We found that allergy of the mother and the presence of 1 or more siblings had most influence on the breastmilk T cell profile (Figure 8A), with a significant positive relationship with expression of most homing receptors (CLA, α4β7, and α4β1), activation markers, and cytokine production but a significant negative relationship to CCR9 expression and a cytotoxic T cell profile (Figure 8B). Here, CCR9 is linked to allergic disease.