Immune Netw.  2014 Aug;14(4):201-206. 10.4110/in.2014.14.4.201.

IL-33 Priming Enhances Peritoneal Macrophage Activity in Response to Candida albicans

• Tran VG
• Cho HR
• Kwon B

• KMID: 2150808
• DOI: http://doi.org/10.4110/in.2014.14.4.201

Abstract

IL-33 is a member of the IL-1 cytokine family and plays a role in the host defense against bacteria, viruses, and fungi. In this study, we investigated the function of IL-33 and its receptor in in vitro macrophage responses to Candida albicans. Our results demonstrate that pre-sensitization of isolated peritoneal macrophages with IL-33 enhanced their pro-inflammatory cytokine production and phagocytic activity in response to C. albicans. These macrophage activities were entirely dependent on the ST2-MyD88 signaling pathway. In addition, pre-sensitization with IL-33 also increased ROS production and the subsequent killing ability of macrophages following C. albicans challenge. These results indicate that IL-33 may increase anti-fungal activity against Candida through macrophage-mediated resistance mechanisms.

Keyword

Peritoneal macrophage; IL-33; Candida albicans; Pro-inflammatory cytokines; Phagocytosis; Fungicidal activity

MeSH Terms

Bacteria
Candida
Candida albicans*
Fungi
Homicide
Humans
Interleukin-1
Macrophages
Macrophages, Peritoneal*
Phagocytosis
Interleukin-1

Figure

• 

  Figure 1 Pre-treatment of peritoneal macrophages with IL-33 increases the production of pro-inflammatory cytokines in response to C. albicans infection. Peritoneal macrophages were pre-treated with 100 ng/ml of IL-33 or PBS for 2 h prior to infection with heat-killed (HK) C. albicans (MOI=10). Levels of IL-6 (A) and TNFα (B) were measured 2 h, 6 h, 12 h, and 24 h after challenge with C. albicans. Data are presented as the mean±SEM of 2-3 trials with similar results. *p<0.05; **p<0.01.

• 

  Figure 2 The effect of IL-33 presensitization on pro-inflammatory cytokine production by peritoneal macrophages is dependent on the ST2-MyD88 signaling axis. (A) Peritoneal macrophages were pretreated with 100 ng/ml of IL-33 or PBS for 2 h prior to infection with heat-killed (HK) C. albicans (MOI=10). ST2 mRNA expression was analyzed by performing qRT-PCR 24 h post-challenge. (B) Peritoneal macrophages were pre-treated with 5µg/ml of anti-mouse ST2 mAb or control IgG for 1 h, at which point 100 ng/ml IL-33 was added to the medium. After a 2 h incubation period, macrophages were then challenged with HK-Candida (MOI=10). Levels of IL-6 and TNFα were determined by ELISA with culture supernatants harvested 24 h post-challenge. (C) The same experiments were repeated with peritoneal macrophages isolated from WT and MyD88 KO mice. Data are presented as the mean±SEM of 2-3 independent experiments. *p<0.05; **p<0.01.

• 

  Figure 3 Pre-sensitization of peritoneal macrophages with IL-33 enhances the phagocytic activity of macrophages in a MyD88-dependent manner. (A, B) IL-33-primed peritoneal macrophages were mixed with FITC-labeled, opsonized HK-Candida (MOI=10) for the indicated time periods. Macrophages containing FITC-labeled C. albicans were analyzed by flow cytometry (A). The percentage of FITC-positive macrophages (left column) and the mean fluorescence intensity for FITC of C. albicans-containing macrophages (right column) are quantified in B. (C) The same experiments were repeated with peritoneal macrophages of WT or MyD88 KO mice. Data are presented as the mean±SEM of 2-3 independent experiments. *p<0.05; **p<0.01.

• 

  Figure 4 IL-33 pre-sensitization enhances ROS production and fungicidal activity in peritoneal macrophages. (A) ROS production was measured as described in Materials and Methods. (B) Peritoneal macrophages were pre-incubated with IL-33 (100 ng/ml) for 3 h before challenge with live, opsonized Candida (MOI=1). Fungal killing activities were determined 15 and 30 min after challenge with C. albicans. Data are presented as the mean±SEM of 2-3 independent experiments. *p<0.05; **p<0.01.

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