Inhibition of lymphocyte transformation by a factor from Pseudomonas aeruginosa

Extracts of the bacteria Pseudomonas aeruginosa contain a specific inhibitor of lymphocyte transformation. Considerable purification of this inhibitor was possible by a) smashing the bacteria with glass beads, and b) extracting the soluble components with phosphate buffered saline, c) partial purification with ethanol fractionation, d) ion-exchange column chromatography (DEAE-Sephacel) and e) final purification by elution from Ultrogel. The inhibitor was active at a concentration of approximately 10 ng/ml in inhibiting two-way mixed lymphocyte culture of histoincompatible murine splenic lymphocytes in vitro. The inhibitor was also capable of suppressing the proliferation of the murine leukaemic cell line L1210.