Inhibition from L-asparaginase of Mixed Lymphocyte Culture Reaction

Abstract

The observation that phytohaemagglutinin (P.H.A.) - blstogenesis of human peripheral blood lymphocytes is inhibited by « E. coli » - L-asparaginase (« Asn-ase ») suggested that this enzyme might cause cellular immunological depression. To obtain more information on the possible immunosuppressive properties of « Asn-ase » the effect of this agent on lymphocyte blastogenesis in mixed-lymphocyte cultures has now been investigated. This system provides a real histo-compatibility test. The study was carried out on blood from 24 subjects. Most were normal volunteers but a few were suffering from plasmocytoma (1), acute leukaemia (1) and chronic lymphatic leukaemia (2). Peripheral-blood lymphocytes were randomly mixed in pairs and cultured. One group of these cultures was taken as control and another group was added to « Asn-ase » to make a concentration of one I.U. per ml of culture medium. These cultures were incubated at 37°C for 7 days. The results were 18.33 ± 7.02 % immunologically activated lymphocytes in the control mixed cultures, as opposed to 1.00 ± 1.29 % in the cultures with « Asn-ase ». These results show that « Asn-ase » is capable of inhibiting the histoincompatibility reaction in a mixed-lymphocyte culture and they strongly support the interpretation that « Asn-ase » has cellular immunosuppressive properties.