Acemannan purified from Aloe vera induces phenotypic and functional maturation of immature dendritic cells

Acemannan, a major carbohydrate fraction of Aloe vera gel, has been known t o have antiviral and antitumoral activities in vivo through activation of i mmune responses. The present study was set out to define the immunomodulato ry activity of acemannan on dendritic cells (DCs), which are the most impor tant accessory cells for the initiation of primary immune responses, Immatu re DCs were generated from mouse bone marrow (BM) cells by culturing in a m edium supplemented with GM-CSF and IL-4. and then stimulated with acemannan , sulfated acemannan. and LPS. respectively. The resultant DCs were examine d for phenotypic and functional properties. Phenotypic analysis for the exp ression of class II MHC molecules and major eo-stimulatory molecules such a s B7-1. B7-2. CD40 and CD54 confirmed that acemannan could induce maturatio n of immature DCs. Functional maturation of immature DCs was supported by i ncreased allogeneic mixed lymphocyte reaction (MLR) and IL-12 production. T he differentiation-inducing activity of acemannan was almost completely abo lished by chemical sulfation. Based on these results, we propose that the a djuvant activity of acemannan is at least in part due to its capacity to pr omote differentiation of immature DCs. (C) 2001 Elsevier Science B.V. All r ights reserved.