'Supernatural' killer cells

Reactivation of latent human cytomegalovirus in CD14(+) monocytes is differentiation dependent

We have previously demonstrated reactivation of latent human cytomegalovirus (HCMV) in myeloid lineage cells obtained from healthy donors. Virus was obtained from allogenically stimulated monocyte-derived macrophages (Allo-MDM), but not from macrophages differentiated by mitogenic stimulation (ConA-MDM). In the present study, the cellular and cytokine components essential for HCMV replication and reactivation were examined in Allo-MDM. The importance of both CD4(+) and CD8(+) T cells in the generation of HCMV-permissive Allo-MDM was demonstrated by negative selection or blocking experiments using antibodies directed against both HLA class I and HLA class II molecules. Interestingly, contact of monocytes with CD4 or CD8 T cells was not essential for reactivation of HCMV, since virus was observed in macrophages derived from CD14(+) monocytes stimulated by supernatants produced by allogeneic stimulation of peripheral blood mononuclear cells. Examination of the cytokines produced in Allo-MDM and ConA-MDM cultures indicated a significant difference in the kinetics of production and quantity of these factors. Further examination of the cytokines essential for the generation of HCMV-permissive Allo-MDM identified gamma interferon (IFN-gamma) but not interleukin-1 or -2, tumor necrosis factor alpha, or granulocyte-macrophage colony-stimulating factor as critical components in the generation of these macrophages. In addition, although IFN-gamma was crucial for reactivation of latent HCMV, addition of IFN-gamma to unstimulated macrophage cultures was insufficient to reactivate virus. Thus, this study characterizes two distinct monocyte-derived cell types which can be distinguished by their ability to reactivate and support HCMV replication and identifies the critical importance of IFN-gamma in the reactivation of HCMV.

Production of natural killer cell activity-augmenting factor (interleukin-6) by human epiphyseal chondrocytes

OBJECTIVE

We sought to determine the capacity of human epiphyseal chondrocytes to modulate the cytotoxic activity of human natural killer (NK) cells by determining whether they release interleukin-6 (IL-6), a cytokine recently shown to stimulate NK cell activity.

METHODS

Conditioned medium from human epiphyseal chondrocyte cultures (Ch-CM) was tested for IL-6 activity using the B9 cell hybridoma assay. Its NK cell-stimulating capacity in the presence of K562 (myelogenous leukemia) cells or human chondrocytes was evaluated in a 4-hour 51Cr-release assay. Ch-CM-derived IL-6/NK cell-augmenting factor activity was partially purified by high-performance liquid chromatography (HPLC) gel filtration and Western blot.

RESULTS

Ch-CM contained an NK cell-augmenting factor (NKAF) which was blocked by IL-2 or IL-6 antibodies. Ch-CM did not contain detectable IL-2 activity, but it stimulated IL-2 production by human peripheral blood lymphocytes (PBL). This IL-2-inducing capacity was inhibited by IL-6 antibodies, indicating that chondrocytes release an IL-6-like activity. Ch-CM significantly enhanced the proliferation of IL-6-dependent B9 hybridoma cells, and Western blot analysis of Ch-CM revealed specific bands corresponding to those of highly purified IL-6. Upon HPLC gel filtration, chondrocyte NKAF copurified with chondrocyte IL-6. Pure IL-6 and chondrocyte IL-6 were tested for their ability to stimulate the cytotoxic activity of human PBL against chondrocytes. Both mediators significantly enhanced chondrocyte killing. Lysis of chondrocytes by PBL was mediated by NK cells, since depletion of CD16+ cells resulted in inhibition of the activity.

CONCLUSION

Thus, upon stimulation, chondrocytes produce IL-6 which, through IL-2 induction, augments the activity of NK cells against K562 target cells as well as against chondrocytes.

