This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Pathology
Necrotising aerioritis with fibrinoid necrosis is characteristic of 
Select and explain. 
A. Immediate hypersensitivity, B. Cell mediated immunity, C. Ag-Ab complex mediated, D. Cytotoxic mediated
C: Ag-Ab complex mediated
Answer: C: Ag-Ab complex mediated 
Explanation: Fibrinoid necrosis is a special form of necrosis, visible by light microscopy , usually in immune reaction in which complexes of antigens and antibodies are deposited in the walls of aeries. The deposited immune complexes together with fibrin that has leaked out of vessels produce a bright pink and amorphous appearance on H & E preparation called fibrinoid. Type 3 hypersensitivity disorder Robbins 9th edition page 111,11