Ionomycin is an ionophore

Ionophore

An ionophore is a lipid-soluble molecule usually synthesized by microorganisms to transport ions across the lipid bilayer of the cell membrane...

 produced by the bacterium Streptomyces conglobatus. It is used in research to raise the intracellular level of calcium

Calcium

Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

 (Ca²⁺) and as a research tool to understand Ca²⁺ transport across biological membranes.
It is also used to stimulate the intracellular production of the cytokines, interferon

Interferon

Interferons are proteins made and released by host cells in response to the presence of pathogens—such as viruses, bacteria, or parasites—or tumor cells. They allow communication between cells to trigger the protective defenses of the immune system that eradicate pathogens or tumors.IFNs belong to...

, perforin

Perforin

Perforin-1 is a protein that in humans is encoded by the PRF1 gene.- Function :Perforin is a cytolytic protein found in the granules of CD8 T-cells and NK cells. Upon degranulation, perforin inserts itself into the target cell's plasma membrane, forming a pore. The lytic membrane-inserting part...

, IL-2, and IL-4 usually in conjunction with PMA

12-O-Tetradecanoylphorbol-13-acetate

12-O-tetradecanoylphorbol-13-acetate , also commonly known as tetradecanoylphorbol acetate, tetradecanoyl phorbol acetate, and phorbol 12-myristate 13-acetate , is diester of phorbol and a potent tumor promoter often employed in biomedical research to activate the signal transduction enzyme protein...

. These cytokines are important in the inflammatory response.

Commercially, Ionomycin can be obtained as a free acid, or as a Ca²⁺ salt.