The histocompatibility complex of rhesus monkeys. II. A major locus controlling reactivity in mixed lymphocyte cultures

The Cynomolgus Macaque MHC Polymorphism in Experimental Medicine

Among the non-human primates used in experimental medicine, cynomolgus macaques (Macaca fascicularis hereafter referred to as Mafa) are increasingly selected for the ease with which they are maintained and bred in captivity. Macaques belong to Old World monkeys and are phylogenetically much closer to humans than rodents, which are still the most frequently used animal model. Our understanding of the Mafa genome has progressed rapidly in recent years and has greatly benefited from the latest technical advances in molecular genetics. Cynomolgus macaques are widespread in Southeast Asia and numerous studies have shown a distinct genetic differentiation of continental and island populations. The major histocompatibility complex of cynomolgus macaque (Mafa MHC) is organized in the same way as that of human, but it differs from the latter by its high degree of classical class I gene duplication. Human polymorphic MHC regions play a pivotal role in allograft transplantation and have been associated with more than 100 diseases and/or phenotypes. The Mafa MHC polymorphism similarly plays a crucial role in experimental allografts of organs and stem cells. Experimental results show that the Mafa MHC class I and II regions influence the ability to mount an immune response against infectious pathogens and vaccines. MHC also affects cynomolgus macaque reproduction and impacts on numerous biological parameters. This review describes the Mafa MHC polymorphism and the methods currently used to characterize it. We discuss some of the major areas of experimental medicine where an effect induced by MHC polymorphism has been demonstrated.

The major histocompatibility complex (CyLA) of the cynomolgus monkey. I. Serologic definition of 21 specificities

Thirty-seven lymphocytotoxic antisera, 27 of which were raised by immunization with skin grafts and blood from partially matched donors, were tested against cells obtained from 218 unrelated animals and 205 offspring from a colony of cynomolgus monkey (Macaca fascicularis). Evidence was obtained for the presence of at least 21 specificities defined by cluster analysis and segregation within families. Allelic relationships between 16 specificities was suggested by segregation patterns, the absence of triplets and statistical analysis of association in the unrelated population sample. The data support a two-locus model, with tentative assignment of seven specificities to the A locus and six to the B locus. That these lymphocyte alloantigens constitute the major histocompatibility complex (MHC) of the cynomolgus monkey is suggested by analogy with other known MHCs and by the increased survival times of skin grafts between paternally matched half sibs compared to haplodistinct full sibs.

Mixed lymphocyte reactivity in cattle

Mixed lymphocyte reactivity (MLR) in cattle was assessed by measuring the extent of cellular proliferation between allogeneic lymphocytes in an in vitro test system. To test for involvement of the bovine major histocompatibility system (BoLA) the MLR tests were done using full-sibling cattle families which had been generated through the use of embryo transfer systems. The results showed that the responses in the MLR tests were associated with the BoLA antigen sharing status between the individuals being tested. Since the tests, were done using full-sibling combinations, this result suggests genetic linkage between the MLR controlling antigens and the BoLA complex.

The RhLA complex of rhesus monkeys. XI: Positive MLC reactions between identical sibs caused by alloimmunization

D-locus identical pairs of monkeys were alloimmunized. An exchange of skin and blood between initially MLC-negative unrelated monkeys frequently led to strong mutual reactivity in mixed cultures. This was not the case when RhLA identical siblings were similarly (mutually) immunized. These data led to the postulation of a second RhLA-linked MLC locus, named D', which exerts its influence only after alloimmunization. Interestingly, strong MLC responsiveness between the RhLA identical siblings could be provoked after further immunization with tissue from a thired party animal. This unexpected MLC-reactivity is ascribed to the in fluence of minor non MHC linked loci which express themselves if the responder has been sensitized against a disparate D'-product. It is suggested that the postulated D' locus has a "helper function" in that it assists in triggering proliferative responses in mixed cultures against the products of these non MHC loci.

The major histocompatibility complex of Rhesus monkeys. XII: Cellular typing for D locus antigens in families

Typing cells (TC) were used for the identification of D locus antigens in rhesus monkey families. The antigens defined by this cellular method always segregated with the other RhLA-controlled markers except in one offspring with a proven recombination within the RhLA region; in that case, the D antigen was inherited in coupling with an antigen of the Ia1 locus (the analog of the human DR locus). With two exceptions, each TC or group of TC's was associated with one of the serologically defined Ia1 antigens. The two exceptions were associated with "blanks" of that series. Interestingly, two independent (mutually MLC responsive) TC groups appeared to be associated with the same Ia1 antigen 75. Equally noteworthy was the observed "inclusion phenomenon" among cells of several TC groups, each associated with a single Ia1 antigen or blank of that series. In these cases, some of the TC's of the group were unidirectionally MLC-responsive against other cells of the same group. Certain pitfalls of cellular typing are discussed; unexpected "false positive" results were attributed to prior immunization with products of non-D loci which have described recently (van Es & Balner 1978b).

