Natural Killer Activity Of Lymphocytes Research Articles

Hemophagocytic lymphohistiocytosis: pouring gasoline on the cytokine storm

Hemophagocytic lymphohistiocytosis should be considered in patients with persistent fever, hepatosplenomegaly, pancytopenia. Hypercytokinemia originated from genetic disorder effecting the cellular defects of cytotoxic T and natural killer lymphocyte activity is the underlying pathophysiology of the disorder. In this review we summarized the recent advances in the management of hemophagocytic lymphohistiocytosis.

The effects of co-transplantation of bone marrow hematopoietic stem cell and thymic multipotent stromal cells on the immune system of mice during its regeneration after cyclophosphamide treatment

The multipotent stromal cells (MSCs) are considered as one of the most promising agents for regenerating the immune system due to its powerful secretion of reparative factors and immunomodulatory properties.The purpose of the study is to investigate the effect of co-transplantation of bone marrow hematopoietic stem cells (HSCs) and thymic multipotent stromal cells (MSCs) on regeneration of murine immune system damaged by cyclophosphamide.Materials and methods. MSCs were obtained from thymuses of C57BL mice using explant technique. Bone marrow cells (BMCs) were obtained by flushing out the femur with nutrient medium. The immune deficiency of mice was modelled by the treatment with cyclophosphamide. After that, the cells were co-transplanted and the parameters of the immune system was evaluated. We determined the total number of erythrocytes, hematocrit, and hemoglobin concentration in peripheral blood; phases of the cell cycle and apoptosis of the cells of the mesenteric lymph nodes; the number of antibody-producing cells in the spleen; delayed type hypersensitivity (DTH); proliferative and cytotoxic activity of natural killer lymphocytes; phagocytic activity, level of spontaneous and induced bactericidal activity of peritoneal macrophages.Results. It was shown that in contrast to BMCs, the use of MSCs alone or co-transplantation of these cells increased the spontaneous proliferative activity of lymphocytes with a significant decrease in the number of lymph node cells in G0/G1 phase by 9.2 % and an increase in the number of lymphocytes in G2-M+S phase by 35 %, as well as restoring cellularity of bone marrow, thymus and lymph nodes in mice treated with cyclophosphamide. Regeneration of erythropoiesis was stimulated by BMCs, which was manifested by the normalization of hematocrit and hemoglobin, and an increase in the number of reticulocytes in the blood by 2.2 times compared with the group of mice receiving cyclophosphamide. Co-transplantation had less pronounced, but similar effect. Transplantation of thymic MSCs stimulated the natural cytotoxicity of splenocytes by 2.7 times and substantially increased the number of antibody-producing cells in the spleen by 1.7 times compared with the group of mice receiving cyclophosphamide. Co-transplantation had a pronounced suppressive effect on the blast transformation reaction induced by phytohemagglutinin by 1.7 times, but showed a stimulating effect on DTH response by 1.46 times. Transplantation of BMCs did not affect the functional activity of the immune system.Conclusion. The effects of co-transplantation of BMCs and thymic MSCs are realized in the several parts: stimulation of hematological parameters recovery (like under the effect of BMCs separately), normalization of cell number of lymphoid organs (as under the impact of thymic MSCs); inhibition of blast transformation activity and stimulation of DTH are the effects of co-transplantation.

The effect of transplantation of bone marrow cells induced by the contact with thymus-derived multipotent stromal cells on the immune system of mice, regenerating after cyclophosphamide treatment

