A long-term study of patients with chronic natural killer cell lymphocytosis

Peripheral neuropathy associated with chronic lymphoproliferative disorders of natural killer cells (CLPD-NK): a case report and literature review

BACKGROUND

Chronic lymphoproliferative disorders of natural killer cells (CLPD-NK) is a rare lymphoproliferative disease. Peripheral neuropathy is an unusual symptom of CLPD-NK. We report a case of peripheral neuropathy associated with CLPD-NK and perform a review of literatures.

CASE PRESENTATION

a 62-year-old woman presented with progressive numbness and weakness in both extremities. Electrophysiological examinations indicated a sensorimotor polyneuropathy. Peripheral blood examination revealed that the number of white blood cells (WBC) and lymphocytes were significantly increased. Flow cytometry analysis identified that 84% of the lymphocytes are NK cells that mainly expressed CD56, combined with variable expression of CD16, CD2, CD7, CD94, granzyme B, perforin, and CD158 but negative for CD3. Sural nerve biopsy revealed that a plethora of NK cells infiltrated into nerve fascicles. On treatment with combined cyclophosphamide and corticosteroids, her symptoms rapidly improved. Moreover, the absolute lymphocyte count and its proportion recovered to normal range after 3 months' treatment.

CONCLUSION

To the best of our knowledge, this is the first case report of peripheral neuropathy associated with CLPD-NK from Chinese. This rare lymphoproliferative disease should be considered if peripheral neuropathy combines with increased WBC or lymphocytes. Immunosuppressive drugs are the major treatment and most patients can achieve a good prognosis.

Case Report: Large Granular Lymphocyte Leukemia (LGLL)-A Case Series of Challenging Presentations

Large granular lymphocyte leukemia (LGLL) represents a rare group of diseases with considerable difficulties in their correct diagnostic workup and therapy. The major challenges lie in their distinction from reactive (including autoimmune) lymphoproliferations. Moreover, monoclonal LGL proliferative diseases are in fact a heterogeneous group of disorders, as recognized by the three subtypes in the current WHO classification. It distinguishes two chronic forms (the focus of this case series), namely T-LGLL and chronic lymphoproliferative disorders of Natural Killer cells (CLPD-NK) as well as aggressive NK-cell leukemia. In the clinical routine, the variable presentations and phenotypes of T-LGLL and CLPD-NK are underappreciated. The relevant differential diagnoses range from benign reactive T-cell expansions to other mature T-cell leukemias to highly aggressive γδ-lymphomas. T-LGLL or CLPD-NK patients suffer from a wide variety of symptoms often including, but not limited to, cytopenias or classical autoimmune phenomena. They receive treatments ranging from mere supportive measures (e.g. antibiotics, growth factors, transfusions) over strategies of immunosuppression up to anti-leukemic therapies. The diagnostic pitfalls range from recognition of the subtle T-cell proliferation, repeated establishment of monoclonality, assignment to a descript immunophenotypic pattern, and interpretations of molecular aberrancies. Here, we report a series of selected cases to represent the spectrum of LGLL. The purpose is to raise awareness among the scientifically or practically interested readers of the wide variety of clinical, immunological, and phenotypic features of the various forms of LGLL, e.g. of T-cell type, including its γδ forms or those of NK-lineage. We highlight the characteristics and courses of four unique cases from two academic centers, including those from a prospective nationwide LGLL registry. Each case of this instructive catalogue serves to transport a key message from the areas of (chronic inflammatory) contexts in which LGLL can arise as well as from the fields of differential diagnostics and of various treatment options. Implications for optimization in these areas are discussed.

Pulmonary infiltration as the initial manifestation of chronic lymphoproliferative disorder of natural killer cells: a case report and literature review

BACKGROUND

Chronic lymphoproliferative disorder of natural killer cells (CLPD-NK) is an extremely rare haematological disease. To the best of our knowledge, pulmonary infiltration in CLPD-NK has not been reported before. Our case study aimed to present the clinical characteristics, chest computed tomography (CT) findings, and flow cytometry immunophenotyping (FCI) results of an unusual case of migratory pulmonary infiltration in a patient with CLPD-NK.

CASE PRESENTATION

A 51-year-old female patient was admitted to our hospital on October 8, 2019. Eight months before this visit, she had been diagnosed with pneumonia in a community hospital with 1 month of low-grade fever and had recovered after oral antibiotic administration. During follow-up, the patient presented with persistent peripheral blood (PB) lymphocytosis and ground-glass opacities on lung CT scans without any symptoms and signs or any evidence of infectious, allergic or autoimmunity pulmonary diseases. Abnormal NK cells were identified in the PB, bone marrow and bronchoalveolar lavage fluid (BALF) using FCI in our hospital. Eventually, the patient was diagnosed with pulmonary infiltration of CLPD-NK. The patient had an indolent clinical course without symptoms, hepatosplenomegaly or palpable lymphadenopathy and did not receive any therapy. The patient has remained in a good performance status 13 months after the diagnosis.

CONCLUSIONS

Our study described a unique case of pulmonary infiltration in a patient with CLPD-NK. The present case highlights the importance of FCI of the BALF in patients with lymphocytosis and pulmonary shadows to avoid misdiagnosis.

Cytotoxic Immunity in Peripheral Nerve Injury and Pain

Cytotoxicity and consequent cell death pathways are a critical component of the immune response to infection, disease or injury. While numerous examples of inflammation causing neuronal sensitization and pain have been described, there is a growing appreciation of the role of cytotoxic immunity in response to painful nerve injury. In this review we highlight the functions of cytotoxic immune effector cells, focusing in particular on natural killer (NK) cells, and describe the consequent action of these cells in the injured nerve as well as other chronic pain conditions and peripheral neuropathies. We describe how targeted delivery of cytotoxic factors via the immune synapse operates alongside Wallerian degeneration to allow local axon degeneration in the absence of cell death and is well-placed to support the restoration of homeostasis within the nerve. We also summarize the evidence for the expression of endogenous ligands and receptors on injured nerve targets and infiltrating immune cells that facilitate direct neuro-immune interactions, as well as modulation of the surrounding immune milieu. A number of chronic pain and peripheral neuropathies appear comorbid with a loss of function of cellular cytotoxicity suggesting such mechanisms may actually help to resolve neuropathic pain. Thus while the immune response to peripheral nerve injury is a major driver of maladaptive pain, it is simultaneously capable of directing resolution of injury in part through the pathways of cellular cytotoxicity. Our growing knowledge in tuning immune function away from inflammation toward recovery from nerve injury therefore holds promise for interventions aimed at preventing the transition from acute to chronic pain.

