The Purification Of RA33/36 Antigen And The Diagnostic Value Of Anti-RA33/36 Antibody In Patients With Rheumatoid Arthritis

Objective To explore the value of RA33/36 antibody for diagnosis of rheumatoid arthritis(RA) and to purify the crude RA33/36 antigen.Methods 1. Using the crude RA33/36 antigen as antigenic sources on immunoblotting, we detected a total number of 1012 sera from 498 patients with RA, 574 patients with other rheumatic diseases and 50 healthy controls. 2. We studied the relation among RA33/36 antibody, the other autoantibodies and clinical manifestations of RA.. 3. The RA33/36 antigen were purified from Ehrlich ascites carcinoma cell nuclear extracts by affinity chromatography on heparin-sepharose CL-6B. Protein-rich fractions were analyzed for the presence of RA33/36 by SDS-PAGE and immunoblotting. Crude antigen and purified antigen were compared in the efficiency of detecting.Results 1. The sensitivity and specificity of RA33/36 antibody in RA were 31.60% and 87.31% in large-sample study, while the sensitivity and specificity of RA33/36 antibody in RA were 32.93% and 88.52% in small-sample study. There were no difference among the specificities of RA33 antibody, RA36 antibody and RA(33/36) antibody, but the sensitivity of RA33 antibody was higher than those of RA36 antibody and RA(33/36) antibody. 2. The positive rate of RA33/36 antibody was 32.03% in early RA. 21 patients had RA33/36 antibody in 72 RA patients whose RF were negtive, and 9 patients had RA33/36 antibody in 41 RA patients whose anti-CCP were negtive. The specificity increased to 98.46% when RA33/36 antibody and anti-CCP were used together. 3. The presence of RA33/36 antibody was not correlated with RF, APF, AKA, anti-Sa, anti-CCP, ESR and clinical manifestations. 4. Both SDS-PAGE and immunoblotting showed that RA33/36 antibody presented mainly in the eluating fractions of buffer C. Compared with the crude antigen, the bands of the partial-purified antigen were much significantly decreased and more clear, but the positive rates had no difference between them . RA36 antibody did not always appear with RA33 antibody. Conclusions 1. The detecting efficiency of RA33/36 antibody is improved when the purified antigen is used on immunoblotting. 2. RA33/36 antibody presents reasonable sensitivity with high specificity to RA and it also can be detected in early RA..So RA33/36 antibody is valuable to the diagnosis of RA. 3. RA33/36 antibody is complementary to RF in the diagnosis of RA . Simultanous detection of RA33/36 antibody and anti-CCP can notably improve the specificity.