Tsuzaka K, Ogasawara T, Tojo T, Mimori T, Satoh M, Homma M
Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan.
J Rheumatol. 1993 May;20(5):822-30.
To estimate the clinical significance of IgG or IgM nonprecipitating anti-Sm antibodies and their immunoglobulin (Ig) class switch.
Ninety-one sera which were positive for anti-nRNP antibodies by double immunodiffusion (DID) were obtained from patients with various rheumatic diseases. Anti-Sm antibody was detected by RNA-immunoprecipitation (RNA-IP). IgG or IgM anti-Sm Ig class was measured by enzyme linked immunosorbent assay using affinity purified D polypeptide from HeLa cells. One hundred sixteen clinical manifestations were compared among these groups of patients.
By RNA-IP and DID, 91 were divided into 43 with nonprecipitating anti-Sm which were not detected by DID but by RNA-IP, 17 no anti-Sm, and 31 precipitating anti-Sm sera. In 43 patients with nonprecipitating anti-Sm, renal involvement was more common than in no anti-Sm patients. Besides, systemic lupus erythematosus (SLE)-type manifestations were less common than in precipitating anti-Sm patients. In these 43 patients, IgM anti-Sm class was common (13/43). Decrease in the ratio of IgM to IgG anti-Sm antibody was observed in proportion to the years of observation in these patients. IgM anti-Sm predominated in these patients with mixed connective tissue disease (MCTD)-type manifestations while IgG anti-Sm did in those with SLE-type features.
Patients with nonprecipitating anti-Sm who have IgM anti-Sm at early stages of disease are more likely to have MCTD-type manifestations and later may shift to SLE-type features. These may reflect the anti-Sm Ig class switches from IgM to IgG.
评估IgG或IgM非沉淀性抗Sm抗体的临床意义及其免疫球蛋白（Ig）类别转换。
从各种风湿性疾病患者中获取91份经双向免疫扩散（DID）检测抗nRNP抗体呈阳性的血清。通过RNA免疫沉淀（RNA-IP）检测抗Sm抗体。使用从HeLa细胞中亲和纯化的D多肽，通过酶联免疫吸附测定法测量IgG或IgM抗Sm Ig类别。比较这些患者组之间的116种临床表现。
通过RNA-IP和DID，91份血清被分为43份非沉淀性抗Sm血清（未通过DID检测到但通过RNA-IP检测到）、17份无抗Sm血清和31份沉淀性抗Sm血清。在43例非沉淀性抗Sm患者中，肾脏受累比无抗Sm患者更常见。此外，系统性红斑狼疮（SLE）型表现比沉淀性抗Sm患者更少见。在这43例患者中，IgM抗Sm类别常见（13/43）。在这些患者中，观察到抗Sm抗体的IgM与IgG比例随观察年限的增加而降低。IgM抗Sm在具有混合性结缔组织病（MCTD）型表现的患者中占主导，而IgG抗Sm在具有SLE型特征的患者中占主导。
疾病早期有IgM抗Sm的非沉淀性抗Sm患者更可能有MCTD型表现，后期可能转变为SLE型特征。这些可能反映了抗Sm Ig类别从IgM转换为IgG。
