Stability and heterogeneity in the anti-microbiota reactivity of human milk-derived Immunoglobulin A

This study investigates the antibacterial reactivity of breastmilk derived immunoglobulin A (BrmIgA) with an array of bacterial isolates commonly found in the preterm infant microbiota. We isolated BrmIgA from de-identified donors and use flow cytometry to characterize the intensity of antibacterial reactivity. Our results show heterogeneity of inter-donor BrmIgA reactivity but intra-donor stability over time. In addition, there was no significant difference in IgA concentration or reactivity between preterm and term donor milk. Lastly, we found that holder pasteurization globally reduces BrmIgA reactivity.