Regulation of human natural killer (NK) cell function: Induction of killing of an NK-resistant renal carcinoma cell line

Natural killer (NK)-like activity against a renal carcinoma cell line, Cur, was assessed. There was no spontaneous killing of Cur cells by human peripheral blood mononuclear cells in 4-hr assays. Cur killing was observed in 18-hr assays, but the magnitude of killing was variable and always markedly less than that against K562. Cur killing was mediated by a nonadherent, nonphagocytic lymphocyte, the activity of which could be modulated both positively and negatively by monocytes or their products. Preincubation of effectors with monocyte supernatant, interleukin 1 (IL-1), -interferon (IFN), or interleukin 2 (IL-2) greatly increased the magnitude of Cur killing and accelerated the kinetics of lysis. The addition of prostaglandin E₂ (PGE₂) duringin vitro activation of NK by IL-2 profoundly inhibited subsequent Cur lysis, whereas only minimal inhibition of K562 lysis was noted. However, following activation with IL-2, lysis of Cur targets was less sensitive to the inhibitory effects of PGE₂. Removal of Leu 11b(+), OKM1(+), orl-leucylleucine methyl ester-sensitive cells markedly decreased both Cur and K562 lysis. Moreover, CD16(+) cells purified with the fluorescence-activated cell sorter were found to mediate Cur killing. Whereas Cur and K562 lysis is mediated by phenotypically similar effector cells, the present studies demonstrate that the cytotoxic functions defined by the ability to lyse these two targets differ in response to a variety of immunoregulatory stimuli.     

Augmentation of natural killer (NK) cell activity by a streptococcal preparation,OK-432, in patients with malignant tumors

Recently, a streptococcal preparation, OK-432 has been used successfully as an immunopotentiator for immunotherapy in patients with malignant tumors in Japan. In this paper, we report that the administration of OK-432 augments the cytotoxic activity of peripheral blood lymphoid cells against a natural killer (NK) cell-sensitive erythroleukemic cell line, K562, in tumor patients. In patients before or after surgery, sufficient amounts of OK-432 strongly augmented the cytotoxic activity within 3 days after the initial administration of OK-432. Thereafter the levels of cytotoxicity declined rapidly. The administration of a lower dose of OK-432 gave a lower increase in cytotoxicity. Enhanced cytotoxicity occurred with the reintroduction of OK-432 but remained at lower levels of activity. Characterization and fractionation of OK-432-induced effector cells revealed that the augmented cytotoxicity seemed to be carried mainly by NK cells. A low titer of interferon was detected in 3 of 10 patients within 72 hr after the first inoculation of the agent. Furthermore, we discuss the potency of OK-432 for the induction of interferon in detail.     

Effects of Chlamydia trachomatis infection on the expression of natural killer (NK) cell ligands and susceptibility to NK cell lysis

Natural killer (NK) cells are an important component of the immediate immune response to infections, including infection by intracellular bacteria. We have investigated recognition of Chlamydia trachomatis (CT) by NK cells and show that these cells are activated to produce interferon (IFN)-gamma when peripheral blood mononuclear cells (PBMC) are stimulated with CT organisms. Furthermore, infection of epithelial cell lines with CT renders them susceptible to lysis by human NK cells. Susceptibility was observed 18-24 h following infection and required protein synthesis by the infecting chlamydiae, but not by the host cell; heat or UV inactivated chlamydiae did not induce susceptibility to NK cell lysis. CT infection was also shown to decrease the expression of classical and non-classical major histocompatibility complex (MHC) molecules on infected cells, thus allowing recognition by NK cells when combined with an activating signal. A candidate activating signal is MICA/B, which was shown to be expressed constitutively on epithelial cells.     

The differential effect of stress on natural killer T (NKT) and NK cell function

When C57Bl/6 mice were exposed to restraint stress for 12 h or 24 h, lymphocytopenia was induced in the liver, spleen, and thymus. We examined which types of lymphocytes were sensitive or resistant to such stress by a immunofluorescence test. T cells of thymic origin were sensitive while NKT and NK cells were resistant. In contrast to the increase in the proportion of NK cells, NK activity of liver lymphocytes against YAC-1 targets decreased at 24 h after stress. On the other hand, their NKT cytotoxicity against syngeneic thymocytes increased in parallel with an increase in their proportion. In perforin -/- B6 mice and B6-gld/gld (Fas ligand-) mice, NK cells were found to mediate cytotoxicity through perforin while NKT cells mediated self-reactive cytotoxicity through Fas ligand. These results suggest that stress increases the proportion of both NK and NKT cells, but that NK cytotoxicity is suppressed while self-reactive NKT cytotoxicity is not, due to a diversity of their functional mechanisms.     

