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CD94, NKG2, Ly49, and killer cell Ig-like receptor (KIR) expressed by orangutan peripheral blood cells were examined by cloning and sequencing cDNA from a panel of individuals. Orthologs of human CD94, NKG2A, D, and F were defined. NKG2C and E are represented by one gene, Popy-NKG2CE, that is equidistant from the two human genes. Several Popy-CD94, NKG2A, and NKG2CE alleles were defined. Popy-Ly49L is expressed in cultured NK cells and has a sequence consistent with it encoding a functional receptor. Orangutan KIR corresponding to the three KIR lineages expressed in humans and chimpanzees were defined. Popy-KIR2DL4 of lineage I is the only ortholog of a human or chimpanzee KIR, but in all individuals examined, the transcripts of this gene produced premature termination, either in the D2 domain or at the beginning of the cytoplasmic domain. Ten Popy-KIR3DL and one Popy-KIR3DS of lineage II are all closely related, but represent the products of at least two genes. The two Popy-KIR2DL and four Popy-KIR2DS of lineage III also represent two genes, both being more related to KIR2DS4 than to other human and chimpanzee KIR of lineage III. The Popy-KIR2D include ones predicted to be specific for the C1 epitope of MHC-C, but none specific for C2. This correlates with the observation that all orangutan MHC-C allotypes examined have the C1 motif.

Here we describe two rainbow trout major histocompatibility complex (MHC) class I genes characterized from lambda phage genomic clones prepared from a single fish. Clone GC71 contains all exons except a leader peptide-encoding exon. An open reading frame is maintained, and thus the gene MhcOnmy-U71 could be expressed in this individual. The class I gene found on clone GC41 lacks exons encoding the leader peptide and cytoplasmic domain. This gene, MhcOnmy-U41p, is a pseudogene due to a deletion in the alpha(2) domain-encoding exon causing premature termination. Both the Onmy-U71 and Onmy-U41p genes are distinguished by long introns between the exons encoding the alpha(1) and alpha(2) domains. Clone GC41 also contains the 3' exons of the LMP7/ PSMB8 gene encoding the gamma-interferon-induced proteosome subunit of rainbow trout.

To assess polymorphism and variation in human and chimpanzee NK complex genes, we determined the coding-region sequences for CD94 and NKG2A, C, D, E, and F from several human (Homo sapiens) donors and common chimpanzees (Pan troglodytes). CD94 is highly conserved, while the NKG2 genes exhibit some polymorphism. For all the genes, alternative mRNA splicing variants were frequent among the clones obtained by RT-PCR. Alternative splicing acts similarly in human and chimpanzee to produce the CD94B variant from the CD94 gene and the NKG2B variant from the NKG2A gene. Whereas single chimpanzee orthologs for CD94, NKG2A, NKG2E, and NKG2F were identified, two chimpanzee paralogs of the human NKG2C gene were defined. The chimpanzee Pt-NKG2CI gene encodes a protein similar to human NKG2C, whereas in the chimpanzee Pt-NKG2CII gene the translation frame changes near the beginning of the carbohydrate recognition domain, causing premature termination. Analysis of a panel of chimpanzee NK cell clones showed that Pt-NKG2CI and Pt-NKG2CII are independently and clonally expressed. Pt-NKG2CI and Pt-NKG2CII are equally diverged from human NKG2C, indicating that they arose by gene duplication subsequent to the divergence of chimpanzee and human ancestors. Genomic DNA from 80 individuals representing six primate species were typed for the presence of CD94 and NKG2. Each species gave distinctive typing patterns, with NKG2A and CD94 being most conserved. Seven different NK complex genotypes within the panel of 48 common chimpanzees were due to differences in Pt-NKG2C and Pt-NKG2D genes.

Rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta) represent two salmonid genera separated for 15--20 million years. cDNA sequences were determined for the classical MHC class I heavy chain gene UBA and the MHC class II beta-chain gene DAB from 15 rainbow and 10 brown trout. Both genes are highly polymorphic in both species and diploid in expression. The MHC class I alleles comprise several highly divergent lineages that are represented in both species and predate genera separation. The class II alleles are less divergent, highly species specific, and probably arose after genera separation. The striking difference in salmonid MHC class I and class II evolution contrasts with the situation in primates, where lineages of class II alleles have been sustained over longer periods of time relative to class I lineages. The difference may arise because salmonid MHC class I and II genes are not linked, whereas in mammals they are closely linked. A prevalent mechanism for evolving new MHC class I alleles in salmonids is recombination in intron II that shuffles alpha 1 and alpha 2 domains into different combinations.