Complement Activation. Normal erythrocytes (left) are protected against complement-mediated lysis primarily by CD55 (brown circles) and CD59 (gold circles). Deficiency of these GPI-anchored complement regulatory proteins results in APC activation on PNH erythrocytes (right). Consequently, MACs form pores in the red cell membrane resulting in osmotic lysis and release of hemoglobin and LDH into the intravascular space.