Cellular Mechanisms of Hemolysis by the Protein Limulin, a Sialic-Acid-Specific Lectin From the Plasma of the American Horseshoe Crab, Limulus polyphemus.

the plasma- based cytolytic system is mediated by a single protein, the sialic acid-binding lectin, limulin (1). Limulin is a member of the pen- traxin protein family and is present in the plasma of the horseshoe crab at 30-50 nM (2). In assays using sheep red cells as the model foreign cell, the entire hemolytic activity of plasma is the province of limulin (1). Hemolysis depends on the sialic acid-binding ac- tivity of limulin, because sialylated glycoconjugates, such as fetuin and the sialic acids N-acetyl neuraminic acid and colominic acid, inhibit hemolysis, and desialylation of the target cells renders them immune to cytolysis (1). Limulin was purified from