Roberts-Thomson P J, Shepherd K, Bradley J, Boey M L
Department of Clinical Immunology, Flinders Medical Centre, Bedford Park, South Australia.
Rheumatol Int. 1990;10(3):95-8. doi: 10.1007/BF02274821.
Low molecular weight IgM (LMW IgM) is the monomeric subunit of the naturally occurring pentameric IgM. It is not seen in health but has been previously observed in systemic lupus erythematosus (SLE) particularly in those patients with active disease and may reflect an adverse prognostic finding. We have therefore studied the presence of LMW IgM in 33 Chinese or Malay SLE patients (Singapore) and 21 Caucasian patients (Adelaide). LMW IgM was measured using filtration chromatography or by a sensitive immunoblotting technique. LMW IgM was observed in all patients in the Adelaide group and in 32 patients in the Singapore group with slightly greater quantities being seen in the Adelaide group. LMW IgM constituted up to 15.3% of the total IgM and was frequently associated with the presence of other low molecular weight IgM oligomers. In both groups LMW IgM correlated significantly with the total IgM levels (P less than 0.01). In a more detailed study in the Singapore group LMW IgM also correlated significantly with the IgM anticardiolipin levels (P = 0.02) but not with IgG anticardiolipin or with IgG or IgM anti-DNA levels or with rheumatoid factor. Patients with more extensive organ involvement had higher levels of LMW IgM but not at a significant level. We conclude that circulating LMW IgM occurs almost universally in SLE, is closely related to the total IgM levels and appears independent of ethnic background. The significance of LMW IgM in this disorder is unclear.
低分子量免疫球蛋白M（LMW IgM）是天然存在的五聚体免疫球蛋白M的单体亚基。在健康状态下未见其存在，但此前在系统性红斑狼疮（SLE）患者中观察到，尤其是在那些患有活动性疾病的患者中，它可能反映了不良的预后发现。因此，我们研究了33名中国或马来裔SLE患者（新加坡）和21名白种人患者（阿德莱德）中LMW IgM的存在情况。使用过滤色谱法或灵敏的免疫印迹技术测量LMW IgM。在阿德莱德组的所有患者以及新加坡组的32名患者中均观察到LMW IgM，阿德莱德组中LMW IgM的含量略高。LMW IgM占总IgM的比例高达15.3%，并且经常与其他低分子量IgM寡聚体的存在相关。在两组中，LMW IgM均与总IgM水平显著相关（P小于0.01）。在对新加坡组进行的更详细研究中，LMW IgM也与IgM抗心磷脂水平显著相关（P = 0.02），但与IgG抗心磷脂、IgG或IgM抗DNA水平以及类风湿因子无关。器官受累更广泛的患者LMW IgM水平较高，但未达到显著水平。我们得出结论，循环中的LMW IgM在SLE中几乎普遍存在，与总IgM水平密切相关，且似乎与种族背景无关。LMW IgM在这种疾病中的意义尚不清楚。
