Multicellular organisms use four main means of chemical signaling pathways for communication— autocrine, paracrine, endocrine, and contact-dependent. Autocrine signaling is a form of communication where a cell interacts with itself. In this type of signaling, the cell secretes a chemical messenger called an autocrine agent. These molecules bind to the receptors present on the same cell surface. As a result, one cell acts as the signaling as well as the target cell. For example, during infection, microbial products trigger white blood cells called T lymphocytes to release a class of small proteins known as cytokines. The cytokines are autocrine agents which bind to the receptors present on the surface of T lymphocytes and activate intracellular cascades that can induce a response, such as cellular proliferation.