What Are Cytokines?

6. Initiating an Immune Response

T-helper cells identify pathogens or foreign substances in the body then release cytokines into the bloodstream. As they travel through, they trigger other cells to mount an immune response and activate T- and B-cells. Activated macrophages surround and break down foreign material, engulf and kill microorganisms, and remove dead cells. This is the start of the cascade induction that results in many cytokine cells being released from multiple cell types; a continuous feedback loop escalates an immune response until the compounds can eliminate the threat.

image_jungle / Getty Images