| Background:Chronic urticaria is a common cutaneous disorder induced by vasoactive mediators such as histamine released from mast cells. Although mast cells can be activated by allergens through cross-linking of cell-surface-bound IgE, this mechanism does not appear to explain most cases of chronic urticaria. Recent work has demonstrated that about one third of patients with CIU have circulating functional histamin-releasing auto-antibodies against the high affinity receptor a -chain (Fc s R I a ). It has now become clear that autoimmunity play a critical role in the pathogenesis of this subset of CIU, which is called autoimmune chronic urticaria.At present, there is no uniform diagnostic criterion of autoimmune chronic urticaria. The detection of anti-Fc R I a auto-antibodies is usually nonspecific and unavailable for clinic. Objective:For the purpose of further exploring the pathogenesis of autoimmune chronic urticaria, this study was carried out in order to:1.obtain a recombinant preparation of the soluble protein of Fc ?R Ia , and develop a convenient and reliable immunoassay to detect the anti-Fc ?R I a auto-antibodies.2. investigate the proportion of autoimmune chronic urticaria and the positive rate of anti-Fc ?R I a auto-antibodies in chronic urticaria patients.3.evaluate the histamine-releasing activity in the sera of patients with chronic urticaria4.study the relationship between the histamine-releasing activity and anti-Fc ?R I a auto-antibodies.5.analyse the clinical features and role of eosinophils activation of patients with autoimmune chronic urticaria. Methods:The cDNA of Fc ?R I a obtained by reverse transcription and amplified, and then linked with pUCm-T vector . The ligation mixtures were transformed into the competent E.coli JM109, and the recombinants were initially screened and identified. The sequences of the interest fragment were analyzed by automated sequencing and compared with the sequences in GenBank. Target DNA fragments were subcloned into expression vector and transformed into the competent E.coli BL(DE3), and induced by IPTG for the recombinant protein expressions. The fusion protein were purified by Ni-NTA adsorption chromatography and characterized by SDS-PAGE.The histamine-releasing activity in the sera of patients with chronic urticaria were evaluated by in vivo skin test with autologous serum and in vitro histamine release assay using human cutaneous mast cells incubated with the sera of patients.Sera from 62 patients with chronic urticaria were screened for the presence of anti- Fc ?R I a auto-antibodies using ELISA and Western blotting. The function of the auto-antibodies was demonstrated by pre-incubating sera from patients with auto-antibodies with rsFc R I a and assay the variety of the percentage histamine release.The clinical features of patients with anti-Fc ?R I a auto-antibodies were evaluated, and the serum total JgE levels and ECP concentration, as well as the number of eosinophils in peripheral blood ,were measured. Results:The clone we got was Fc R I a exactly, and the fusion protein of Fc ?R I a were obtained successfully.Twenty-four patients showed a weal response to autologous serum ( 38.71% ) . Sera from patients with chronic urticaria released a significant quantity of histamine compared with control subjects, the histamine-releasing percentage varied from 3.1 % to 79.5% with a mean of 16.44% and a standard deviation (SD) of 14.26%, and 27 of 62 chronic urticaria sera (43.55% ) elicited histamine release more than 15%. Thepercentage histamine release was also elevated in ASST+ chronic urticaria patients compared to ASST- chronic urticaria patients.Anti-Fc R I a auto-antibodies were found in sera from 22/62 ( 35.5 % ) patients with chronic urticaria. Pre-incubation of their sera with rsFc e R I a inhibited histamine release from mast cells.There was no significant difference between patients with and without anti-Fc ?R I a auto-antibodies in the age distribution or in the dura...
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