Impaired cellular immunecompetence in infectious mononucleosis as assessed by a local graft-versus-host reaction in rats and restoration of the immunecompetence by trypsin

Lymphocytes from 11 patients with acute infectious mononucleosis were tested for functional capacity by means of a local graft-versus-host reaction (GVHR) and for T lymphocyte markers by the spontaneous rosette-formation test (E rosette). All of the patients showed an increased percentage (49–75%) and high absolute numbers (2078–8736/mm 3 ) of E rosette-forming cells but no functional activity, i.e., a negative GVHR. Repeated examinations performed in four patients at intervals up to 6 months after the initial test showed a significant drop in the number of E rosette-forming cells although the GVHR remained negative. Trypsinization of lymphocytes performed in nine of the 11 patients resulted in recovery of immunecompetence of the T lymphocytes in five; in contrast, trypsinization of normal control lymphocyte abolished their ability to mount a normal GVHR. In view of the number of cases in which infectious mononucleosis has been followed by lymphoproliferative diseases, the importance of long-term follow-up in patients who have undergone an episode of infectious mononucleosis is stressed.