Increasing the growth temperature from 28 to 37°C reduced the expression of -1,2-oligomannoside epitopes on mannoproteins of Candida albicans serotypes A and B. In contrast, -1,2-mannosylation of phospholipomannan (PLM) remained constant despite a slight decrease in the relative molecular weight (M r ) of this compound. At all growth temperatures investigated, serotype A PLM displayed an M r and an antigenicity different from those of serotype B PLM when they were tested with a panel of monoclonal antibodies.Genotypic or phenotypic regulation of surface antigens depends on adaptive pathways that are used by numerous pathogens to escape from host defenses. In Candida albicans, molecular rearrangement of cell wall molecules, dimorphism (17,29), and phenotypic switching (34) are thought to help the yeast avoid the host response. Sequences of -1,2-linked mannose residues are located at the C. albicans cell surface, and they act as adhesins (20,25), induce protective antibodies (9, 15) and cytokines (19), and are thought to contribute to virulence. These biological activities have been demonstrated by using -1,2-oligomannosides released from C. albicans cell wall mannan by mild acid hydrolysis. Structural analysis by nuclear magnetic resonance (30) and fluorophore-assisted carbohydrate electrophoresis (14,26,30) has demonstrated that the quantities and chain lengths of -1,2-oligomannosides released from the mannan vary according to the growth conditions (namely, pH and temperature or hydrophobicity). In the serological classification of Tsuchiya et al. (41) used to develop the Iatron kit (Iatron Laboratories, Tokyo, Japan), -1,2-oligomannosides reacted with two different factor sera depending on the degree of polymerization and the nature of the mannose residues at the reducing end. Factor serum 5 epitopes are homopolymers of -1,2-linked mannose present in the mannan acid-labile fraction of serotypes A and B (33). Factor serum 6 has been shown to correspond to one or two -mannose residues at the nonreducing end of ␣-1,2-linked lateral chains of the mannan acid-stable region and is specific for serotype A (22). Along with factor serum 13b, which is reactive with some serotype B strains (36), this factor serum allows discrimination of C. albicans serotypes A and B, which differ in adhesins, epidemiology, and resistance to antifungal drugs (1,3,16,28). A large number of monoclonal antibodies (MAbs) generated against C. albicans have been shown to react with -1,2-oligomannosides (15, 37, 39). Immunofluorescence or electron microscopy studies involving anti--1,2-oligomannoside MAbs have demonstrated the highly heterogeneous expression of -1,2-oligomannoside epitopes inside a colony, between morphotypes, or between cells of the same morphotype (either hyphae or yeasts) (10,13,29,38). One of the reasons for this complex expression is that C. albicans -1,2-oligomannosides not only are present in mannan but are also associated with other carrier molecules. These molecules include mannoproteins and a glycolipid, ph...