We suggest that in CLL patients, and particularly in patients with Ig-C5a/abnormal C5, the decrease in C2 levels and increase in C3 levels affects the levels of C2a and C3b, can interfere with the balance between available C2a and C3b components of the C5 convertase, and therefore can affect its assembly, levels and activity. Here, C3 is linked to B-cell chronic lymphocytic leukemia.