Chronic natural killer cell 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.

An algorithmic approach to the diagnosis of NK and T cell lymphomas

Lymphomas of natural killer (NK) and T cell lineages are uncommon disorders, although as a group they are more usually encountered in Asia compared to Western populations. In part due to their rarity, diagnosis and classification of T cell lymphomas often pose a challenge to clinicians and pathologists. Although there are morphological features that are characteristic of certain subtypes, correct classification of NK and T cell neoplasms relies heavily on the immunophenotype. With few exceptions, non-random genetic alterations such as translocations are less often seen in T cell neoplasms, adding to the diagnostic difficulty. Given these limitations, pathological diagnosis and classification of NK and T cell lymphomas are anything but straightforward. This paper attempts to present a practical algorithmic approach for the general pathologist who is confronted with these neoplasms.

Scleritis and multiple systemic autoimmune manifestations in chronic natural killer cell lymphocytosis associated with elevated TCRalpha/beta+CD3+CD4-CD8- double-negative T cells

BACKGROUND/AIMS

Chronic natural killer lymphocytosis (CNKL) has been associated with systemic autoimmunity; however, its association with scleritis or ocular autoimmunity has not been characterised. The natural killer (NK) cell function and immunophenotype of a patient with CNKL who developed bilateral scleritis and multiple systemic autoimmune findings were evaluated.

METHODS

The ophthalmic records of a patient with CNKL and scleritis were reviewed over a 6-year period. Flow cytometry was performed to evaluate T cell, NK and B cell populations. NK cellular functions (ie, NK cytotoxicity and cytokine/chemokine production following interleukin 2 (IL2) stimulation) were evaluated.

RESULTS

A 56-year-old woman with vitiligo, psoriatic arthritis, thyroiditis, erythema nodosum, bilateral anterior scleritis and Sjogren syndrome was managed with multiple immunosuppressive medications, including prednisone, mycophenolate mofetil and methotrexate. Flow cytometry showed a persistent elevation of CD56(+)CD3(-) NK cells greater than 40%, which was consistent with CNKL. NK cell cytotoxicity assay identified a deficiency of K562 cell lysis in the patient (1.46 mean-fold greater in control vs patient). NK cytokine/chemokine production following IL2 stimulation was also deficient (2.5-32.5-fold greater in control). Cytokines/chemokines assessed included pro-inflammatory (interferon gamma, tumor necrosis factor alpha, IL1, monocyte chemotactic protein 1) and immunoregulatory cytokines (IL4, IL5 and IL10). An abnormal elevation of TCRalpha/beta(+) CD3(+)CD4(-)CD8(-) T cells suggestive of autoimmune lymphoproliferative syndrome was observed; however, apoptosis dysfunction was not found.

CONCLUSION

The association of increased but dysfunctional NK cells in the context of multiple systemic and ocular manifestations suggests a role of NK cells in the pathogenesis of our patient's disease. Further studies regarding NK cell dysfunction and ocular autoimmunity are needed.

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.

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.

Chronic natural killer cell lymphocytosis is associated with elevated cytotoxic activity of natural killer cells

The authors describe a 16-year-old girl who has suffered from chronic natural killer cell lymphocytosis (CNKL) for 12 years. From age 4 years, she has shown a persistent lymphadenopathy and lymphocytosis. Clinically, she developed allergic skin involvement, thrombocytopenia, and peripheral polyneuropathy. Annual flow cytometry analyses of lymphocyte subsets revealed persistently elevated NK cell levels (55-75% of the lymphocyte fraction and 0.7-10 x 10(3) NK cells per microliter of blood). Furthermore, IgE serum concentrations were markedly increased. Based on CD16, CD161, and CD94 surface antigen expression, the NK cell population was characterized as mature NK cells. Functional analysis of these cells showed a 2-fold increase of intrinsic cytotoxic activity toward K-562 cells compared with NK cells from healthy controls. The authors present a clinical case of rare CNKL. The patient's NK cells possess significantly increased cytotoxic activity. These findings are discussed in context with elevated IgE concentrations.

