INCREASED LEVELS OF SOLUBLE CD8 AND CD4 IN PATIENTS WITH INFECTIOUS-MONONUCLEOSIS

Plasma levels of soluble CD8 (sCD8) and soluble CD4 (sCD4) in 44 patie nts with infectious mononucleosis (IM) were studied. A marked increase in sCD8 (22366 +/- 2702 U/ml; control: 219 +/- 10 U/ml; P < 0.0001) a nd significant increase in sCD4 (19.3 +/- 0.9; control: 8.1 +/- 0.2, P < 0.0001) strongly suggest activation of both CD8(+) and CD4(+) lymph ocytes, which is important in restraining Epstein-Barr virus-infected B lymphocytes. Levels of sCD8 strongly correlated with the percentage and the absolute number of both CD8(+) and CD8(+)-HLA-DR(+) lymphocyte s. In addition, we showed increased release of sCD8 from lymphocytes i n vitro and increased ratio between plasma sCD8 and the number of CD8( +) lymphocytes in blood, indicating that elevation of plasma sCD8 is d ue to expansion of CD8(+) subset as well as increased sCD8 release fro m each CD8(+) cell. Increased sCD4 release from CD4(+) lymphocytes, th e number of which is not increased in the blood during IM, was also se en. Patients with more severe fever had higher levels of sCD8 and sCD4 . During convalescence sCD8 and sCD4 levels showed progressive decreas e; however, even at 60-119 d after onset the levels of sCD8 and sCD4 r emained higher than normal, suggesting prolonged lymphocyte activation . These results suggest that sCD8 and sCD4 are useful in monitoring im mune activation during IM.