Figure 4.

(A) Organization of ILT cluster I. Sequence of the six ILT genes clustered within 150 kb centromeric of the KIR from PAC 52N12¹. All genes are in the same 5′ to 3′ orientation from centromere to telomere and, with exception of the ILT1 gene, are less than 6 kb in size. Fragments of ILT and LAIR exons were found throughout the entire sequence (indicated as open blocks). The exon/intron organization of the two inhibitory ILT genes, ILT2 and ILT3, is conserved, although two exons accounting for two additional Ig domains are present in the ILT2 gene. Some variation was observed between the genes encoding for putative activating ILTs: ILT1 contains an 11-kb intron between the fourth Ig domain and the stalk exon, and an extra stalk exon was found in the LIR6 gene that is not in any other activating member. In four genes, we predicted an extra 5′ untranslated region exon as seen in some LIR6 and ILT2 transcripts. (B) Dot matrix analysis of the sequence from PAC 52N12¹. The plot shows the region encompassing the five ILT genes and one LIR locus on both axes (see Fig. 4A for details). In contrast to the KIR loci (Fig. 2A), the sequences of the intergenic regions are not conserved.