C3 and multiple sclerosis: We have previously shown that the downstream anaphylatoxin, C5a is elevated in the cerebrospinal fluid (CSF) of preterm infants when compared to term-born controls (6) and numerous studies beyond the neonatal period have also implicated complement C3 dysregulation in CNS pathology including neurodevelopmental disorders (48), multiple sclerosis (49), traumatic brain injury (50) and neurodegeneration (51).