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A 28-month-old girl with acute lymphoblastic leukemia (ALL) showing a t(4;11)(q21;q23) karyotype successfully underwent allogeneic bone marrow transplantation (BMT) at relapse. The chimeric MLL-AF4 message on her bone marrow (BM) specimens, examined by reverse transcriptase-polymerase chain reaction, was detectable at diagnosis, relapse, and just before BMT but became undetectable following BMT. She has since maintained complete remission. This observation suggests that detection of the chimeric message in BM may be useful to predict clinical outcome in patients with t(4;11) ALL.

Epstein-Barr virus (EBV)-associated T/NK-cell lymphoproliferative disease (LPD) has been linked to several different disorders. Its prognosis is generally poor and a treatment strategy has yet to be established. There are reports, however, that hematopoietic stem cell transplantation (HSCT) can cure this disease. To clarify the current situation regarding allogeneic hematopoietic stem cell transplantation (allo-HSCT) for EBV-associated T/NK-LPD, a nationwide survey was performed in Japan. Data for 74 patients were collected. There were 42 cases of chronic active EBV infection (CAEBV), 10 cases of EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH), and 22 cases of EBV-associated lymphoma/leukemia (EBV-lymphoma/leukemia). Of those with CAEBV, 54% had the EBV-infected T-cell type and 59% with EBV-lymphoma/leukemia had the EBV-infected NK-cell type. Most patients with EBV-HLH and EBV-lymphoma/leukemia received allo-HSCT within 1 year after onset compared to only 14% of patients with CAEBV. The event-free survival (EFS) rate following allo-HSCT was 0.561 +/- 0.086 for CAEBV, 0.614 +/- 0.186 for EBV-HLH, and 0.309 +/- 0.107 for EBV-lymphoma/leukemia. The EFS of allo-HSCT with conventional conditioning was 0.488 +/- 0.074 and with reduced-intensity conditioning was 0.563 +/- 0.124. Thus, in a substantial number of cases, EBV-associated T/NK-LPD can be cured by either allogeneic conventional stem cell transplantation or reduced-intensity stem cell transplantation.

Epstein-Barr virus (EBV) occasionally infects T and NK cells and causes EBV-infected T/NK-cell lymphoproliferative disease (LPD), which comprises chronic active EBV infection, EBV-associated hemophagocytic syndrome, mosquito allergy, hydroa vacciniforme, aggressive NK-cell leukemia, and NK/T-cell lymphoma. The diagnosis is proven by the monoclonal proliferation of EBV-infected T or NK cells, which is a time-consuming and complicated method. T-cell monoclonality is helpful for the screening of EBV-infected T-cell LPD in patients with EBV-genome burden and is easily shown with T-cell-receptor rearrangement or the T-cell repertoire, whereas NK-cell monoclonality is difficult to prove due to its lacking such rearranged receptors. We investigated a set of killer immunoglobulin-like receptors (KIRs) and also CD94-NKG2 heterodimers on NK cells, namely the NK-cell repertoire. Skewed repertoires were seen in all patients with EBV-infected NK-cell LPD, but not in any patients with EBV-infected T-cell LPD and were restored only after successful treatment. The normal KIR repertoire is variable for each individual and it seems difficult to detect minimal residual EBV-infected lymphocytes. However, the NK-cell repertoire is feasible for identifying EBV-infected NK-cell LPD and evaluating the treatment effect.

Since the initial report of unusual manifestations possibly associated with chronic active Epstein-Barr virus (EBV) infection (CAEBV), nearly three decades have passed. During this period, reported cases with this entity have dramatically increased in the world. Additionally, recent development of diagnostic procedures, including molecular biological and immunological techniques, have provided us with the ability to define certain diseases, especially malignant disorders. Guidelines, derived mainly from the current literature and recent experiences with CAEBV in Japan, for diagnosing CAEBV are proposed to clarify this enigmatic disease.

In order to elucidate the possibility of lymphoproliferation in cases of chronic active Epstein-Barr virus infection (CAEBV), to clarify the clonality and genotype of proliferating lymphocytes, and to search for the factors that induce lymphoproliferation, we studied 11 cases of CAEBV, using genetical and immunological techniques. Epstein-Barr virus (EBV) DNA in peripheral mononuclear cells was detected in eight cases by Southern blotting. Among those eight cases, monoclonal proliferation of EBV DNA-positive cells was observed in three cases and oligoclonal proliferation in three cases. In the cases of monoclonal proliferation, one case manifested T-cell lymphoproliferation and the rest natural killer (NK) cell lymphoproliferation. The anti-EBV antibody titers in the study did not have any relativity to lymphoproliferation. On the other hand, three of the four cases of NK cell lymphoproliferation and one of the two cases of T-cell lymphoproliferation exhibited hypersensitivity to mosquito bites (HMB) in their clinical histories, while none of the three nonlymphoproliferation cases did. These facts indicate that T-cell and NK cell lymphoproliferative diseases (LPDs) could be more closely associated with EBV infection than we had previously expected. Also, the anti-EBV antibody titers may not be the indicator of EBV-associated LPD, and HMB may be one of the factors that induce EBV-associated LPD.