A novel system of polymorphic and diverse NK cell receptors in primates.

There are two main classes of natural killer (NK) cell receptors in mammals, the killer cell immunoglobulin-like receptors (KIR) and the structurally unrelated killer cell lectin-like receptors (KLR). While KIR represent the most diverse group of NK receptors in all primates studied to date, including humans, apes, and Old and New World monkeys, KLR represent the functional equivalent in rodents. Here, we report a first digression from this rule in lemurs, where the KLR (CD94/NKG2) rather than KIR constitute the most diverse group of NK cell receptors. We demonstrate that natural selection contributed to such diversification in lemurs and particularly targeted KLR residues interacting with the peptide presented by MHC class I ligands. We further show that lemurs lack a strict ortholog or functional equivalent of MHC-E, the ligands of non-polymorphic KLR in "higher" primates. Our data support the existence of a hitherto unknown system of polymorphic and diverse NK cell receptors in primates and of combinatorial diversity as a novel mechanism to increase NK cell receptor repertoire.

The origin of the primate Mhc-DRB genes and allelic lineages as deduced from the study of prosimians.

MHC class II genes of the DRB family were partially sequenced from 10 individuals representing six species of prosimians: Galago senegalensis, G. moholi, Otolemur garnetti, Loris tardigradus, Petterus (Lemur) fulvus, and Lemur catta. Altogether, 41 different genes were discerned, all distinct from genes identified previously. Comparative analysis of the sequences has led to the following conclusions. First, the DRB loci present in human populations diverged from one another before the divergence of prosimian and anthropoid primates. Second, major allelic lineages of the DRB1 locus, such as DRB1*03 (DRB1*13) and DRB1*04, were established more than 85 million years ago. Third, the DRB6 gene was inactivated before the separation of prosimians and anthropoids, and has remained a pseudogene for more than 85 million years. Fourth, the primate DRB region is structurally and functionally unstable. In Lemur catta, for example, all DRB genes have apparently been lost and their function taken over by DOB and/or DPB genes. DRB genes are, however, present in a related species, Petterus (Lemur) fulvus. Fifth, the prosimian DRB3 genes are all inactive; their function seems to have been taken over by new genes. Sixth, several of the prosimian DRB genes and pseudogenes have recently been duplicated. In Otolemur garnetti, for example, one chromosome carries at least three copies of the DRB3 pseudogene.

Survey of nonhuman primates for antibodies reactive with Epstein-Barr virus (EBV) antigens and susceptibility of their lymphocytes for immortalization with EBV.

The susceptibility to transformation with Epstein-Barr virus (EBV) and the prevalence of antibodies reactive to EBV were examined in 43 primate species. In vitro EBV infection was revealed in lymphocytes from Old World monkeys, including patas monkeys and the colobines, as well as in lymphocytes from the apes. Antibodies reactive to EBV-early antigen/viral capsid antigen (EA/VCA) were detected in all the species of Old World monkeys and apes examined and in two out of seven species of New World monkeys.

Epitope expression on primate lymphocyte surface antigens.

The cross-reactivity of peripheral blood mononuclear cells from 28 nonhuman primates was investigated with ten kinds of Leu series of monoclonal antibodies specific to human T-, natural killer/killer-, and B-cells. The chimpanzees possessed all ten epitopes examined but the orangutan lacked Leu4 and Leu7 epitopes and the gibbons lacked Leu4, Leu7, and Leu12 epitopes. In addition to the above epitopes, the Old World monkeys lacked Leu1 and Leu10 epitopes. The Leu3a/Leu2a cell ratios varied from 0 to 1.56 among the 12 macaque species and this enabled classification of these species into three groups. In the New World monkeys, Leu2a epitope was absent, whereas Leu11a epitope was detected in several species and Leu3a epitope was found only in the owl monkeys. The prosimians expressed only HLA-DR epitope.

Immunodiffusion systematics of the primates. III. The strepsirhini.

Immunodiffusion comparisons have been run using 26 antisera including seven made to strepsirhine species. Spur size data resulting from these comparisons have been analyzed by computer and depict Strepsirhini as a monophyletic group within Primates including Lemuriformes and Lorisiformes. Cheirogaleidae is retained with Lemuriformes. Indriidae rather than Cheirogaleidae is depicted as closer to Lemur. Evidence is presented indicating that Lorisiformes is composed of three groups rather than two as in traditional classifications. The three groups, which are considered here to diverage at a family level, are Galagidae, Lorisidae, and Perodicticidae.