遗传性补体第2成份(C_2)缺乏是西欧白人最常见的补体缺乏.其近半数患者有自身免疫病,最常见的全身性红斑狼疮、Henoch-Sch?nlein紫癜,或多发性肌炎.C_2、C_4、因子B都位于第6号染色体短臂,C_2与因子B同位于HLA-B同DR位点之间,但各受不同的调节基因控制.血清C_2主要由肝合成,但单核吞噬细胞也在肝外合成C_2.C_2遗传缺乏个体的体外外周血单核 The lack of hereditary complement component 2 (C_2) is the most common lack of complement in whites in Western Europe, and nearly half of them have autoimmune disease, the most common systemic lupus erythematosus, Henoch-Schönlein purpura, or polymyositis. , C_4 and factor B are located on the short arm of chromosome 6. C_2 and factor B are located between the HLA-B and DR sites, but each is regulated by different regulatory genes. Serum C_2 is mainly synthesized by the liver, but mononuclear phagocytosis Cells are also extrahepatic synthesis of C_2.C_2 genetic lack of individual peripheral blood mononuclear cells