Natural killer cell leukemia as a cause of peripheral neuropathy and meningitis: case report

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.

Natural Killer Cells Degenerate Intact Sensory Afferents following Nerve Injury

Sensory axons degenerate following separation from their cell body, but partial injury to peripheral nerves may leave the integrity of damaged axons preserved. We show that an endogenous ligand for the natural killer (NK) cell receptor NKG2D, Retinoic Acid Early 1 (RAE1), is re-expressed in adult dorsal root ganglion neurons following peripheral nerve injury, triggering selective degeneration of injured axons. Infiltration of cytotoxic NK cells into the sciatic nerve by extravasation occurs within 3 days following crush injury. Using a combination of genetic cell ablation and cytokine-antibody complex stimulation, we show that NK cell function correlates with loss of sensation due to degeneration of injured afferents and reduced incidence of post-injury hypersensitivity. This neuro-immune mechanism of selective NK cell-mediated degeneration of damaged but intact sensory axons complements Wallerian degeneration and suggests the therapeutic potential of modulating NK cell function to resolve painful neuropathy through the clearance of partially damaged nerves.

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Cytotoxic NK cells infiltrate the damaged peripheral nerve within days of injury

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Injured sensory axons express NKG2D ligand RAE1 to signal degeneration by NK cells

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Clearance of damaged axons reduces development of chronic pain after nerve injury

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NK cells complement Wallerian degeneration to aid functional regeneration of PNS

CD56-Negative Aggressive NK Cell Leukemia Relapsing as Multiple Cranial Nerve Palsies: Case Report and Literature Review

Background

Aggressive natural killer cell leukemia (ANKL) is extremely rare and habitually manifests as a systemic disease with multiorgan failure that rapidly evolves to death. The neoplastic natural killer (NK) cells usually harbor the Epstein-Barr virus (EBV) with a latent viral infection pattern type II; they often have a cytoplasmic CD3ε⁺ and surface CD3⁻, CD2⁺, and CD56⁺ immunophenotype, and they show complex genetic abnormalities affecting multiple tumor suppressor genes and oncogenes. We present a rare case of CD56-negative ANKL and review the clinical and laboratorial criteria for the diagnosis, as well as the available therapies.

Case Presentation

A European 36-year-old male presented with acute onset fever, pallor, weakness, and jaundice. He had hepatosplenomegaly, severe pancytopenia, hepatic cytolysis, and very high serum lactic dehydrogenase levels. The bone marrow studies resulted in the diagnosis of an EBV-positive, CD56-negative ANKL. The patient failed to respond to gemcitabine and cisplatin-based polychemotherapy, dying three months later with leukemic meningitis and multiple cranial nerves palsies.

Conclusions

The diagnosis of ANKL is difficult and requires both clinical suspicion and an extensive laboratorial approach. Absence of CD56 expression on the neoplastic NK cells may impose difficulties in the diagnosis, which requires morphological, immunophenotypic, histopathological, immunohistochemical, cytogenetic, and molecular studies.

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.

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 cells and the syndrome of chronic natural killer cell lymphocytosis

Natural killer (NK) cells provide anti-infectious, anti-neoplastic, and immunomodulatory function effected by both cytokine production and direct cellular cytotoxicity that is not major histocompatibility complex-restricted. NK cells lack truly specific cell surface determinants as well as antigen-specific receptors. Recent information suggests a variety of receptor-ligand interactions that underlie recognition and treatment of target cells by NK cells. Primary NK cell disorders in humans are currently classified into NK cell lymphomas and chronic NK cell lymphocytosis (CNKL). In this review, we summarize current understanding of the biology of NK cells and describe the clinical manifestations of CNKL.

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

Chronic natural killer cell lymphocytosis is a persistent state of natural killer (NK) cell (CD3-CD16/CD56+) excess in the peripheral blood that is not associated with clinical lymphoma. In 16 consecutive patients (median age 60.5 years, range 7-77), males were overrepresented (M:F 7:1) and the median absolute NK cell count was 4.09 x 10(9)/l (range 1.2-16.6). Bone marrow examination was performed in 14 patients and showed atypical granulomata in two; chromosome studies in seven patients were normal. Clonal T-cell receptor gene rearrangement was not found in any of 12 patients evaluated. At presentation, seven patients (44%) had no clinical symptoms or signs and the others had vasculitic skin lesions (three patients), non-neutropenic fever (three patients), recurrent neutropenic infection (two patients), musculoskeletal symptoms (two patients), peripheral neuropathy (two patients), aphthous ulcers (one patient), and splenomegaly (one patient). Five patients had anaemia, five had neutropenia, and two had thrombocytopenia. After a median follow-up of 5.1 years (range 0-10.2) from immunophenotypic diagnosis or 5.7 years (range 0.1-14.1) from documentation of absolute lymphocytosis, vasculitic glomerulonephritis developed in one patient, accelerated splenomegaly developed in a patient receiving myeloid growth factor treatment, and severe aplastic anaemia developed in one patient. Treatment with nonsteroidal anti-inflammatory drugs or immunosuppressive agents was variably successful.