A 78-year-old man is brought to the operating room for a L2-5 total laminectomy. His medical history includes hypertension, diabetes mellitus, type II, and COPD. Following the induction of anesthesia with propofol and rocuronium the patientís blood pressure decreases to 45/20 mmHg and an urticarial rash noted on the arms and chest. The pathophysiological mechanism MOST likely responsible for the hypotension is:

A) Antibody (IgM or IgG) binding to antigen on a target host cell
B) T-cell mediated activation of macrophages
C) The formation of immune complexes
D) IgE-mediated degranulation of mast cells and basophils