The influence of the microbiota on the immune response to transplantation

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.