The effect of transplantation of syngeneic bone marrow cells (BMCs) after their contact in vitro with thymus-derived multipotent stromal cells (MSCs) for regeneration of damaged by cyclophosphamide immune system of mice was studied.Materials and methods. MSCs were obtained from C57BL/6 mice’s thymus by explants method. BMCs were obtained by flushing the femurs. BMCs were induced for 2 hours on the monolayer of thymus-derived MSCs. The immune deficiency of mice was modelled using cyclophosphamide injection. After that, cell transplantation was performed and the state of the immune system was assessed. The number of erythrocytes, hematocrit, hemoglobin concentration in the peripheral blood; the phases of the cell cycle and apoptosis of mesenteric lymph node cells were determined. The amount of antibody-producing cells in the spleen and the delayed hypersensitivity response was determined. The study of proliferative and cytotoxic activity of natural killer lymphocytes, the analysis of phagocytosis, spontaneous and induced bactericidal activity of peritoneal macrophages were performed.Results. It was shown that unlike intact bone marrow cells, BMCs induced by thymus-derived MSCs provided increased spontaneous proliferative activity of lymphocytes with a decrease in the number of lymph node cells in G0/G1 phase by 6.2 % and an increase the number of lymphocytes in S+G2/M phase by 28 % in comparison with the group of mice treated with cyclophosphamide, as well as the recovery of cellularity of the bone marrow, lymph nodes and spleen. At the same time in the lymph nodes, the number of cells in the apoptosis increased. BMCs induced by MSCs showed a pronounced negative effect on natural cytotoxicity, reducing its rates by 3 times compared with the group of cyclophosphamide-treated mice, and on adaptive immunity: the rates of delayed hypersensitivity response decreased by 1.7 times, number of antibody-producing cells by 1.8 times. Red blood cell regeneration was stimulated by intact BMCs, which was manifested by the normalization of hematocrit and hemoglobin and an increase in the number of reticulocytes in the blood by 2.2 times compared with the group of mice treated with cyclophosphamide.Conclusion. Transplanted BMCs improve erythropoiesis in mice after cyclophosphamide treatment, and BMCs, previously induced by thymus-derived MSCs, lose this ability. BMCs after co-culture are strongly activated to impact on the immune system, which is most likely due to the effect of contact interaction with thymus-derived MSCs, which is known, effectively affect hematopoietic cells and possess immunomodulatory properties.

Genes controlling the activation of natural killer lymphocytes are epigenetically remodeled in intestinal cells from germ-free mice.

Remodeling of the gut microbiota is implicated in various metabolic and inflammatory diseases of the gastrointestinal tract. We hypothesized that the gut microbiota affects the DNA methylation profile of intestinal epithelial cells (IECs) which could, in turn, alter intestinal function. In this study, we used mass spectrometry and methylated DNA capture to respectively investigate global and genome-wide DNA methylation of intestinal epithelial cells from germ-free (GF) and conventionally raised mice. In colonic IECs from GF mice, DNA was markedly hypermethylated. This was associated with a dramatic loss of ten-eleven-translocation activity, a lower DNA methyltransferase activity and lower circulating levels of the 1-carbon metabolite, folate. At the gene level, we found an enrichment for differentially methylated regions proximal to genes regulating the cytotoxicity of NK cells (false-discovery rate < 8.9E−6), notably genes regulating the cross-talk between NK cells and target cells, such as members of the NK group 2 member D ligand superfamily Raet. This distinct epigenetic signature was associated with a marked decrease in Raet1 expression and a loss of CD56+/CD45+ cells in the intestine of GF mice. Thus, our results indicate that altered activity of methylation-modifying enzymes in GF mice influences the IEC epigenome and modulates the crosstalk between IECs and NK cells. Epigenetic reprogramming of IECs may modulate intestinal function in diseases associated with altered gut microbiota.—Poupeau, A., Garde, C., Sulek, K., Citirikkaya, K., Treebak, J. T., Arumugam, M., Simar, D., Olofsson, L. E., Bäckhed, F., Barrès, R. Genes controlling the activation of natural killer lymphocytes are epigenetically remodeled in intestinal cells from germ-free mice.

The cellular factors of innate immunity in nonpsychotic patients at high risk for schizophrenia

