ABSTRACT
In general, it has been understood that specific antibodies against 1,6-β-monoglucosyl branched 1,3-β-glucans are difficult to develop in mice (Adachi et al., 1994). However, other 1,3-β-glucans having a long 1,6-β-glucosyl branch, CSBG, obtained from the Candida yeast cell wall, can induce a specific antibody in some mouse strains and humans (Masuzawa et al., 2003). This finding suggests that such fungal cells can stimulate the acquired immune system via 1,3-β-glucans in addition to proteinous substances. The physiological role of the β-glucan antibody in the host defense should be examined in future studies. Please refer to Chapter 9 in this book.
Surfactant proteins function as carbohydrate recognition molecules with Ca2+ dependency, which belong to the C-type lectin family. Surfactant proteins are produced by lung alveolar type II epithelial cells and play important roles in modulating alveolar surface tension, regulating secretion, and mediating innate immunity (Kuroki and Voelker, 1994). Surfactant protein A (SP-A), a major surfactant protein, is similar to surfactant protein D (SP-D). Both proteins are composed of a short N-terminal region involved in covalent cross-linking, followed by a collagen-like domain, a neck region, and a C-terminal carbohydrate recognition domain (CRD) (Kuroki and Voelker, 1994). SP-D forms a predominantly cruciform-like dodecamer, whereas SP-A forms a bouquet-like octadecamer. The carbohydrate recognition of SP-D is demonstrated to be specific for 1,6-α and 1,6-β-glucosyl chains (Allen et al., 2001). The amino acid residues in CRD, Glu321/Asn323, and Glu329/Asn341, associate with C3-OH and C4-OH of the glucose residues via a hydrogen bond, respectively (Allen et al., 2001). The SP-D multimer accelerates to form multivalent ligand interaction, which may contribute to the host defense by aggregating fungal cells, such as Aspergillus and Candida (Kishor et al., 2002).