A Stab in the Back: An Unusual Case of Cutaneous Neural Infiltration as a Manifestation of Chronic Lymphoproliferative Disorder of Natural Killer Cells

Chronic lymphoproliferative disorder of natural killer cells (CLPDNK) is a rare heterogenous indolent disorder comprising a persistent peripheral blood cell count of more than ≥2 × 10/L natural killer cells for over 6 months. We report an unusual case of cutaneous neural infiltration as a manifestation of CLPDNK. A 52-year-old woman with a background of CLPDNK was referred to dermatology with a painful rash primarily affecting her back. Skin biopsies revealed a neurotropic atypical lymphoid infiltration. Results of immunohistochemistry studies showed CD8, CD56, granzyme B, perforin positivity, and CD3 negativity in keeping with an atypical neurotropic lymphoid infiltrate consistent with cutaneous involvement by the patient's known CLPDNK. Cutaneous lesions and peripheral neuropathy in patients with CLPDNK have been reported; however, the involvement of cutaneous peripheral nerves as described in our case has not been reported before.

NK-Cell Lymphomas

NK-cell malignancies are rare aggressive diseases associated with poor clinical outcome. There is a significant geographic variation in their incidence. At least a part of the reason for that is the fact that Epstein-Barr virus plays an important role in pathogenesis, and importantly, the plasma viral titer reflects disease burden and response to therapy. Extranodal NK/T-cell lymphoma, nasal type (ENKL), is the most common disease subtype in NK-cell malignancies. Conventional anthracycline-based chemotherapy was historically used for ENKL, only to produce dismal outcome. More recently, concurrent chemoradiation therapy for early-stage disease and non-anthracycline-based L-asparaginase containing chemotherapy have been studied, showing improved clinical response and survival, with long-term survival rates of 60-70% and 50-60%, respectively. Stem cell transplant can provide long-term disease control in recurrent or refractory disease settings, but the role of frontline use of such approach is yet to be determined. Several novel therapeutic approaches have shown promising results, and enrollment to clinical trials is the essential key to improve the treatment outcome in the future.

Dysfunction of immune system in the development of large granular lymphocyte leukemia

OBJECTIVES

Large granular lymphocyte (LGL) leukemia is a rare type of lymphoproliferative disease caused by clonal antigenic stimulation of T cells and natural killer (NK) cells.

METHODS

In this review, we focus on the current knowledge of the immunological dysfunctions associated with LGL leukemia and the associated disorders coexistent with this disease. Novel therapeutic options targeting known molecular mechanisms are also discussed.

RESULTS AND DISCUSSION

The pathogenesis of LGL leukemia involves the accumulation of gene mutations, dysregulated signaling pathways and immunological dysfunction. Mounting evidence indicated that dysregulated survival signaling pathways may be responsible for the immunological dysfunction in LGL leukemia including decreased numbers of neutrophils, dysregulated signal transduction of NK cells, abnormal B-cells, aberrant CD8+ T cells, as well as autoimmune and hematological abnormalities.

CONCLUSION

A better understanding of the immune dysregulation triggered by LGL leukemia will be beneficial to explore the pathogenesis and potential therapeutic targets for this disease.

Phenotypic profile of expanded NK cells in chronic lymphoproliferative disorders: a surrogate marker for NK-cell clonality

Currently, the lack of a universal and specific marker of clonality hampers the diagnosis and classification of chronic expansions of natural killer (NK) cells. Here we investigated the utility of flow cytometric detection of aberrant/altered NK-cell phenotypes as a surrogate marker for clonality, in the diagnostic work-up of chronic lymphoproliferative disorders of NK cells (CLPD-NK). For this purpose, a large panel of markers was evaluated by multiparametric flow cytometry on peripheral blood (PB) CD56^low NK cells from 60 patients, including 23 subjects with predefined clonal (n = 9) and polyclonal (n = 14) CD56^low NK-cell expansions, and 37 with CLPD-NK of undetermined clonality; also, PB samples from 10 healthy adults were included. Clonality was established using the human androgen receptor (HUMARA) assay. Clonal NK cells were found to show decreased expression of CD7, CD11b and CD38, and higher CD2, CD94 and HLADR levels vs. normal NK cells, together with a restricted repertoire of expression of the CD158a, CD158b and CD161 killer-associated receptors. In turn, NK cells from both clonal and polyclonal CLPD-NK showed similar/overlapping phenotypic profiles, except for high and more homogeneous expression of CD94 and HLADR, which was restricted to clonal CLPD-NK. We conclude that the CD94^hi/HLADR⁺ phenotypic profile proved to be a useful surrogate marker for NK-cell clonality.

Clinicopathological and phenotypic features of chronic NK cell lymphocytosis identified among patients with asymptomatic lymphocytosis

INTRODUCTION

Chronic natural killer (NK) cell lymphocytosis is currently a provisional entity. This study demonstrated NK cell lymphocytosis in patients with asymptomatic lymphocytosis and presented the hematological and phenotypic findings.

METHODS

Flow cytometry analysis was performed for investigation of unexplained peripheral lymphocytosis. NK cells were determined by the phenotype of CD3-/CD16+/CD56+. Chronic NK cell lymphocytosis was defined by a NK cell count of ≥ 2 × 10(9)/L, persistent for over 6 months, no evidence of B- or T-cell clonality and no hematologic disorders.

RESULTS

Among 190 patients with peripheral lymphocytosis, 15(7.9%) patients, age 42-72 years, were identified to have NK cell lymphocytosis, with a median NK cell count of 3.1 × 10(9)/L (range 2.1-7.3 × 10(9)/L). Persistent NK cell lymphocytosis was confirmed with a median follow-up of 18 months. CD56(bright) NK cell populations were seen in eight patients and CD56(dim) NK cells in seven patients. CD57 co-expression was seen in both CD56(dim) and CD56(bright) cells. CD7, CD2, or CD8 expression was seen in some of the NK populations. The NK cell lymphocytosis appeared stable and no progression to NK cell leukemia during the follow-up period.

CONCLUSION

This study demonstrated that chronic NK cell lymphocytosis, similar to monoclonal B lymphocytosis or T-cell clones, may account for asymptomatic lymphocytosis. There were no identifiable causes of the NK cell expansion. The variable phenotype may represent the heterogeneity and pathological features of NK lymphocytosis.

