A method for obtaining agonist, antagonist and inverse agonist, to a given physiological receptor is disclosed. For the method, use is made of in silico design synthetic immunogens, which are caused to act in vitro on human lymphocyte-containing cell populations. A preferred receptor is human CD152, particularly the regions of CDR1, CDR2 and CDR3 that elicit antibodies serving as antagonist, inverse agonist and agonist, respectively. Also provided is a method in the treatment of human peripheral lymphocytes for use in the screening of CD152 ligands that yield pharmacological effects.