beta-Glucans in food modify colonic microflora by inducing antimicrobial protein, calprotectin, in a Dectin-1-induced-IL-17F-dependent manner
MUCOSAL IMMUNOLOGY
Authors: Kamiya, T.; Tang, C.; Kadoki, M.; Oshima, K.; Hattori, M.; Saijo, S.; Adachi, Y.; Ohno, N.; Iwakura, Y.
Abstract
Dectin-1 (gene symbol: Clec7a) is a receptor for beta-glucans that play an important role for the host defense against fungi. Recently, we showed that Clec7a(-/-) mice are resistant against dextran sodium sulfate (DSS)-induced colitis because of regulatory T-cell population expansion in the colon. The regulatory T-cell expansion is caused by expansion of commensal Lactobacillus murinus whose growth is suppressed by an antimicrobial protein, calprotectin S100A8/A9. In this report, we showed that S100A8 was mainly produced by mouse colonic epithelial cells. S100A8 was not induced directly by Dectin-1 but by Dectin-1-induced cytokines, especially interleukin-17F (IL-17F), that were produced by several types of innate immune cells including CD11c(+)/CD11b(+) myeloid cells in colonic lamina propria. S100A8/A9 heterodimer preferentially suppressed the growth of L. murinus that was increased in both Clec7a(-/-) and II17f(-/-) mice. Furthermore, similar expansion of L. murinus and DSS-colitis resistance were observed in mice fed with beta-glucanfree food. These observations suggest that food-derived b-glucans control the specific commensal microbiota via the Dectin-1-IL-17F-calprotectin axis to maintain the intestinal homeostasis.
Polymorphisms of the immune-modulating receptor dectin-1 in pigs: their functional influence and distribution in pig populations
IMMUNOGENETICS
Authors: Shinkai, Hiroki; Toki, Daisuke; Okumura, Naohiko; Takenouchi, Takato; Kitani, Hiroshi; Uenishi, Hirohide
Abstract
Dectin-1, a C-type lectin receptor that recognizes fungal beta-glucans, is involved in antifungal immunity and the regulation of intestinal immune homeostasis. Dectin-1 is involved in both synthesis and maturation of interleukin-1 beta, a key pro-inflammatory cytokine in immunity. Here, we assessed the genetic diversity in the gene encoding dectin-1 (CLEC7A) within various pig populations and examined the influence of these polymorphisms on the two different signaling pathways after ligand recognition. An amino-acid polymorphism located in the carbohydrate-recognition domain, leucine to serine at position 138 (L138S), which occurred exclusively in Japanese wild boars at low frequency, significantly increased NF-kappa B induction but not caspase-8 activity after stimulation with zymosan. In contrast, other amino-acid polymorphisms present at comparatively high frequency in commercial pig populations had little influence on ligand recognition. These results suggest that functionally neutral polymorphisms in dectin-1 are widespread in pig populations.