The centromeric part of the human natural killer (NK) receptor complex: lectin-like receptor genes expressed in NK, dendritic and endothelial cells

The human natural killer (NK) receptor complex encompasses a region of abou t 2 Mb on the short arm of chromosome 12. It contains at least 18 lectin-li ke receptor genes, of which some are expressed in NK and NK/T cells and fun ction as NK receptors. Close to the CD94 and NKG2 NK receptor genes in the centromeric part, a novel family of genes, expressed in myeloid, dendritic and/or endothelial cells, recently became evident. These genes encode a rec eptor for oxidized low density lipoprotein in endothelial cells and three o ther receptors potentially serving regulatory functions in dendritic cells. Although the overall structure of the human NK receptor complex is similar to the syntenic rodent regions, the centromeric part lacks the cluster of Ly49 genes. This supports the notion that recognition of MHC class Ia molec ules has evolved separately in rodents and humans in the lectin-like Ly49 a nd the killer immunoglobulin-like receptors, respectively. In the telomeric part, other lectin-like genes expressed in different hematopoietic lineage s are found. The receptors of the NK receptor complex apparently serve impo rtant functions in several leukocytes and in endothelial cells, and the exa ct role of these receptors, their ligands, and their distinct and co-ordina te regulation in different cell lineages warrants further investigation.