In order to extend our current understanding of HLA-C polymorphism, four new alleles have been cloned and sequenced: Cw*1801 in a donor of mixed origin, Cw*02024 in a Senegalese individual, Cw*1205 and Cw*1604 in European Caucasoid blood donors. HLA-Cw*1801, which most likely results from an interallelic recombination between Cw*0704 and 0401 alleles, was not associated with B*8101, but with either B*4403 or B18. The Cw*02024 allele differs from Cw*02022 by a silent mutation in exon 3. Both Cw*1801 and Cw*02024 appear to be rather frequent in populations of African origin but have not yet been detected in Caucasoids. HLA-Cw*1604 differs from Cw*1601 by two nucleotides at codon 156 leading to a Gln to Trp substitution. This new Cw16 subtype was subsequently identified in three additional unrelated families, all of South-European origin, and presented an unusual association with B*4402 in all cases. HLA-Cw*1205 is a composite allele with the alpha1 domain of Cw*1602 and the alpha2 domain of Cw*1203. It appears to be rare, at least in European Caucasoids. Three of these four alleles may have resulted from gene conversion-like or interallelic recombination events.

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Summary The ovine major histocompatibility complex (MhcOvar) class II region was investigated by Southern blot hybridizations using ovine probes specific for the second exons of Ovar‐DRB and Ovar‐DQB genes. Multiple bands were revealed when genomic DNA was digested with each of five restriction enzymes (Bam HI, Eco RI, Hin dIII, PvuII and TaqI), and successively hybridized with the two radiolabeled ovine probes. Restriction fragment length polymorphisms (RFLPs) were analysed in 89 sheep originating from six inbred families and the inheritance of the fragment patterns was determined. Forty‐one fragments were recorded with the DQB probe; 32 were detected with the DRB probe. They constituted 9 DQB and 10 DRB allelic patterns. Twelve DQB‐DRB haplotypes were resolved in this study.