Active free secretory component and secretory IgA in human milk: do maternal vaccination, allergy, infection, mode of delivery, nutrition and active lifestyle change their concentrations?

Previous viral symptoms and individual mothers influenced the leveled duration of human milk antibodies cross-reactive to S1 and S2 subunits from SARS-CoV-2, HCoV-229E, and HCoV-OC43

“…Her infant had negative PCR results for RNA SARS-CoV-2 at birth but had elevated IgG in serum, suggesting that infants can acquire passive immunity against SARS-CoV-2 by ingesting human milk from mothers recovering from COVID-19. Individual mothers likely influence the kinetics of human milk antibodies due to the differences of previous infections (time since disease onset and severity), preexisting immunity, age, genetic factors, and other factors affecting the immune response [ 18 , 31 ].…”

“…Finally, it is unlikely that the lactation time affected antibody levels in human milk reactive to SARS-CoV-2 as all samples were collected between 3 and 5.5 months of postpartum time. Our previous study demonstrated that the antibody concentrations were not affected by the postpartum time when human milk collection was collected after 4 months of lactation [ 18 ].…”

“…The levels of SIgM/IgM, IgG, and SIgA/IgA reactive to SARS-CoV-2 and HCoVs were determined using ELISAs as described in our recent study with some modifications [ 9 ]. Briefly, ELISAs were recorded with a microplate reader (SpectraMax iD5, Molecular Devices, Sunnyvale, CA) as reported in our recent studies on human milk antibodies [ 17 , 18 ]. Frozen HM samples were rapidly thawed at 37° and centrifuged at 1301× g for 20 min at 4 °C.…”

Lactoferrin and Immunoglobulin Concentrations in Milk of Gestational Diabetic Mothers

“…Their action on the mucosal surface of the gastrointestinal tract is supported by LF, which acts as an immunomodulator responsible for up- and downregulation of both innate and adaptive immune cells, and participates in maintaining homeostasis [ 50 ]. Although milk immunoglobulins are exposed to a varying degree to be digested by the newborn, all milk isotypes that pass through the intestines are found in the feces of infants [ 98 ], with the most abundant being SIgA due to the secretory component crucial for higher resistance to proteolytic cleavage [ 47 , 98 , 99 ]. However, it should be emphasized that not only IgA activity is important.…”

“…The major immune components delivered with maternal milk are lactoferrin (LF) and secretory immunoglobulin A (SIgA) [ 37 , 38 , 39 , 40 ]. Both molecules effectively support the immature newborn’s immune system and protect against colonization of gastrointestinal and respiratory tracts by pathogens, reducing the incidence of respiratory infections, sepsis, necrotizing enterocolitis, and diarrhea [ 41 , 42 , 43 , 44 , 45 , 46 , 47 ]. However, the mechanisms of biological action are different.…”