Chronic natural killer lymphoproliferative disorders: characteristics of an international cohort of 70 patients

BACKGROUND

The 2008 World Health Organization (WHO) classification distinguishes three entities among the large granular lymphocytic leukemia (LGL leukemia): T-cell LGL leukemia (T-LGL leukemia), aggressive natural killer (NK) cell leukemia, and chronic NK lymphoproliferative disorders (LPD), the later considered as a provisional entity. Only a few and small cohorts of chronic NK LPD have been published.

PATIENTS AND METHODS

We report here clinicobiological features collected retrospectively from 70 cases of chronic NK LPD, and compared with those of T-LGL leukemia.

RESULTS

There were no statistical differences between chronic NK LPD and T-LGL leukemia concerning median age [61 years (range 23-82 years)], organomegaly (26%), associated autoimmune diseases (24%), and associated hematological malignancies (11%). Patients with chronic NK LPD were significantly less symptomatic (49% versus 18%, P < 0.001) and the association with rheumatoid arthritis was more rarely observed (7% versus 17%, P = 0.03). The neutropenia (<0.5 × 10(9)/l) was less severe in chronic NK LPD (33% versus 61%, P < 0.001) without difference in the rate of recurrent infections. STAT3 mutation was detected in 12% of the cohort, which is lower than the frequency observed in T-LGL leukemia. Thirty-seven percent of the patients required specific therapy. Good results were obtained with cyclophosphamide. Overall and complete response rates were, respectively, 69% and 56%. Overall survival was 94% at 5 years.

CONCLUSION

This study suggests very high similarities between chronic NK LPD and T-LGL leukemias. Since chronic NK LPD is still a provisional entity, our findings should be helpful when considering further revisions of the WHO classification.

Functional Significance of CD57 Expression on Human NK Cells and Relevance to Disease

Historically, human NK cells have been identified as CD3(-)CD56(+)CD16(±) lymphocytes. More recently it has been established that CD57 expression defines functionally discrete sub-populations of NK cells. On T cells, CD57 expression has been regarded as a marker of terminal differentiation and (perhaps wrongly) of anergy and senescence. Similarly, CD57 expression seems to identify the final stages of peripheral NK cell maturation; its expression increases with age and is associated with chronic infections, particularly human cytomegalovirus infection. However, CD57(+) NK cells are highly cytotoxic and their presence seems to be beneficial in a number of non-communicable diseases. The purpose of this article is to review our current understanding of CD57 expression as a marker of NK cell function and disease prognosis, as well as to outline areas for further research.

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.

Natural killer cells in human autoimmune disorders

Natural killer (NK) cells are innate lymphocytes that play a critical role in early host defense against viruses. Through their cytolytic capacity and generation of cytokines and chemokines, NK cells modulate the activity of other components of the innate and adaptive immune systems and have been implicated in the initiation or maintenance of autoimmune responses. This review focuses on recent research elucidating a potential immunoregulatory role for NK cells in T-cell and B-cell-mediated autoimmune disorders in humans, with a particular focus on multiple sclerosis, rheumatoid arthritis, and systemic lupus erythematous. A better understanding of the contributions of NK cells to the development of autoimmunity may lead to novel therapeutic targets in these diseases.

Elevated serum granulysin and its clinical relevance in mature NK-cell neoplasms

Mature natural killer (NK)-cell neoplasms include extranodal NK/T cell lymphoma, nasal type (ENKL), aggressive NK-cell leukemia (ANKL) and chronic lymphoproliferative disorders of NK cells (CLPD-NK). Granulysin, a cytolytic granule protein, is expressed in cytotoxic T cells and NK cells, and is found in the sera as well, and functions as a cytotoxic and proinflammatory protein. Cytolytic proteins, such as granzyme B and perforin, have been shown to play crucial pathophysiological roles in NK/T cell neoplasms and have also been utilized for diagnostic purposes. Granulysin in NK-cell proliferative disorders, however, has yet to be fully analyzed. To elucidate the clinical relevance of granulysin in mature NK-cell neoplasms, we measured serum granulysin and analyzed cytolytic molecules immunohistologically. The median concentrations of serum granulysin were 39.0, 2.85, 2.8 and 1.35 ng/ml in ANKL, ENKL, CLPD-NK and healthy subjects, respectively (P < 0.01). Serum granulysin was significantly elevated in patients with ANKL compared with the levels in ENKL (P = 0.006) and CLPD-NK (P = 0.037). Furthermore, serum granulysin was correlated with whole-blood EBV viral load in ENKL and ANKL (P = 0.005) and was significantly reduced after treatment. Different expression patterns of cytolytic granule proteins were observed among the mature NK-cell neoplasms. Granulysin is closely associated with the characteristics of NK-cell neoplasms and serum granulysin may serve as a novel biomarker for these disorders.

Lymphoma classification: the quiet after the storm

The classification of malignant lymphomas remained controversial for over 30 years. The first scheme was proposed by Rappaport in the '60th and was based on incorrect histogenetic concepts. To overcome these limitations, several groups formulated new proposals in '70th. Among these two merited attention: the Lukes and Collins and the Kiel Classifications. They were based on the assumption that each lymphoma category might be related to a precise differentiation step of the lymphoid system, thus excluding any correlation with histiocytes, present on the Rappaport scheme. The Kiel Classification became very popular in Europe, while the one of Luke and Collins did not meet success in the United States (U.S.). In 1978, the National Cancer Institute proposed an international trial to compare the classifications used in Europe and U.S. The result was the genesis of the Working formulation, the tool for lymphoma classification in the U.S. up to the early '90th, but which was conversely rejected in Europe. In order to get over this lack of transatlantic communication, in 1994 the Revised European-American Lymphoma (REAL) Classification was proposed by the International Lymphoma Study Group. Its goal was to list "real" entities, each defined by the presence of homogeneous morphologic, phenotypic, cytogenetic, molecular, and clinical criteria, along with the possible recognition of its normal counterpart. The REAL Classification became the model for the WHO Classification of all haematopoietic tumours published in 2001. The present review aims to analyse future perspectives after the fourth edition of the WHO Classification released in 2008.

A case of endocapillary glomerulonephritis associated with peripheral blood natural killer cell proliferation

A 69-year-old male was admitted to our hospital due to rapidly progressive glomerulonephritis. A peripheral blood smear showed a marked increase in large granular lymphocytes. Flow cytometry analysis of the blood showed a marked increase in CD3-negative and CD56-positive natural killer (NK) cells. A renal biopsy showed a characteristic pathological pattern that involved endocapillary proliferation, a predominance of mononuclear cells and mesangiolysis. Prednisolone was administered, and the patient’s renal function subsequently improved concomitant with the amelioration of NK cell proliferation. In our case, there was evidence of a strong association between NK cell proliferation and glomerulonephritis.

