The absence of direct antimicrobial activity in extracts of cytotoxic lymphocytes

An important mechanism used by the immune system in resisting infections by intracellular pathogens is the destruction of host cells by cytolytic lymphocytes. Whether these lymphocytes display a more direct antimicrobial action remains unclear. We have attempted to answer this question by testing extracts of cytolytic lymphocytes, prepared by cell fractionation, against three bacterial species - Escherichia coli, Salmonella typhimurium, and Listeria monocytogenes. We also tested these extracts against two viruses - pseudorabies virus and vesicular stomatitis virus. The extracts showed negligible activity against the test organisms under the conditions used.