Persistent lymphocytosis of natural killer cells after splenectomy

NK-cell neoplasms in Japan

Neoplasms putatively originating from precursor and mature natural killer (NK) cells are rare, and their clinical features are unclear. A nationwide survey was performed in Japan to clarify the clinical features of these neoplasms diagnosed between 1994 and 1998, and data for 237 patients who met the criteria for putative NK cell-lineage neoplasms were analyzed. Among them, 11 had myeloid/NK-cell precursor acute leukemia, 15 blastic NK-cell lymphoma, 21 precursor NK-cell acute lymphoblastic leukemia, 22 aggressive NK-cell leukemia/lymphoma, 149 nasal-type NK-cell lymphoma (123 nasal and 26 extranasal) and 19 chronic NK lymphocytosis. The median overall survival time of patients with aggressive NK-cell leukemia/lymphoma was 2 months, which for chronic NK lymphocytosis was more than 8 years, and that for the other types of NK-cell neoplasms was between 6 and 22 months. Nasal NK-cell lymphoma and extranasal NK-cell lymphoma share the same histology. The age of affliction was the same, but the sex was different with males predominantly having nasal NK-cell lymphoma and females extranasal NK-cell lymphoma. Patients with extranasal NK-cell lymphoma had the tendency to exhibit a more advanced state of disease, with significantly higher International Prognostic Index and LDH levels, and significantly lower hemoglobin and platelet levels. The overall survival, however, did not differ significantly. Precursor NK-cell acute lymphoblastic leukemia and blastic NK-cell lymphoma were arbitrarily defined by the presence or absence of 30% or more of blastic cells in the bone marrow or peripheral blood, but there were no significant differences for affected age, gender, involved sites or prognosis. Aggressive NK-cell leukemia/lymphoma and extranasal NK-cell lymphoma were arbitrarily defined by the presence or absence of 30% or more of large granular lymphocytes in the bone marrow or peripheral blood and it is possible that aggressive NK-cell leukemia/lymphoma is a leukemic phase of extranasal NK-cell lymphoma. The incidence of skin involvement, however, was significantly higher for extranasal NK-cell lymphoma, suggesting that the two diseases are different. In nasal NK-cell lymphoma, Epstein-Barr virus in tumor cells was detected in all patients tested, suggesting its causative role.

Treatment strategies for Epstein-Barr virus-associated hemophagocytic lymphohistiocytosis (EBV-HLH)

In Epstein-Barr virus (EBV) infection, the virus immortalizes B lymphocytes and cytotoxic T lymphocytes (CTLs) are directed toward both latent and lytic viral antigens expressed on EBV-infected B-cells. Various EBV-associated diseases occur as a result of this disruption of immune surveillance. In the majority of EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH) cases, the major cell types containing EBV DNA are not B-cells, but clonally proliferating T-cells or NK-cells. Proliferation of these cells produces severe immune reactions in the host, and the clinical features related to massive cytokine production at the onset of disease are unique and distinct from other EBV-associated diseases. In the treatment of EBV-HLH, therapeutic infusion of EBV-specific CTLs appears to be ineffective, and eradication of EBV-containing cells is useful but not sufficient to save lives, because of high incidence of acute mortality due to cytokine-induced multiple organ failure and neutropenia-associated opportunistic infections. The optimal treatment strategy for this disease consists of three steps: (1) control of cytokine storm including coagulopathy and multiple organ failure, (2) control of opportunistic infections, and (3) eradication of clonally proliferating EBV-containing T- or NK- cells by immunochemotherapy and, if necessary, hemopoietic stem cell/bone marrow transplantation (SCT/BMT).

Splenectomy in haemophagocytic lymphohistiocytosis: report of histopathological changes with CD19+ B-cell depletion and therapeutic results

The pathogenesis of haemophagocytic lymphohistiocytosis (HLH) in children without a known familial pattern of inheritance is often difficult to establish. Splenic enlargement, one of the main clinical findings in this disorder, has led to the use of splenectomy for uncontrollable coagulopathy, persistent cytopenia or both. This procedure is also thought to be a useful tool in making a differential diagnosis in cases of the immunochemotherapy-resistant HLH. We report here five cases of splenectomized childhood HLH, in which subsets of mononuclear spleen cells were analysed either by flow cytometry or immunohistochemistry, and the results were compared with those from cases of hereditary spherocytosis (controls). There was a statistically significant depletion of CD19+ B cells in the HLH cases (3.8 +/- 3.2% vs. 52.6 +/- 4.5%, P < 0. 0001) associated with an increase of T cells in three cases and of natural killer cells in another. The histopathological findings included atrophic white pulps, B-cell depletion with fibrosis and haemosiderosis in all five cases. Despite temporary therapeutic benefits, three of the HLH patients had a rapidly deteriorating post-splenectomy course and all three eventually died. These results demonstrate striking depletion of B cells in the enlarged spleens of children with HLH, which may be an intrinsic feature of HLH pathogenesis. Further study is needed to establish the therapeutic value of splenectomy in this disease.