The root of many evils: indolent large granular lymphocyte leukaemia and associated disorders

Large granular lymphocytes (LGL) leukaemia can arise from either natural killer (NK) cells or cytotoxic T lymphocytes (CTL). The T-cell form of LGL leukaemia has significant overlap with other haematological disorders and autoimmune diseases. Here we provide an overview of LGL biology. We also focus discussion on the indolent LGL leukaemia related disorders and their causal relationships. We then discuss the potential relationships and distinctions between indolent LGL leukaemia and non-malignant clonal lymphocyte expansion that occur in otherwise healthy individuals, especially elder people.

The leukemias of mature lymphocytes

The leukemias of mature B cells and T cells are a limited set of diseases in which blood and bone marrow are the primary sites of involvement. Although they may superficially resemble one another, they have distinct clinical and pathologic features and must be distinguished from one another. In this article, the major clinical, morphologic, phenotypic, and molecular genetic features of the mature B- and T-cell leukemias are reviewed, and differential diagnostic considerations are discussed.

Clinical and virological characterization of persistent human infection with simian foamy viruses

Persons occupationally exposed to nonhuman primates (NHPs) can be persistently infected with simian foamy virus (SFV). The clinical significance and person-to-person transmissibility of zoonotic SFV infection is unclear. Seven SFV-infected men responded to annual structured interviews and provided whole blood, oral, and urogenital specimens for study. Wives were tested for SFV infection. Proviral DNA was consistently detected by PCR in PBMCs of infected men and inconsistently in oral or urogenital samples. SFV was infrequently cultured from their PBMCs and throat swabs. Despite this and a long period of intimate exposure (median 20 years), wives were SFV negative. Most participants reported nonspecific symptoms and diseases common to aging. However, one of two persons with mild thrombocytopenia had clinically asymptomatic nonprogressive, monoclonal natural killer cell lymphocytosis of unclear relationship to SFV. All participants worked with NHPs before 1988 using mucocutaneous protection inconsistently; 57% described percutaneous injuries involving the infecting NHP species. SFV likely transmits to humans through both percutaneous and mucocutaneous exposures to NHP body fluids. Limited follow-up has not identified SFV-associated illness and secondary transmission among humans.

The human androgen receptor X-chromosome inactivation assay for clonality diagnostics of natural killer cell proliferations

Clonality is a frequently exploited characteristic of lymphoid malignancies. However, in the natural killer (NK) cell subset of large granular lymphocyte proliferations, clonality is difficult to prove because of the lack of specific genetic markers, such as immunoglobulin or T-cell receptor gene rearrangements. The human androgen receptor (HUMARA) assay, a polymerase chain reaction-based X-chromosome inactivation assay, is a potential diagnostic tool in these disorders. Although there is much experience with X-chromosome inactivation assays in myeloid proliferations, these assays have found only very limited application in clonality assessment of NK cell proliferations. We applied the HUMARA assay in laboratory diagnostics for detection of clonality in NK cell proliferations. We describe its test performance and report three cases in which clonality of NK cell populations was investigated by use of this assay. Our results demonstrate the usefulness of the HUMARA assay in the diagnostic workup of NK cell proliferations.

Chemokine system and tissue infiltration in aggressive NK-cell leukemia

NK cell-type lymphoproliferative disease of granular lymphocytes can be subdivided into aggressive NK-cell leukemia (ANKL) and chronic NK-cell lymphocytosis (CNKL). Hepatosplenomegaly is observed in ANKL patients, and hepatic failure is a common cause of death. Significant numbers of ANKL cells were pathologically observed in sinusoidal and interlobular regions of the liver, and in the splenic red pulp. In our previous study, ANKL cells were simultaneously positive for CXCR1 and CCR5. So, in order to elucidate the mechanism in the systemic migration of ANKL cells, we investigated the expression of the corresponding chemokines in ANKL compared with CNKL. The serum level of IL-8, MIP-1alpha and MIP-1beta was significantly elevated in ANKL patients, and ANKL cells were highly positive for IL-8, RANTES, MIP-1alpha and MIP-1beta according to intracellular staining and RT-PCR. These chemokines were also positively stained in hepatocytes. The interaction between Fas and Fas ligand (FasL) is supposed to be one of the mechanisms for liver dysfunction in ANKL. The serum concentration of soluble FasL was significantly high in ANKL patients, and ANKL cells expressed FasL protein in the cytoplasm. These results suggest that the chemokine system plays an important role in the transmigration of FasL-expressing ANKL cells.

Chronic lymphocytosis of functionally immature natural killer cells

BACKGROUND

The development of natural killer (NK) cells in the bone marrow is not well characterized. We recently described a mouse (referred to as an NK cell-deficient [NKD] mouse) with a selective deficiency in NK cells caused by the insertion of a transgene construct into the genetic locus for the basic leucine zipper transcription factor ATF-2. NK cells in this mouse were both phenotypically and functionally immature and accumulated in the bone marrow at a stage at which constitutive NK cell proliferation occurs in wild-type mice.

OBJECTIVE

We hypothesized that excess IL-15 could potentially overcome this developmental block, allowing normal emigration of mature NK cells from the bone marrow to the periphery.

METHODS

Double-transgenic mice were generated by crossing the NKD mice with transgenic mice overexpressing IL-15.

RESULTS

The double-transgenic mice had a dramatic accumulation of phenotypically immature NK cells in the bone marrow and subsequently in the blood, liver, and spleen. NK cells from these double-transgenic mice manifested functional deficits similar to those observed in NK cells from NKD mice, as assessed by decreased cytokine production and cytotoxicity.

CONCLUSION

Rather than bypass the observed developmental defect in NKD mice, excess IL-15 drove a massive accumulation of phenotypically and functionally immature NK cells in the bone marrow and periphery.

CLINICAL IMPLICATIONS

We propose that these double-transgenic mice will serve as a murine model of chronic NK cell lymphocytosis in human patients.

