The lectin pathway is initiated differently from the classical and alternative pathway. MASP cleaves C4 and then the reaction follows the steps of the classical pathway. Similar to the alternative pathway, the lectin pathway does not require Abs. 6. C7 binds next. The C5b67 inserts into the phospholipid bilayer.
Nucleated cells are more resistant than red cells.
If the complex is removed, the membrane can be repaired. This explains why complement lysis of tumor cells through MAbs is often not effective. Released mediators induce contraction of smooth muscle, increase vascular permeability. Also C5a induces the increase of CR1 from 5000 to 50,000. This prevents deposition of complexes in the tissues and subsequent tissue destruction.