Amebocyte

Amebocyte is an amoeboid cell found in the circulatory fluids of many invertebrates, including echinoderms, mollusks, and some arthropods. The name, from Greek ameba meaning changeable and -cyte meaning cell, reflects its irregular, motile shape and ability to extend pseudopods during movement and phagocytosis.

Amebocytes function as part of the innate immune system, patrolling body fluids, engulfing bacteria and debris by phagocytosis, and contributing to wound repair. In coelomocytes of echinoderms and in molluscan hemolymph, they can change shape, migrate to sites of injury, and release enzymes and antimicrobial substances. Some amebocytes participate in encapsulation and coagulation processes to isolate foreign material.

In certain species, including the horseshoe crab (Limulus polyphemus), amebocytes are central to blood clotting. When endotoxins are detected, amebocytes release factors that cause the blood to gel, a reaction exploited in the Limulus amebocyte lysate (LAL) test to detect bacterial endotoxins in medical products and vaccines.

Amebocytes are a general term for amoeboid circulatory cells in invertebrates and are distinct from vertebrate leukocytes, though they perform related immune functions such as phagocytosis. Their study informs understanding of invertebrate immunity and has practical applications in biotechnology and bioassays.