Malignant granular lymphoproliferation after Epstein‐Barr virus infection: Partial immunologic reconstitution with interleukin‐2

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Abstract
This report describes a patient who developed a malignant proliferation of granular lymphocytes following Epstein‐Barr virus (EBV) infection. For many months, his illness resembled prolonged infectious mononucleosis with persistent fatigue, fever, leukocytosis, and serologic evidence of recent primary EBV infection. After approximately I year, however, he developed progressive granular lymphocytosis and extensive lymphocytic infiltration of the bone marrow and liver. Tests for EBV DNA in pre‐ and postmortem tissue samples using a sensitive DNA hybridization technique were negative. Southern blot analysis of DNA prepared from blood mononuclear cells demonstrated clonal T‐cell antigen receptor gene rearrangement. Despite increased numbers of circulating lymphocytes with the morphology and surface phenotype of normal donor natural killer (NK) cells, the patient's NK activity was consistently depressed in a standard in vitro assay. However, in vitro incubation with interleukin‐2 (IL‐2), but not with α‐ or ‐γ‐interferon, increased the NK activity of the patient's lymphocytes. Intravenous recombinant IL‐2 treatment transiently increased the patient's blood NK activity and was associated with seroconversion to EBV nuclear antigens but failed to affect the progression of his disease. Our findings indicate that clonal granular lymphocytic proliferation may develop after EBV infection and confirm the utility of DNA hybridization analysis in distinguishing monoclonal from benign immunoreactive lymphoproliferation. Furthermore, our results suggest that certain functionally inert neoplastic granular lymphocytes acquire NK activity when exposed to IL‐2.