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.

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.

Pure red cell aplasia associated with expansion of CD3+ CD8+ granular lymphocytes expressing cytotoxicity against HLA-E+ cells

T-cell granular lymphocyte-proliferative disorder (T-GLPD) is characterized by the proliferation of cytotoxic T lymphocytes, and is often associated with pure red cell aplasia (PRCA). The mechanism involved in the development of PRCA in T-GLPD is unknown. Peripheral blood mononuclear cells were isolated from 20 patients with T-GLPD. Ten patients had associated PRCA. Granular lymphocytes (GLs) of T-GLPD are positive for CD94, but not NKG2A. To clarify the functional role of CD94 in T-GLPD, we performed a cytotoxicity assay against the trophoblast cell line, BeWo, which is known to express human leucocyte antigen (HLA)-E, a natural ligand of CD94, and is deficient in other HLA class I and class II antigens. GLs isolated from T-GLPD with PRCA patients killed BeWo cells more significantly than GLs from T-GLPD without PRCA patients. Furthermore, GLs from T-GLPD with PRCA were significantly stimulated by a monoclonal antibody against CD94, whereas those of T-GLPD without PRCA were not. Taken together, HLA-E, a ligand of CD94, was suggested to stimulate CD94+ cells to kill HLA-E+ cells in T-GLPD with PRCA. GLs of T-GLPD with PRCA have a potential positive activity against HLA-E+ cells, whereas GLs from T-GLPD without PRCA do not. CD94 may play a key role in the pathogenesis of PRCA in T-GLPD.

A case of clinical indolent natural killer cell lineage large granular lymphocytic leukemia in a patient with rheumatoid arthritis

We report a case of natural killer (NK) cell leukemia with unusual biological features in a 65-year-old woman with a 20-year history of rheumatoid arthritis. She presented with neutropenia, thrombocytopenia, splenomegaly and bone marrow infiltration. Immunophenotyping (CD2+ CD3- CD4- CD5- CD8- CD16+ CD56-) confirmed NK cell leukemia. Her neutropenia and thrombocytopenia resolved following splenectomy and she has remained well with stable disease for 12 months on oral low-dose methotrexate. In contrast to all previous reports, in this instance the phenotype of large granular lymphocytic (LGL) leukemia occurring in the context of rheumatoid arthritis was NK-cell rather than T-cell. Furthermore, the clinical course was indolent, whereas, all prior literature reports have described a very aggressive clinical course for this disorder with a median survival of just 3.5 months. This case illustrates previously unrecognized heterogeneity in the natural history of this disorder.

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.

Demonstration of aberrant T-cell and natural killer-cell antigen expression in all cases of granular lymphocytic leukaemia

The diagnosis of granular lymphocytic leukaemia (GLL) requires the presence of an immunophenotypically distinct T-cell (T-GLL) or natural killer-cell (NK-GLL) population. Flow cytometric immunophenotyping was performed on 21 T-GLL patients, 11 NK-GLL patients and 20 normal control subjects using antibodies to T and NK cell-associated antigens in order to accurately identify the distinguishing features of T-GLL and NK-GLL. The NK antigens evaluated included: CD16, CD57, CD94, CD161, and the killing inhibitory receptors (KIRs) CD158a, CD158b and CD158e (p70). Abnormal T-antigen expression was present in all T-GLL patients. CD57 was frequently expressed in T-GLL, however, one-third of patients showed partial CD57 expression similar to that seen in T cells from normal control subjects. Ten T-GLL were KIR positive; all expressed a single KIR isoform. All NK-GLL showed a distinctive, abnormal immunophenotype. Four NK-GLL expressed a single KIR isoform; the remaining seven patients lacked all tested KIRs, which is also a distinct, abnormal finding. Immunoperoxidase staining of bone marrow biopsy specimens from NK-GLL patients with antibodies to CD8, TIA-1 and granzyme B revealed the disease-specific distinctive staining patterns previously found in T-GLL. These studies delineate the unique immunophenotypic features diagnostic of T-GLL and provide strong evidence that NK-GLL, like T-GLL, represents a clonal lymphoproliferative disorder.

