MECHANISMS OF REJECTION: Edited by Jerzy W. Kupiec-WeglinskiThe influence of the microbiota on the immune response to transplantationBartman, Carolinea,b; Chong, Anita S.c; Alegre, Maria-LuisadAuthor Information aDivision of Hematology, Children's Hospital of Philadelphia bPerelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania cDepartment of Surgery, Section of Transplantation, The University of Chicago dDepartment of Medicine, Section of Rheumatology, The University of Chicago, Chicago, Illinois, USA Correspondence to Maria-Luisa Alegre, MD, PhD, The University of Chicago, 924 E. 57th St., JFK-R321, Chicago, IL 60615, USA. Tel: +1 773 834 4317; e-mail: [email protected] Current Opinion in Organ Transplantation: February 2015 - Volume 20 - Issue 1 - p 1-7 doi: 10.1097/MOT.0000000000000150 Buy Metrics Abstract Purpose of review In the past decade, appreciation of the important effects of commensal microbes on immunity has grown exponentially. The effect of the microbiota on transplantation has only recently begun to be explored; however, our understanding of the mechanistic details of host–microbe interactions is still lacking. Recent findings It has become clear that transplantation is associated with changes in the microbiota in many different settings, although what clinical events and therapeutic interventions contribute to these changes remains to be parsed out. Research groups have begun to identify associations between specific communities of organisms and transplant outcomes, but it remains to be established whether microbial changes precede or follow transplant rejection episodes. Finally, results from continuing exploration of basic mechanisms by which microbial communities affect innate and adaptive immunity in various animal models of disease continue to inform research on the microbiota's effects on immune responses against transplanted organs. Summary Commensal microbes may alter immune responses to organ transplantation, but direct experiments are only beginning in the field to identify species and immune pathways responsible for these putative effects. Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.