C1q, together with C1r and C1s, in the ratio of 1:2:2, form the C1 complex which is the first component of the classical complement pathway. C1q is composed of 18 polypeptide chains (six A, six B, six C) (MW 460 kDa). All contain an 81-aa collagen-like region composed of (Gly-Xaa-Yaa) repeating…