Factors predictive of post-transplant erythrocytosis

Ninety-three patients with PTE (that is, hematocrit 51% or greater) were identified among 431 renal transplant recipients, an incidence of 21.6%. Thirty-eight patients underwent blood volume measurements, and 22 of these had high red cell volume and therefore were considered to have true PTE. To analyze factors predictive of erythrocytosis, a control group with normal hematocrit was randomly selected from our renal transplant population and compared with the 93 patients with PTE, and with the 22 who had true PTE. Using step-wise logistic regression analysis, we identified three variables that were consistent predictors of PTE. In order of significance, the serum creatinine value at the onset of PTE appears to most strongly predict the occurrence of PTE (P less than 0.0001). As creatinine value increases, the probability of PTE decreases. Next was immunosuppression, where double immunosuppressive therapy was associated with a greater probability of PTE than triple therapy (P less than 0.0001). The overall incidence of PTE in patients on double therapy was 34%, while that for those on triple therapy 10.4%. Last was duration of dialysis for which increasing values correspond to increasing probability of PTE (P = 0.004). Comparison of the serum erythropoietin (EPO) levels for patients and controls yielded a nonsignificant result (P = 0.2507 and P = 0.383 for all patients with PTE and true PTE, respectively), and therefore EPO levels were inappropriately elevated for the level of hematocrit in the PTE group. Only the number of rejections and duration of follow-up (r = -0.3507) were significantly correlated with EPO (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Murine models of autoimmune diabetes: nonspecific cytotoxic lymphocytes derived from pancreatic islets in the presence of IL-2

Our aim was to derive T lymphocyte lines that specifically recognize islet antigens in murine models of autoimmune diabetes. Islets of Langerhans infiltrated with lymphocytes were isolated either from mice previously injected with multiple low doses of streptozotocin or from NOD-WEHI mice and were cultured in the presence of the T cell growth factor, interleukin 2 (IL-2). With islets from both models of autoimmune diabetes, rapidly proliferating, large granular lymphocytes emerged after 7-10 days and destroyed the islets and other cells such as fibroblasts in the cultures. Cytotoxicity assays showed that these cells were capable of destroying both P815 and YAC-1 tumor cells. In contrast to lymphocytes present initially in the islet infiltrates which express predominantly the L3T4 marker, the large granular lymphocytes were shown to be Ly-2 positive. They also expressed the alpha beta T cell receptor and contained mRNA for the alpha beta T cell receptor demonstrable by in situ hybridization. While morphologically similar to NK cells these large granular lymphocytes bear T cell markers and destroy a broader range of targets. They may represent a minor population of T lymphocytes particularly responsive to IL-2 although other studies show that T cells generally can develop a similar phenotype after prolonged culture with IL-2. The lack of target cell specificity indicates that these IL-2-stimulated large granular lymphocytes are unlikely to mediate the immunopathogenesis of diabetes in these animal models.

Suppression of human granulocyte-macrophage colony formation in vitro by natural killer cells

This study has demonstrated the ability of human bone marrow natural killer (NK) cells to inhibit the formation of granulocyte-macrophage colonies from autologous bone marrow derived committed progenitors in vitro. NK cell activity was demonstrated in all marrow samples and could be significantly increased by pretreatment of the bone marrow mononuclear cells with IFN-alpha. Bone marrow preincubated with IFN-alpha produced significantly fewer colonies in both Day 7 and Day 14 colony assays compared with untreated marrow. Removal of active NK cells by Leu 11b and complement significantly increased the number of colonies observed in both Day 7 and Day 14 assays, but this was not the case when NK cell-depleted marrow was treated with IFN-alpha prior to the GM assays. These results have further shown that NK cells and IFN-alpha are involved in regulating granulopoiesis by demonstrating that IFN-alpha can inhibit granulocyte/macrophage colonies in the presence or absence of NK cells in the bone marrow.

