Basophil activation testing.
MP
Whole blood samples drawn into 4 mL lithium heparin phlebotomy tubes (BD Biosciences) before food challenge at each visit were utilized for basophil activation testing. Whole blood was incubated with mouse IgM anti-human-IgE monoclonal antibody (clone 6061P, Hybridoma Labs), the indicated dilutions of peanut extract (Greer), 1 μM fMLP (Sigma), or vehicle (Greer incipient control solution) in PAGCM buffer (piperazine-N,N′-bis[2-ethanesulfonic acid] + bovine serum albumin [MP Biomedicals] + glucose [Sigma-Aldrich] + 1.7 mM calcium + 1.7 mM magnesium) for 30 minutes at 37°C. Cells were then fixed using Phosflow Fix Buffer (BD Biosciences), centrifuged at 400