Deficiency in circulating natural killer (NK) cell subsets in common variable immunodeficiency and X-linked agammaglobulinaemia

Absolute and relative NK cell numbers were determined in peripheral whole blood by flow cytometry in patients with common variable immunodeficiency (CVID) (n = 55) and X-linked agammaglobulinaemia (XLA) (n = 19) on regular immunoglobulin (IVIG) therapy. Absolute CD3-CD16+ NK cell numbers were significantly reduced in CVID patients (median 108/microl, range 23-815), compared with normal subjects (n = 60) (289/microl, range 56-640, P < 0.001). Total lymphocyte concentrations were significantly lower in CVID (median 1587/microl, range 523-7519) compared with normal subjects (median 2019/microl, range 1124-3149, P = 0.004), with the percentage of NK cells also being significantly decreased (median 7.5%, range 3.0-33. 0%, compared with 14.2%, range 2.6-30.8%, P < 0.001). In XLA, absolute NK cell numbers (median 140/microl, range 32-551, P < 0. 001) but not relative numbers were significantly reduced compared with normal controls. We excluded the possibility that IVIG interferes with in vitro binding of CD16 MoAbs. Further analysis of NK cell subsets showed a deficiency of both CD16+ and CD56+ cells in CVID, most marked in the CD3-CD8dim subpopulation, which may be due to increased homing of these cells to the gut. Serial studies on a small number of patients suggest that IVIG therapy has no short-term effect on NK cells, although we cannot exclude an effect with prolonged use. Although there are no obvious clinical effects of the NK depletion in CVID and XLA, this may be a factor in their predisposition to cancer.     

Peripheral T cell and natural killer (NK) T cell lymphomas: a clinicopathological study from a single Australian centre

McKelvie P A, Thompson P A & Tam C S
(2012) Histopathology  61, 212–233 Peripheral T cell and natural killer (NK) T cell lymphomas: a clinicopathological study from a single Australian centre Aims: Using pathological and clinical review, to identify all cases diagnosed as peripheral T cell and natural killer (NK) T cell lymphoma over 10 years from one metropolitan Australian hospital. Methods and results: Subtyping was performed using World Health Organization (WHO) 2008 criteria and a comprehensive immunohistochemical panel. Clinical data including follow‐up were obtained. There were 47 cases, including 11 peripheral T cell lymphomas, not otherwise specified (NOS), nine extranodal NK T cell lymphomas, nasal type (eight nasal), eight primary cutaneous anaplastic large cell lymphomas, seven angioimmunoblastic T cell lymphomas, three anaplastic lymphoma kinase (ALK)‐positive anaplastic large cell lymphomas, four ALK‐negative anaplastic large cell lymphomas, three enteropathic T cell lymphomas and two subcutaneous panniculitis‐like T cell lymphomas. Follow‐up of 46 of 47 cases (median time 45 months) revealed that 50% (23 of 46) of patients died. Five‐year survival rates were: peripheral T cell lymphoma, NOS 39%; angioimmunoblastic T cell, 43%; nasal NK T 67%; ALK‐negative anaplastic large cell lymphoma 67% (at 2 years); ALK⁺ anaplastic large cell lymphoma 33%; subcutaneous panniculitis‐like T cell lymphomas 100%; primary cutaneous anaplastic large cell lymphoma 86%; and enteropathic T cell lymphoma 33% (at 1 year). One patient with Lennert lymphoma suffered four late cutaneous relapses. Conclusions: This first Australian clinicopathological series of peripheral T cell and NK T cell lymphoma shows epidemiological and survival data similar to those for Europe and North America.     

