Ketchum P A, Novitsky T J
Associates of Cape Cod, Falmouth, MA.
Methods Mol Med. 2000;36:3-12. doi: 10.1385/1-59259-216-3:3.
Horseshoe crabs fight off infectious agents with a complex array of proteins present in amebocytes, the major cell type in their hemolymph. These amebocytes contain both large and small granules (1). When exposed to bacteria or other infectious agents the amebocytes release proteins into their surroundings by exocytosis. The small granules of Limulus amebocytes contain antibacterial proteins, including polyphemusins and the big defensins (2). The large granules contain the Limulus anti-lipopolysaccharide factor (LALF) and the clot-forming group of serine protease zymogens. Exocytosis is initiated by the reaction of amebocytes with lipopolysaccharide (LPS) from Gram-negative bacteria or other microbial components. LPS is also called endotoxin because it is found in the outer membrane of the gram-negative bacterial cell wall. A solid clot forms in response to the lipid A portion of LPS, thereby walling off the infection site or preventing the loss of blood when the animal is damaged physically (3).
鲎通过血淋巴细胞（其血淋巴中的主要细胞类型）中存在的一系列复杂蛋白质来抵御感染因子。这些血淋巴细胞含有大颗粒和小颗粒（1）。当暴露于细菌或其他感染因子时，血淋巴细胞通过胞吐作用将蛋白质释放到周围环境中。鲎血淋巴细胞的小颗粒含有抗菌蛋白，包括鲎抗菌肽和大防御素（2）。大颗粒含有鲎抗脂多糖因子（LALF）和形成凝块的丝氨酸蛋白酶原组。胞吐作用由血淋巴细胞与革兰氏阴性菌的脂多糖（LPS）或其他微生物成分的反应引发。LPS也被称为内毒素，因为它存在于革兰氏阴性菌细胞壁的外膜中。针对LPS的脂质A部分会形成固体凝块，从而隔离感染部位或防止动物身体受损时失血（3）。
