Nonspecificity of the Limulus Amebocyte Lysate Test: Positive Reactions with Polynucleotides and Proteins

Abstract

A positive limulus amebocyte lysate (LAL) test has been considered specific for the presence of bacterial endotoxins. The present studies indicated that a variety of compounds such as thrombin, thromboplastin, polyriboinosinic-polyribocytidylic acid [poly (I) · poly (C)], polyriboadenylic-polyribouridylic acid [poly (A) · poly (U)] and ribonuclease all resulted in a positive LAL test. In addition, two other pyrogenic compounds, human leukocytic pyrogen and dextrans, reacted negatively in this assay. When bacterial endotoxins are known to be present, the LAL test remains the most sensitive assay for their measurement. However, it is essential to take the nonspecificity of the reaction into account when interpreting positive LAL tests of unknown solutions.