Changes in the parameters of innate immunity in patients with schizophrenia are observed already in the first episode. The study was performed to find out whether these changes take place prior to disease manifestation, and what role do they play in the pathogenesis of schizophrenia. Thirty-five male nonpsychotic patients at high risk of psychosis, aged between 17 to 23 years, were examined. Phagocyte activity (PA) of neutrophils in the blood serum was evaluated by the number of active neutrophils, i.e. phagocytic index (PhI), and phagocytic number (PhN), which was determined by counting latex particles absorbed with a single phagocytic cell. Cytotoxic activity of natural killer lymphocytes (NK CA) was evaluated by the number of cell targets K-562, which remained non-degraded after the contact with natural killer cells. The influence of monocytes on NKCA was determined as well. Compared to controls, patients had the lower PhI level (p<0.001) which was compensated by the increase in PhN levels, and the lower NK CA level which was increased due to the influence of monocytes. Negative correlations between PhI and PhN (r= -0.83, p<0.01) and between the level of NKCA and PhI (r= -0.83, p<0.05) as well as the positive correlation between PhN and SOPS scores (r=0.69, p<0.01) were found. After treatment, there was the decreasein the severity of mental disorders (p<0.001). The level of PhAN was normalized in 61.9% of patients compared to 36.7% before treatment. After treatment, the proportion of patients with normal levels of NK CA was the same as before treatment (40 and 35%, respectively). The immune disturbances revealed in the study may play a role in the pathogenesis of the disease and have predictive value for schizophrenia.

Restoration of innate host defense responses by oral supplementation of branched‐chain amino acids in decompensated cirrhotic patients

It has been reported that host defense responses, such as phagocytic function of neutrophils and natural killer (NK) cell activity of lymphocytes, are impaired in cirrhotic patients. The aim of the present study was to examine the effects of oral supplementation of branched-chain amino acids (BCAA) on host defense mechanisms in peripheral blood of patients with decompensated cirrhosis. Ten patients with decompensated cirrhosis received 12 g BCAA daily for 3 months. Phagocytic function of neutrophils and NK activity of lymphocytes as well as serum albumin levels and Fisher's ratios were determined before and at 1 and 3 months of BCAA supplementation. For quantification of phagocytic function, fluorescent intensities of cells in the neutrophil region in the cytogram were determined by flow cytometry after incubation of whole blood with fluorescent microspheres. NK activity was estimated by (51)Cr release assay using K-562 cell line as target cells. Phagocytic function of neutrophils was significantly improved by 3-month BCAA supplementation (P < 0.01). Thechanges of NK activity were also significant at 3 months of supplementation compared with before supplementation (P < 0.01). Fisher's ratios were significantly increased at 3 months of BCAA supplementation compared with those before oral supplementation (P < 0.05), although the changes of serum albumin level were not statistically significant. BCAA oral supplementation improved phagocytic function of neutrophils and NK activity of lymphocytes in cirrhotic patients. BCAA supplementation may reduce the risk of bacterial and viral infection in patients with decompensated cirrhosis.

Anti-myeloma activity of natural killer lymphocytes.

Natural killer (NK) cells are assumed to contribute to a graft-versus-leukaemia effect. In vitro experiments have shown that many leukaemic cells are NK-cell sensitive. Nevertheless, no data concerning the influence of purified NK cells on malignant myeloma (MM) cells exist. We co-incubated NK cells with three different MM cell lines and fresh bone marrow samples of nine MM patients. The proportion of vital MM cells was determined before and after co-cultivation by a flow-cytometry-based assay. All MM cells tested, with the exception of one cell line (NCI H929), were susceptible to a NK-cell attack even without exogenous interleukin 2 (IL-2). The mean killing of the native MM samples was 23.1 +/- 5.4% and 34.5 +/- 6.5% at 10:1 and 20:1 effector:target ratio respectively, This corresponded to about 2/3 of those values obtained with the highly sensitive line K562. In contrast, CD34-positive haematopoietic stem cells as well as peripheral mononuclear cells were completely resistant under similar experimental conditions (1.3% killing). To elucidate the underlying triggering mechanisms, we measured human leucocyte antigen (HLA)-class I expression of the MM cells. No evidence for HLA loss, which could have explained the NK-cell recognition if it occurred, was demonstrated. These findings may contribute to the understanding of in vivo NK-cell activation and encourage clinical applications of NK cells for MM patients.

Role of γ-globulin-associated fraction containing carbohydrate component inin vitro regulation of human natural killer activity

Carbohydrate-rich components released from fractions of aggregated and protein aggregate-free γ-globulins decreased the cytotoxicity of natural killer cells in relation3H-uridine-labeled standard human K562 erythroblasts. In a dose of 0.1 μg/ml, these components decreased activity of natural killer lymphocytes by 57% and 42%, respectively. The data suggest that γ-globulin-associated fractions containing carbohydrate components are involved in the regulation of human natural killer activity.

