Interleukins.

Interleukins are polypeptides that act on leukocytes and other tissue targets. Interleukin-1, produced by macrophages and other cells, activates lymphocytes and also induces several components of the host's acute-phase response to infection and injury. Interleukin-2, produced by T lymphocytes, is a growth factor for helper, suppressor, and cytotoxic T lymphocytes. By several criteria, interleukins can be considered the hormones that regulate immune and inflammatory responses.