Definition of two LD antigens in rhesus monkeys

Two rhesus (Macaca mulatta) monkey lymphocyte-defined (LD) antigens have been identified using two typing cells as stiumlators in a one-way mixed leukocyte culture (MLC) assay. An analysis of the genetic behavior of these LD antigens in six rhesus monkey families revealed that both antigens were linked with RhLA. One probable recombinant indicated that the LD locus lies outside the two known RhLA-SD loci and the locus which controls the serum protein, properdin B(Bf). These two antigens, LD1 and LD2, had observed gene frequencies of 0.07 and 0.25, respectively. Neither of these two new LD antigens was significantly associated with any serologically defined (SD) antigen.

RhLA complex of Rhesus monkeys. X. Implications of the association between D and Ia1 locus antigens

A high association has been found between D-locus determinants defined by cellular methods (typing cells) and the serologically defined B cell or Ia antigens controlled by the Ia1 locus. Data from recombinant offspring in two rhesus families place the Ia1 locus within RhLA, in the close vicinity of the D or major MLC locus. In fact, identity between the products of those two loci cannot be excluded. Further, it was shown that cells proven to be homozygous for Ia1 antigens, are nearly always typing cells (and therefore homozygous for D-locus determinants) and, conversely, that proven typing cells carry only a single Ia1 antigen and are thus probably homozygous for Ia1 products. In addition, it could be demonstrated that matching for Ia1 antigens greatly facilitates the detection of unrelated individuvals who are mutually non-reactive in MLC. This "predictive value" of Ia1 matching has important implications for the selection of optimal donors for organ transplantation.

Inhibition of MLC responder and stimulator function with allo-antisera in rhesus monkeys

Ten antisera containing antibodies directed against specificities controlled by the Ia1 locus of rhesus monkeys were tested for their ability to inhibit the MLC reaction. In cultures with responding cells from the serum producer, all sera with anti-Ia1 activity depressed the stimulatory capacity of cells carrying the Ia1 antigen in question. In other responder/stimulator combinations, the stimulation-inhibition was Ia1-related for the majority of the antisera. These data provide further evidence for a possible identity (or close association on the cell membrane) between Ia1 and D locus determinants of rhesus monkeys. In addition, some sera showed an inhibitory effect also on responder cells (with cells from the serum producer as stimulators). There was no apparent relation of response inhibition to the Ia1 specificities detected by antisera.

Definition of 17 Rhesus monkey histocompatibility antigens, including one new antigen

The lymphocytotoxic activity of 144 rhesus allonantisera was evaluated in 112 unrelated rhesus monkeys and 33 pedigreed rhesus families. This study was conducted using a standard complement-dependent microcytotoxicity assay. A computer-assisted chi2 analysis of the reactivity of these sera in the unrelated monkeys generated 23 groups of highly correlated antisera. The two-locus model of the mammalian major histocompatibility complex was assumed for the monkey, and genetic criteria for RhLA antigens were determined prior to study. Seventeen groups of antisera met these predetermined criteria. Six were products of the B locus and 11 were products of the A locus. Sixteen were similar or identical to antigens previously described by us or by Balner and coworkers in The Netherlands. One has not been previously described. A frequency analysis indicated that these 17 antigens represented approximately 74% of the total expression of these two loci.

The major histocompatibility complex of rhesus monkeys. VI. Serology and genetics of Ia-like antigens

The serology and genetics of11 new cell surface alloantigens of rhesus monkeys are described: They are controlled by the mamor histocompatibility complex but are distinct from the conventional serologically defined (SD) antigens ofRhL-A. The new specifications are termed "Ia-like" because ofserological, immunocytological and other characteristics reminiscent of Ia-antigens of the mouse. Population and family analyses led to the postulation of two segregant series controlling eight of the 11 Ia-like specificities of the monkey. Strong linkage disequilibria with SD2 antigens and genetic mapping on the basis of segregation studies in recombinant offspring in the monkey families, places at least one of the two loci in the vicinity of the SD2 locus of RhL-A, not in the region of the major MLC or LD1 locus. For this and other reasons, the new B-cell alloantigens of rhesus monkeys are not believed to be similar to or associated with the stimulator antigens of LD1. The biological function(s) of the Ia-like antigens of primates are as yet unknown.