T-cell large granular leukemia and related proliferations

Session 9 of the 2005 Society for Hematopathology/European Association for Haematopathology Workshop focused on large granular lymphocyte (LGL) leukemias and related disorders. T-cell LGL (T-LGL) leukemias, discussed herein, account for 2% to 3% of cases of small lymphocytic leukemia. T-LGL diseases cover a heterogeneous spectrum of disorders that include reactive conditions, typically associated with autoimmune disease, to outright leukemia. These disorders are found in older people, with an average age at initial examination of approximately 60 years and a median survival of more than 10 years in T-LGL leukemia. Systemic symptoms and neutropenia are common at initial examination. Lymphocytosis, composed of small mature lymphocytes with increased cytoplasm, is common. The spleen and bone marrow are involved in T-LGL leukemia, although morphologic findings may be subtle. The immunophenotype is typically that of CD3+/CD8+ cytotoxic T cells. Some cases may be due to chronic immune stimulation, with subsequent clonal escape and proliferation of a neoplastic population of lymphocytes.

KIR and disease: a model system or system of models?

The discovery of an unexpected level of diversity among the killer cell immunoglobulin-like receptors has led to a search for their role in human disease. Due to their polymorphism and also that of their human leukocyte antigen class I ligands, these studies are difficult to perform and complex to interpret. Nevertheless, as the number of data sets increase, consistent trends and themes are beginning to emerge in both viral and inflammatory disorders. In this review, we summarize the findings from a number of disease association studies and discuss these in the context of the activating and inhibitory roles of the members of this gene family.

Successful treatment of primary Sjögren's syndrome with chronic natural killer lymphocytosis by high-dose prednisolone and indomethacin farnesil

We report a patient with Sjögren's syndrome and chronic natural killer lymphocytosis, who developed severe neutropenia, autoimmune hemolytic anemia, and immune thrombocytopenia. High-dose prednisolone therapy improved the hemolytic anemia and thrombocytopenia, but not the CD16(+) CD56(-) NK lymphocytosis completely. Interestingly, indomethacin farnesil (a prodrug of indomethacin) was effective for myalgia and also decreased the number of CD16(+) CD56(-) NK cells. NK lymphocytosis is rarely associated with autoimmune disease, but the combination of indomethacin and steroid therapy may have a favorable effect for such patients.

Large natural killer cell lymphoma arising from an indolent natural killer cell large granular lymphocyte proliferation

Natural killer cell large granular lymphocyte proliferation is a relatively rare disorder that typically runs a chronic, indolent course. We present a patient with a 3 1/2-year history of natural killer cell large granular lymphocyte proliferation terminating in large cell lymphoma with natural killer cell features. The diagnosis of natural killer cell large granular lymphocyte proliferation was based on flow cytometric demonstration of an expanded population of CD3- CD16+/CD56+ lymphocytes in the peripheral blood. The patient experienced various rheumatologic symptoms, but was hematologically stable for 3 1/2 years. He then developed fevers, night sweats, weight loss, and a left lower lobe lung mass. Resection of the mass showed a large cell lymphoma with immunohistochemical positivity for CD2, CD7, CD56, and T-cell intracellular antigen-1, compatible with natural killer cell origin. In situ hybridization for Epstein-Barr virus and polymerase chain reaction analysis for T-cell receptor gene rearrangement were negative. To our knowledge, this is the second documented report of chronic natural killer cell large granular lymphocyte proliferation terminating in an aggressive large natural killer cell lymphoma.

[Leptin: a link between obesity and osteoarthritis?]

In addition to aging, obesity is one of the most common underlying causes of osteoarthritis (OA). Mechanical loading, together with biochemical and systemic factors linked to altered lipid metabolism, are thought to contribute to the onset of OA. It has been suggested that OA is a systemic metabolic disease associated with lipid disorders affecting joint homeostasis. These gradual changes may be due to the local effect of adipokines, and especially leptin. Indeed, their relative levels in joints differ from that found in plasma. In particular, leptin levels are increased and adiponectin and resistin levels are reduced This hypothesis is supported by--leptin overexpression in OA cartilage and its correlation with the degree of cartilage destruction,--abundant leptin synthesis by osteophytes, and--the high leptin levels found in OA joints from female patients. This link between OA and adipokines provides new leads regarding the prevention of OA and the identification of new drug targets.

Large Granular Lymphocyte Leukemia

Clonal disorders of large granular lymphocytes (LGLs) represent a spectrum of biologically distinct lymphoproliferative diseases originating either from mature T cells (CD3+) or natural killer (NK) cells (CD3-). Both subtypes, T-cell and NK-cell LGL leukemia, can manifest as indolent or aggressive disorders. The majority of patients with T-cell LGL leukemia have a clinically indolent course with a median survival time >10 years. Immunosuppressive therapy with low-dose methotrexate, cyclophosphamide, or cyclosporine A can control symptoms and cytopenias in more than 50% of patients, but this approach is not curative. Several cases of an aggressive variant (CD3+ CD56+) of T-cell LGL leukemia with a poor prognosis have also been reported. Aggressive NK-cell LGL leukemia is usually a rapidly progressive disorder associated with Epstein-Barr virus (EBV), with a higher prevalence in Asia and South America. This disease is usually refractory to conventional chemotherapy, with a median survival time of 2 months. Chronic NK-cell leukemia/lymphocytosis is a rare EBV-negative disorder with an indolent clinical course. The malignant origin of this subtype is uncertain because clonality is difficult to determine in LGLs of NK-cell origin.

An aggressive extranodal NK-cell lymphoma arising from indolent NK-cell lymphoproliferative disorder

Indolent NK-cell lymphoproliferative disorder, also known as chronic natural killer (NK) cell large granular lymphocytosis (leukemia), is a very rare entity in the World Health Organization (WHO) Classification of Tumors of Hematopoietic & Lymphoid Tissues. Unlike aggressive NK-cell leukemia, which is malignant, the WHO does not specify whether indolent NK-cell lymphoproliferative disorder is reactive or neoplastic. Patients with indolent NK-cell lymphoproliferative disorder are usually asymptomatic older adults who have a nonprogressive, very stable clinical course. We report an unusual case of an aggressive extranodal NK-cell lymphoma, non-nasal type, which presented as a subcutaneous tissue mass, which apparently transformed from a preexisting, untreated indolent NK-cell lymphoproliferative disorder in an 65-year-old otherwise healthy white man. The extranodal NK-cell lymphoma and the NK-cell lymphoproliferative disorder in the blood and bone marrow share a distinctive and identical NK-cell immunophenotype and genotype: CD56/CD8/TIA-1-positive and surface CD3-negative, negative for Epstein-Barr virus infection, and no evidence of T-cell and B-cell receptor gene rearrangements. To the best of our knowledge, such aggressive lymphomatous transformation in an indolent NK-cell lymphoproliferative disorder has not been previously reported.

