Commensal Fungi in Health and Disease

Abstract

Fungi are increasingly being recognized as common members of the microbiomes found on nearly all mucosal surfaces, and interest is growing in understanding how these organisms may contribute to health and disease. In this review, we investigate recent developments in our understanding of the fungal microbiota or "mycobiota" including challenges faced in characterizing it, where these organisms are found, their diversity, and how they interact with host immunity. Growing evidence indicates that, like the bacterial microbiota, the fungal microbiota is often altered in disease states, and increasingly studies are being designed to probe the functional consequences of such fungal dysbiosis on health and disease.

Keywords: Candida; commensal fungi; microbiome; mycobiome.

Figure 1. Alterations in commensal fungi may affect the host in diverse ways

Changing intestinal fungi either by adding (probiotic) or subtracting (anti-fungal drugs) organisms can alter the makeup of the bacterial microbiota (1). Fungi detected by the intestinal immune system can lead to inflammatory or tolerant immune responses and can direct immune cell trafficking (2). Phagocytes digesting fungi can release fungal-derived molecules into circulation that may have immunoregulatory effects (3). Finally, intestinal fungi release and consume metabolites that can lead to activation or suppression of immune responses.