The sheep CD1 gene family contains at least four CD1B homologues

We identified four cDNA sequences encoding sheep homologues of the CD1 molecule. The sheep sequences were selected from λgt11 thymocyte cDNA libraries by hybridization with a humanCD1C probe and a homologous sheep probe. TheSCD1B-42 andSCD1A25 sequences encode complete CD1 molecules. The third sequence,SCD1B-52, which is closely related toSCD1B-42 and may be an allele, has the sequence encoding the α3 region precisely deleted. The fourth sequence,SCD1T10, is truncated at the 5′ end. All four sequences are related to the humanCD1B and domestic rabbitCD1B-like sequences at both nucleotide and amino acid level. Comparison of the derivedCD1 amino acid sequences with the sequence of major histocompatibility complex class I molecules showed that the sheep CD1 molecules, like human CD1 molecules, lack most of the conserved class I residues known to be involved in interaction with 132-microglobulin and the CD8 molecule. They do not contain the peptide docking residues involved in anchoring peptides in the peptide binding groove of class I molecules. Southern hybridization of sheep DNA with a sheepCD1 exon 4/ga3 probe showed that the sheep genome encodes at least sevenCD1 genes. The implications of these analyses for CD1 function are discussed. The nucleotide sequence data reported in this paper have been submitted to the EMBL/GenBank nucleotide sequence databases and have been assigned the accession numbers Z36890 (SCD1A25), Z36891 (SCD1B-42), Z36892 (SCD1B-52), and X90567 (SCDIT10)