78-P : DIFFERENTIAL TRANSCRIPTION PROFILES FOR MHC CLASS I GENES IN ORANGUTANS: NEGLIGIBLE TRANSCRIPTION OF C AND PARTICULAR B LOCUS/LINEAGE IN PERIPHERAL BLOOD DERIVED CELL-LINES

Aim Humans and orangutans shared a common ancestor about 12-16 million years ago. Two orangutan species are officially recognized; one inhabiting Borneo ( Pongo pygmaeus ) and the other Sumatra ( Pongo abelii ). Orangutans possess A , B , and C genes that are homologous to their HLA equivalents. Unlike humans where each of these is found as a single copy gene on a haplotype, orangutan haplotypes may possess a duplicated B gene whereas others lack C . In theory, orangutans may express from 3 to 8 different classical MHC class I allotypes. Conventional sequencing of cDNA derived from six different orangutan samples, using 4 different primer sets, suggested that certain alleles, in particular MHC-C, are less well transcribed. Therefor we aimed to investigate the transcription/expression profile of the orangutan MHC class I genes. Methods cDNA, derived from five different orangutan EBV transformed B-cell-lines (two Popy and three Poab ), was used as starting material. Generic primers were designed, and relevant amplicons were sequenced in both directions using massively parallel sequencing. Results The analyses showed that the A locus is most abundantly transcribed. The B locus exhibits differential transcription patterns that seem to be dependent on the B allotype present in an animal. The present analyses show an almost negligible transcription of the B ∗03-locus/lineage. In addition, the C locus, if present, appears to be minutely transcribed. Moreover, the cell-surface expression of several MHC allotypes was assessed using various monoclonal antibodies. Conclusions The present data suggest a minor immunological role for B ∗03-lineage and C -locus molecules in orangutangs as they appear to be virtually absent on peripheral blood derived cells. Besides, all animals investigated transcribe at least one variant of the B ∗08-lineage that encodes the C1-epitope, the ligand for particular killer cell Ig-like receptor, and most likely compensate for the partial loss of the C -locus in orangutans.