Experimental Induction and Termination of Acute Psychological Stress in Human Volunteers: Effects on Immunological, Neuroendocrine, Cardiovascular, and Psychological Parameters

The present research investigated the effects of controlled experimental manipulations of stress on biological and psychological reactions. Fifty young adult male volunteers were exposed to a 12-min period of stress induced by the threat of an unavoidable, painful electric shock. A 12-min period without this threat preceded or followed the stress period. Blood was drawn during the 4th and the 12th minute of each period. Anticipatory threat led to significant elevations in the proportions and cytotoxic activity of natural killer (NK) lymphocytes, plasma epinephrine levels, pulse rate, and reported level of tension, and to a reduction in the CD4/CD8 ratios. The no-threat period induced a return to baseline values for epinephrine, pulse rate, and tension, and lower than baseline levels for cytotoxic activity of NK lymphocytes, within a similarly short time span. The findings underline the rapidity with which physiological changes may transpire in the course of a brief and acute period of psychological stress, and the rapidity of their reversal upon relief from the stressor.

Ursodeoxycholic acid corrects defective natural killer activity by inhibiting prostaglandin E2 production in primary biliary cirrhosis

We evaluated the effect of ursodeoxycholic acid on the defective natural killer activity in primary biliary cirrhosis. Administration of ursodeoxycholic acid (600 mg daily) for one month significantly increased natural killer activity in patients with primary biliary cirrhosis (P < 0.05). Ursodeoxycholic acid also enhanced the in vitro natural killer activity of lymphocytes from healthy volunteers, while other hydrophobic bile acids depressed it. Furthermore, ursodeoxycholic acid reduced the prostaglandin E2 concentration in culture supernatants of lymphocytes from healthy volunteers to a lower level than that in culture incubated with chenodeoxycholic acid (P < 0.05) or control cultures (P < 0.01). Urosdeoxycholic acid normalized the defective natural killer activity in primary biliary cirrhosis by reducing the levels of other hydrophobic bile acids and inhibiting prostaglandin E2 production, suggesting that it may be a useful immunomodulating agent for primary biliary cirrhosis.

MIB 1 Immunostaining in Stage I Squamous Cervical Carcinoma: Relationship with Natural Killer Cell Activity

The aim of the study was to investigate the prognostic significance of estimating tumor cell proliferation in stage I cervical squamous carcinoma by analyzing MIB 1 immunostaining with respect to the lesion size, lymphatic spread, and clinical outcome. A possible relationship between MIB 1 index and natural killer activity was also discussed. The medical records of 34 patients with stage I squamous cervical carcinoma who had undergone primary radical surgery at the Institute of Gynecologic and Obstetrics, Ancona University, between 1988 and 1993, were recruited from our series of 57 consecutive cases and reviewed. Thirty-one patients were considered eligible for the study and evaluated for age, demographic characteristics, tumor histologic grade, tumor size, lymphatic spread, and adjuvant radiotherapy. The expression of primary tumor proliferation related to Ki67 antigen was immunohistochemically evaluated by monoclonal MIB 1 antibody (Immunotech, Marseille Cedex, France) on microwave oven-processed formalin-fixed paraffin-embedded tissue. The basal natural killer cell activity of peripheral blood lymphocytes was evaluated against K562 cell line and expressed in lytic units for each patient. The MIB 1 immunostaining was significantly related with tumor size ( P = 0.001) and lymphatic spread ( P = 0.009); in contrast, there was no relationship between grade of histologic differentiation and MIB 1 immunostaining. The Cox proportional hazards analysis showed a significant independent relationship between MIB 1 immunostaining and disease-free survival ( P = 0.004). The analysis of natural cytotoxicity defined a significant inverse relationship between peripheral blood lymphocyte's natural killer activity and tumor MIB 1 immunostaining ( r = -0.07, with P = 0.03). Our data defined the prognostic significance of tumor cell proliferation immunostaining, an interesting parameter correlated with the disease-free survival in locally advanced cervical carcinoma. The relationship between MIB 1 index and natural killer activity is interesting; natural cytotoxicity seems to he altered in the host with respect to the cervical carcinoma characteristics.

Selective inhibitory effects of stress hormones on natural killer (NK) cell activity of lymphocytes from AIDS patients.

