BACKGROUND: Antibodies to the acetylcholine receptor (AChR) titin and the ryanodine receptor (RyR) occur in myasthenia gravis (MG). These antibodies are capable of complement activation in vitro. The involvement of the complement system should cause consumption of complement components such as C3 and C4 in vivo. MATERIALS AND METHODS: Complement components C3 and C4 were assayed in sera from 78 AChR antibody-positive MG patients and 52 healthy controls. Forty-eight of the patient sera contained titin antibodies as well, and 20 were also RyR antibody-positive. RESULTS: MG patients with AChR antibody concentrations above the median (11.2 nmol/l) had significantly lower mean C3 and C4 concentrations in serum compared to those with AChR antibody concentrations below the median. Titin antibody-positive MG patients, titin antibody-negative early-onset MG patients, titin antibody-negative late-onset MG patients, and controls had similar C3 and C4 concentrations. Nor did mean C3 and C4 concentrations differ in MG patients with RyR antibodies. Patients with severe MG (grades 4 and 5) had similar C3 and similar C4 levels compared to those with mild MG (grades 1 and 2). CONCLUSION: An increased in vivo complement consumption was detected in MG patients with high AChR antibody concentrations, unrelated to MG severity and non-AChR muscle antibodies.
重症肌无力病人血清中存在补体的消耗
与重症肌无力相关的乙酰胆碱受体抗体和titin抗体在体外可激活补体。补体系统的累及在体内可引起C3和C4等补体成份的消耗。近期Romi等检测了78例乙酰胆碱受体抗体阳性病人和52健康对照者的C3、C4补体成份。其中有48例病人titin抗体阳性，20例raynodin抗体阳性。结果发现AChR抗体滴度超过11.2 nmol/l者血清中C3和C4的浓度明显低于AChR抗体滴度低者。Titin阳性MG病人、titin阴性发病早的MG病人、titin阴性发病晚的MG病人以及正常对照的C3和C4浓度相似。Raynodin抗体阳性者的C3、C4水平也无明显差异。病情严重者与轻者的C3、C4水平相似。作者总结认为AChR抗体滴度高者体内可检测到密功能型的补体成份的消耗，但与病情严重性和非AChR 抗体无关。
J Neuroimmunol. 2005 Jan;158(1-2):191-4.
