The information summarized in Table 1 is indeed going to rapidly evolve with the exponential increase of community level genome-wide surveys of the microorganisms inhabiting the various microenvironments of the human body (i.e., gut, skin, oral mucosa, and urogenital tract) [23], their environmental reservoir [24], and the human populations living in different geographic regions [6, 8]. Understanding the prevalence and distribution of microbial eukaryotes in addition to prokaryotic

microorganisms in the human body may have important consequences for human health. While current studies of the human mycobiota focus mainly on pathogens or opportunistic fungi, most resident microbial eukaryotes do not cause infections, and are instead either beneficial or commensal. Elucidating community-wide changes in the human mycobiota, LDK378 nmr rather than only the presence or absence

of specific taxa, will be crucial to understanding the cause of, and potential treatment for, several multifaceted polymicrobial diseases [25]. Immune responses to fungi require PRRs, such as TLRs, C-type lectin receptors, and the galectin family of proteins [26-28] to trigger intracellular signaling cascades that initiate and direct innate and adaptive immune responses check details [29]. By sensing conserved molecular structures on fungi, namely the PAMPs, PRRs promote the activation of the immune system and the clearance of fungi, with specific immune responses generated depending on the cell type involved. In a recent review [30], we highlighted the roles and mechanisms of dectin-1, dectin-2, and DC-SIGN in orchestrating antifungal to immunity, exploring how these PRRs help maintain homeostasis between potential disease-causing organisms and resident microbial populations. Indeed, the immune system does not remain ignorant of commensal, passenger (transient), or opportunistic fungi, and sensing these different fungi through PRRs serve to ensure that

both the symbiotic host–microbial relationship and a homeostatic balance between tolerogenic and proinflammatory immune responses are maintained. In light of this, tissue homeostasis and its possible breakdown in fungal infections and diseases play a fundamental role. A number of seminal reviews have addressed the importance of both resistance — the ability to limit microbial burden — and tolerance — the ability to limit the host damage caused by an uncontrolled response — as mechanisms of immune responses to fungi and the reader is directed to these for more in-depth information about specific immune mechanisms [31-34]. Monocytes, macrophages, neutrophils as well as epithelial and endothelial cells [35], mostly contribute to the antifungal innate immune response through phagocytosis and direct pathogen killing. By contrast, uptake of fungi by DCs promotes the differentiation of naïve T cells into effector Th-cell subtypes (Fig. 1).