Abstract
Previous study revealed that a specific lignin-carbohydrate preparation, named as lignin-rich enzyme lignin (LREL) derived from plant husk, is a novel toll-like receptor 4 ligand and shows a potent immune-stimulatory activity against dendritic cells (DCs) in vitro. In this report, we investigated immune-stimulatory activity of LREL in vivo. Single intraperitoneal (i.p.) or oral treatment of LREL elicited activation of systemic and mucosal DCs, which were accompanied by significant elevation of cell surface activation markers and ratio of IL-12p40 producing cells. In addition, LREL-fed mice showed not only mucosal DCs activation but also significant increase of IFN-γ+ CD4+ T cells in mesenteric lymph node (MLN), respectively. We further examined the effect of LREL oral immunization in combination with ovalbumin (OVA) on the activation of acquired immune system. In LREL administered group, total mucosal IgA concentration was significantly increased, while antigen-specific immunoglobulin A (IgA) concentration was not changed between groups. On the other hand, both total and antigen-specific IgG concentrations in plasma were significantly increased in the LREL administered group. Taken together, oral treatment of LREL is able to affect mucosal and systemic antibodies induction and might be useful for effective immune-stimulatory functional foods and mucosal vaccine adjuvant.
Highlights
Lignin is a well-known major natural compound that is derived from the cell walls of plants [1]
We previously found that lignin-rich enzyme lignin (LREL), one of the fractions extracted from edible plant tissues which contains lignin-carbohydrate, was able to activate bone marrow derived dendritic cells (BM-DCs) and its activity was comparable to LPS [6]
We focused on the in vivo immune-modulatory effects of LREL, which was originally discovered as a novel toll-like receptor 4 (TLR4) ligand (TLR4L) derived from barley husk, and showed that it activated splenic (SPN) DCs and natural killer (NK) cells after single dose administration via a systemic route
Summary
Lignin is a well-known major natural compound that is derived from the cell walls of plants [1]. Some polysaccharides in the cell walls are linked to lignin through hydroxycinnamic acids, forming ester-ether bridges which form structurally complex lignin-carbohydrates [3,4,5]. Due to the molecular complexity, stable preparations of lignin-carbohydrates have proved to be difficult, and very little attention has been paid to the biological activities of lignin-containing substances. We previously found that lignin-rich enzyme lignin (LREL), one of the fractions extracted from edible plant tissues which contains lignin-carbohydrate, was able to activate bone marrow derived dendritic cells (BM-DCs) and its activity was comparable to LPS [6]. LREL derived from barley husk was shown to activate BM-DCs via toll-like receptor 4 (TLR4) [6]
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