A Complement Renaissance
More than 600 million years ago, primitive components of the complement system likely fashioned the first humoral immune system. The modern complement system comprises more than 30 proteins that react in a dizzying array of interconnectedness to identify and quell invading pathogens. Within seconds of activation, millions of fragments may be released into the milieu to trigger a local inflammatory reaction.
Because of its proinflammatory, immune-enhancing, and destructive capabilities, tight regulation is critical. It should come as no surprise, then, that nearly half of complement's components act to mitigate its effects. Host tissues normally express such inhibitors and are...