoimmune disorder that is, just like several forms of human arthritis, influenced by a genetic background. Immunization of young rhesus monkeys (Macaca mulatta) with type II collagen (CII) induced CIA in about 70% of the animals. One major histocompatibility complex (MHC) class I allele was present only in young animals resistant to CIA and absent in arthritic animals. This strong association suggests that the MHC class I allele itself, or a closely linked gene, determines resistance to CIA. The mechanism controlling the resistance to CIA becomes less efficient in aged animals since older rhesus monkeys, which were positive for the resistance marker, developed a mild form of arthritis. At the cellular level it is demonstrated that resistance to CIA is reflected by a low responsiveness of T cells to CII. This association between a specified MHC class I allele and resistance to an autoimmune disease points at the importance of the MHC class I region in the regulation of the immune response to an autoantigen.

Acquired resistance to type II collagen-induced arthritis in rhesus monkeys is reflected by a T cell low-responsiveness to the antigen

Ten out of 14 rhesus monkeys developed arthritis after a single immunization with bovine type II collagen (B-CII). In contrast to primary resistant monkeys, arthritic animals showed a B-CII specific T cell proliferation during the induction phase of the disease. All surviving animals showed a full remission of the disease. Two monkeys acquired resistance to collagen-induced arthritis (CIA) after one period of disease, but in three animals a booster immunization with B-CII induced a slight flare-up. It is demonstrated that B-CII immunized rhesus monkeys have the capacity to restore resistance to CIA. The development of resistance to CIA is reflected by a decreased T cell responsiveness to B-CII. It is shown that the lack of IL-2 plays a role in B-CII-induced T cell low-responsiveness. A potential role of CD8+ T cells in the down regulation of the T cell response to B-CII is discussed.

Monoclonal antibodies for immunohistochemical labeling of immunocompetent cells in frozen sections of rhesus monkey tissues

Twenty-eight anti-human and two rhesus specific monoclonal antibodies (MAbs) were evaluated for immunohistochemical peroxidase staining reactivity in rhesus monkeys lymph nodes, thymus, liver, and skin allografts. Reactivity with the following antigens was assessed: MHC class I, II-DR, -DQ, and -DP antigens; leukocyte markers CD1, CD2, CD3, CD4, CD8, CD14, CD16, CD25, CD57; a proliferation associated nuclear antigen; interferon-gamma and tumor necrosis factor-alpha. Twenty-three MAbs proved to be suitable for immunohistochemical staining on frozen sections.

Autoimmunity in non-human primates: the role of major histocompatibility complex and T cells, and implications for therapy

Two autoimmune disease models were studied in rhesus monkeys: type II collagen-induced arthritis (CIA) and experimental allergic encephalomyelitis (EAE). Unrelated outbred animals were used in these studies. In both models disease resistant and susceptible individuals could be identified. Susceptibility correlated with in vitro cellular responsiveness to antigen in the CIA model. In both models resistant as well as susceptible individuals developed a humoral response to the inducing antigen. However, there is an indication that IgM antibodies play a crucial role in the induction of CIA. No clear association between major histocompatibility complex (MHC) type and disease incidence was found although a higher frequency of a certain DR type was observed in EAE susceptible monkeys. It is likely that both the antigen binding capacity of the MHC class II molecules and the T-cell repertoire play an important role in determining whether disease will develop or not.

Major histocompatibility complex ancestral haplotypes in the chimpanzee: identification using C4 allotyping

In humans, certain major histocompatibility complex (MHC) supratypes mark unique DNA segments which have been conserved from a common but remote ancestor. In order to determine whether these ancestral haplotypes (AHs) exist in nonhuman primates, C4 allotyping was undertaken on 71 chimpanzees. Four large pedigrees were available. There are at least seven codominant C4 alleles at two loci. Null alleles are also present. It was possible to assign class I, class II, and C4 alleles to 37 unrelated haplotypes; several supratypes occurred two or more times. These putative AHs included some with alleles which resemble those carried by certain human AHs. These data provide evidence that similar MHC AHs are present in the chimpanzee and human. The present approach provides a basis for comparative studies examining the evolutionary and functional significance of the MHC.

