To determine whether clinical sensitivity to peanut allergen (as defined by the eliciting dose during food challenge) is inversely associated with the the relative frequency within a peanut-specific Th2 effector CD4+ CD45RA- T cell subset (based on expression of GATA-3, RASGRP1, IL4R and other validated Th2 signature genes) before the DBPCFC or 6-8 weeks after the DBPCFC.