Blood and Guts: How the Intestinal Microbiome Shapes Hematopoiesis and Treatment of Hematologic Disease

Over the past ten years there has been a marked increase in recognition of the interplay between the intestinal microbiome and the hematopoietic system. Despite their apparent distance in the body, a large literature now supports the relevance of the normal intestinal microbiota to steady state blood production, affecting both hematopoietic stem and progenitor cells and differentiated immune cells. Microbial metabolites enter the circulation where they can trigger cytokine signaling that influences hematopoiesis. Furthermore, the state of the microbiome is now recognized to affect outcomes from hematopoietic stem cell transplant, immunotherapy, and cellular therapies for hematologic malignancies. Here we review the mechanisms by which microbiota influence hematopoiesis in development and adulthood, as well as the avenues by which microbiota are thought to impact stem cell transplant engraftment, graft versus host disease, and efficacy of cell and immunotherapies. We highlight areas of future research that may lead to reduced adverse effects of antibiotic use and improved outcomes for patients with hematologic conditions.