Which term describes a signal that acts on the same cell that secretes it?

• A. Autocrine
• B. Paracrine
• C. Endocrine
• D. Neurocrine

Answer: (A)

Autocrine signaling describes a messenger released by a cell that acts on receptors on the same cell that released it. This self-targeting mechanism lets the cell regulate its own activity and often amplify its response during activation. For example, a T cell may secrete interleukin-2 and also respond to it via IL-2 receptors on its own surface, promoting its own growth and survival. In contrast, paracrine signals affect nearby cells in the same tissue, endocrine signals travel through the bloodstream to distant targets, and neurocrine signals are released by neurons to affect adjacent neurons or effector cells at synapses. So the term that best fits a signal acting on the same cell is autocrine.