anti-GBM antibodies, ten patients showed sustained positivity in serum MPO-ANCA and experienced at least one relapse event during follow up. For each of these ten patients, three serum samples were collected respectively: active phase of initial onset before initiation of immunosuppressive therapy; remission after immunosuppressive therapy; and active phase of relapse. “Remission”was defined as “absence of disease activity attributable to active disease qualified by the need for ongoing stable maintenance immunosuppressive therapy”, as described previous- Detection of MPO-ANCA and Anti-GBM Antibodies ANCA assays were performed by indirect immunofluorescence using ethanol-fixed human neutrophils. Antigen-specific enzyme-linked immunosorbent assay was performed against purified myeloperoxidase . The sensitivity and specificity of the MPO-ANCA ELISA assay were 50% and 97%, respectively. Anti-GBM assays were performed by ELISA using purified bovine aNC1 as solid phase antigen, with confirmation of antibody specificity by ELISA against recombinant human a3NC1. Preparation of Recombinant MPO Fragments Six linear 17358052 fragments of myeloperoxidase, i.e., P, L, H1, H2, H3 and H4 were prepared as deletion mutants of MPO from E.coli. The amino acid sequences of the six fragments were as follows: 49164 for propeptide, 165272 for light chain, 279409 for the N terminal of the heavy chain, 399519 for the second part of the heavy chain; similarly, 510631 for H3 and 622745 for H4. The cDNA of human MPO was a gift from Dr. The amplification was performed in a DNA thermal cycler by programmed incubation for 30 sec at 94uC, for 30 sec at 55uC, and for 30 sec at 72uC and repeated 30 times. were digested with enzymes NdeI and NotI and inserted into the expression vector pET28a. P, H2 and H4 were inserted into Hind III and PshA I sites of plasmid pET-42a. H1 and H3 was inserted into NdeI and XhoI sites of plasmid pET-30a. Confirmation of the Base Sequences of the Fragments After the ligation of plasmid vectors and the target fragments, the newly 
formed plasmids were transformed into competent bacteria DH5a. Positive bacteria were selected by selective culture-medium and the positive plasmid was sequenced by SinoGenoMax Company. The base sequence of the target fragments were confirmed by DNAMAN Construction of MPO Fragments Genes The PCR products of different MPO fragments were digested with enzymes and inserted into the plasmid vectors. L chain Epitopes of MPO-ANCA software. The correctly constructed plasmid were selected and transformed into competent bacteria BL21 7986199 for expression. Determination of the Purity of Recombinant Peptides The recombinant proteins were treated with a sampling buffer for 3 min at 100uC. Then the recombinant proteins were applied to 12% JW-55 biological activity sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The gel was stained with MemGel staining solution. Expression of Recombinant P, L, H1, H2, H3 and H4 Constructs in Vectors E. coli expressing each fragment of MPO was inoculated into 10 ml of Luria-Bertani medium supplemented with kanamycin in a shaker flask. The cells were grown with shaking overnight at 37uC. The bacterial suspension was diluted to 1/100 with fresh medium and further incubated at 37uC with shaking at 250 rpm. When the absorbance at 600 nm became approximately 0.60.8, IPTG was added, and the mixture was incubated for a further 4 hr. The cells were harvested by centrifugation at 8000 rpm for 2 min. Determination of the Reactivity