Shown are the different structures for the glucuronoxylomannan (GXM) of Cryptococcus serotypes A to D. Serotypes A and D belong to C. neoformans, and serotypes B and C belong to C. gattii. The mannose backbone of GXM has variable degrees of O-acetylation (not shown). GlcpA, glucopyranosyluronic acid; Manp, mannopyranan; Xylp, xylopyranosyl. (Reproduced and adapted with permission from Cherniak, R., Valafar, H., Morris, L.C., and Valafar, F. 1998. Cryptococcus neoformans Chemotyping by Quantitative Analysis of 1H Nuclear Magnetic Resonance Spectra of Glucuronoxylomannans with a Computer-Simulated Artificial Neural Network. Clin. Diagn. Lab. Immunol. 5, 146–159.)