Candida albicans cell wall glycans, host receptors and responses: elements for a decisive crosstalk.

Candida albicans has adapted to live on the mucosal surfaces of animals. The human species has accepted it. By contrast to numerous other commensals, C. albicans has a prominent ability to invade virtually all tissues of a host presenting with natural or acquired defects in homeostasis. C. albicans uses considerable energy to synthesize glycans, which are present either as polymers or as glyconjugates. These glycan molecules play a prominent role in the biology of C. albicans by controlling the structure and plasticity of the cell wall, and are also involved in yeast-host interactions. These glycans are recognized as 'non-self' by host innate and adaptative immunity. The signal they induce in the host depends on the 'glycan code', which is determined by the nature of the sugar, the anomer type of linkage and branching, and the length of the oligosaccharide chains. However, this model is not static because the nature of the C. albicans molecule carrying such glycan codes and their expression at the cell wall surface also determines the host response, and, in turn, the regulation of cell wall glycan arrangement dynamics in C. albicans depends on host stimuli. Candida glycans therefore play an important role in the continuous interchange that regulates the balance between saprophytism and parasitism, and resistance and infection. A goal of current research concerning the virulence attributes of C. albicans will be to determine to what extent this species is able to regulate its glycan code as a response to the host.