Blood samples
At baseline and follow up visits, 10mL of venous blood will be collected
by trained study staff. The blood will be processed for plasma,
peripheral blood mononuclear cells, and granulocytes within 4 hours of
receiving the sample. Plasma will be stored at -80C for batched analysis
of specific IgE and specific IgG4 against whole peanut/tree nuts and
corresponding components by ImmunoCAP (Phadia AB, Uppsala, Sweden).
Peripheral blood mononuclear cells and granulocytes will be isolated
using a Ficoll-paque density gradient and stored in liquid nitrogen for
exploratory immunological studies. In addition, follow up visit blood
samples will have Basophil Activation Tests (BATs) performed within 4
hours, with basophils isolated and tested for expression of activation
markers CD63 and CCR3+ following specific peanut/tree nut allergen
stimulation in vitro.