Kawasaki disease (KD) is a systemic vasculitis with cardiac and noncardiac complications. antibodies ability to activate endothelial cells resulting in increased IL-6 secretion adhesion molecule expression and monocytic cell line (U937) adherence to HUVEC. Five of the mice that received KD-AECA developed murine AECA after 3 months. None of the mice that received N-Ig produced AECA. The murine AECA increased monocyte adhesion to EC Dilmapimod studies reported that sera of patients with KD induced activation or damage to EC although there were conflicting data concerning the ability of AECA to affect resting prestimulated cells [25 27 31 32 However as some investigators failed to detect significant difference between the frequency of AECA in patients with KD in comparison to children with other febrile diseases [33] there is still some debate about the actual role of AECA in KD development. In order to assess directly the role of AECA in KD we employed an experimental model of active immunization previously used to evaluate the pathogenic role of several autoantibodies. This method is based on Jerne’s theory that the idiotypic determinant of each autoantibody is complemented by that of another creating an idiotypic network. This is manifested by the production of anti-idiotypic antibodies that further stimulate the generation of antibodies to the anti-idiotypic antibody [34]. We [35] and others [36-38] have demonstrated that upon immunization of na?ve mice with an autoantibody (Ab-1) an anti-autoantibody (Ab-2) is generated and four to eight months later an anti-anti-autoantibody (Ab-3) may be detected with similar characteristics as Ab-1. Furthermore the mice develop clinical and laboratory manifestations typically associated with the human disease from which the inducing autoantibody was obtained [39]. This model proved the pathological role that AECA anti-neutrophil cytoplasm antibodies (ANCA) and antiphospholipid antibodies (APLA) have in Wegener’s granulomatosis (WG) and systemic lupus erythematosus (SLE) respectively [40-42]. The present study provides evidence that AECA derived from a patient with KD can induce the Dilmapimod production of mouse AECA followed by clinical and histological abnormalities similar to those observed in KD. MATERIALS AND METHODS Immunoglobulin purification and preparation Serum was obtained from a 2-year-old patient with KD prior to any treatment that had a high titre of Igs that bound EC. The patient suffered from 5 days of fever Dilmapimod and TSPAN18 fulfilled all the criteria for the diagnosis of KD according to the American Heart Association [43] with no evidence of cardiac or renal involvement. He was treated with intravenous Ig and did not suffer from any cardiac or vascular sequels from his disease. Anti-cardiolipin (aCL) anti-dsDNA anti-ssDNA or ANCA were not detected in his serum. IgG and IgM were purified from the sera on Protein A column (Pharmacia Upsala Sweden) and anti-human IgM (Sigma Chemical Co. St. Louis MO. USA) respectively as described previously [44]. KD-AECA (IgG and IgM) were further purified from the Igs by incubation on confluent monolayers of human umbilical vein endothelial cell (HUVEC). The AECA were then eluted by glycine HCL (0·2 m pH 2·5) neutralized with Tris buffer and concentrated as previously described [45]. F(ab)2 fragments were prepared from the Igs by pepsin digestion (2% w/w Sigma Chemical Co.) as described previously [46]. We used two negative controls: pooled Igs from 10 healthy controls (N-Ig) and F(ab)2 fragments of IgG from a patient with Behcet’s disease (Behcet’s-IgG) that bound significantly less to HUVEC and did not activate HUVEC. F(ab)2 AECA from a patient with Takayasu arteritis (Takayasu-AECA) was used as a positive control [46]. AECA detection F(ab)2 AECA binding to EC was determined by cyto-ELISA utilizing nonfixed EC as previously described [46]. Different sources of EC were used: HUVEC [47]; SV-40 immortalized microvascular bone marrow endothelial cells (TrHBMEC) kindly provided by Dr Dilmapimod S. Rafii Weill Medical College of Cornell University New York NY USA [48]. To obviate the binding of heterophile antibodies the preparation was supplemented with 10%.