Attribution of C1s protective role solely to the generation of downstream opsonins for apoptotic cells clearance is inadequate as deficiency of the downstream opsonic C3 component, produced from the action of C3 convertase (C4bC2a), lacked similar association with SLE.29,51 Hence, we attempt to distill the involvement and mechanism of C1s proteolytic role and contribution to programmed cell death. The gene discussed is C1S; the disease is systemic lupus erythematosus.