DIgR1, a novel membrane receptor of the immunoglobulin gene superfamily, is preferentially expressed by antigen-presenting cells

A novel membrane receptor of immunoglobulin gene superfamily (IgSF) has been identified from mouse dendritic cells (DC) and designated as DC-derived Ig-like receptor 1 (DIgR1). It encodes a 228-amino-acid (aa) residue polypeptide with a 21-aa signal peptide, a 20-aa transmembrane region, a 189-aa extracellular region, and a 19 aa intracellular region. Its extracellular region contains a single V domain of Ig. So it is a novel type I transmembrane glycoprotein of IgSF. DIgR1 shows significant homologies to human CMRF-35 antigens and polymeric immunoglobulin receptors (pIgR). The mRNA expression of DIgR1 was highly abundant in mouse spleen. The preferential expression of DIgR1 mRNA is observed in the known antigen-presenting cells (APC) including DC, monocytes/macrophages, and B lymphocytes. A 40 kDa of protein in NIH/3T3 cells transfected with the DIgR1 cDNA was detected by Western blot analysis using anti-DIgR1 polyclonal antibodies. The expression of DIgR1 protein on DC is not regulated by LPS stimulation. Further study should be conducted to investigate what were biological functions of DIgR1 in the immunobiology of APC.