Complement-dependent induction of autophagy via cell surface receptors:
The complement system is activated by detection of PAMPs/DAMPs by the system’s germline-encoded soluble pattern recognition receptors, leading to production of complement protein cleavage products that signal to cells via specific receptors (Kohl, 2006). It is well-recognised that this extracellular fluid-phase detection system can therefore trigger responses in cells, such as induction of phagocytosis, chemotaxis, exocytosis, and muscle contraction, to name a few. The complement system can therefore be seen as a danger-sensing system able to induce and direct appropriate responses in host cells, and one such response is autophagy, which can be triggered by the following cell-surface complement receptors.