Enhancement of antibody-dependent cellular cytotoxicity of neonatal cells by interleukin-2 (IL-2) and IL-12

Local Interleukin-12 Treatment Enhances the Efficacy of Radiation Therapy by Overcoming Radiation-Induced Immune Suppression

Radiation therapy (RT) recruits myeloid cells, leading to an immunosuppressive microenvironment that impedes its efficacy against tumors. Combination of immunotherapy with RT is a potential approach to reversing the immunosuppressive condition and enhancing tumor control after RT. This study aimed to assess the effects of local interleukin-12 (IL-12) therapy on improving the efficacy of RT in a murine prostate cancer model. Combined treatment effectively shrunk the radioresistant tumors by inducing a T helper-1 immune response and influx of CD8+ T cells. It also delayed the radiation-induced vascular damage accompanied by increased α-smooth muscle actin-positive pericyte coverage and blood perfusion. Moreover, RT significantly reduced the IL-12-induced levels of alanine aminotransferase in blood. However, it did not further improve the IL-12-induced anti-tumor effect on distant tumors. Upregulated expression of T-cell exhaustion-associated genes was found in tumors treated with IL-12 only and combined treatment, suggesting that T-cell exhaustion is potentially correlated with tumor relapse in combined treatment. In conclusion, this study illustrated that combination of radiation and local IL-12 therapy enhanced the host immune response and promoted vascular maturation and function. Furthermore, combination treatment was associated with less systemic toxicity than IL-12 alone, providing a potential option for tumor therapy in clinical settings.

Maturation of the immune system in the fetus and the implications for congenital CMV

Congenital cytomegalovirus (CMV) infection is the most prevalent and consequential congenital infection, among others, that affects approximately 0.6% of all live births worldwide. Timing of maternal infection and maternal immune status largely determine the likelihood of a symptomatic infection. However, recent studies suggest that the fetal immune system, long perceived as naïve and immature, may also play a role in deciding the outcome of congenital CMV infection. Here, we review the development of four immune cells most pertinent to CMV control in the human fetus. αβT cells, B cells, natural killer (NK) cells, and γδT cells are all present, mature and partially functional in utero, and are capable of mounting some form of response to congenital CMV infection. Whether this response is negligible, effective, or harmful remains an open question. Expanding our knowledge of normal and abnormal immune development could provide clinicians with more accurate tools for the detection, monitoring, and treatment of congenital CMV infection in fetuses.

The newborn human NK cell repertoire is phenotypically formed but functionally reduced

BACKGROUND

Infection is a leading cause of death worldwide in babies under 1 month of age. Better vaccines and therapeutics are desperately needed for this vulnerable population.

METHODS

Because newborns rely heavily on the innate immune system, we evaluated cell phenotype and function of some of the earliest cellular responders during infection, natural killer (NK) cells. We used mass cytometry to provide a comprehensive comparison of NK cells from umbilical cord blood and adult peripheral blood.

RESULTS

In unsupervised analyses, including viSNE and principal component analysis, the structure of the cord blood and adult NK cell repertoires are highly similar, distinguishable mainly by maturity-related markers expressed on rare subpopulations of cells. However, in functional analyses, cord blood NK cells show reduced degranulation and cytokine production following target recognition, as well as antibody-dependent cell-mediated cytotoxicity and apoptosis induction in targets.

CONCLUSIONS

These findings show that the structure of the NK cell repertoire is intact at birth, suggesting great potential for vaccine and therapeutic strategies targeting this cell population. © 2016 International Clinical Cytometry Society.

Specific phenotype and function of CD56-expressing innate immune cell subsets in human thymus

Whereas innate immune cells, such as NK and innate lymphoid cells (ILCs), have been characterized in different human tissues, knowledge on the thymic CD56-expressing cell subsets is limited. In this study, the rare subpopulations of thymic CD56⁺CD3^- cells from samples of >100 patients have been successfully analyzed. The results revealed fundamental differences between thymic and peripheral blood (PB) CD56⁺CD3^- cells. Thymic tissues lacked immunoregulatory CD56^highCD16^dim NK cells but showed two Eomes⁺CD56^dim subsets on which common NK cell markers were significantly altered. CD56^dimCD16^high cells expressed high amounts of NKG2A, NKG2D, and CD27 with low CD57. Conversely, CD56^dimCD16^dim cells displayed high CD127 but low expression of KIR, NKG2D, and natural cytotoxicity receptors (NCRs). Thymic CD56⁺CD3^- cells were able to gain cytotoxicity but were especially immunoregulatory cells, producing a broad range of cytokines. Finally, one population of thymic CD56⁺ cells resembled conventional NK cells, whereas the other represented a novel, noncanonical NK subset.

