method of preventing binding of immune cells to other cells, bst2 decoy, chimeric construct, monoclonal antibody, method to isolate a bst2 ligand, transgenic mouse whose somatoplasm cells and germ cells comprise a functionally impaired bst2 or damp gene, mouse transgenic whose somatoplasma cells and germ cells comprise a damp gene that is totally or partially replaced by a bst2 gene, method for reducing inflammation in a patient, method for treating a patient for symptoms of a disease associated with inflammation, and method test for determining a chemical compound effective to inhibit bst2-mediated cell-cell binding