This gene encodes a member of a family of immunoreceptors that are expressed predominantly in monocytes and B cells, and at lower levels in dendritic cells and natural killer cells. The encoded protein lacks the transmembrane region found in other members of this family. It acts as a soluble receptor for class I major histocompatibility complex (MHC) antigens. Alternatively spliced transcript variants encoding different isoforms have been found. This gene is located in a cluster of related genes on chromosome 19 and is polymorphic in human populations, with many individuals containing a deletion of this genomic region.