Characterization of monoclonal antibody specific to the Z39Ig protein, a member of immunoglobulin superfamily.

Z39Ig, a recently identified immunoglobulin (Ig) superfamily member, is localized in the pericentromeric region of human chromosome X and detectable in all human tissue, but it is predominantly expressed in fetal human tissues as well as in adult lungs and placenta. In the present study, we generated a monoclonal antibody against Z39Ig protein to investigate the immunological role of Z39Ig protein on various immune cells. The anti-Z39Ig mAb that we generated specifically bound to Z39Ig protein on human promonocytic THP-1 cells, monocytes isolated from human peripheral blood mononuclear cells (PBMC) and mature CD14(+) dendritic cells (DC) differentiated from umbilical-cord blood CD34(+) hematopoietic progenitor cells. In addition, a signal through the Z39Ig protein induced an obvious cell surface expression of HLA-DR on THP-1 cells mediated by MHC class II transactivator (CIITA). These data suggest that the Z39Ig protein might be a critical molecule to regulate an immune response mediated by phagocytosis and/or antigen presentation.