NK cell-based immunotherapies in Pediatric Oncology

The past decade has seen several anticancer immunotherapeutic strategies transition from "promising preclinical models" to treatments with proven clinical activity or benefit. In 2013, the journal Science selected the field of Cancer Immunotherapy as the overall number-1 breakthrough for the year in all of scientific research. In the setting of cancer immunotherapy for adult malignancies, many of these immunotherapy strategies have relied on the cancer patient's endogenous antitumor T-cell response. Although much promising research in pediatric oncology is similarly focused on T-cell reactivity, several pediatric malignancies themselves, or the chemo-radiotherapy used to achieve initial responses, can be associated with profound immune suppression, particularly of the T-cell system. A separate component of the immune system, also able to mediate antitumor effects and less suppressed by conventional cancer treatment, is the NK-cell system. In recent years, several distinct immunotherapeutic approaches that rely on the activity of NK cells have moved from preclinical development into clinical testing, and some have shown clear antitumor benefit. This review provides an overview of NK cell-based immunotherapy efforts that are directed toward childhood malignancies, with an emphasis on protocols that are already in clinical testing.

Affinity-purified respiratory syncytial virus antibodies from intravenous immunoglobulin exert potent antibody-dependent cellular cytotoxicity

Mixed infections are one of the major therapeutic challenges, as the current strategies have had limited success. One of the most common and widespread conditions of mixed infection is respiratory syncytial virus-mediated pathology of the respiratory tract in children. There is a dire need for the development of novel therapeutic approaches during mixed infections. Therapeutic intravenous immunoglobulin preparations, obtained from plasma pools of healthy donors have been used in immune deficiencies. This study was thus designed to characterize the functional efficacy of RSV-specific antibodies in IVIg. To explore the functional ability of these affinity-purified RSV-specific antibodies, the antibody-dependent and complement dependent cytotoxicity was determined using peripheral cells of healthy donors. This study demonstrates the existence of highly potent RSV-specific antibodies in IVIg preparations and provides the basis for the use of IVIg as broad-spectrum protective shield to RSV-infected children during mixed infections.

IL-15 and macrophage secretory factors facilitate immune activation of neonatal natural killer cells by lipoteichoic acid

Neonates possess a relatively "naive", yet inducible immune system. Our hypothesis is that upon strategic antigen exposure, cytokine priming and sensitization by accessory cells, natural killer (NK) cells could be activated to become a functional phenotype. We investigated the in vitro stimulation of cord blood (CB) and adult NK cells upon challenge with lipoteichoic acid (LTA), interleukin (IL)-15 and LTA-primed autologous macrophage-conditioned medium, using CD107a and CD69 phenotypes as indicators of activation. We also examined response of CB macrophages to LTA, in terms of P44/42 extracellular signal-regulated kinases (ERK1/2) activation and cytokine secretion. LTA significantly induced secretion of inflammatory cytokines tumor necrotic factor (TNF)-α, IL-6, IL-12 and activated the upstream signal of ERK1/2 phosphorylation in neonatal macrophages. The magnitude of responses to stimulation differed between neonatal and adult NK cells. Co-stimulation with IL-15 was critical for expansion of the CD69 and CD107a NK subpopulations in both neonatal and adult cells, upon a LTA challenge. NK cell activation could be enhanced by LTA-primed autologous macrophages through secretory factors. Our results indicated that neonatal macrophages and NK cells can evoke immunologic responses to a Gram-positive bacterial antigen. The combinatory priming strategy is relevant for development of novel protocols, such as IL-15 treatment, to compensate for the immaturity of the innate immune system in newborns against bacterial infections.

Therapeutic antitumor efficacy of anti-epidermal growth factor receptor antibody, cetuximab, against malignant pleural mesothelioma