To examine the potential role of stress hormones in the progression of HIV infections, we developed an in vitro model system that investigates the effects of cortisol, adrenocorticotropin-releasing hormone (ACTH) and beta-endorphin on the natural killer cell activity of lymphocytes from normal subjects and AIDS patients. The system employs a 4 hr 51Cr release assay and K562 target cells. Direct addition of cortisol (0.05, 0.1, and 0.2 microgram/ml) or ACTH (10(-6) to 10(-8) M) to the mixture of effector and prelabeled target cells did not produce any significant immunoregulatory effects on the NK cell activity of normal lymphocytes. Direct addition of beta-endorphin (10(-13) to 10(-17) M) to the mixture of effector and prelabeled target cells did not produce any significant immunoregulatory effects on the NK cell activity of lymphocytes from normal or AIDS subjects. However, cortisol and ACTH significantly inhibited the NK activity of lymphocytes from AIDS patients. The selective inhibitory effects of cortisol and ACTH in patients with HIV infections are consistent with a model which proposes that stress related neurohormones and/or neuropeptides may be involved in the progression of HIV infections.

HPV DNA positivity and natural killer cell activity in the clinical outcome of mild cervical dysplasia: integration between virus and immune system.

The objective was to examine the prevalence of human papillomavirus (HPV) DNA infection in mild cervical dysplasia and to evaluate longitudinally the persistence of HPV DNA positivity in an observational study, aiming at identifying the role of peripheral blood lymphocyte natural killer activity in the natural history of dysplastic disease. Twenty-three patients with histologically proven mild cervical dysplasia were selected. The HPV DNA positivity, determined by polymerase chain reaction, and cervical dysplasia were monitored cytologically and colposcopically at the 3rd (time 1), 6th (time 2) and 12th months (time 3), and defined by biopsies for routine histology taken at times 2 and 3. For each patient included in the study, the immune reactivity was evaluated at the time of diagnosis and afterwards, longitudinally during the follow-up. The immune status analysis included T lymphocyte subsets (CD3, CD4, CD8, CD56, CD16 monoclonal antibodies by Beckton Dickinson, Mountain View, Calif., USA) and determinations of natural killer cell activity (against the sensitive cell line K 562). Eighteen out of the 23 women with mild cervical dysplasia (78.3%) were found positive for HPV DNA, with a significantly high representation of HPV DNA type 16 (55.6% of cases). At the end of the study, 12 out of 18 HPV-DNA-positive women became negative (defined by two or more negative tests) for the original HPV DNA type, with 66.7% of spontaneous HPV DNA negativization rate (p = 0.6).(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of cytokines on oxygen radical products from pulmonary alveolar cells and peripheral monocytes, and natural killer activity of lymphocytes in lung cancer

The effects of cytokines on oxygen radical products from pulmonary alveolar cells and peripheral monocytes, and natural killer activity of lymphocytes in lung cancer

Selective effect of alcohol on cellular immune responses of lymphocytes from AIDS patients

In this study we examined the in vitro effects of alcohol on the proliferative responses of lymphocytes from healthy donors and AIDS patients to a recombinant fusion peptide, env-gag, corresponding to portions of the gp 41 envelope (env) and internal core (gag) proteins of HIV. The effects of alcohol (ETOH) on the natural killer (NK) cell activities of lymphocytes from healthy donors and patients with AIDS were also investigated. Peripheral blood mononuclear cells from both normal donors and AIDS patients produced significant levels of lymphocyte proliferative responses to the HIV env-gag peptide; however, these responses were significantly higher in patients with AIDS, showing the specificity of the response. The env-gag-induced proliferative responses of lymphocytes from normal subjects were significantly suppressed when cultures contained only higher levels of ETOH (0.2% and 0.3%), whereas ETOH even at a lower level (0.1%) produced significant suppression of the env-gag-induced proliferation of lymphocytes only from AIDS patients. Direct addition of ETOH at concentrations of 0.1%, 0.2%, and 0.3% to cultures of lymphocytes from normal donors and NK target cells did not produce significant suppression of NK cell activities. However, ETOH at concentrations of 0.2% and 0.3% significantly suppressed the NK activities of lymphocytes from AIDS patients, and the suppressive effect was observed at all E:T cell ratios examined. Control peptide from the Escherichia coli expression vector did not produce any significant effect on lymphocyte proliferative responses or NK activity of both normal donors and AIDS patients. ETOH at various concentrations (0.1%, 0.2%, and 0.3%) or env-gag (10 ng/ml), when individually added to cultures of NK effector and target cells and allowed to remain throughout the 4-h assay period, produced no significant suppression of the NK activity of normal lymphocytes. This suggests a selective inhibitory effect of ETOH on lymphocyte proliferative responses and NK activity of lymphocytes from AIDS patients. Thus ETOH at intoxicating levels may have immunomodulatory effects on the host's immune responses to HIV infection.