Prolonged treatment response in aggressive natural killer cell leukemia

We describe a case of natural killer (NK) cell leukemia with acute presentation, systemic symptoms and hepatosplenomegaly. The uniform and aberrant phenotype of NK cells with infiltration of bone marrow and spleen was in keeping with a malignant diagnosis. Aggressive presentation was demonstrated by marked constitutional symptoms and significant tumor burden (liver, spleen, blood, bone marrow). The subsequent clinical course has been indolent, but this may have been influenced by treatment. Treatment consisted sequentially of splenectomy, intravenous pentostatin and the combination of cyclosporine A and recombinant human erythropoietin and has resulted in survival of over 48 months. We discuss the difficulties in the diagnosis of this condition, explore possible causes of cytopenia(s), and highlight the role of immunosuppression in controlling disease manifestations in large granular lymphocyte proliferative disorders.

The involvement of NK cells in ankylosing spondylitis

A role for NK cells in the regulation of autoimmunity has been demonstrated. Since there is a strong association between Ankylosing Spondylitis (AS) and HLA-B27, which is specifically recognized by the NK-inhibitory receptor KIR3DL1, this study evaluated the potential involvement of NK cells in AS. We studied 19 AS patients and 22 healthy volunteer donors and assessed the percentage, activity and receptor expression of peripheral blood NK cells. We also evaluated candidate-inflammatory mediators in sera. We found that AS patients have significantly higher percentages of NK cells. However, we found no differences between the ability of NK cells derived from AS and healthy controls to recognize target cells expressing HLA-B27. Remarkably, we observed that the NK-inhibitory receptor CEACAM1 (carcino-embryonic antigen-cell adhesion molecule) is highly expressed among AS-derived NK cells. Furthermore, engagement of CEACAM1 inhibited NK activity in these patients. Finally, we demonstrated that CEACAM1 expression is induced by IL-8 and SDF-1 (stromal cell derived factor), both of which are present in high levels in the sera of AS patients. These results may indicate that NK cells and CEACAM1 play a role in AS pathogenesis and implicate chemokines in the mechanism of CEACAM1 expression.

Methylation status analysis of cell cycle regulatory genes (p16INK4A, p15INK4B, p21Waf1/Cip1, p27Kip1 and p73) in natural killer cell disorders

Natural killer (NK) cell disorders are rare diseases. Genetic abnormalities of the several tumor suppressor genes, including p15INK4B, p16INK4A/p14ARF, p53, p73, and Rb genes have been reported. Deletions and point mutations of these genes are frequently detected in these diseases. It has been reported that tumor suppressor genes are inactivated by DNA methylation of the promoter region and/or first exon of the genes in a variety of human cancers. In this study we analyze the methylation status of the genes associated with cell cycle regulation, including p16INK4A, p15INK4B, p21/Waf1/Cip1, p27/Kip1, p73, and p14ARF, by methylation specific (MS) PCR and/or bisulfite sequencing. We examined 29 cases of NK cell disorders (five aggressive NK cell leukemia/lymphoma, three blastic NK cell lymphoma/leukemia, five nasal NK cell lymphoma, three myeloid/NK cell precursor acute leukemia, 13 chronic NK lymphocytosis). We found methylation of the first exon of the p16INK4A gene in two cases (one aggressive, one blastic), and methylation of the p14ARF gene in one aggressive NK cell leukemia. Bisulfite sequencing revealed that methylation of the p15 and p27 genes was rare in these disorders. MS-PCR suggested that the p73 and p21 genes were methylated in seven cases, respectively (p73: one blastic, one nasal, five chronic; p21: one myeloid/NK, one aggressive, one nasal, and four chronic); bisulfite sequencing confirmed that methylated alleles of these genes were dominant in the samples except three cases (one myeloid/NK, one aggressive, and one chronic) in which methylated alleles of the p21 genes were less than 34% of all alleles. These results suggested that inactivation of the cell cycle regulatory genes by DNA methylation could be associated with tumorigenesis in NK cell disorders, not only aggressive subtypes but also chronic subtype.

CD16+CD57– Natural Killer Cells in Multifocal Motor Neuropathy

We analyzed the CD16+CD57- lymphocyte subset, which is considered to have strong natural killer (NK) cell activity, in peripheral blood from patients with chronic immune-mediated neuropathies and patients with other neurological diseases. We found that the ratio of CD16+CD57- NK cells to total lymphocytes was increased in 4 of 6 patients with multifocal motor neuropathy (MMN) with persistent conduction block. Since the CD16 molecule is an Fc receptor for immunoglobulin G (IgG), high-dose intravenous immunoglobulin (IVIg) may interfere with CD16+CD57- NK cells via Fc receptor blockade. In addition, cyclophosphamide (Cy) is often used to suppress NK cells. Therefore, our findings may partly account for the effectiveness of IVIg or Cy, which is the current treatment of choice for MMN.

Significance of chemokine receptor expression in aggressive NK cell leukemia

Natural killer (NK) cell-type lymphoproliferative diseases of granular lymphocytes can be subdivided into aggressive NK cell leukemia (ANKL) and chronic NK cell lymphocytosis (CNKL). One reason for the poor outcome in ANKL is leukemic infiltration into multiple organs. The mechanisms of cell trafficking associated with the chemokine system have been investigated in NK cells. To clarify the mechanism of systemic migration of leukemic NK cells, we enrolled nine ANKL and six CNKL cases, and analyzed the expression profiles and functions of chemokine receptors by flowcytometry and chemotaxis assay. CXCR1 was detected on NK cells in all groups, and CCR5 was positive in all ANKL cells. Proliferating NK cells were simultaneously positive for CXCR1 and CCR5 in all ANKL patients examined, and NK cells with this phenotype did not expand in CNKL patients or healthy donors. ANKL cells showed enhanced chemotaxis toward the ligands of these receptors. These results indicated that the chemokine system might play an important role in the pathophysiology of ANKL and that chemokine receptor profiling might be a novel tool for discriminating ANKL cells from benign NK cells.

Peripheral neuropathy associated with chronic natural killer cell lymphocytosis

We report a patient with steroid-responsive peripheral neuropathy which developed with chronic natural killer cell lymphocytosis (CNKL). A 70-year-old female with a 2-week history of progressive motor and sensory neuropathy showed a marked increase of natural killer (NK) cells in the blood, and was diagnosed as having CNKL. Nerve conduction studies (NCS) revealed a mixed axonal and demyelinating neuropathy. A sural nerve biopsy revealed infiltration of NK cells into the nerve fascicles, and demyelinating changes with axonal degeneration. The infiltrating NK cells were adjacent to myelinated fibers, showing damage of Schwann cell membrane. Treatment with oral prednisolone resulted in rapid improvement of the sensory disturbance and weakness with a significant decrease of NK cells in the blood and disappearance of the conduction blocks in NCS. This is the first case of CNKL associated neuropathy in which infiltration of NK cells was demonstrated in the nerve fascicles. Our observations suggest that the infiltrating NK cells may directly damage myelin and Schwann cells, thus causing demyelination.

