Effective clearance of an infection requires that the immune system rapidly detects and neutralizes invading parasites, while strictly avoiding self-antigens that would result in autoimmunity. The sophisticated cellular machinery and signaling pathways that coordinate an effective immune response have generally been considered to be properties of the eukaryotic immune system. However, growing evidence suggests that many of the sophisticated immune systems in eukaryotes came from bacteria. We aim to discover, understand, and repurpose these immune systems for novel applications in biotechnology and medicine.