3,6,8,9 Interleukin-4 (IL-4) is the principal stimulus for CCL26 expression,10 whereas CCL11 and CCL24 are upregulated by IL-4 and pro-inflammatory cytokines such as interleukin-1β (IL-1β) and tumour

necrosis factor-α (TNF-α).11 CCL26 acts predominately as a CCR3 agonist,3 yet it also acts as an antagonist for CCR1, CCR2 and CCR5.12,13 This has led to the speculation that CCL26 may have a modulatory role in inflammation. CCR2, in particular, is a major pro-inflammatory chemokine receptor expressed by monocytes and macrophages, and CCL26 has been shown to block monocyte responses to monocyte chemotactic protein-1 (MCP-1), a major ligand for CCR2.12 The purpose of this study was to determine if monocytic cells could synthesize and express CCL26, because this could provide an autoregulatory mechanism during inflammation. We examined the ability of human peripheral PCI-32765 mouse blood monocytes, monocyte-derived macrophages (MDMs) and the monocytic cell line U937 to express CCL26 messenger RNA (mRNA) and protein. We showed that monocytic cells express CCL26 in response to IL-4 and that TNF-α, IL-1β and interferon-γ (IFN-γ)

modulate IL-4-mediated CCL26 synthesis and expression. Human recombinant TNF-α, IL-1β, IFN-γ, IL-4 and mouse non-immune immunoglobulin G1 (IgG1) were purchased from R&D Systems, Inc. (Minneapolis, MN). Lymphoprep was from BioLynx Inc. (Brockville, ON, Canada) Advanced RPMI-1640, penicillin–streptomycin–glutamine (PSG), TRIzol reagent, Superscript II and NeutrAvidin were from Invitrogen Life Technologies (Carlsbad, CA). Fetal bovine serum (FBS) was from Hyclone (Logan, UT). Hanks’ balanced CHIR-99021 cell line salt solution (HBSS), 3,3′,5,5′ tetramethyl benzidine liquid substrate (TMB), Tween-20 and Triton X-100 were purchased from Sigma Chemicals (Oakville, Canada). Affinity purified goat anti-(human

eotaxin-3) sera and biotinylated anti-(human eotaxin-3) Ig were purchased from PeproTech (Rocky Hill, NJ). Supersignal West Pico chemiluminescent reagent was from Pierce (Rockford, IL). TaqMAN PCR master mix for use in standard polymerase chain reaction (PCR) was from Qiagen (Mississauga, Canada). TaqMAN universal PCR master mix for use in real-time PCR and the 18S primer/probe kit were from Applied Biosystems (Warrington, IMP dehydrogenase UK). Rabbit anti-[human signal transducer and activation of transcription 6 (STAT6)], rabbit anti-(human phospho-STAT6) and rabbit anti-(human β-actin) Igs were purchased from New England Biolabs Ltd (Pickering, Canada). All other reagents were from VWR International (Edmonton, Canada). Human promonocytic U937 cells were obtained from the American Type Culture Collection (Manassas, VA) and maintained as recommended. Whole blood was obtained from healthy volunteers, as approved by the Ethics Committee at the University of Calgary. Platelet-rich plasma was removed from heparinized whole blood following centrifugation at 250 g for 20 min.