Abstract: The invention relates to a method of treating or monitoring/diagnosing a disease state mediated by activated macrophages. The method comprises the step of administering to a patient suffering from a macrophage mediated disease state an effective amount of a composition comprising a conjugate or complex of the general formula Ab-X where the group Ab comprises a ligand capable of binding to activated macrophages, and when the conjugate is being used for treatment of the disease state, the group X comprises an immunogen, a cytotoxin, or a compound capable of altering macrophage function, and when the conjugate is being used for monitoring/diagnosing the disease state, X comprises an imaging agent. The method is useful for treating a patient suffering from a disease selected from the group consisting of rheumatoid arthritis, ulcerative colitis, Crohn's disease, inflammation, infections, osteomyelitis, atherosclerosis, organ transplant rejection, pulmonary fibrosis, sarcoidosis, and systemic sclerosis.