Overview of the endocrine and immune systems

Abstract

The endocrine and immune systems of fish play essential roles in communication and signaling. While the endocrine system uses hormones as signaling molecules to communicate with different organs and tissues, the immune system uses cytokines and chemokines to communicate between immune cells and coordinate responses to infections. In turn, hormones produced by the endocrine system can modulate immune cell activity, and cytokines can signal the release or inhibition of certain hormones. Therefore, while the endocrine and immune systems have distinct roles, they are interconnected and influence each other to maintain the body's overall balance and response to internal and external challenges. The following overview introduces the reader to the breadth of physiological systems affected by the endocrine and immune systems in fish and highlights their hierarchical organization.