Polymorphism and linkage disequilibrium of immunoglobulin-like transcript 3 gene

SummaryImmunoglobulin-like transcript 3 (ILT3) is an inhibitory receptor molecule expressed by dendritic cells, monocytes, and endothelial cells. Upon upregulation of ILT3 expression, antigen presenting cells (APCs) become tolerogenic, triggering the differentiation of antigen-specific CD8+ and CD4+ regulatory T cells. To analyze the polymorphism of ILT3, we screened DNA from a panel of 150 healthy subjects for single nucleotide polymorphisms (SNPs) within genomic region encoding the extracellular domain (exons 1–8). Here we report the identification of 15 SNPs, including nine nonsynonymous, three synonymous base-pair substitutions, and three intronic, including one deletion polymorphism within 3.6 kb of the ILT3 genomic region. Analysis of three physically linked SNP in healthy individuals indicates that c.356-41-46del, a 6–base-pair (bp) deletion located in intron 3/4, is predominantly associated with c.678A allele, a nonsynonymous SNP located in exon 5. Linkage studies in five nuclear families showed that these two minor alleles co-segregate. Our results demonstrate that ILT3 is highly polymorphic and may be associated with susceptibility to immune disorders.