Interleukin (IL)-1, IL-6, and tumor necrosis factor- protein levels were determined using ELISA kits (R&D Systems, Minneapolis, MN, USA), C5b-9 membrane attack complex (MAC) levels were detected using C5b-9 ELISA kits (MyBioSource, San Diego, CA, USA), and the nerve growth factor (NGF) concentrations were measured by using the ChemiKine NGF ELISA kit (Millipore, Billerica, MA, USA) according to the manufacturers instructions

Interleukin (IL)-1, IL-6, and tumor necrosis factor- protein levels were determined using ELISA kits (R&D Systems, Minneapolis, MN, USA), C5b-9 membrane attack complex (MAC) levels were detected using C5b-9 ELISA kits (MyBioSource, San Diego, CA, USA), and the nerve growth factor (NGF) concentrations were measured by using the ChemiKine NGF ELISA kit (Millipore, Billerica, MA, USA) according to the manufacturers instructions. of postoperative incisional pain, however. Immunohistochemical experiments showed that CD20+ cells accumulate VU 0240551 near the healing fracture but few such cells collect in skin or sciatic nerves. On the other hand, IgM-containing immune complexes were deposited in VU 0240551 skin and sciatic nerve after fracture in wild-type, but not in MT fracture/cast, mice. Additional experiments exhibited that complement system activation and deposition of membrane attack complexes were partially blocked by anti-CD20+ treatment. Collectively, our results suggest that CD20-positive B cells produce antibodies that ultimately support the CRPS-like changes in the murine fracture/cast model. Therapies directed at reducing B-cell activity may be of use in treating patients with CRPS. Keywords: Autoimmunity, B cell, Complex regional pain syndrome, Pain, Fracture 1. Introduction Complex regional pain syndrome (CRPS) is usually a painful, disabling, and often chronic condition. Acute CRPS often improves over the first 12 months, particularly if therapy is initiated early in the course of the condition [1]. However, CRPS present for a period of 1 1 1 year or greater seldom spontaneously resolves [55], and worsens in most patients from years 1 to 8 after onset [65]. More than 80% of patients with chronic CRPS are severely disabled [59]. Current therapies for CRPS include physical, interventional, pharmacological, and alternative approaches [7, 11]. Unfortunately, the effectiveness of most of these therapies is limited, and no therapy reliably cures chronic CRPS. The syndrome encompasses a disparate collection of signs and symptoms involving the sensory, motor, and autonomic nervous systems, bone demineralization, skin growth changes, and vascular dysfunction, all limited to a single extremity in most cases [40]. Our lack of understanding of the pathophysiological mechanisms supporting this enigmatic condition limits our ability to predict susceptibility and prevents the rational design of new therapies. The recent suggestion that CRPS may be supported by immunological mechanisms provides an entirely novel framework in which to study CRPS and consider new approaches to treatment. Identifying an autoimmune VU 0240551 mechanism for CRPS might help to explain the broad nature of the syndromes signs and symptoms as well as troubles in achieving adequate symptom control, remission, or remedy using standard therapies. Exploration of CRPS-related immune system activation began with the serendipitous observation of symptom improvement in CRPS patients treated with intravenous immunoglobulin (IVIG) for unrelated conditions [15]. Eventually, a randomized trial of low-dose IVIG showed intermediate duration control of CRPS symptoms in some patients [14]. An autoimmune mechanism was suggested by experiments demonstrating that immunoglobulin G (IgG) prepared from the sera of CRPS patients bound to cultured autonomic neurons, with little evidence of such interactions when sera from patients with other types of neuropathies were used [30]. Later experiments using a beating cardiomyocyte preparation suggested that most CRPS, but not healthy, patients had autoantibodies binding to and activating the M-2 muscarinic and/or the -2 adrenergic receptor [29]. Additional evidence for autoimmune mechanisms in CRPS includes VU 0240551 genetic data supporting CRPS associations with specific human leukocyte antigens [9, 62, 64], studies showing that IgG from CRPS patients worsens nociceptive sensitization in laboratory animals [61], and case reports of Langerhans antigen presenting cell proliferation in CRPS-affected skin [4]. While many of the aforementioned data involve small patient numbers and heterogeneous patient Ifng populations, these intriguing reports suggest that autoimmune mechanisms may support CRPS. Our group has worked extensively with a rodent model of CRPS involving tibial fracture followed by weeks of cast immobilization [18]. It has been used successfully to study the effects of fracture on neuropeptide signaling, the sympathetic nervous system, mast cell infiltration, epidermal cytokine production, and other CRPS-related phenomena [20, 36, 37, 52].We hypothesized that we would discover evidence of autoimmunity contributing to the nociceptive and neurovascular CRPS-like changes manifest in this model. 2. Materials and methods 2.1. Animals All animal experiment protocols were approved by the Veterans Affairs Palo Alto Health Care System Institutional Animal Care and Use Committee (Palo Alto, CA, USA) and followed the animal subjects guidelines of the International Association for the Study of Pain. Male C57BL/6J mice and MT mice in the same background strain were obtained from The Jackson Laboratory (Sacramento, CA, USA) at 8C12 weeks of age. Experiments were done.