Significantly, Salmi and colleagues observed MECA-79+ vessels in human arthritic joints; yet, because of the antibody’s failure to significantly inhibit binding of activated mucosal immunoblasts to these vessels, the authors concluded that MECA-79-reactive ligands contributed little to disease-associated leukocyte recruitment [26]. an animal model suitable for investigating the role of PNAd in chronic inflammation, we examined the expression of PNAd as well as GlcNAc6ST-1 and -2 in collagen-induced arthritis in mice. Here we show that PNAd is usually expressed in the vasculature of arthritic synovium in mice immunized with collagen but not in the normal synovium of control animals. This de novo expression of PNAd correlates strongly with induction of transcripts for both GlcNAc6ST-1 and GlcNAc6ST-2, as well as the expression of GlcNAc6ST-2 protein. Conclusion Our results demonstrate that PNAd and the sulfotransferases GlcNAc6ST-1 and 2 are induced in mouse collagen-induced arthritis and suggest that PNAd antagonists or inhibitors of the enzymes may have therapeutic benefit in this widely-used mouse model of RA. Background Chronic inflammatory diseases such as rheumatoid arthritis (RA), asthma, inflammatory bowel disease (IBD), and multiple sclerosis still present a large unmet medical need despite recent therapeutic advances such as inhaled steroids (asthma) or TNF antagonists (RA and IBD). Thus, significant subpopulations of patients, in particular those with severe disease, respond only poorly to these treatments [1,2]. Furthermore, patients treated with TNF antagonists are at risk for severe infections [3]. Therefore, modulation of leukocyte-endothelial adhesion, an obligatory step in the recruitment of inflammatory cells to lesions, has been widely considered as an option and perhaps complementary approach for therapy of chronic inflammation [4,5]. One of the molecules involved in leukocyte trafficking is usually MC-Val-Cit-PAB-vinblastine L-selectin, a member of the selectin family of cell adhesion molecules, which is usually expressed on leukocytes [6]. During the process of lymphocyte homing to lymph nodes, L-selectin mediates rolling of lymphocytes on high endothelial venules (HEV). This is the first step in a cascade of adhesion and signaling events that culminate in the recruitment of both na?ve and central memory lymphocytes into lymph nodes [7]. The major class of ligands recognized by L-selectin consists of a family of sialomucins defined by the adhesion-blocking antibody known as MECA-79. Collectively these ligands are termed peripheral node vascular addressin (PNAd) [8] or sulfoadhesin [9]. One of the shared features of these ligands is usually 6-O-sulfated N-acetylglucosamine, which is essential for antibody as well as L-selectin binding [10-12]. This modification is found on 6-sulfo sLex which is a minimal acknowledgement determinant for L-selectin [13,14]. The 6-O-sulfation of N-acetylglucosamine of PNAd MC-Val-Cit-PAB-vinblastine components occurs in the Golgi compartment and is catalyzed by Golgi-associated N-acetylglucosamine 6-O-sulfotransferases (GlcNAc6STs) [15-17]. Using gene deletion by homologous recombination in mice, we have shown that GlcNAc6ST-2, the high endothelial cell restricted N-acetylglucosamine 6-O-sulfotransferase also known as HEC-GlcNAc6ST, LSST, or GST-3 (gene name em chst4 /em in mouse) is largely responsible for the GlcNAc-6-sulfation of PNAd and contributes substantially to L-selectin ligand activity and MECA-79 reactivity [18,19]. A related enzyme known as GlcNAc6ST-1 or GST-2 [20] (gene name em chst2 /em ) also contributes to sulfoadhesin biosynthesis but to a lesser degree [17,21,22]. While being constitutively expressed in the HEV of lymph nodes and other secondary lymphoid organs, the induction of PNAd has been reported in activated vessels in synovial biopsies MC-Val-Cit-PAB-vinblastine from RA patients [23-26], in a model of Lyme disease arthritis in severe combined immunodeficient (SCID) mice infected with em Borrelia burgdorferi (B. burgdorferi) /em [27], as well Rela as in many other inflammatory lesions [28]. In addition, extralymphoid induction of PNAd in inflammatory lesions was shown to correlate with the de novo expression of GlcNAcST-2 in human RA [25] as well as animal models of autoimmunity [16,29]. These findings suggested, that blockade of PNAd, either directly, or indirectly through inhibition of the responsible sulfotransferase(s), might be efficacious for anti-inflammatory therapy [30]. As any drug discovery effort relies on strong and predictive animal models, we have MC-Val-Cit-PAB-vinblastine analyzed the expression of sulfoadhesin and GlcNAc6ST-1 and -2 in murine collagen-induced arthritis (CIA), a widely used animal model which is usually predictive for therapeutic benefit in human rheumatoid arthritis [31-33]. Our data show that PNAd is usually expressed in this model in arthritic but not in healthy synovial tissue, and that GlcNAc6ST-1 and 2 are induced in MC-Val-Cit-PAB-vinblastine arthritic synovium at the transcript level for both enzymes and at the protein level for at least GlcNAc6ST-2. Results GlcNAc6ST-1 and -2 transcript are upregulated in arthritic but not in normal synovium In order to investigate the potential relevance of GlcNAc6ST-1 and -2 in the CIA model, we compared the expression of transcripts for these enzymes in arthritic and control synovial tissue by quantitative PCR. We also measured transcripts levels for genes.