Natural killer cell neoplasms

Lymphoid neoplasms that are derived from natural killer (NK) cells are uncommon but distinct clinicopathologic disease entities. Three types have been recognized and categorized in the latest World Health Organization classification: extranodal NK cell lymphoma, nasal-type; aggressive NK cell leukemia; and blastic NK cell lymphoma. All NK tumor cells express the NK cell marker CD56, but they lack the expression of surface CD3 and the rearrangement of T-cell receptor genes, which distinguish them from T-lymphoid neoplasms. There is also a strong association with the Epstein-Barr virus, except in blastic NK cell lymphoma. Extranodal involvement by the NK cell tumor is common, especially in the nasal cavity, the skin, and the gastrointestinal tract. All 3 NK cell neoplasms are characterized by aggressive clinical course and poor response to treatment. Although the optimal treatment modality remains to be determined, good initial response to combined radiation therapy and chemotherapy has been observed in localized disease. Further studies in the basic biology of the NK cell and the pathology of NK cell neoplasms may shed light on the development of newer and more effective therapy.

Clinicobiological, immunophenotypic, and molecular characteristics of monoclonal CD56-/+dim chronic natural killer cell large granular lymphocytosis

Indolent natural killer (NK) cell lymphoproliferative disorders include a heterogeneous group of patients in whom persistent expansions of mature, typically CD56(+), NK cells in the absence of any clonal marker are present in the peripheral blood. In the present study we report on the clinical, hematological, immunophenotypic, serological, and molecular features of a series of 26 patients with chronic large granular NK cell lymphocytosis, whose NK cells were either CD56(-) or expressed very low levels of CD56 (CD56(-/+dim) NK cells), in the context of an aberrant activation-related mature phenotype and proved to be monoclonal using the human androgen receptor gene polymerase chain reaction-based assay. As normal CD56(+) NK cells, CD56(-/+dim) NK cells were granzyme B(+), CD3(-), TCRalphabeta/gammadelta(-), CD5(-), CD28(-), CD11a(+bright), CD45RA(+bright), CD122(+), and CD25(-) and they showed variable and heterogeneous expression of both CD8 and CD57. Nevertheless, they displayed several unusual immunophenotypic features. Accordingly, besides being CD56(-/+dim), they were CD11b(-/+dim) (heterogeneous), CD7(-/+dim) (heterogeneous), CD2(+) (homogeneous), CD11c(+bright) (homogeneous), and CD38(-/+dim) (heterogeneous). Moreover, CD56(-/+dim) NK cells heterogeneously expressed HLA-DR. In that concerning the expression of killer receptors, CD56(-/+dim) NK cells showed bright and homogeneous CD94 expression, and dim and heterogeneous reactivity for CD161, whereas CD158a and NKB1 expression was variable. From the functional point of view, CD56(-/+dim) showed a typical Th1 pattern of cytokine production (interferon-gamma(+), tumor necrosis factor-alpha(+)). From the clinical point of view, these patients usually had an indolent clinical course, progression into a massive lymphocytosis with lung infiltration leading to death being observed in only one case. Despite this, they frequently had associated cytopenias as well as neoplastic diseases and/or viral infections. In summary, we describe a unique and homogeneous group of monoclonal chronic large granular NK cell lymphocytosis with an aberrant activation-related CD56(-/+dim)/CD11b(-/+dim) phenotype and an indolent clinical course, whose main clinical features are related to concomitant diseases.

T-cell large granular lymphocyte leukemia and related disorders

T-cell large granular lymphocyte (LGL) leukemia is a clonal proliferation of cytotoxic T cells, which causes neutropenia, anemia, and/or thrombocytopenia. This condition is often associated with autoimmune disorders, especially rheumatoid arthritis, and other lymphoproliferative disorders. The diagnosis is suggested by flow cytometry demonstrating an expansion of CD8(+)CD57(+) T cells and is confirmed by T-cell receptor gene rearrangement studies. Mounting evidence suggests that LGL leukemia is a disorder of dysregulation of apoptosis through abnormalities in the Fas/Fas ligand pathway. In most patients, this is an indolent disorder, and significant improvement of cytopenias can be achieved with immunosuppressive agents such as steroids, methotrexate, cyclophosphamide, and cyclosporin A. This review provides a concise, up-to-date summary of LGL leukemia and the related, more aggressive, malignancies of cytotoxic T cells and natural killer cells.

DNA microarray analysis of natural killer cell-type lymphoproliferative disease of granular lymphocytes with purified CD3-CD56+ fractions

Natural killer (NK) cell-type lymphoproliferative disease of granular lymphocytes (LDGL) is characterized by the outgrowth of CD3(-)CD16/56(+) NK cells, and can be further subdivided into two distinct categories: aggressive NK cell leukemia (ANKL) and chronic NK lymphocytosis (CNKL). To gain insights into the pathophysiology of NK cell-type LDGL, we here purified CD3(-)CD56(+) fractions from healthy individuals (n=9) and those with CNKL (n=9) or ANKL (n=1), and compared the expression profiles of >12 000 genes. A total of 15 'LDGL-associated genes' were identified, and a correspondence analysis on such genes could clearly indicate that LDGL samples share a 'molecular signature' distinct from that of normal NK cells. With a newly invented class prediction algorithm, 'weighted distance method', all 19 samples received a clinically matched diagnosis, and, furthermore, a detailed cross-validation trial for the prediction of normal or CNKL status could achieve a high accuracy (77.8%). By applying another statistical approach, we could extract other sets of genes, expression of which was specific to either normal or LDGL NK cells. Together with sophisticated statistical methods, gene expression profiling of a background-matched NK cell fraction thus provides us a wealth of information for the LDGL condition.

