We all know that our bodies have an immune system that protects us from infections. A special part of this protection is called the complement system, or just complement.

It was first identified in the late 1800’s as something in the blood of sheep that could be used in humans to treat anthrax.

Today, researchers describe it as a highly complex system that circulates in our blood waiting to be activated. When triggered, complement starts a chain reaction (known as a complement cascade) that attacks foreign and damaged cells by eating them, blowing them up, and hauling them away as waste (not a precise description, but the imagery comes close).

That’s very good news because we rely on it every day to stay healthy. Unfortunately, researchers have discovered that the complement system, which is meant to “complete” or “enhance” the immune system, has the potential to do us great harm.

How the Complement System Can Hurt Us

It is thought that the complement system may actually play a detrimental role in many diseases that involve the immune system. These include asthma, lupus, arthritis, heart disease, multiple sclerosis, the rejection of transplanted organs, Alzheimer’s and macular degeneration.

Poor regulation of the complement system seems to be the problem. Scientists have good reason to believe that two of its ingredients named “factor H” and “C3” can get out-of-whack and do us harm.

Summary

The main role of complement is to recognize and facilitate the removal of waste products (like Drusen in the case of macular degeneration), dead cells, and bad things that invade the body and cause disease.

The complement system needs to be tightly regulated to avoid excessive activation.

Strong genetic links have been made between poor regulation of complement activation in the back of the eye and macular degeneration.Scientists around the world are working hard to develop effective drugs and delivery systems to regulate the complement system. Apellis Pharmaceuticals, for example, has just submitted a New Drug Application to the US Food and Drug Administration for intravitreal pegcetacoplan, a targeted C3 therapy for the treatment of macular degeneration. According to their website, recent studies have provided evidence that pegcetacoplan meaningfully slows disease progression and has the potential to preserve vision longer.