MIF and immune system toxicity: Hence, this work should provide a basis for investigation of several aspects of hapten-modification of MIF in immunotoxicity, such as: a) the role of proline in formation of immunogenic complexes, b) how administration of hapten-modified MIF, instead of hapten, would affect the potency of contact sensitization, c) where and when the MIF-hapten conjugates are formed, d) the role of different types of hapten bindings (e.g. covalent binding to proteins vs. p-i effects) and e) immunoregulation by haptenated proteins in immunotoxicity beyond contact sensitization.