BLT-ESTERASE IN INFECTIOUS-MONONUCLEOSIS

Peripheral blood lymphocytes of three patients suffering from infectio us mononucleosis due to Epstein-Barr virus (EBV) infection were analys ed for BLT-esterase expression in peripheral blood lymphocytes by a we ll established cytochemical staining method. During the acute phase of disease with presence of clinical symptoms a very high level of up to 90% BLT-esterase-expressing lymphocytes were detected. The increased percentage of lymphocytes expressing BLT-esterase coincided with the t ime of greatest symptoms and the peak elevation of hepatocellular enzy mes. The still moderately elevated level only gradually decreased to n ormal during the further recovery period of 2 months during which the patients described episodes of weakness. Peripheral blood lymphocyte p henotype analysis revealed a marked CD8 lymphocytosis, a CD4/CD8 ratio of about 0.2, low number of CD19(+) B cells, and a high level of DR() CD3(+) lymphocytes. Reduction of BLT esterase expression during the recovery period coincided with reduction of CD8(+) DR(+) lymphocytes. By a combination of BLT-esterase staining with immunocytochemical phen otype analysis, 95% of CD8(+) lymphocytes were found to be BLT-esteras e-positive. BLT-esterase might be involved in the immunodefence agains t EBV in infectious mononucleosis by inducing apoptosis in EBV-transfo rmed B cells.