Microbiota from mothers regulates lung immunity in newborns

LISBON: A new study led by Bruno Silva Santos, group leader and vice-director at the Instituto de Medicina Molecular Joo Lobo Antunes (iMM; Portugal), and published in the scientific journal Cell Reports discovered that T cells influence the transfer of maternal microbiota during birth and nursing, as well as the lung immune response in newborns.

Before birth, the lungs are filled with a sterile liquid that is replaced by gas in the first breath after birth, which causes an immune reaction involving substantial lung tissue remodelling, called the "first breath response". Now, researchers at iMM implicated a specific type of immune cells, gd T cells, in this immune response in mice.

"We found that newborns born and raised by mothers lacking gd T cells acquire a different gut microbiota. The intestinal microorganisms in these mice are not able to produce sufficient amounts of a type of molecules that are important to modulate the lung immune response to the first breath", explains the leader of the study, Bruno Silva Santos, adding: "As a result, these pups have an exacerbated first breath immune response".

The type of immune response induced after the first breath is also relevant in other contexts. The researchers observed a similar pattern in the progeny of mothers lacking gd T cells in response to an infection by a parasite that induces lung damage.

"We saw that either antibiotic treatment to kill the microorganisms in the gut, or supplementation with short-chain fatty acids, the molecules that are down in mice with exacerbated immune responses, abolish the differences between mice born from mothers with and without these immune cells. This shows that the effects observed in the pups are indirect and linked to these molecules produced by the microbiota", adds Pedro Papotto, first author of the study which he initiated during his PhD at iMM.

The complexity of the work takes another level on the transfer of microbiota from mothers to newborns. "We found that the transfer of microorganisms from mothers is not restricted to the process of birth. If pups born from mothers lacking gd T lymphocytes are raised with mothers with these cells, their immune response is restored.

In fact, our study suggests that the majority of the bacterial communities must be transferred after birth, during nursing", explains Pedro Papotto. It is already known that the developing immune system is sensitive to factors derived from mothers.

Now, in this study, the researchers found that maternal gd T cells, which were never associated with this process, are involved in the development of newborns' lung immunity by exerting an effect on the gut microorganism's colonization. This also adds to the growing body of evidence on gut microbiota's physiological and therapeutic roles.