Treatment of severe Epstein-Barr virus-induced polyclonal B-lymphocyte proliferation by anti-B-cell monoclonal antibodies. Two cases after HLA-mismatched bone marrow transplantation.

We treated two children who developed Epstein-Barr virus-induced polyclonal B-cell proliferation after HLA-mismatched bone marrow transplantation for congenital immunodeficiency with two monoclonal anti-B-cell antibodies. Lymphoproliferative syndrome occurred between 50 and 60 days after bone marrow infusion, and was diagnosed by the presence of spontaneously growing B cells containing Epstein-Barr-nuclear antigen in the blood and bone marrow. The mouse monoclonal anti-B-cell antibodies used were a CD21-specific antibody recognizing the CR2 receptor on B cells (BL13, IgG1) and a CD24-specific antibody binding B cells at all steps of differentiation (ALB9 IgG1). Both antibodies were given intravenously (0.2 mg/kg/body weight.d for 10 days). All clinical and biological manifestations resolved within 3 weeks of treatment. Recurrence was not seen at 18- and 15-month follow-ups. T-cell function developed normally; B-cell function remained partially deficient in one patient 21 months after bone marrow transplantation. These results suggest that monoclonal anti-B-cell antibodies could be useful in controlling severe polyclonal lymphoproliferative syndrome in profoundly immunodeficient patients after bone marrow transplantation.