Abstract: The invention relates to monoclonal antibodies against leucocyte-specific G protein-coupled receptors (L-GCR). These antibodies are obtainable by the following steps: (a) introduction of an L-GCR-coding nucleic acid into cells and expression of L-GCR, (b) immunization of an animal with L-GCR-expressing cells of (a), and (c) fusion of spleen cells from the immunized animal of (b) with myeloma cells and production of monoclonal L-GCR antibody-producing hybridoma cells. Furthermore, the invention relates to processes for the production of such antibodies, their use and kits containing the same. In addition, the invention concerns a process for the production of monoclonal GCR antibodies.