Altered natural killer (NK) cell frequency and phenotype in latent autoimmune diabetes in adults (LADA) prior to insulin deficiency

Approximately 10% of the patients diagnosed with type 2 diabetes (T2D) have detectable serum levels of glutamic acid decarboxylase 65 autoantibodies (GADA). These patients usually progress to insulin dependency within a few years, and are classified as being latent autoimmune diabetes in adults (LADA). A decrease in the frequency of peripheral blood natural killer (NK) cells has been reported recently in recent‐onset T1D and in high‐risk individuals prior to the clinical onset. As NK cells in LADA patients have been investigated scarcely, the aim of this study was to use multicolour flow cytometry to define possible deficiencies or abnormalities in the frequency or activation state of NK cells in LADA patients prior to insulin dependency. All patients were GADA‐positive and metabolically compensated, but none were insulin‐dependent at the time blood samples were taken. LADA patients exhibited a significant decrease in NK cell frequency in peripheral blood compared to healthy individuals (P = 0·0018), as reported previously for recent‐onset T1D patients. Interestingly, NKG2D expression was increased significantly (P < 0·0001), whereas killer cell immunoglobulin‐like receptor (KIR)3DL1 expression was decreased (P < 0·0001) within the NK cell population. These observations highlight a defect in both frequency and activation status of NK cells in LADA patients and suggest that this immunological alteration may contribute to the development of autoimmune diabetes by affecting peripheral tolerance. Indeed, recent evidence has demonstrated a regulatory function for NK cells in autoimmunity. Moreover, the decrease in NK cell number concords with observations obtained in recent‐onset T1D, implying that similar immunological dysfunctions may contribute to the progression of both LADA and T1D.     

Ly49E expression points toward overlapping,but distinct,natural killer (NK) cell differentiation kinetics and potential of fetal versus adult lymphoid progenitors

Using a new antibody, we found previously that contrary to adult natural killer (NK) cells, fetal NK cells have a unique phenotype, as they exclusively express Ly49E. This can be explained by an intrinsic different NK differentiation potential of fetal versus adult lymphoid progenitors, by immaturity of fetal NK cells or by instability of Ly49E expression. Here, we show that adult progenitor cells were still capable of differentiating into Ly49E-expressing NK cells but at a much lower frequency. Surprisingly, Ly49E expression in vitro did not require stromal cells. Kinetic analysis in vivo showed that Ly49E was expressed early, together with CD94/NKG2 and Ly49G2, followed by Ly49C, and finally Ly49D. Transfer of sorted Ly49E-positive fetal NK cells showed stable Ly49E expression, and later, part of these cells up-regulated other Ly49 members. These data indicate that although there are intrinsic differences, there is no strict fetal and adult wave of NK cell differentiation.     

Enhancing effect of natural killer cell stimulatory factor (NKSF/interleukin-12) on cell-mediated cytotoxicity against tumor-derived and virus-infected cells

Natural killer cell stimulatory factor (NKSF) or interleukin-12 (IL-12) is a heterodimeric cytokine with pleiomorphic effects on T and NK cells, including induction of lymphokine production, mitogenesis, and enhancement of spontaneous cytotoxic activity. Similarly to IL-2, NKSF/IL-12 enhances NK cell-mediated cytotoxicity within a few hours and independently from induced proliferation. This effect is independent from other induced cytokines, because it is not prevented by antibodies neutralizing interferon (IFN)-α, IFN-β IFN-γ, IL-2 or tumor necrosis factor (TNF)-α and, unlike the induction of IFN-γ production by peripheral blood lymphocytes, it does not require HLA class II-positive accessory cells. Enhanced cytotoxicity is accompanied by morphologic changes in NK cells, including a significant increase in the number of cytoplasmic granules. In addition to the previously described ability to enhance the cytotoxic activity of NK cells against tumor-derived target cells, NKSF/IL-12 is also a potent stimulator of cytotoxicity against virus-infected cells, either fibroblasts acutely infected with herpes viruses or T cell lines chronically infected with human immunodeficiency virus-1. NK cell-mediated antibody-dependent cytotoxicity or anti-CD16 antibody-redirected lysis is not significantly enhanced by NKSF/IL-12. However, the ability of resting peripheral blood T cells to mediate anti-CD3 antibody-redirected lysis is enhanced by 18-h incubation with NKSF/IL-12, indicating that this lymphokine can modulate the cytotoxic capability of both NK and T cells.     