Suppression of natural killer cell activity by granulocytes in patients with aplastic anemia: role of granulocyte colony-stimulating factor

Patients with aplastic anemia were tested for natural killer (NK) activity, and the roles of granulocytes and granulocyte colony-stimulating factor (G-CSF) in the regulation of cytotoxicity were evaluated. Blood lymphocytes showed low or no NK activity against K562 targets. The depression of NK activity was more frequently recorded for patients who were not in remission and those who received G-CSF administration. Granulocytes of aplastic anemia patients with impaired NK activity suppressed the lytic activity of NK cells. By contrast, granulocytes from normal controls and aplastic anemia patients with normal NK activity had no suppressive activity. There was a good correlation between NK activity of lymphocytes and suppressive activity of granulocytes. Blocking of direct contact of suppressor and effector cells by cell chambers abolished suppression of cytotoxicity. NK suppression by granulocytes was resistant to treatment with catalase or superoxide dismutase. In vitro stimulation with G-CSF of granulocytes that naturally had no suppressive activity resulted in development of suppressive function, whereas granulocytes with natural suppressive activity were not further stimulated in vitro by G-CSF to express augmented activity. These results suggest that the presence of suppressor granulocytes in the blood could be one cause of the impaired NK activity in patients with aplastic anemia.

Effect of Neuropeptide Y on Natural Killer Activity of Normal Human Lymphocytes

The in vitro effect of neuropeptide Y (NPY) on natural killer (NK) cell activities of normal lymphocytes was investigated. NPY at 10−9 to 10−12M concentrations produced significant suppression of NK activity against K 562 target cells. NPY at 10−9 to 10−12M concentrations also produced significant inhibitory effects on NK activities of NK-enriched large granular lymphocytes against LAV-infected 8E5/LAV target cells. The suppression was dose dependent against both targets. NPY-induced suppression of NK activity of lymphocytes against K 562 target cells was specifically reversed by rabbit anti-NPY antisera at 1:800 and 1:1600 dilutions, showing the specificity of reactions. Pretreatment of target cells with NPY concentrations capable of inhibiting NK activity did not affect the sensitivity of K 562 target cells for lysis by effector cells. Inhibition of cytotoxicity was not due to direct toxicity of effector cells, because lymphocytes treated with NPY showed normal levels of 51Cr release and their viability was comparable to that of untreated control cells. These studies demonstrated that NPY, a product of sympathetic nervous system activation, may have a significant immunoregulatory effect on NK cell activities of normal lymphocytes that may be of clinical significance.

Interferon-alpha in malignant and viral diseases. A review.

