BackgroundImmunosuppressive therapies have led to improved survival for lung transplant (LT) recipients but these therapies can lead to hypogammaglobulinemia (HGG) and potentially an increased risk of infection. Large prospective studies have not been performed to evaluate the impact of HGG on outcomes for LT recipients.MethodsThis is a single-center prospective observational study of LT recipients. Pretransplant and posttransplant IgG levels were measured and related to infection, rejection, antibiotic use, and immunosuppression use.ResultsOne hundred thirty-three LT recipients were prospectively evaluated. Pretransplant IgG values were higher than IgG values at the time of transplant or any time thereafter (all P < 0.0001). Severe HGG (IgG < 400 mg/dL) was highest at the time of transplant (32.4%) while at 3, 6, 9, and 12 months posttransplant the prevalence of severe HGG was 7.4%, 7.5%, 8.9%, and 6.3%, respectively. Severe HGG was associated with 2 or more pneumonias (P = 0.0006) and increased number of antibiotic courses (P = 0.003) compared with the subjects without severe HGG. Pretransplant IgG level and less than 30% of pretransplant protective pneumococcal antibody levels were identified as pretransplant risk factors for severe HGG. In multivariate analysis, chronic obstructive pulmonary disease as the underlying disease and the use of basiliximab as the induction agent in conjunction with higher prednisone and mycophenolate dosing were most predictive of severe HGG (P = 0.005), whereas the combination of age, severe HGG and number of acute steroid courses were most predictive of total days of pneumonia (P = 0.0001).ConclusionsOur large prospective study identifies risk factors for severe HGG after LT and demonstrates that LT recipients with severe HGG are at increased risk for recurrent pneumonias and more antibiotic courses.

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Immunoglobulin A (IgA) is secreted into breast milk and is critical for both protecting against enteric pathogens and shaping the infant intestinal microbiota. The efficacy of breast milk–derived maternal IgA (BrmIgA) is dependent upon its specificity; however, heterogeneity in BrmIgA binding ability to the infant microbiota is not known. Using a flow cytometric array, we analyzed the reactivity of BrmIgA against bacteria common to the infant microbiota and discovered substantial heterogeneity between all donors, independent of preterm or term delivery. Surprisingly, we also observed intradonor variability in the BrmIgA response to closely related bacterial isolates. Conversely, longitudinal analysis showed that the antibacterial BrmIgA reactivity was relatively stable through time, even between sequential infants, indicating that mammary gland IgA responses are durable. Together, our study demonstrates that the antibacterial BrmIgA reactivity displays interindividual heterogeneity but intraindividual stability. These findings have important implications for how breast milk shapes the development of the preterm infant microbiota and protects against necrotizing enterocolitis.

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Immunoglobulin A (IgA) is secreted into breast milk and is critical to both protecting against enteric pathogens and shaping the infant intestinal microbiota. The efficacy of breast milk-derived maternal IgA (BrmIgA) is dependent upon its specificity, however heterogeneity in BrmIgA binding ability to the infant microbiota is not known. Using a flow cytometric array, we analyzed the reactivity of BrmIgA against bacteria common to the infant microbiota and discovered substantial heterogeneity between all donors, independent of preterm or term delivery. We also observed intra-donor variability in the BrmIgA response to closely related bacterial isolates. Conversely, longitudinal analysis showed that the anti-bacterial BrmIgA reactivity was relatively stable through time, even between sequential infants, indicating that mammary gland IgA responses are durable. Together, our study demonstrates that the anti-bacterial BrmIgA reactivity displays inter-individual heterogeneity but intra-individual stability. These findings have important implications for how breast milk shapes the development of the infant microbiota and protects against Necrotizing Enterocolitis.

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