The Active/Passive Immunotherapy of the present invention combines active immunization to a hapten or immunogen (H/I) and passive immunization with the same H/I conjugated to an antigen binding ligand. The prior immunization to the H/I grants active standing immunity to the H/I whereas the antigen binding ligand grants instant passive binding to the target antigen. The ligand - H/I conjugate acts as a 'sandwich' molecule to provide binding sites to both the target antigen and immune cells to thereby usurp the active standing immunity for the H/I to passive instant immunity for the pathological target antigen. Particular advantages of the present invention include that chemicals as well as peptides can be used as antigen binding ligand, and the full immune repertoire of humoral and/or cellular immunity can be instantly and selectively mobilized and targeted to a pathological antigen. Thus, the present Active/Passive Immunotherapy can provide a generic defense against the myriad of pathological antigens including microbes and other infectious agents, toxins, as well as autoimmune and cancer antigens.