Thorough examination of myeloid populations may elucidate their involvement in promoting the aberrant T cell phenotypes observed in our patient cohort. promoted secretion of IL-1 and IL-6 when co-cultured with naive CD4+ T cells. Additionally, systemic inflammation in AS patients significantly correlated with increased proportions of activated CCR9+ CD4+ T cells. Conclusion. CD14? CD16+ mononuclear cells may contribute to AS by promoting Th17 responses, and antigen-presenting cells of mucosal origin are likely to contribute to systemic inflammation in AS. culture with GM-CSF and IL-4 (mo-DCs) . These express reduced surface MHC II expression compared with cells from healthy individuals, but no alteration in production of IL-23 or other cytokines [15, 16]. On the other hand, studies do suggest that ER stress of DCs could lead to excessive IL-23 production , and as such they are intriguing candidate cells in initiating this effector pathway. In this regard, however, the relevance of data generated using cultured monocytes to DC biology is unclear . We consider it critical now to determine the contributions of bone fide DCs and other myeloid lineages to AS pathogenesis. Our previous analyses revealed a systemic deficiency in a specific DC population in B27-TG rats, which in turn promoted elaboration of Th17 responses . Because this cytokine axis may be associated with AS pathology, we hypothesized that myeloid populations could be similarly altered in AS patients. Accordingly, we performed deep phenotyping of blood and SF leucocyte populations and now show that the frequency of circulating CD1c+ DCs is diminished in AS patients. Conversely, proportions of CD14? CD16+ mononuclear cells are elevated and functionally promote CCR6 induction and IL-6 and IL-1 secretion following T cell interaction. Furthermore, we identify a correlation between systemic inflammation and a gut-homing phenotype among T cells from AS patients. Thus, we provide novel insight into the pathways that can promote chronic inflammation mediated through the Th17 axis. Materials and methods Hydroxypyruvic acid Patients AS patients meeting the modified New York criteria  were recruited from the Glasgow Royal Infirmary rheumatology clinic between March 2011 and June 2013. Informed, written consent was obtained from all study participants according to the Declaration of Helsinki. Ethical approval for the study was awarded by the West of Scotland Research Ethics Service (Institute of Infection, Immunity and Inflammation Research Tissue Bank, REC: 11/S0704/7). Consenting age- and sex-matched healthy controls (HCs) were recruited under ethics approved by the College of Medical, Veterinary, and Life Sciences Ethics Committee, University of Glasgow (Project #2013007). Patient clinical features are outlined in supplementary Table S1, available at Online. Reagents Cells were cultured in RPMI 1640 supplemented Hydroxypyruvic acid with 10% fetal calf serum, 100 U/ml penicillin, IB1 100 g/ml streptomycin, 2 mM l-glutamine and 50 M 2-mercaptoethanol (complete medium). Peripheral blood Hydroxypyruvic acid mononuclear cell isolation Isolation of peripheral blood mononuclear cells was performed over a HistopaqueC1077 gradient. Following centrifugation, the peripheral blood mononuclear cell layer was harvested. Antibodies Directly conjugated or biotin-labelled antibodies targeting CD3 (UCHT-1), CD4 (OKT4), CD14 (M5E2), CD15 (W6D3), CD16 (3G8), CD19 (HIB19), CD25 (BC96), CD45RA (HI100), CD56 (MEM-188), HLA-DR (L243), TcR (IP26) and CXCR3 (GO25H7) were from Biolegend (San Diego, CA, USA). Antibodies targeting CCR9 (248621) and CCR10 (314305) were purchased from R&D systems (Minneapolis, MN, USA). CD1c (AD5-8E7) and anti-SLAN (M-DC8, DD-1) antibodies were from Miltenyi Biotec (Auburn, CA, USA). CD11c (B-ly6), CD141 (1A4), CCR6 (11A9) and CCR4 (1G1) antibodies were purchased from BD Biosciences (Oxford, UK). Flow cytometry Following Fc receptor inhibition (eBioscience, San Diego, CA, USA), staining was performed in PBS with 2% fetal calf serum and 2 Hydroxypyruvic acid mM EDTA. Where biotin-conjugated antibodies were used, a streptavidin step was performed. Samples were acquired using LSR II (BD Biosciences) or MACSQuant (Miltenyi Biotec) flow cytometers, or purified using a FACSAria cell sorter (BD Biosciences). Data were analysed using FlowJo software (version 9.2; Tree Star, Ashland, OR, USA). Naive CD4+.