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Scientists from the Institut Pasteur in Paris, the Institut Pasteur of Shanghai and INSERM research unit 1041, "Immune Regulation and Vaccinology", in collaboration with the Paris Public Hospital Network, have recently demonstrated the existence of immunological memory cells in fetuses. These cells are developed in utero and are capable of producing an inflammatory-type immune response. The results of this study, published May 28, 2014 in the journal Science Translational Medicine, suggest that it may be possible to develop vaccine-induced immunological memory, during pregnancy and specific to the fetus, which would increase immunity in infants during the first months of life.
Immunological memory relies on the action of memory T lymphocyte cells. These cells are able to "remember" previous infections and provide the body with a quick immune response in the event of re-exposure to the same pathogen. During pregnancy, the fetus’ immune system develops within what is considered to be a sterile environment, meaning that their immunological memory is not activated. Therefore, until now, as long as no infectious pathology manifested in the fetus, newborn T lymphocytes were considered "naïve" (without memory). And, although the fetus can receive protective immunity from its mother via the transfer of antibodies for any infections she has contracted or vaccinations she has received, memory T lymphocytes are not transferred.
However, this knowledge was recently called into question when Richard Lo-Man and his group of scientists working within the research unit 1041 "Immune Regulation and Vaccinology" (Institut Pasteur/INSERM) led by Professor Claude Leclerc, discovered a small population of memory T lymphocytes present in newborns. This would indicate that, despite the absence of pathogenic agents in the sterile in utero environment, the fetus develops its own immunological memory during the pregnancy which is active and functional at birth. These lymphocytes are able to rapidly produce antimicrobial cytokine-type molecules which ensure that the newborn has an effective inflammatory immune response.
If the same principle can be applied to vaccines, that is, if vaccines could be administered to pregnant women and were capable of stimulating immunity in their unborn children, the discovery of this process might open up the possibility of vaccinating fetuses in utero. This strategy of vaccine-induced immunity for unborn children could increase immunity in infants during their first months of life.
Illustration: Memory lymphocytes isolated from the blood of a male newborn. The nuclei (blue) show the X (red) and Y (green) sex chromosomes, proving that the cells are those of the fetus and not those of the mother. Fluorescence microscopy. © Institut Pasteur
Inflammatory effector-like memory CD4 T cells develop in the sterile environment of the fetus, Science Translational Medicine, 28 mai 2014.
Xiaoming Zhang (1,2,3), Brian Mozeleski (1,2), Sebastien Lemoine (1,2), Edith Dériaud (1,2), Annick Lim (4), Dania Zhivaki (1,2), Elie Azria (5,6), Camille Le Ray (7,8), Gwenaelle Roguet (9), Odile Launay (8,9,10), Anne Vanet (11,12,13), Claude Leclerc (1,2), Richard Lo-Man (1,2)
(1) Régulation Immunitaire et Vaccinologie, Institut Pasteur, Paris, France
(2) INSERM U1041, France
(3) Unit of Innate Defense and Immune Modulation, Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China
(4) Department Immunology, Institut Pasteur, Paris, France
(5) Department of Obstetrics and Gynecology, Hospital Bichat Claude Bernard, Paris, France
(6) Paris 7 Université Diderot, Paris, France
(7) APHP, Department of Obstetrics and Gynecology, Maternité Port Royal, Paris, France
(8) Université Paris Descartes, Sorbonne Paris Cité, Paris, France
(9) INSERM CIC1417, Paris, France
(10) APHP, Hopital Cochin, Paris, France
(11) Université Paris Diderot, Sorbonne Paris Cité, F-75013, Paris, France
(12) CNRS, UMR7592, Institut Jacques Monod, F-75013, Paris, France
(13) Atelier de Bio Informatique, F-75005, Paris, France
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