Apoptosis in Infectious Mononucleosis

Abstract

Apoptosis of lymphocytes in infectious mononucleosis (IM) was studied. Apoptotic cells (APCs) were defined by morphological characteristics, such as nuclear fragmentation, undergoing apoptosis. Among 10 of 27 IM patients (37.0%) APCs≥3 per 500 peripheral white blood cells were observed on admission, but not in normal individuals. Sequential changes of proportions of both APCs and atypical lymphocytes (examined in 2 cases) showed a similar pattern, although APCs began to appear somewhat later and peak level of APCs were lower in comparison with those of atypical lymphocytes. APCs were positive for both anti-T cell and anti-Fas antigen monoclonal antibodies. Fas-positive cells were frequent in the early stage of IM, and returned to the normal range with the decrease of atypical lymphocytes. Sequential analyses of DNA fragmentation, done in one case, revealed that DNA fragmentation appeared with increase of APCs and disappeared with the decrease of APCs. These results suggest that apoptosis of T-cells in IM participates in the reconstitution of a proportion of lymphocytes disturbed by EB virus.