Activated killer cell lymphoma: an erythrophagocytic syndrome simulating histiocytic medullary histiocytosis

We report a detailed analysis of a lymphoma-induced erythrophagocytic syndrome mimicking histiocytic medullary reticulosis. Phenotypic analysis of cell surface molecules demonstrated a T cell-like phenotype. However, more extensive analysis showed that this phenotype was not typical of any element of the normal T cell lineage. The markers were consistent with a subset of natural killer cells, the lymphokine-activated killer (LAK) cell. The lymphoma cells, like normal LAK cells, were shown to be capable of non-specific cytotoxicity. Moreover, consistent with the reported regulatory effects of certain non-specific killer cells on hemopoiesis, the lymphoma cells were able to suppress in-vitro hemopoiesis, especially maturation of erythroid precursors, although a soluble factor could not be directly demonstrated. Both of these activities were blocked by a monoclonal antibody (9.IC3) which inhibits NK cell function. These findings imply that this tumour is a neoplastic counterpart of the cell identifiable in vitro as an LAK cell.

Methylprednisolone therapy in aplastic anaemia: correlation of in vitro tests and lymphocyte subsets with clinical response

20 patients with aplastic anaemia were treated with methylprednisolone 1 g/d for 3 d followed by prednisolone 60 mg on alternate days. At 3 months after therapy, 7 of 20 patients (35%) showed recovery, 2 had died and 11 were non-responders. Only newly diagnosed patients were responders. Results of in vitro tests were correlated with clinical response. The first test was designed to determine whether removing various subpopulation of cells would increase the numbers of progenitor cells. In the second test blood cells were collected at 1 month after starting treatment and assayed for progenitor cells. Data from both tests did not correlate with the response to therapy. Lymphocyte subsets were measured in the blood before and at 1 month after treatment. The absolute numbers of OKT3+, OKT4+ and OKT8+ cells were significantly decreased compared to the normal population. The number of HNK1+ cells was also decreased but no significant difference was observed. Responders had a higher number of HNK1+ cells compared to non-responders. No significant differences of OKT3+, OKT4+ and OKT8+ cells among responders and non-responders were observed. Therefore a high number of HNK1+ cells prior to therapy may identify patients responding to the treatment.

Modulation of human natural killer cell function by cytokines and rheumatic disease

The activity of natural killer (NK) cells can be modified by a number of factors that either increase or suppress cytotoxicity. We have investigated in detail the cytokine induced killing of a NK resistant renal carcinoma cell line Cur by human NK cells. Preincubation of peripheral blood mononuclear cells with interferon alpha (IFN alpha), interleukin 2 (Il-2), interleukin 1 (Il-1) and tumor necrosis factor alpha greatly increased the rate and magnitude of Cur killing. Positively selected CD16 (+) cells were found to respond to cytokine stimulation and to mediate Cur killing. The effects of Il-2 and IFNa could be upregulated by costimulation of effector cells with Il-1 or TNF alpha. It was shown that TNF alpha induced Il-2 receptor expression on CD16(+) cells alone and even more in combination with Il-2. Studies of NK cell function in various rheumatic diseases revealed reduced NK cytotoxicity in peripheral blood and synovial fluid (SF), both in rheumatoid arthritis (RA) and juvenile rheumatoid arthritis (JRA). By contrast, normal NK function was found in patients with ankylosing spondylitis (AS) and psoriatic arthritis. A discordance with regard to the percentage of Leu 7 positive mononuclear cells and NK function in peripheral blood and SF was demonstrated. Minimal expression of Leu 7 positive cells and cytotoxicity was present in synovial membranes. NK function in rheumatic disease was largely independent of drug therapy. Natural killer (NK) cells are a subset of lymphocytes that mediate spontaneous cytotoxicity against certain tumor and virus infected cells without any known prior sensitation.(ABSTRACT TRUNCATED AT 250 WORDS)

The lymphoproliferative disease of granular lymphocytes. A heterogeneous disorder ranging from indolent to aggressive conditions

A multiparameter analysis, which included the evaluation of clinical features, cell morphology, karyotype, phenotypic and functional immunologic findings, and T-cell receptor beta-chain configuration was performed on 34 patients with lymphoproliferative disease of granular lymphocytes (LDGL). The two-fold aim of the study was to identify the most useful tools that would more accurately characterize these patients and to deal with the problem of classifying these lymphoproliferative disorders. The data presented in this article suggest that a single parameter may not be sufficient to define the nature of the proliferating cells or to predict the clinical course of the disease and prognosis for the patient. The use of a multiparameter approach, however, may reach this goal, thus providing important prognostic and therapeutic information. Our study supports the concept that lymphoproliferative disease of granular lymphocytes is a heterogeneous disorder that ranges from indolent and possibly reactive conditions to the manifestation of aggressive malignancies.

