Complement system

Looks like

About thirty proteins in the plasma, switching each other on in a chain once one meets a germ.

What it does

Punches holes in bacteria, coats them for swallowing and calls white cells in.

Keeping it well

Deficiencies bring repeated meningitis or gonorrhoea; some drugs that block complement require meningitis vaccines.

Related conditions

• Allergy & anaphylaxis
• HIV infection
• Neonatal sepsis
• Neutropenic sepsis
• Primary immunodeficiency
• Sepsis
• Toxic shock syndrome
• Transplant rejection & graft-versus-host disease