Epidermal growth factor receptor (EGFR) is commonly overexpressed in malignant pleural mesothelioma (MPM). Cetuximab is a chimeric mouse-human antibody targeted against EGFR and induces potent antibody-dependent cellular cytotoxicity (ADCC). The action of cetuximab against MPM cells has not been well studied. Therefore, in this study, we investigated the antitumor activity of cetuximab against MPM cell lines, particularly with respect to ADCC activity in vitro and in vivo. EGFR expression of MPM cells was measured by a quantitative flow cytometric analysis and immunohistochemistry. The effect of cetuximab on growth inhibition was assessed using a modified MTT assay. The ADCC activity was measured by a 4-h ⁵¹Cr release assay using fresh or IL-2-activated peripheral blood mononuclear cells. In vivo antitumor activity of cetuximab was evaluated using an orthotopic implantation mouse model. Cetuximab-mediated ADCC activity against MPM cells was observed at low concentration (0.25 mg/ml) and was enhanced by IL-2, whereas no direct effect on growth inhibition was detected. A logarithmic correlation was observed between the number of EGFRs on MPM cells and ADCC activity. Low EGFR expression on the MPM cells, which was weakly detectable by immunohistochemistry, was sufficient for maximum ADCC activity. In the mouse model, cetuximab treatment with or without IL-2 significantly inhibited intrathoracic tumor growth and prolonged their survival. Our study shows that cetuximab has potent anti-MPM activity both in vitro and in vivo, mainly through the immunologic mechanism of ADCC. Cetuximab has the potential to be used as a novel therapy for MPM patients.

Does IVIg administration yield improved immune function in very premature neonates?

Intravenous immunoglobulin (IVIg) has been evaluated as an adjunctive therapy for neonatal sepsis with modest clinical success despite strong biological plausibility. Multiple factors contribute to this outcome, but perhaps none greater than the limited immune system function in newborns, especially in the very premature neonates. For very premature neonates (<30 weeks gestational age), understanding the effects of IVIg on specific immature immune system functions is particularly relevant given their preponderance to develop sepsis and therefore potentially benefit from IVIg-mediated immunoenhancement. Here, we review the available evidence for enhanced immune function after IVIg administration in very premature neonates and highlight areas for future research.

IL-2-activated cord blood mononuclear cells

BACKGROUND

[corrected] Recent findings in cord blood (CB) research indicate the potential clinical usefulness of IL-2-activated CB in eradication of minimal malignant residual disease after hematopoietic stem cell transplantation. This feasible approach to immunotherapy merits further pre-clinical investigations using human tumor models of hematologic malignancy.

METHODS

The aim of our study was to compare the anti-tumor potential of CB mononuclear cells (MNC), matured in the presence of IL-2, to BM, and to determine phenotype and cytokine secretion in IL-2 CB MNC culture during the peak of their anti-leukemia cytotoxic activity. Phenotype change was analysed with flow cytometry, cytokine secretion with ELISA tests and cytotoxic activity with cytotoxicity assays.

RESULTS

Following IL-2 maturation, the phenotype of CB MNC was remarkably changed. Lengthening IL-2 culture to 8 days significantly increased CD8+, CD16+ CD56+, CD56+ and CD56+ CD8+ populations. Interestingly, FACS analyzes revealed the occurrence of CD8+ CD56+ cells that were not present in non-stimulated CB. Cultures progressively produced higher levels of INF-gamma, TNF-alpha and GM-SCF. The IL-2-activated cells manifested potent lytic capabilities against both NK- and LAK-sensitive tumor cell targets.

DISCUSSION

At the peak of cytotoxic activity during 8-day IL-2 CB MNC culture, we found increased numbers of various cytotoxic cells and increased secretion of cytokines that may contribute further to their potential therapeutic effect. The duration of CB IL-2 cultures may be crucial for successful application of CB in transplant situations to boost the CB GvL.

Low dose gamma-rays activate immune functions via induction of glutathione and delay tumor growth

We examined whether the increase of glutathione level induced by low dose gamma-ray irradiation is involved in the appearance of enhanced natural killer (NK) activity and antibody-dependent cellular cytotoxicity (ADCC), leading to delayed tumor growth in Ehrlich solid tumor-bearing mice. NK activity in ICR mouse splenocytes significantly increased from 4 h to 6 h after whole-body gamma-ray irradiation at 0.5 Gy, and thereafter decreased almost to the zero-time level by 24 h post-irradiation. ADCC also increased significantly in a similar way. Reduced glutathione exogenously added to splenocytes obtained from normal mice enhanced both NK activity and ADCC in a dose-dependent manner. Since immune functions were enhanced through the induction of cellular glutathione after low-dose irradiation, the inhibitory effect of the radiation on tumor growth was then examined in Ehrlich solid tumor-bearing mice. Tumor growth after inoculation was significantly delayed by the radiation. These results suggest that low-dose gamma-rays activate immune functions via an induction of glutathione, leading to a delay of tumor growth.

