Hand-Mirror Lymphocytes in Infectious Mononucleosis

The identification of a morphologically unique lymphocyte in the peripheral blood of patients with infectious mononucleo-sis (IM) led to additional studies. Examination of Wright-stained smears of EDTA anticoagulated blood obtained from 25 patients with IM at presentation revealed significantly increased (p < 0.0001) percentages of hand-mirror lymphocytes (HML) (mean 9.2%) compared with normal controls (mean 2.7%) or controls with nonspecific viral syndromes (mean 2.2%). Follow-up blood samples obtained on 10 of these patients demonstrated a marked increase in the HML count (mean 23.1 %) that coincided with the onset of recovery. E-rosette separation of Ficoll-Hypaque-derived peripheral blood lymphocytes from 5 patients with early recovery IM showed the HML to be present almost exclusively in the T-cell population. representing about 25 % of the T cells. Identical procedures on 5 controls showed less than 5 % HML in the 1-cell sample. Cytochemistries supported a 1-cell derivation for HML. Electron microscopic examination of HML in IM demonstrated that these cells have unique ultrastructural features that may be related to functions of cellular attachment and cytotoxicity. I NFECTIOUS MONONUCLEOSIS (IM) is caused by Epstein-Barr virus (EBV). ’ The lymphoid hyperplasia and atypical lymphocytosis observed in the disorder represent a host reaction o