Comparison of Human Milk Immunoglobulin Survival during Gastric Digestion between Preterm and Term Infants

Abstract

Human milk provides immunoglobulins (Igs) that supplement the passive immune system of neonates; however, the extent of survival of these Igs during gastric digestion and whether this differs between preterm and term infants remains unknown. Human milk, and infant gastric samples at 2 h post-ingestion were collected from 15 preterm (23⁻32 week gestational age (GA)) mother-infant pairs and from 8 term (38⁻40 week of GA) mother-infant pairs within 7⁻98 days postnatal age. Samples were analyzed via ELISA for concentration of total IgA (secretory IgA (SIgA)/IgA), total secretory component (SC/SIgA/SIgM), total IgM (SIgM/IgM), and IgG as well as peptidomics. Total IgA concentration decreased by 60% from human milk to the preterm infant stomach and decreased by 48% in the term infant stomach. Total IgM and IgG concentrations decreased by 33% and 77%, respectively, from human milk to the term infant stomach but were stable in the preterm infant stomach. Release of peptides from all Ig isotypes in the term infant stomach was higher than in the preterm stomach. Overall, the stability of human milk Igs during gastric digestion is higher in preterm infant than in term infants, which could be beneficial for assisting the preterm infants' immature immune system.

Keywords: antibodies; breast milk; lactation; passive immunity; peptidomics; prematurity; proteolysis.

Figure 1

Immunoglobulin concentrations in human milk and gastric samples at 2 h postprandial time from paired mother-infant delivered prematurely (23–32 week of gestational age (GA), 7–98 days of postnatal age) and at term (38–40 week of GA, 16–42 days of postnatal age). Concentration of total IgA (SIgA/IgA) (A) in preterm infant samples and (B) in term infant samples; Concentration of total secretory component (SC/SIgA/SIgM) (C) in preterm infant samples and (D) in term infant samples. Values are mean ± SEM, n = 15 for preterm infants and n = 8 for term infants. Asterisks show statistical significant differences between variables (*** p < 0.001; * p < 0.05) using the Wilcoxon matched-pairs signed-rank test.

Figure 2

Immunoglobulin concentrations in human milk and gastric samples at 2 h postprandial time from paired mother-infant delivered prematurely (23–32 week of gestational age (GA), 7–98 days of postnatal age) and at term (38–40 week of GA, 16–42 days of postnatal age). Concentration of total IgM (SIgM/IgM) (A) in preterm infant samples and (B) in term infant samples; Concentration of IgG (C) in preterm infant samples and (D) in term infant samples. Values are mean ± SEM, n = 15 for preterm infants and n = 8 for term infants. Asterisks show statistical significant differences between variables (*** p < 0.001; * p < 0.05) using the Wilcoxon matched-pairs signed-rank test.

Figure 3

Peptide counts and abundance of human immunoglobulin fragments in human milk and gastric samples at 2 h postprandial time from paired mother-infant delivered prematurely (23–32 week of gestational age (GA), 7–98 days of postnatal age) and at term (38–40 week of GA, 16–42 days of postnatal age). (A,D) Ig alpha-chain (from SIgA/IgA) and (B,E) Ig mu-chain (from SIgM/IgM); (C,F) Ig gamma-chain (from IgG). Values are mean ± SEM, n = 15 for preterm infants and n = 8 for term infants. Asterisks show statistical significant differences between variables (*** p < 0.001; ** p < 0.01; * p < 0.05) using the Mann–Whitney test (unpaired samples).

Figure 4

Peptides counts and abundance of SC (f19–603 of PIgR) in human milk and gastric samples from mother–infant pairs with preterm delivery (23–32 week of gestational age (GA), 7–98 days of postnatal age) and term delivery (38–40 week of GA, 16–42 days of postnatal age. Peptides counts of SC (A) in preterm infant samples; (B) in term infant samples. Peptide abundance of SC (C) in preterm infant samples and (D) in term infant samples. Values are mean ± SEM, n = 15 for preterm infants and n = 8 for term infants. Asterisks show statistical significant differences between variables (** p < 0.01; * p < 0.05) using the Wilcoxon matched-pairs signed-rank test.