Quantitative and functional analysis of a human lymphocyte subset with the T-helper (Leu 3/T 4+) phenotype and natural killer (NK)-cell characteristics in patients with malignancy

Approximately 20% of normal blood lymphocytes expressing the T-helper (Leu 3/T 4⁺) surface phenotype display natural killer (NK)-like features such as cytoplasmic granules and the ability to bind NK-cell targets. In this study, we have assessed the frequency, phenotypic features, and functional capabilities of such cells in a variety of lymphoid malignancies or solid tumors. In each patient group, the percentage of granular lymphocytes within the Leu 3/T 4⁺ T-helper subset was significantly increased. A large percentage of these cells coexpressed the Leu 7 or Leu 15 marker. When Leu 3⁺ cells from patients with high proportions of such NK-like cells (or Leu 3⁺-Leu 15⁺ cells from selected patients) were isolated with a fluorescence-activated cell sorter, these cells did not proliferate in response to allogeneic cells or T-cell mitogens, nor did they provide help for B-cell differentiation. They also did not suppress T-cell proliferative responses or B-cell differentiation. Freshly prepared Leu 3⁺ granular lymphocytes did not display NK-cell cytotoxic functions. However, after short-term culture in the presence of phytohemagglutinin (PHA), Leu 3⁺-Leu 15⁺ cells expressed T-cell growth factor (TCGF) receptors, had a detectable proliferative response to exogenous TCGF, and acquired the ability to lyse NK-cell targets. These studies demonstrate that, in a variety of malignancies, the lymphocyte subpopulation expressing the T-helper (Leu 3/T 4⁺) phenotype may be comprised largely of cells with NK-like features and functional capabilities distinct from those of classical helper T cells.     

Cellular immunosenescence in F344 rats: decreased natural killer (NK) cell activity involves changes in regulatory interactions between NK cells, interferon, prostaglandin and macrophages

Natural killer (NK) activity of F344 rat spleen cells remained constant between 1 and 18 months of age under specific pathogen-free (SPF) conditions. Between 18 and 24 months of age, however, there was a dramatic decline in activity which remained at a low baseline throughout the normal lifespan. Removal of adherent cells on G-10 Sephadex columns revealed age-related changes in adherent cell regulation of NK activity. Young (4-6 week) NK activity was consistently decreased by adherent cell removal while old (24-30 month) NK activity was slightly but reproducibly increased. Moreover, splenic macrophages from old rats purified by adherence to microexudate-coated surfaces were highly suppressive to young nonadherent NK activity. A role for endogenous prostaglandin (PG) in suppressed old rat NK activity was suggested by the effectiveness of anti-PGE2 in vivo to boost old NK activity. Although old rat NK activity was boosted to a relatively greater extent by interferon (IFN) in vitro than was young NK activity, IFN-boosted NK activity of old rats was much more sensitive to PGE2 inhibition than was IFN-boosted young rat NK activity. IFN treatment in vitro or poly(I:C) treatment in vivo induced protection against PGE2 inhibition of NK activity in young rats, while no resistance to PGE2 inhibition was induced in old rat NK cells by similar treatments. In vivo, the same protocol of IFN administration which boosted young rat NK activity further suppressed old rat activity. These results support the hypothesis that immunosuppression related to aging, which supersedes the boosting effect of IFN, involves the combined effects of suppressor macrophages (via PGE2) and intrinsic changes in effector (NK) cells which render them more sensitive to PGE2 inhibition.     

Cytotoxicity of human natural killer (NK) cell subsets for Plasmodium falciparum erythrocytic schizonts: stimulation by cytokines and inhibition by neomycin.

Quantification of human peripheral blood NK subsets has been made in a group of Kenyan adults and children with acute P. falciparum malaria. Results were compared with data obtained from three age- and sex-matched control cohorts: parasitaemic but asymptomatic children; aparasitaemic children and adults; and adult Caucasians with no previous history of malaria. Separated NK subsets were tested in vitro for cytotoxicity to erythrocytic schizonts of P. falciparum in the presence and absence of cytokines. There was a statistically significant quantitative and qualitative depression of the CD3-CD56+ subset in patients with acute malaria and this was accompanied by an expansion of the 'non-functional' CD3-CD57+CD16-CD56- subset. Both CD3-CD16+ and CD3-CD56+ NK cells from all patients and donors lysed schizonts, and this cytotoxicity was enhanced by the addition of recombinant interferon-alpha and/or IL-2, notably with the CD3-CD56+ subset. Interestingly, asymptomatic donors had the highest levels of CD3-CD56+ NK cells, which also demonstrated an enhanced response to cytokine stimulation. Cytotoxicity to schizonts was accompanied by the release of soluble NK cell lytic factors. Neomycin suppressed cytotoxicity in a dose-dependent manner, indicating that the lysis of schizonts by NK cells involves phospholipase C-mediated phosphoinositide metabolism. Our findings define a role for NK cells in immunity to malaria through the lysis of infected erythrocytes as a first-line defence against the parasite.     