Preliminary amino acid sequences of transplantation antigens: genetic and evolutionary implications

Preliminary amino acid sequence data on the transplantation antigens of mouse and man have led to provocative hypotheses about the genetic organization and evolution of genes coded by the major histocompatibility complex of mammals. New microsequencing techniques should permit a detailed analysis of these gene products and an eventual choice among the alternative hypotheses now posed. These data have made it apparent that the H-2 complex is a fascinating and complicated chromosomal region which will continue for some time to intrigue immunologists, geneticists, biochemists, and cell biologists.

Rhesus lymphocyte alloantigens. III. Identification of new antigens

Rhesus monkey lymphocytotoxic alloantisera were tested in 437 random unrelated monkeys and in members of 19 pedigreed families. Groups of sera or individual sera identified 11 specificities. Genetic analysis of the associations of these antigens revealed behavior consistent with the current concept of the major histocompatibility complex of several mammalian species including man in that the antigens could be grouped into two series of closely linked co-dominantly expressed alleles.

Mapping of the immune response genes in the major histocompatibility complex of the Rhesus monkey

Interest in the Ir genes of rheus monkeys stems from their phylogenetic relationship to man and the extensive data already available on the major histocompatibility complex of the monkey. At least two independent dominant H-linked Ir genes have been identified in the rhesus. These genes control the ability of monkeys to respond to the random linear copolymer of glutamyl alanine (GA), or the dinitrophenyl conjugate of glutamyl lysine (DNP-GL). These synthetic polymers can elicit weak delayed-type skin reactions and strong humoral responses in some monkeys. In a series of unrelated monkeys phenotyped for the serologically defined RhL-A specificities of both segregant series, there were no correlations between any RhL-A specificity and responder status to the GA or DNP-GL polymers. However, segregation analysis of 21 rhesus families sired by 3 fathers indicated the capacity of the offspring to form antibodies was associated with genes coded for in the RhL-A complex. In three monkeys, verified recombination within the RhL-A complex between the genes coding for the serologically defined determinants (SD loci) and the gene(s) controlling the lymphocyte-activating determinants (Lad loci) responsible for mixed lymphocyte reactivity was established. In two of these monkeys the immune response genes controlling the DNP-GL response segregated with the Lad genes, while in the third case the Ir-GL gene segregated with the SD loci, tentatively localizing the Ir-GL gene between the SD and Lad loci. In addition, we have shown that genetically distinct genes control responsiveness to DNP-GL and GA. These genes were separated by recombination, thus one monkey inherited the Lad, Ir-GL, and SD loci from one paternal haplotype and by crossing over inherited the gene controlling GA responsiveness from the other paternal haplotype. The fine structure mapping of the RhL-A gene complex is compared with the H-2 and HL-A gene complexes. Several striking similarities were noted.

Progress in rhesus histocompatibility typing resulting from the Second International Nonhuman Primate Histocompatibility Workshop (1973)

The Second International Nonhuman Primate Histocompatibility Workshop permitted comparison of rhesus monkey alloantisera developed in various laboratories on a single common panel of related and unrelated monkeys. Analysis of the data permits the conclusion that at least nine specificities are recognized by more than one laboratory, including six at the first locus and three at the second locus.

Histocompatibility testing in dogs. II. Leukocyte typing in relation to the mixed lymphocyte culture (MLC) reactivity

The correlation between MLC reactivity (LD) and serological leukocyte typing (SD) was studied in a beagle colony. Disparity for a serologically defined non-DL-A lymphocyte antigen did not correlate with MLC reactivity. Lymphocytes of colony members with common ancestors and SD identical DL-A haplotypes did not stimulate each other in the MLC. This implies that LD typing in the beagle coolony can be generally predicted by DL-A SD typing. Consequently, lymphocytes of sibs homozygous for a given DL-A SD haplotype could be shown, with few exceptions, to be also homozygous for MLC determinants. Cells of these homozygous sibs can be used in MLC typing as reference cells for DL-A LD specificities. Two exceptions to the expected linkage between DL-A SD typing and MLC reactivity were found. These findings could not be explained by recombination with the DL-A region assuming a single major LD locus coding for MLC. Thus, suggestive evidence for more than one single LD locus has been obtained.

Serotyping for MLC gene products: I. Presumptive evidence that ABCIL may detect MLC factors

Serum from a grand multiparous Inuit (Eskimo) woman, who is HL-A identical but stimulatory in MLC with cells of her husband, contains strong ABCIL reactivity. This serum is operationally monospecific against a cell membrane determinant on lymphocytes, but not platelets, of some unrelated persons. Cells of those who are ABCIL positive with this serum always give a lower MLC stimulation index compared with their MLC responsiveness to cells that are ABCIL negative. This serum also contains good MLC inhibitory activity but only in those one way MLC reactions in which it reacts, by ABCIL, with the stimulating cells. It is postulated that the ABCIL activity is directed against a common MLC factor on lymphocytes.