Changes in blood leukocyte distribution during double-blind, placebo-controlled food challenges in children with atopic dermatitis and suspected food allergy

Background: The development of clinical reactions to food antigens is associated with cellular changes. The aim of this study was to determine whether the clinical outcome of double-blind, placebo-controlled food challenges would correlate with changes in blood leukocyte distribution. Methods: Double-blind, placebo-controlled food challenges were performed in 17 children with atopic dermatitis sensitized to hen's egg or cow's milk and in 9 children with atopic dermatitis but not sensitized to food. Blood leukocyte distribution and lymphocyte subsets were determined prior to and 24 h after challenges. Results: In food-sensitized children the numbers of leukocytes and lymphocytes decreased significantly after allergen challenge independent of the clinical outcome of the provocation (p < 0.002 in both cases). This decrease was seen in T (CD3+) and B (CD19+) cell subsets (p < 0.007 and p < 0.0005, respectively). The CD4/CD8 ratio increased (p < 0.04). The number of memory cells (CD45R0) dropped (p < 0.02 for CD4 and p < 0.004 for CD8) and there was a loss of L-selectin (p < 0.003 for CD4 and CD8). No changes in thrombocytes, neutrophils, eosinophils and basophils were observed. None of these changes were seen in the sensitized patients during placebo challenges or in the non-sensitized group of children. Conclusion: Changes in the leukocyte distribution after allergen challenge seem to be associated with sensitization, but not with the clinical outcome of the oral food challenge. They reflect important changes in the immune system in response to allergens, but are not useful in monitoring double-blind, placebo-controlled food challenges.