Collagen-induced arthritis in an outbred group of rhesus monkeys comprising responder and nonresponder animals. Relationship between the course of arthritis and collagen-specific immunity

It is speculated that the autoimmune response to type II collagen (CII) is a driving force in the pathogenesis of human rheumatoid arthritis (RA). In this report, we describe the relationship between the induction of collagen arthritis and the CII-specific humoral, as well as cellular, immune response in rhesus monkeys. Ten of 14 monkeys immunized with bovine type II collagen (B-CII) developed polyarthritis. Susceptible animals showed a T cell response to B-CII; resistant animals did not. After the primary immunization, the humoral response to B-CII, as well as to rhesus monkey type II collagen, was dominated by antibodies of the IgM isotype in the susceptible animals and by antibodies of the IgG isotype in the resistant animals. Because of the close phylogenic relationship between the rhesus monkey and humans, these data contribute valuable information about the role of CII-specific immunity in the pathogenesis of human RA.

RFLP analysis of the rhesus monkey MHC class II DR subregion

Restriction fragment length polymorphism (RFLP) analysis was performed on a panel of 39 serologically typed DR homozygous monkeys. DNA was digested with the restriction enzyme TaqI and hybridizations were carried out with a human leukocyte antigen (HLA)-DR beta 3'UT-specific probe. In addition a panel of 18 monkeys was analyzed comprising experimental autoimmune encephalomyelitis (EAE) susceptible and nonsusceptible animals. The number of DRB/TaqI fragments detected for the various DR specificities varied from two to six, suggesting that the number of DRB genes per haplotype is not constant. RFLP typing allows that most serologically defined DR specificities can be subdivided. This knowledge was applied to define the DR specificities of the animals used for EAE experiments.

Synergistic immunosuppressive effects of monoclonal antibodies specific for interferon-gamma and tumor necrosis factor alpha. A skin transplantation study in the rhesus monkey

Interferon gamma and tumor necrosis factor alpha play a significant role in the upregulation of host immunity and inflammation, for example by induction and enhancement of the expression of major histocompatibility complex class I and II antigens on a wide variety of cell types, both in vitro and in vivo. In this study two crossreactive monoclonal antibodies, one specific for human IFN-gamma (MD1), the other specific for human TNF-alpha (61E71), were tested for immunosuppressive potencies in a skin transplantation study in the rhesus monkey. Treatment with either MD1 or 61E71 alone did not prolong skin-graft-survival times. In combination, however, these antibodies augmented graft survival times significantly. Infiltration of the skin grafts by lymphocytes and histiocytes was delayed, and upregulation of MHC class I and II expression was retarded. This is the first reported demonstration of a synergistic effect of mAbs specific for IFN-gamma and TNF-alpha in the suppression of allograft rejection in primates.

The importance of non-human primates for preclinical testing of immunosuppressive monoclonal antibodies

Monoclonal antibodies (MAb) specific for lymphocyte markers can be considered as very specific immunomodulating drugs for treatment of allograft rejection and autoimmune diseases. Although the selection of potentially useful specificities of MAb can be made in rodents, human specific MAb can only be evaluated in man or a closely related species in which these human specific MAb are equally reactive. Because of the restricted reactivity of human specific MAb, non-human primates are the only available species for efficacy and safety studies. This article illustrates the usefulness of such studies in rhesus monkeys and chimpanzees for the testing of T cell specific MAb and other MAb interfering with the immune response in transplantation and autoimmunity.

The chimpanzee major histocompatibility complex class II DR subregion contains an unexpectedly high number of beta-chain genes

The major histocompatibility complex (MHC) class II DR subregion of the chimpanzee was studied by restriction fragment length polymorphism (RFLP) analysis. Genomic DNA obtained from a panel of 94 chimpanzees was digested with the restriction enzyme Taq I and hybridized with an HLA-DR beta probe specific for the 3' untranslated (UT) region. Such a screening revealed the existence of 14 distinct DRB/Taq I gene-associated fragments allowing the definition of 11 haplotypes. Segregation studies proved that the number of chimpanzee class II DRB/Taq I fragments is not constant and varies from three to six depending on the haplotype. Comparison of these data with a human reference panel manifested that some MHC DRB/Taq I fragments are shared by man and chimpanzee. Moreover, the number of HLA-DRB/Taq I gene-associated fragments detected in a panel of homozygous typing cells varies from one to three and corresponds with the number of HLA-DRB genes present for most haplotypes. However, a discrepancy is observed for the HLA-DR4, -DR7, and -DR9 haplotypes since a fourth HLA-DRB pseudogene present within these haplotypes lacks its 3' UT region and thus is not detected with the probe used. These results suggest that chimpanzees have a higher maximum number of DRB genes per haplotype than man. As a consequence, some chimpanzee haplotypes must show a dissimilar organization of the MHC DR subregion compared to their human equivalents. The implications of these findings are discussed in the context of the trans-species theory of MHC polymorphism.