CD4 and allergic disease: We utilized this strategy to enrich for intestinal CD4+ T cells responding to dietary protein in three contexts: (1) feeding, where mice are fed OVA, representing the steady-state response to food; (2) allergy, where primary exposure to OVA is with CT, resulting in allergic sensitization; and (3) tolerance, where mice are fed OVA alone prior to OVA/CT, resulting in oral tolerance and protection against allergy (Fig. 6 A).