A study about modulation of dendritic cell function by mannose-based oligo- and polysaccharides

概要

Mannans are natural polysaccharides with a high d-mannose content and exist in various forms in yeasts, fungi,
bacteria, and plants. According to this strict definition, mannans are mainly composed of D-mannose. Mannan
can also be largely divided into α and β types, which consist of α- and β-linkages, respectively. Depending on
their origin, mannans have various types of backbones and branch linkages. Recent studies have shown that
α-mannan derived from yeasts and β-glucomannan from konjac possess immunomodulatory effects that
suppress the development of allergic rhinitis by inducing the anti-inflammatory cytokine IL-10 in dendritic cells
(DCs). In contrast, other studies have suggested the presence of α-mannan from pathogenic Candida albicans
induces an inflammatory response in DCs. Mannans and mannooligosaccharides appear to exhibit
immunological functions by activating antigen-presenting cells (APCs) via pattern recognition receptors (PPRs).
However, many types of mannans and mannose-based oligosaccharides exist. Thus far, it is necessary to
determine how mannan- or mannose-based oligosaccharides interact with receptors that activate APCs.
DCs and macrophages are professional APCs. Both cell types express various types of PPRs for antigen
capture and major histocompatibility complex (MHC) class II molecules for antigen presentation on the cell
surface. DCs and macrophages capture antigens, process them into antigenic peptides, and present them as
complexes of MHC class II molecules to CD4+ T cells. CD4+ T cells are activated when the T-cell receptor (TCR)
binds to the complex. Upon activation, naïve CD4+ T cells differentiate into effector or regulatory T cells. Effector
T cells play a crucial role in the induction of cellular and humoral immune responses, whereas regulatory T cells
suppress the activation of effector T cells to prevent excessive immune responses. ...

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