I Pathogenic mechanisms Ag+ body-IgG, IgM, IgA immune complexes(Ic) soluble tc ICs are deposited from the circulation into vascular basement membranes ① ②↓FcR activation of complement plat and basophils C3a, C5a -mast cell release of vasoactive amines basophils ③ Neutrophils vasodilation aggravate /sonoma edema enzymes damage the tissueI. Pathogenic mechanisms Ag→body→IgG, IgM, IgA ↓ immune complexes (IC) ↓ soluble IC ↓ ICs are deposited from the circulation into vascular basement membranes ①↓ ② ↓FcR activation of complement plat. and basophils ↓ C3a, C5a →mast cell → release of vasoactive amines ↓ basophils ③ Neutrophils vasodilation ↓ lysosomal edema enzymes→damage the tissue aggravate