Trained Immunity Carried by Non-immune Cells

“Trained immunity” is a term proposed by Netea to describe the ability of an organism to develop an exacerbated immunological response to protect against a second infection independent of the adaptative immunity. This immunological memory can last from 1 week to several months and is only described in innate immune cells such as monocytes, macrophages, and natural killer cells. Paradoxically, the lifespan of these cells in the blood is shorter than the duration of trained immunity. This observation suggested that trained immunity could be carried by long lifespan cells such as stem cells and non-immune cells like fibroblasts. It is now evident that in addition to performing their putative function in the development and maintenance of tissue homeostasis, non-immune cells also play an important role in the response to pathogens by producing anti-microbial factors, with long-term inflammation suggesting that non-immune cells can be trained to confer long-lasting immunological memory. This review provides a summary of the current relevant knowledge about the cells which possess immunological memory and discusses the possibility that non-immune cells may carry immunological memory and mechanisms that might be involved

Immune properties of dental pulp stem cells in an infectious context

Les cellules souches de la pulpe dentaire humaine (DPSCs) sont des cellules souches mésenchymateuses (MSCs) isolées de la pulpe dentaire. Les DPSCs sont capables de s’auto-renouveler et se différencier en plusieurs types cellulaires tel que les odontoblastes, les ostéoblastes, les chondrocytes, les neuroblastes et les adipocytes. Les propriétés immunitaires des DPSCs sont de plus en plus étudiées, elles hébergent des récepteurs de types Toll à la surface, possedent une activité immuno-modulatrice.Cependant, les propriétés immunitaires comme celles décrites dans les cellules immunitaires professionnelles telles que la phagocytose, la production de composés anti-microbiens et le nouveau concept « Trained immunity » pourraient être étudiées. une brève revue a été élaborée pour mettre en évidence l'ensemble des propriétés immunitaires des DPSCs décrites dans la littérature. Ensuite, expérimentalement, nous avons montré que les DPSCs pouvaient internaliser le pathogène bactérien Bartonella quintana. En outre, nous avons décrit la capacité des DPSCs à développer une immunité entrainée “trained immunity”. Il s’agit d’une mémoire inflammatoire concernant deux cytokines IL-6 et MCP-1. La stimulation des DPSCs avec le ligand bactérien LPS ou PGN induit une augmentation de l’expression et de la production de l'IL-6 et du PGN après un second stimulus. Dans l'ensemble, l'étude des propriétés immunitaires des DPSCs montre que ces dernières peuvent agir comme des cellules immunitaires.Dental pulp Stem cells (DPSCs) are mesenchymal stem cells (MSCs) isolated from the dental pulp. DPSCs are able to self-renew and differentiate into several cell types such as odontoblasts, osteoblasts, chondrocytes, neuroblasts and adipocytes.The immune properties of DPSCs are being studied more and more, they harbor Toll-like receptor on the surface and have an immunomodulatory activity.However, immune properties such as those described in professional immune cells such as phagocytosis, production of antimicrobial compounds and the new concept "Trained immunity" could be studied.A brief review has been developed to highlight the set of immune properties of DPSCs described in the literature. Then, experimentally, we showed that DPSCs could internalize the bacterial pathogen Bartonella quintana.In addition, we have described the ability of DPSCs to develop trained immunity. It is an inflammatory memory concerning two cytokines IL-6 and MCP-1. Priming DPSCs with the bacterial ligand LPS or PGN induces an increase in the expression and production of IL-6 and PGN after a second stimulus.Overall, the study of the immune properties of DPSCs shows that DPSCs can act as immune cells

Human dental pulp stem cells: A sanctuary for relapsing Bartonella quintana

International audienceBartonella quintana is a facultative intracellular bacterium responsible for relapsing fever, an example of non-sterilizing immunity. The cellular sanctuary of B. quintana in-between febrile relapses remains unknown but repeated detection of B. quintana in dental pulp specimens suggested long-term half-life dental pulp stem cells (DPSCs) as candidates. As the capacity of DPSCs to internalize microscopic particles was unknown, we confirmed that DPSCs internalized B. quintana bacteria: Gimenez staining and fluorescence microscopy localized B. quintana bacteria inside DPSCs and this internalization did not affect the cellular multiplication of DPSCs during a one-month follow-up despite the increase in the bacterial load. B. quintana-infected DPSCs did not produce Tumor Necrosis Factor-α whereas an important production of Monocytes Chemoattractant Protein-1 was observed. These unprecedented observations suggest the possibility that DPSCs are shelters for the long-term persistence of B. quintana in the host, warranting further experimental and clinical investigations