Immune-stimulating complexes (ISCOMs), coloured transmission electron micrograph (TEM). These are complexes of sugar-steroids and an antigen. They are designed to stimulate the immune system in the same way as a vaccine, and the antigen can be chosen to match the antigen on a pathogen, such as a virus. Introducing the ISCOM to the body primes the immune system for a real encounter with the pathogen whose antigen the ISCOM carries. Magnification: x285,000 when printed 10cm wide.