Abstract: The present invention discloses the method of inhibiting complement activation mediated by factor B inhibitors, that involves: (a) inhibiting factor B binding to properdin-bound C3b; (b) inhibiting the release of Bb; (c) inhibiting the activation of neutrophils, monocytes, platelets, and endothelium; or (d) inhibiting/reducing the formation of PC3bBb, C3a, C5a, and MAC. The present invention also discloses the novel use of factor B inhibitors in the treatment of various immunological disorders, resulting either primarily from direct immune responses such as rheumatoid arthritis, anaphylactic shock, myasthenia gravis, asthma, Alzheimer's disease, and the like, or secondarily from clinical conditions such as cardiopulmonary bypass inflammation, vascular stenosis and restenosis, burn injury, and the like.