Human leukocyte antigens: an update on structure, function and nomenclature

The study of human leukocyte antigens, predominantly by monoclonal antibody techniques, is a rapidly changing area of basic research and clinical investigation. This review outlines some of the results and trends of research in this field. Of particular importance is the updating of the current nomenclature. The CD classification of these antigens has become the standard form in published literature and provides a basis for standardization of clinical reporting. The current CD classification is presented in the form of a list, with a brief summary of each antigen beside each entry. The results reviewed range from the section on CD1 antigen in which the data presented are primarily concerned with the underlying biology of the antigens to the section on clinical application which has little biological content.

Specific helper T cell reactivity against autologous erythrocytes implies that self tolerance need not depend on clonal deletion

Using a culture system which supports primary T cell proliferative responses to various antigens we have detected mouse red blood cell (RBC)-reactive T cells in lymphoid tissues from untreated mice. The release of significant amounts of interleukin 2 (IL2) indicates that T helper (or helper/inducer) cells are activated by stimulation with RBC. Upon restimulation in vitro these cells proliferate specifically against mouse RBC with the kinetics and magnitude characteristic of a secondary response. Since autologous RBC are tolerated in vivo in spite of the presence of such specifically reactive T helper cells, these findings imply that self tolerance, even to certain nonsequestered antigens, may depend largely on regulatory mechanisms rather than on clonal deletion or inactivation.

Selective inhibition of human natural killing and antibody-dependent cellular cytotoxicity by a polyanion

A high molecular polyanion, Liquoid, was found to inhibit at nontoxic concentrations (12-50 micrograms/ml) the natural killing (NK) and the antibody-dependent cellular cytotoxic (ADCC) activity of human peripheral blood mononuclear cells selectively. Whereas NK of the K 562 target cell was slightly or not at all affected, the spontaneous lysis of PDe-B-1, an EBV-transformed B-cell line, was strongly inhibited or even completely abolished. ADCC activity could only be inhibited by Liquoid if the target cells were mycoplasma-free, while the polyanion had no effect when mycoplasma-contaminated target cells were used. Liquoid did not alter the target binding capacity of the NK effector cells and did not activate monocytes or induce other suppressive cells. Alpha interferon, but neither beta nor gamma interferon, was able to neutralize the NK reduction. These results suggest that Liquoid inhibits a target cell-related, selective process in the post-binding stage of NK cell lysis.

Administration of recombinant interleukin 2 to mice enhances production of hemopoietic and natural killer cells

Seven days of continuous perfusion of mice with human recombinant interleukin 2 (rIL 2) (approximately 3 X 10(4) U/day) increased the percentage of large mononuclear leukocytes (LML) among bone marrow, spleen, lymph node cells and liver interstitial cells (LIC). An increase in the lymphokine-activated killer (LAK) activity was evident in these organs. The greatest increase in the number of LML and in the LAK activity was observed among the liver interstitial cells (about 500-fold increase). The LML were nonphagocytic, Thy-1+, sIg-, Ly 2+, L3T4- and asialo Gm1+. Perfusion of athymic nude mice, or of thymectomized, irradiated radiation chimera, showed that the Thy-1+, LAK+ LML were the thymus and T lymphocyte-independent progeny of Thy-1- marrow precursors. The LML had no T cell function in a graft-vs.-host reactivity assay, neither did they have an inhibitory effect on T lymphocyte function in vivo. rIL 2 perfusion did not significantly affect the medullary hemopoiesis but did strongly enhance the extramedullary hemopoiesis, particularly within the interstice of the liver: the number of erythroid and myeloid cell was increased as well as the number of colony-forming units per spleen and colony-forming units per culture for various lineages (20-50-fold increment). These results show that in vivo, rIL 2 has a global enhancing effect on hemopoiesis together with a more selective influence on the production of LML.