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Nineteen renal allograft recipients developed B-cell lymphoproliferative diseases. Clinically there were two groups: a) young patients (mean age, 23 years) who presented soon (mean, 9 months) after transplantation or antirejection therapy with fever, pharyngitis, and lymphadenopathy resembling infectious mononucleosis, and b) older patients (mean age, 48 years) who presented later (mean, 6 years) after transplantation with localized tumor masses. Histologically, the diseases were classified as polymorphic diffuse B-cell hyperplasia (PDBH) or polymorphic B-cell lymphoma (PBL). Immunologic cell typing revealed either polyclonal or monoclonal B-cell proliferations. Malignant transformation of polyclonal proliferations in two patients was suggested by the finding of clonal cytogenetic abnormalities. Epstein-Barr virus (EBV) specific serology, staining of biopsy specimens for the Epstein-Barr nuclear antigen, and EBV DNA molecular hybridization studies implicated EBV as the cause of both PDBH and PBL. Acyclovir, an antiviral agent that blocks EBV replication in vitro, inhibited oropharyngeal shedding of EBV and caused complete remission in four patients with polyclonal B-cell proliferations. The monoclonal tumors were acyclovir resistant. We suggest that surgical treatment, radiotherapy, or chemotherapy may be more appropriate therapy in selected patients with acyclovir resistant tumors. Therapeutic decisions require not only documentation of the viral etiology of these tumors, but also immunologic and cytogenetic analysis to determine the stage of tumor evolution in individual patients.

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B cell lymphoproliferative disorders (BLPD) developed in eight patients following bone marrow transplantation (BMT) for leukemia (five patients) or immunodeficiency (three patients). Recipients of T depleted marrow from a mismatched donor were at particularly high risk of this complication. Six of 25 (24%) recipients of mismatched T depleted bone marrow developed BLPD. In contrast, none of 47 matched T depleted transplants, one of ten (10%) who received non-depleted marrow from an unrelated donor, and only one of 424 matched non-depleted transplants were associated with BLPD. Epstein-Barr virus (EBV) specific serology and DNA hybridization studies demonstrating five to 50 copies of EBV genome/cell in involved tissues implicate this virus as an associated etiologic agent. Restriction fragment length polymorphism (RFLP) and cytogenetic analysis of involved tissue demonstrated donor origin (five of seven) or host origin (two of seven). Histologic appearance was similar to EBV-induced polymorphic B cell proliferations described following solid organ transplantation, or which occur de novo in primary immunodeficiency. Six of seven patients with adequate tissue available for study were found to have monoclonal proliferations by: in situ immunofluorescence (six of seven), and/or immunoglobulin gene rearrangement, (four of six). Cytogenetic analysis of involved tissues from four patients showed a normal karyotype, whereas two had multiple clonal chromosomal abnormalities. Seven patients died despite aggressive attempts at therapy with combinations of antiviral, immunologic, and chemotherapeutic agents.

NALM-6-M1, one of eight leukemia cell lines cultured from the blood of a 19-year-old boy with non-T, non-B acute lymphoblastic leukemia (ALL) i n relapse, was characterized. This cell line was found t o be more than 90% cytoplasmic lmmunoglobulin positive (clg+) for both mu heavy and lambda light chains, but surface immunoglobulin (slg) and complement receptor (CR) negative. NALM-6-M1 was clg-for alpha, delta, and gamma heavy chains and kappa light chain. About