A 36-Year-Old Woman with Fistulizing Perianal Crohn Disease Comes to the Office

A 36-year-old woman with fistulizing perianal Crohn disease comes to the office for a follow-up appointment.  Eight weeks ago, the patient began receiving intermittent injections of infliximab, a chimeric human-mouse monoclonal antibody targeted against tumor necrosis factor-alpha.  She reports improvement in fistula discharge and discomfort but has experienced fever, diffuse joint pain, and an itchy rash 5-7 days after each of the recent treatments.  The symptoms spontaneously resolve after 2-3 days.  The patient has no other medical conditions and has no history of drug allergies.  A delayed drug reaction due to formation of antibodies against foreign drug components is suspected.  Which of the following mechanisms is most likely responsible for resolution of these drug reactions?

A) Activation of the mononuclear phagocyte system
B) Apoptosis of tissue mast cells and eosinophils
C) Clearance of intact drug molecules by kidneys
D) Endocytosis and degradation of mast cell-bound IgE
E) Regulatory T-cell-mediated cytotoxic T-cell suppression