The role of STAT3

for normal signalling of the IL-6 receptor has important consequences for normal host defence. Together with other cytokines such as IL-1β and IL-23, the IL-6/STAT3 pathway is crucial for the normal development of CD4+–T helper type 17 (Th17) cells [6,7]. Because IL-17 has an important role in the activation of neutrophil-dependent immunity [8], defective Th17 generation as a result of STAT3 mutation may play an important role in the pathogenesis of HIES. In a recent paper, Milner et al. have demonstrated that T lymphocytes from patients with HIES are unable to differentiate into Th17 after mitogenic stimulation [9]. These data were supported by two reports that also showed defective generation of Th17 when anti-CD3/anti-CD28/IL-2

or cytokine cocktails were used [10,11]. These studies reported the defective generation of Th17 using mitogenic cocktails in patients with established check details PI3K phosphorylation mutations in the SH2 and DNA-binding domains of STAT3. In contrast, patients with atopic dermatitis and high IgE, but without skin and respiratory infections and without STAT3 mutations, had normal Th17 responses [9,12]. In the present paper, we aimed to extend these initial findings by investigating the generation of Th17 cells and IL-17 production by relevant microbial stimuli for HIES. In addition, we assessed Th17 profiles in three distinct groups of patients: ‘classical’ HIES patients with STAT3 mutations in the SH2/DNA-binding domains, ‘classical’ HIES without STAT3 mutations and a family with ‘variant’ HIES that we described as having a milder clinical phenotype [13], with deletion of a triplet in the linker domain. The differences in the degree of IL-17 production defects after stimulation with Staphylococcus aureus or Candida albicans determined the severity of the clinical phenotype. Eight patients with a clinical diagnosis of HIES at the out-patient clinic for infectious diseases and immunodeficiencies of the Department of General Internal Medicine Oxymatrine of Radboud University Nijmegen Medical Centre were enrolled into the study. Three of these patients were family members. After

informed consent, blood was collected from eight healthy, non-smoking volunteers who were free of infectious or inflammatory disease and the enrolled HIES patients by venipuncture into 10 ml ethylenediamine tetraacetic acid (EDTA) syringes (Monoject; BD Vacutainer, Plymouth, UK). STAT3 mutation analysis was kindly performed in the Laboratory of Human Molecular Biology and Genetics, Catholic University of the Sacred Heart, Milan, Italy (head Professor Roberto Colombo). C. albicans American Type Culture Collection (ATCC) MYA-3573 (UC820), a strain well described elsewhere [14], was used. C. albicans was grown overnight in Sabouraud broth at 37°C, cells were harvested by centrifugation, washed twice and resuspended in culture medium (RPMI-1640 Dutch modification; ICN Biomedicals, Aurora, OH, USA) [15]. C.