In the 35 years since the discovery of interferon, significant biological activity has been described for interferon-alpha (IFN alpha) in various cancers, particularly haematological malignancies such as hairy cell leukaemia and chronic myelogenous leukaemia. Except for localised therapy in bladder and ovarian cancer, activity against most solid tumours has been disappointing. Other notable exceptions include Kaposi's sarcoma, renal cell carcinoma and malignant melanoma, tumours known to be susceptible to immunological attack. More recently, broad spectrum antiviral activity has been demonstrated for both recombinant and naturally occurring IFN alpha. Hepatitis C is responsive to IFN alpha in about 40% of patients, but long term remissions are rare. In contrast, long term suppression of hepatitis B is common following IFN alpha therapy. Both diseases respond in a dose proportional fashion, with daily doses of 5 million units (MU) significantly more effective than lower doses. The mechanism of action in viral diseases involves the expression of unique antiviral proteins such as endonuclease and 2'-5'-oligoadenylate synthetase which enhance the destruction of viral RNA. General cellular protein synthesis is also inhibited, including cytochrome P450 enzymes. This forms the basis for potential drug interactions, with IFN alpha slowing the clearance of highly metabolised drugs such as theophylline. As an antitumour agent, the mechanism of action of IFN alpha is unclear, particularly in haematological cancers. In melanoma and renal cell carcinoma, antitumour effects may be mediated by augmented immune responses including activation of natural killer lymphocytes and enhanced expression of cell surface antigens (e.g. MHC I and II). Conversely, antibody formation to recombinant IFN alpha may result in a loss of activity. This has been observed in both renal cell cancer and hepatitis B and C. The elimination half-life of IFN alpha is short, 4 to 5 hours, but biological activity extends for 2 to 3 days after administration, which facilitates daily or thrice weekly administration. Clearance of IFN alpha is mediated by catabolism in the renal tubules; no intact drug is excreted in the urine. It is probable that the antiviral indications of IFN alpha will expand as the agent is more clearly recognised as a primary endogenous defence against various viral conditions.

Interleukin-2 bolus therapy induces immediate and selective disappearance from peripheral blood of all lymphocyte subpopulations displaying natural killer activity: Role of cell adhesion to endothelium

As early as 10–15 min after the start of a 30 min interleukin-2 (IL-2) infusion, a rapid, virtually complete disappearance of all natural killer (NK) lymphocyte subpopulations (including both CD3 − CD56 + and CD3 + CD56 + cells with either alpha/beta or gamma/delta T-cell receptor) was observed from peripheral blood. In contrast, the number of T lymphocytes (CD3 + CD56 −) was unmodified for at least 2 h after IL-2 injection. The IL-2-induced, rapid disappearance from peripheral blood of NK and NK-like lymphocytes may be related to their massive adherence to the activated endothelium. In this regard, IL-2 infusion caused a very rapid rise of tumour necrosis factor-alpha (TNF-α) plasma concentration, whereas other cytokines, such as interferon-gamma (IFN-γ), were induced only at later times. In vitro experiments indicated that IL-2, either alone or better combined with TNF-α, exerts a rapid and selective stimulatory effect on NK adhesion to endothelial cells. On the basis of these findings, we suggest that the activation of NK lymphocytes induced by IL-2, alone or combined with TNF-α, plays a key role in mediating the massive and selective adherence of NK and NK-like cells following IL-2 bolus infusion.

Differential staphylococcal protein a-induced enhancement of natural killer cell activity of lymphocytes from HIV-seropositive individuals

A decrease in Natural Killer (NK) cell activity is a common feature of the immune dysfunction found in patients with HIV-induced acquired immune deficiency syndrome (AIDS). We and others have shown earlier that staphylococcal protein A (SpA) preparations enhance NK cell activity against tumor targets. The present study was aimed at exploring whether the decreased NK activity of lymphocytes from HIV seropositive subjects could be modulated or restored in vitro by SpA. Two types of HIV-seropositive subjects were studied: hemophiliac and non-hemophiliac; matched controls were chosen among hospital staff and HIV-seronegative hemophiliac volunteers. In vitro proliferation and interleukin-2 (IL-2)/interferon gamma (IFNγ) release in response to mitogens were also studied. NK cell responses of peripheral blood lymphocytes (PBL) of HIV-seropositives were lower than those of seronegatives. However, exposure of PBL from HIV-seropositive individuals to SpA boosted their NK cell responses against NK-resistant target cells of tumor origin. The decrease in NK activity could not be attributed to the low number of NK cells, since no significant difference in NK cell number was observed between HIV-seropositive individuals and controls. Mitogen-induced blastogenic responses were present in all four groups, as was the mitogen-induced IFNγ release. We conclude that impaired NK activity and its boosting against NK-resistant targets after SpA induction is an important characteristic of lymphocytes of HIV-seropositive individuals regardless of the disease state and that this NK defect may not be irreversible. Our experimental model appears to open the door for mechanistic and molecular studies of the NK cell defect as well as for devising a new strategy for an immunotherapeutic approach to boost NK activity in HIV-infected subjects.