Inhibition of natural killer (NK) cell activity against varicella-zoster virus (VZV)-infected fibroblasts and lymphocyte activation in response to VZV antigen by nitric oxide-releasing agents

The addition of nitric oxide (NO)-releasing agents, S-nitroso-N-acetyl-DL-penicillamine (SNAP), 1-hydroxy-2-oxo-2,3-bis(2-aminoethyl)-1-triazene (NOC18), 30{(±)-(E)-ethyl-2′-[(E)-hydroxyimino]-5-nitro-3-hexenecarbamoyl}-pyridine (NOR4) significantly inhibited NK cell activity against VZV-infected cells, while antibody-dependent cell-mediated cytotoxicity (ADCC) against VZV-infected cells was unaffected. Interferon-alpha (IFN-α) production by non-adherent peripheral blood mononuclear cells (NPBMC) cultured with VZV-infected cells was decreased by the addition of NO-releasing agents. Lymphocyte proliferation and the expression IL-2 receptor (CD25) in response to VZV antigen were also inhibited by the addition of NO-releasing agents. These results suggest that the production of NO by an inflammatory process may lead to inhibition of NK cell- and T cell-mediated immunity to VZV infection.     

Natural killer (NK) cell activity during HIV infection: a decrease in NK activity is observed at the clonal level and is not restored after in vitro long-term culture of NK cells.

NK cell activity is impaired in HIV-infected patients. The mechanisms behind the altered NK functions are not clear, and conflicting data concerning NK and antibody-dependent cellular cytotoxicity (ADCC) activity have been reported. In order to investigate whether this impairment is also observed at the clonal level and whether it is related to a defect at the target cell binding and/or the post-binding level, we evaluated highly purified NK cell lines and cloned NK cells obtained from 22 HIV-infected patients at different stages of disease and compared them with normal controls for their ability to: (i) kill K-562 and U-937 cell lines using a 51Cr release assay; (ii) bind and kill K-562 and U-937 cells at the single cell binding level; (iii) release NK cytotoxic factor (NKCF), tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma); (iv) kill anti-IgM preincubated Daudi cell line (ADCC activity). This study with cloned NK cells or NK cell lines from HIV-infected individuals showed: (i) a decrease in their lytic capability against target cell lines; (ii) a low ability to form conjugates with K-562 and U-937 cell lines with respect to controls; (iii) a decreased ability to kill bound target cells; (iv) low levels of released NKCF, TNF-alpha and IFN-gamma after incubation with U-937 cells. Taken together, these findings suggest that the impaired NK cell function during HIV infection is also observed at the clonal level and is related to defects both at the target and post-binding levels. However, the precise mechanisms remain to be determined. The inability to restore normal NK activity after long-term culture in the presence of high levels of recombinant IL-2 is in agreement with the hypothesis of a 'general anergic process' during HIV infection.     

Immunomodulation by vitamin B12: augmentation of CD8+ T lymphocytes and natural killer (NK) cell activity in vitamin B12-deficient patients by methyl-B12 treatment

It has been suggested that vitamin B12 (vit.B12) plays an important role in immune system regulation, but the details are still obscure. In order to examine the action of vit.B12 on cells of the human immune system, lymphocyte subpopulations and NK cell activity were evaluated in 11 patients with vit.B12 deficiency anaemia and in 13 control subjects. Decreases in the number of lymphocytes and CD8+ cells and in the proportion of CD4+ cells, an abnormally high CD4/CD8 ratio, and suppressed NK cell activity were noted in patients compared with control subjects. In all 11 patients and eight control subjects, these immune parameters were evaluated before and after methyl-B12 injection. The lymphocyte counts and number of CD8+ cells increased both in patients and in control subjects. The high CD4/CD8 ratio and suppressed NK cell activity were improved by methyl-B12 treatment. Augmentation of CD3-CD16+ cells occurred in patients after methyl-B12 treatment. In contrast, antibody-dependent cell-mediated cytotoxicity (ADCC) activity, lectin-stimulated lymphocyte blast formation, and serum levels of immunoglobulins were not changed by methyl-B12 treatment. These results indicate that vit.B12 might play an important role in cellular immunity, especially relativing to CD8+ cells and the NK cell system, which suggests effects on cytotoxic cells. We conclude that vit.B12 acts as an immunomodulator for cellular immunity.     