Advances in the diagnosis and classification of chronic lymphoproliferative disorders

In this review, we have highlighted recent advances in chronic lymphoproliferative disorders that commonly involve the peripheral blood. As we have seen, our concepts of certain diseases are changing. Molecular genetic and immunophenotypic studies are allowing more precise characterization of CLL and defining important biologic markers that predict clinical behavior. Prolymphocytic leukemia is now more narrowly defined and its relationship to nucleolated variants of MCL is now apparent. With new reagents and techniques applied to problems such as identification of Sezary cells and T-cell monoclonality determination, our ability to diagnose, monitor, and provide prognostic information is improving. Insight into the biology of these diseases also may provide new therapeutic targets in the future.

Natural killer cells and autoimmunity

Autoimmune diseases are often characterized as clinical syndromes caused by the inappropriate activation of T or B cells resulting in systemic or organ-specific damage. However, studies support a role for the innate immune system, and in particular natural killer (NK) cells, in stimulating or suppressing autoimmunity. This review focuses on recent research elucidating a potential immunoregulatory role for NK cells in modulating T and B cell-mediated autoimmunity.

Clinical features in T-cell vs. natural killer-cell variants of large granular lymphocyte leukemia

OBJECTIVE

Standard clinical and laboratory evaluations and novel laboratory techniques were used to identify patients with T-cell large granular lymphocyte leukemia (LGLL) and those with natural killer-cell variants of LGLL for comprehensive clinical evaluation.

METHODS

We used bone marrow histologic analysis, immunophenotypic markers of clonality, and T-cell-receptor gene rearrangement studies to identify patients.

RESULTS

The study identified 44 patients with T-cell LGLL and 14 with natural killer-cell LGLL. The two disorders were similar in sex and age distribution of patients; peripheral blood lymphocyte, neutrophil, and platelet counts; and incidence of rheumatoid arthritis. Among the two groups, patients with the T-cell LGLL presented with significantly lower hemoglobin concentrations (P < 0.04) and a higher frequency of palpable splenomegaly (P < 0.01).

CONCLUSION

Overall disease progression and response to immunosuppressive therapy are similar between T-cell and natural killer-cell variants of LGLL.

Update in the pathologic features of mature B-cell and T/NK-cell leukemias

Modern diagnosis of mature B- and T-cell leukemias requires integration of morphologic, immunophenotypic, and molecular genetic features. This integrative approach has allowed more precise definitions of specific disease entities. This in turn provides better information for clinicians to select proper therapy and determine prognosis. The characteristic pathologic features of these disorders are reviewed.

Natural killer cell neoplasms: a distinctive group of highly aggressive lymphomas/leukemias

Natural killer (NK) cell neoplasms, which include extranodal NK/T-cell lymphoma (nasal and extranasal) and aggressive NK cell leukemia, are generally rare, but they are more common in people of Oriental, Mexican and South American descent. These neoplasms are highly aggressive, and show a strong association with Epstein-Barr virus. Extranodal NK/T-cell lymphoma most commonly affects the nasal cavity and other mucosal sites of the upper aerodigestive tract. Patients present with nasal obstruction or midfacial destruction. Despite the early stage of disease at presentation, overall survival is poor. Patients with the extranasal form of the lymphoma often present with high-stage disease, commonly involving the skin, gastrointestinal tract, testis, and soft tissue, and the prognosis is even worse. Histologically, the lymphoma can show a broad cytologic spectrum, but apoptosis, necrosis, and angioinvasion are common. The most common immunophenotype is CD2(+), surface CD3(-), cytoplasmic CD3(+), CD56(+). Based on currently available data, treatment of nasal NK/T-cell lymphoma should consist of radiotherapy, with or without multiagent chemotherapy. More research is required to ascertain the role of high-dose chemotherapy with stem cell rescue and that of non-multidrug resistance-related chemotherapeutic agents. Aggressive NK cell leukemia affects younger patients, who present with poor general condition, fever, and disseminated disease; they often die within a short time from systemic disease or complications such as multi-organ failure. The peripheral blood and bone marrow show atypical large granular lymphocytes, which exhibit an immunophenotype similar to that of extranodal NK/T-cell lymphoma. Aggressive NK cell leukemia must be distinguished from T-cell large granular lymphocyte leukemia and indolent NK cell lymphoproliferative disorder, both of which are indolent.

Functional inhibitory human leucocyte antigen class I receptors on natural killer (NK) cells in patients with chronic NK lymphocytosis

Chronic natural killer (NK) lymphocytosis is a rare disorder characterized by an indolent clinical course. Despite high NK cell numbers, many patients present with only mild clinical symptoms, and are often asymptomatic. NK cells are equipped with a range of receptors that bind human leucocyte antigen (HLA)-class I molecules. The killer immunoglobulin-like receptors (KIR, CD158) bind groups of HLA alleles, the CD94/NKG2 receptors bind HLA-E, and the CD85j (ILT2, LIR-1) receptor binds to the relatively non-polymorphic alpha3 domain of HLA molecules. Inhibitory HLA class I receptors silence NK cells against cells expressing normal levels of HLA class I. Analysis of NK cells in six patients with chronic NK lymphocytosis revealed a high level of the inhibitory CD94/NKG2A receptor on all NK cells. In four patients, KIR were absent, in one patient a single KIR was expressed in the absence of self-ligand, and in one patient CD85j and multiple KIR were expressed. Cytotoxicity assays demonstrated that all HLA class I receptors were functional. The ability of monoclonal antibodies to block the receptors and allow killing of autologous target cells established that both receptor and ligand expression were adequate for inhibitory function. We propose that the silent behaviour of NK cells in patients with chronic NK lymphocytosis is due to effective inhibitory HLA class I receptors.

Cutaneous findings associated with chronic natural killer cell lymphocytosis

BACKGROUND

Chronic Natural Killer Cell Lymphocytosis (CNKL) is a recently described rare proliferative disorder. We noted an association of cutaneous disorders with CNKL in our clinical experience.

METHODS

We reviewed the medical records of all known patients with CNKL at our institution.

RESULTS

Five of 14 patients (36%) with CNKL had associated chronic cutaneous disease: two had livedoid vasculopathy; one, urticarial vasculitis; one, peripheral T-cell lymphoma; and one had complex recurrent aphthous stomatitis. In each case, except the one with lymphoma, the cutaneous disease was present before CNKL was diagnosed and CNKL persisted for the duration of the cutaneous disease. All five patients had increased numbers of large granular lymphocytes on a peripheral blood smear and three or four in the bone marrow (one patient did not undergo bone marrow biopsy).

CONCLUSIONS

Although CNKL and the reported skin diseases have occurred in the same patients, a causal link cannot yet be established. With CNKL, dermatologists must recognize associated cutaneous diseases, monitor patients for systemic disorders and cytopenias, and appropriately refer patients to a hematologist.