Sequential changes of the five immunoglobulin classes and other responses in infectious mononucleosis

Serum total IgG, IgA, IgM, IgD, and IgE concentrations, heterophil antibody titer, Epstein-Barr virus (EBV)-specific antibodies titer, and hematologic changes were studied longitudinally in 19 patients with EBV-induced infectious mononucleosis who were followed up for 1.5-34 months. In 9 patients, the changes in these variables were compared with baseline data on a pre-illness serum sample. All 5 immunoglobulins (Ig) showed a significant rise during the acute illness followed by a drop during convalescence, and a gradual 'normalization' within several months to a year. On the average, IgE peaked to 276% during the first week, IgM to 176% at about 10 days, IgA to 154% at 15-20 days, IgG to 135% at 10-15 days, and IgD to 141% during the first 2 months after onset. IgE and IgM levels were significantly suppressed during convalescence by an average of about 40 and 25% of pre-illness level, respectively. A relationship was noted between Ig rise and the increase in circulating atypical lymphocytes. The data clearly demonstrate the polyclonal nature of Ig production during the acute phase of EBV-induced mononucleosis, with a striking and early reactivity of IgE.