The impaired NK cell cytolytic function in viremic HIV-1 infection is associated with a reduced surface expression of natural cytotoxicity receptors (NKp46, NKp30 and NKp44)

Signals leading to NK cell triggering are primarily mediated by natural cytotoxicity receptors (NCR) upon binding to as-yet-undefined cell surface ligand(s) on normal hematopoietic cells, pathogen-infected cells or tumor cells. In this study we tried to determine whether the decreased NK cell cytolytic function that is observed in HIV-1-infected patients may be related to a decreased expression of NCR. In HIV-1-infected patients, freshly drawn, purified NK cells expressed significantly decreased surface densities of NKp46 and NKp30 NCR. The low surface density of NKp46, NKp30 and NKp44 was also confirmed in in-vitro-activated NK cell populations and NK cell clones derived from HIV-1 patients compared with uninfected donors. This defective NCR expression in HIV-1 patients was associated with a parallel decrease of NCR-mediated killing of different tumor target cells. Thus, the present study indicates that the defective expression of NCR represents at least one of the possible mechanisms leading to the impaired NK cell function in HIV-1 infection and it can contribute to explain the relatively high frequency of opportunistic tumors reported in cohorts of untreated patients before the occurrence of profound immunosuppression (<200 CD4(+) cells/mm(3)).     

Clinicopathological analysis of the age-related differences in patients with Epstein-Barr virus (EBV)-associated extranasal natural killer (NK)/T-cell lymphoma with reference to the relationship with aggressive NK cell leukaemia and chronic active EBV infection-associated lymphoproliferative disorders

Takahashi E, Ohshima K, Kimura H, Hara K, Suzuki R, Kawa K, Eimoto T & Nakamura S for the NK‐cell Tumor Study Group
(2011) Histopathology 59 , 660–671 Clinicopathological analysis of the age‐related differences in patients with Epstein–Barr virus (EBV)‐associated extranasal natural killer (NK)/T‐cell lymphoma with reference to the relationship with aggressive NK cell leukaemia and chronic active EBV infection‐associated lymphoproliferative disorders Aims: Extranodal natural killer (NK)/T‐cell lymphoma (NKTL), comprising nasal NKTL and extranasal NKTL (ENKTL), is associated with Epstein–Barr virus (EBV). A bimodal age distribution was noted in NKTL patients. We examined the clinicopathological differences between two age groups of ENKTL patients (n = 23) and compared the findings with those of aggressive NK cell leukaemia (ANKL; n = 10) and monoclonal chronic active EBV infection‐associated T/NK‐cell lymphoproliferative disorders [chronic active EBV infection/TNK‐lymphoproliferative disorders (CAEBV/TNK‐LPD)] of NK‐cell type (n = 45). Methods and results: Distinct differences existed between elderly (>50 years; n = 13) and younger (≤50 years; n = 10) ENKTL patients; the latter showed a higher disease stage (P = 0.0286), worse performance status (P = 0.0244), more frequent B symptoms (P = 0.0286) and more frequent liver, spleen and bone marrow involvement (P = 0.0222, 0.0005 and 0.0259, respectively). Few clinicopathological differences existed between younger ENKTL and ANKL patients. Patients with monoclonal CAEBV/TNK‐LPD of NK‐cell type (n = 45) showed features similar to those in younger ENKTL/ANKL patients, except a more juvenile onset of CAEBV‐related symptoms and better prognosis. However, the onset age of overt leukaemia/lymphoma in CAEBV/TNK‐LPD patients and overall survival thereafter were similar to those in younger ENKTL/ANKL patients. Conclusions: ENKTL (≤50 years) is distinct from that in elderly patients and may encompass ANKL and overlap in the clinicopathological profile with NK‐cell type CAEBV/TNK‐LPD.