Immunomodulators are bio-active agents, which suppress, weaken or alter the activity of the immune system. This may consequently weaken inflammatory responses. Immunomodulators (immunosuppreessors) are most often used in organ transplantation to prevent rejection of an implant.

Autoimmune diseases are situations, where the immune system attacks one's own cells, tissues and organs, erroneously recognizing them as alien factors.
Immunomodulators may be used to cure autoimmune deseases.