Organization of the leukocyte receptor cluster (LRC) on human Chromosome 19q13.4

A large number of cDNAs coding for killer cell inhibitory receptors (KIR) and immunoglobulin-like transcripts (ILT) have already been described, and some of the respective genes are known to map in 19q13.4. To understand the genetic relationships of these transcripts, some of which may be alleles from polymorphic loci, it is necessary to determine the genomic organization of the region. To do so, we performed long-range restriction enzyme mapping of the 19q13.4 region along with YAC and PAC contig construction. Eighteen genes could be assigned to a chromosomal segment of about 600 kb. Twelve KIR loci are contained within ~200 kb, bordered by the locus for the Fc receptor for IgA (FCAR) at the telomeric side and by a 150-kb cluster containing ILT loci at the centromeric side. A further region with a maximal size of 135 kb containing at least one ILT gene was identified further centromeric, separated by ~50 kb from the ILT region near the KIR cluster. The entire KIR/ILT region revealed a considerable degree of genetic polymorphism as shown, for example, by different restriction maps of two sets of PACs spanning the same region. We suggest the designation 'Leukocyte Receptor Cluster' (LRC) for this chromosomal segment.