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.

Abnormal NK cell lymphocytosis detected after splenectomy: association with repeated infections, relapsing neutropenia, and persistent polyclonal B-cell proliferation

We report the case of a boy with hereditary spherocytosis who presented with mild microcytic hypochromic anemia and recurrent leg ulcers that had been present since childhood. Chronic natural killer (NK) cell and B-cell lymphocytosis was detected 1 year after therapeutic splenectomy during investigation of recurrent episodes of neutropenia and persistent lymphocytosis. NK cells proved to be abnormal at immunophenotyping studies, and B-cells were polyclonal and displayed a normal immunophenotype. Genotypic analysis of T-cell receptor (TCR)-beta and TCR-gamma genes showed a germ-line pattern. The clinical course of this patient was characterized by multiple pulmonary infections and amygdalitis. We discuss the potential roles of persistent immune stimulation due to chronic hemolysis and severe leg ulcers and of splenectomy in the origin of NK cell lymphocytosis and the relationship between NK cells and recurrent infections, relapsing neutropenia, and polyclonal B-cell response.

Differentiation stage of natural killer cell-lineage lymphoproliferative disorders based on phenotypic analysis

In the normal developmental pathway of natural killer (NK) cells, pre-NK cells express CD161, immature NK cells express CD161 and CD56, and mature NK cells express CD161, CD56 and CD94. To identify the normal counterpart of NK cells from which neoplastic cells originate, surface antigens were analysed. Blastic NK-cell lymphoma/leukaemia lacked CD94 and CD161 but had CD56. Aggressive NK-cell leukaemia/lymphoma and nasal NK-cell lymphoma, although morphologically immature, expressed both CD56 and CD94 and strong NK activity. Cells from chronic NK lymphocytosis expressed CD56 and CD94.

Decreased natural killer (NK) cell function in chronic NK cell lymphocytosis associated with decreased surface expression of CD11b

Chronic natural killer cell lymphocytosis (CNKL) is characterized by greatly increased numbers of natural killer (NK) cells and patients with this disease may survive for long periods. This is in contrast to patients with leukemic proliferations of NK cells who can have a rapidly progressive clinical course. We identified a pediatric patient who was largely healthy who had CNKL and we sought to determine if the expanded CD16(+)CD3(-) population in this patient functions differently than classical NK cells. Cytotoxic activity against NK cell-sensitive K562 target cells was present, but lower than that in control donors when calculated as lytic units per CD16(+)CD3(-) cell. This cytolytic activity was inducible in patient samples by IL-2/IL-12 stimulation proportionately to that induced in samples from control donors. Intracellular perforin was also present and induced in patient CD16(+)CD3(-) cells similarly to controls. Other presumed NK cell activities, such as IL-2/IL-12 induced IFN-gamma expression and initiation of apoptosis evidenced by annexin V binding after CD16 crosslinking were present in patient samples. Patient CD16(+)CD3(-) cells, however, differed from classical NK cells, as the majority did not express CD56, CD57, CD8, or CD11b. Most convincingly, there was a 5 log decrease in CD11b expression in patient CD16(+)CD3(-) cells compared to control as determined by mean channel fluorescence. These observed differences may explain the relatively benign phenotype of this disorder.

Aggressive natural killer (NK) cell lymphoma: report of a pediatric case and review of the literature

We report a rare pediatric case of aggressive natural killer (NK) cell lymphoma, characterized by acute onset hepatosplenomegaly and respiratory distress, and infiltration by large granular lymphocytes with the phenotype of CD3-CD16-CD56+. The patient has remained in complete remission after short-pulse intensive chemotherapy, and myeloablative therapy followed by allogeneic bone marrow transplantation. We compare our case with 7 other children with NK cell leukemia reported from other institutions.