Trained immunity and epigenetic memory in long-term self-renewing hematopoietic cells

Immunologic memory is a feature typically ascribed to the adaptive arm of the immune system. However, recent studies have demonstrated that hematopoietic stem cells (HSCs) and innate immune cells such as monocytes and macrophages can gain epigenetic signatures to enhance their response in the context of reinfection. This suggests the presence of long-term memory, a phenomenon referred to as trained immunity. Trained immunity in HSCs can occur via changes in the epigenetic landscape and enhanced chromatin accessibility in lineagespecific genes, as well as through metabolic alterations. These changes can lead to a skewing in lineage bias, particularly enhanced myelopoiesis and the generation of epigenetically modified innate immune cells that provide better protection against pathogens on secondary infection. Here, we summarize recent advancements in trained immunity and epigenetic memory formation in HSCs and self-renewing alveolar macrophages, which was the focus of the Spring 2022 International Society for Experimental Hematology (ISEH) webinar. (c) 2023 ISEH - Society for Hematology and Stem Cells. Published by Elsevier Inc. All rights reserved.

Automated summary

Immunologic memory is traditionally associated with the adaptive immune system, but recent studies show that hematopoietic stem cells and innate immune cells can acquire epigenetic changes to improve their response upon reinfection. This phenomenon, known as trained immunity, involves alterations in the epigenetic landscape and metabolic processes, resulting in the generation of epigenetically modified innate immune cells that provide enhanced protection against pathogens. This article summarizes the recent advancements in trained immunity and epigenetic memory formation in hematopoietic stem cells and alveolar macrophages.