Elsevier

Immunology Letters

Volume 118, Issue 1, 15 June 2008, Pages 72-81
Immunology Letters

Memory Th-17 cells specific for C. albicans are persistent in human peripheral blood

https://doi.org/10.1016/j.imlet.2008.03.004Get rights and content

Abstract

Th-17 cells, a new subset of effector CD4+ T cells, have been identified in mice and in humans. In the present study, we show that a high level of IL-17 and a high frequency of IL-17-producing cells were detected by ELISA and ELISPOT assay, respectively, when human PBMCs were stimulated with both anti-CD3 and anti-CD28. Further analysis of IL-17-producing cells by flow cytometry showed that CD4+ T cells were the main contributor to IL-17 production, and IL-17 production could be directly induced by purified CD4+ T cells at the protein and transcriptional levels. Phenotypic analyses revealed that the majority of IL-17-producing CD4+ T cells were memory cells with the expression of CD45RO, CD69, CCR6 and CCR4, and approximately 70% of IL-17-producing CD4+ T cells expressed CCR7. In addition, Th-17 cells were different from Th1, Th2 and Treg cells, because the expression of IL-17, IFN-γ, IL-4 or Foxp3 was restricted to distinct CD4+ T subsets. Importantly, stimulation of PBMCs with heated-inactivated Candida albicans (C. albicans) yeast or hyphae induced IL-17 production at the protein and transcriptional levels. These data suggest that memory Th-17 cells are present in healthy individual PBMCs and some memory Th-17 cells might play an important role in the defense against the infections of fungi such as C. albicans.

Introduction

Th-17 cells are recently identified as a unique subset of Th cells [1]. Th-17 cells are distinct from the Th1 and Th2 cells based upon the production of cytokines, biological functions and differentiation pathways. Th1 cells produce interferon-γ (IFN-γ) and mediate protection against intracellular microbes such as Mycobacterium tuberculosis, whereas Th2 cells release IL-4, IL-5 and IL-13 and mediate protection against parasites, but are also responsible for allergic disorders [2], [3]. Th-17 cells produce IL-17A and IL-17F that promote inflammatory responses against bacterial infections and are involved in some autoimmune diseases such as rheumatoid arthritis, multiple sclerosis and psoriasis [4], [5], [6], [7], [8], [9]. The cytokine microenvironments play a critical role in Th cells differentiation during immune responses. IL-12 induces Th1 differentiation and IL-4 drives Th2 differentiation [10], whereas TGF-β and IL-6 in mouse or IL-6 and IL-1β in humans mediate Th-17 differentiation [11], [12], [13], [14].

Recently, the role of IL-17 in protective immunity against infections has been elucidated. IL-17 and its receptor have been linked to resistance to infections by extracellular microbes such as Klebsiella pneumoniae and Candida albicans [6], [15]. However, most studies on Th-17 cells are focused on experimental animal models, but very little information on human Th-17 is available. In the present study, we found that IL-17 could be induced at protein and transcriptional levels following stimulation of normal human PBMCs with anti-CD3 and anti-CD28. Further analysis of IL-17-producing cells demonstrated that IL-17 was mainly produced by memory CD4+ T cells but not by memory CD8+ T cells. Importantly, some memory Th-17 cells in PBMCs from healthy individuals were specific for C. albicans, indicating that healthy people can generate memory Th-17 cells against fungi.

Section snippets

Subjects

Thirty-nine voluntary healthy adults (30 females and 9 males, mean ± S.D. age of 33.7 ± 9.7 years, range 21–61 years) were selected as our subjects. The umbilical cord blood was obtained from six full-term newborn infants without infections or treatment of immunosuppressive medicines before expulsion of the placenta. Adequate informed consent was obtained from all individuals involved in this study. The study was approved by the Medical School Review Board at Sun Yat-sen University, China.

Monoclonal abs

Induction of IL-17 by PBMCs at protein and transcriptional levels

To determine whether IL-17 could be induced by PBMCs under different stimulation conditions with polyclonal stimuli, PBMCs were isolated from 16 healthy donors and incubated in the absence or presence of anti-CD3 or anti-CD3 plus anti-CD28. After incubation for 3 days, IL-17 in the cell-free culture supernatants was determined by specific ELISA. As shown in Fig. 1A, when PBMCs were cultured in medium, there was no detectable level of IL-17 production. After stimulation with anti-CD3, a

Discussion

In the present study, we provide clear evidence that memory and effector Th-17 cells are apparent in healthy individual PBMCs and some memory Th-17 cells are specific for C. albicans.

In the first experiment, we found that PBMCs from healthy adults could be induced to produce IL-17 at protein and transcriptional levels in response to polyclonal stimuli. Further analysis of IL-17-producing cells by flow cytometry after a short-time stimulation demonstrated that CD4+ T cells are the main

Acknowledgments

The authors thank Miss Sharon Mathis, vaccine research center, NIAID, NIH, USA, for her kind critical reading and linguistic revision of the manuscript. This study was supported by a grant from the National Key Basic Research Program of China (973) (grant no. 2007CB512404).

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