Immunology

Fungal Immunology

There are approximately 100, 000 species of fungi and these are ubiquitous in the environment. Some form spores which we inhale on a daily basis (e.g. Aspergillus spp), and others live as human commensal organisms (e.g. Candida spp). Despite the close encounters we have with fungi, how our immune system recognises and protects us from fungal pathogens is only just beginning to be well understood of the fungi that cause disease, many are opportunistic pathogens, meaning they only cause disease under certain circumstances − such as when the immune system becomes weakened. For example, chemotherapy, immunosuppressive drugs and HIV infection all result in an impaired immune system, meaning that fungi can then more easily infect these vulnerable patients. Fungi are recognised by cells of the innate immune system (e.g. Dendritic cells and macrophages) which bind components of fungal cell walls using pattern recognition receptors (prrs) on their surface. C-type lectin receptors (clrs, e.g. Dectin-1) are particularly important prrs in anti-fungal immunity, although several other prrs are also involved including the Toll-like receptors (tlrs, e.g. TLR2). Fungal diseases represent an important paradigm in immunology, as they can result from either a lack of recognition by the immune system or overactivation of the inflammatory response.