Serum complement C1q

Serum complement C1q is an important component of complement C1. It has a molecular weight of 390,000 and is composed of six identical subunits. It is a symmetrical hexamer. When more than two C1q are bound to the IgM or Fc segment of IgG in the immune complex The C1q configuration changes, leading to the sequential activation of C1r and C1s, and the classical pathway of complement activation is initiated. One-way immunodiffusion method is commonly used in clinical practice to measure C1q.