Protecting Our Newborns via Passive Immunity

Mother provide immune protection both in utero and during breast-feeding.

Passive Immunity:

Our immune systems are vital for our protection against the various pathogens we are exposed to. There are two arms of immune protections: Innate and adaptive immune responses. Innate immunity provides protection through recognition of pathogen-associated products, triggering an immune response aims to clear the pathogen. The adaptive immune response is more trained and establishes long-term protection against pathogens that you have previously been exposed to. A major component of the adaptive immune response is formation of antibodies that can target pathogens and prevent or limit infection. Infants require time to develop their adaptive immune responses, therefore depending on the innate immune system. In addition, passive immunity also plays an important role in protecting infants.

Passive immunity is the transfer of already made antibodies to a person. For infants, a method of obtaining passive immunity is through the transfer of maternal antibodies. Maternal antibodies can pass through the placenta produced by the mother which can be transferred to the infant to provide IgG antibodies that are pathogen specific. IgG is one of the antibodies found within tissues and in circulation, therefore is involved in systemic protection. Interestingly, the range of pathogen-specificity in these antibodies is also impacted by maternal immune experience, therefore it is common for mothers to be receive vaccinations or boosters during pregnancy to support passive immunity for the infant.

Additionally, antibodies can be transferred through breastfeeding. Segretory IgA (sIgA) antibodies can be found both in colostrum and in breastmilk. sIgA is abundant at mucosal sites, including the gut and the respiratory tract. Considering the many pathogens to which we are exposed enter via the respiratory tract or the gut, IgA is a crucial protective mechanism against infection. Breast milk is the primary source of sIgA for newborns, as they have not developed adaptive immune responses to generate their own sIgA, therefore also making maternal sIgA essential for establishment of the gut microbiome in newborns.

In addition to transfer of antibodies, immune cells can also be transferred both in utero via via the placenta or postpartum through breast milk. Many of the cells transferred through breast milk express mucosal homing markers, therefore allowing these cells to migrate to mucosal sites, such as the gut and the respiratory tract, where they can provide local protection against infections. Furthermore, human-milk oligosaccharides (HMOs) are also transferred via breastmilk. HMOs, which are unique to human milk, aid in protection by preventing binding of invading pathogens to host cells, acting as a preventative mechanisms of protection against infection.

Recommended vaccines during pregnancy:

The Tdap vaccine, which confers protection against tetanus, diphtheria, and acellular pertussis Vaccination during pregnancy has significantly reduced neonatal deaths cause by tetanus and diphtheria. The other recommended vaccine is the influenza virus vaccine, specifically using the inactivated virus vaccine. Influenza A infection is implicated in pediatric deaths, with the CDC reporting a mortality rate of 11.1 per 1 million in children under 6 months of age.

 Not only does influenza vaccination protect the mother against circulating influenza strains, but also increased protection for infants.

 References:

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2.     Cinicola, B., Conti, M. G., Terrin, G., Sgrulletti, M., Elfeky, R., Carsetti, R., Fernandez Salinas, A., Piano Mortari, E., Brindisi, G., De Curtis, M., Zicari, A. M., Moschese, V., & Duse, M. (2021). The Protective Role of Maternal Immunization in Early Life. Frontiers in pediatrics, 9, 638871. https://doi.org/10.3389/fped.2021.638871

3.     Albrecht, M., Pagenkemper, M., Wiessner, C., Spohn, M., Lütgehetmann, M., Jacobsen, H., Gabriel, G., Zazara, D. E., Haertel, C., Hecher, K., Diemert, A., & Arck, P. C. (2022). Infant immunity against viral infections is advanced by the placenta-dependent vertical transfer of maternal antibodies. Vaccine, 40(11), 1563–1571. https://doi.org/10.1016/j.vaccine.2020.12.049

4.     Albrecht, M., & Arck, P. C. (2020). Vertically Transferred Immunity in Neonates: Mothers, Mechanisms and Mediators. Frontiers in immunology, 11, 555. https://doi.org/10.3389/fimmu.2020.00555

5.     Suryadevara M. (2024). Passive Immunization Strategies to Prevent Severe Respiratory Syncytial Virus Infection Among Newborns and Young Infants. Journal of the Pediatric Infectious Diseases Society, 13(Supplement_2), S110–S114. https://doi.org/10.1093/jpids/piae058

6.     Langel, S. N., Blasi, M., & Permar, S. R. (2022). Maternal immune protection against infectious diseases. Cell host & microbe, 30(5), 660–674. https://doi.org/10.1016/j.chom.2022.04.007

Assessed and Endorsed by the MedReport Medical Review Board