Evaluation of cytotoxic function and apoptosis in interleukin (IL)-12/IL-15-treated umbilical cord or adult peripheral blood natural killer cells by a propidium-iodide based flow cytometry

Both deficient natural killer (NK) cell effector function and increased propensity to apoptosis of neonatal NK cells contribute to the increased susceptibility to infection in the neonates. Interleukin (IL)-12 and IL-15 are two immunoregulatory cytokines known to enhance cytolytic function of neonatal NK cells. The present study aims to simultaneously investigate the effect of IL-12/IL-15 on K562 cytotoxicity as well as NK cells apoptosis of enriched umbilical cord blood (CB) and adult peripheral blood (APB) NK cells, using flow cytometric cytotoxicity assays. The results indicated that (i) prior to cytotoxicity assays, CB NK cells underwent greater degree of spontaneous apoptosis than did APB NK cells; (ii) both IL-12 and IL-15 inhibited the spontaneous apoptosis of CB NK cells, while IL-15 promoted the apoptosis in APB NK cells; (iii) the deficient K562 cytotoxicity of CB NK cells could be enhanced to levels comparable with that of APB NK cells by IL-15; (iv) IL-15 increased the percentages of apoptosis in NK-K562 conjugates in a dose-dependent manner in both CB and APB with a greater effect seen with APB NK cells; (v) target-induced apoptosis was observed with APB NK cells which were further enhanced with IL-15. However, CB NK cells, unstimulated or IL-15-activated, were resistant to K562-induced apoptosis. Thus, the multi-parameter flow cytometry analysis not only demonstrates better for the deficient CB NK function but also provides greater details for cytotoxic mechanisms of NK cells.

Transient detection of proinflammatory cytokines in sera of colostrum-fed newborn calves

To obtain basic information on the state of proinflammatory cytokines in newborn calves, we determined the kinetics of 5 cytokines (IL-1beta, IL-6, TNF-alpha, IFN-gamma and IL-1 receptor antagonist) in sera of newborns during the first 4 weeks of life. At birth, none of the 5 cytokines were detected in almost all serum samples, but the cytokines became detectable within 12 hr after being fed colostram. The mean concentrations of the cytokines reached peak levels by 24 hr and then gradually decreased and became undetectable by 4 weeks after birth. Cytokine mRNA expressions in peripheral blood mononuclear cells of newborns were observed without reference to the cytokine concentrations in sera. Serum cytokines detected in newborn calves are probably colostral origin.

Synergistic effect of interleukin-2 and a vaccine of irradiated melanoma cells transfected to secrete staphylococcal enterotoxin A

We have previously reported that immunization of mice with melanoma cells transfected to secrete the superantigen, Staphylococcal enterotoxin A (SEA), increased the production of antibodies to the B700 melanoma antigen, stimulated the production of endogenous interleukin 2 (IL-2), activated the expression of CD4, CD8 and CD25 T cell markers and enhanced NK cell activity. Now we show that immunization of mice with a vaccine of irradiated sea-transfected melanoma cells coupled with IL-2 therapy was even more effective in inhibiting the growth of primary melanoma tumors and the development of lung metastases than was the irradiated melanoma cell vaccine alone or IL-2 alone. The morphological and immunological effectiveness of the therapy was dose-dependent on IL-2.

Elevation of glutathione induced by low-dose gamma rays and its involvement in increased natural killer activity

We examined the relationship between the induction of an increase in the level of glutathione and the elevation of natural killer (NK) activity in mouse splenocytes by a low dose of gamma rays. The glutathione levels in mouse splenocytes increased significantly between 2 h and 6 h after whole-body gamma irradiation at 0.5 Gy, peaked at 4 h, and then decreased almost to the level before irradiation by 12 h postirradiation. A significant enhancement of NK activity was found in the splenocytes obtained from whole-body-irradiated mice between 4 and 6 h postirradiation. Reduced glutathione (GSH) added exogenously to splenocytes obtained from normal mice enhanced both the total cellular glutathione content and the NK activity in a dose-dependent manner. Other precursors of de novo GSH synthesis, such as cysteine, N-acetylcysteine and oxidized glutathione, also increased the activity. These enhancements were completely blocked by buthionine sulfoximine, an inhibitor of de novo GSH synthesis. We conclude that the induction of endogenous glutathione in living cells immediately after low-dose gamma irradiation is at least partially responsible for the appearance of enhanced NK activity.

Evidence for the direct action of thymulin on avian NK cells

The ability of thymulin to directly enhance NK cell-mediated cytotoxicity was examined. Specific cell population depletions were done in K and SLD chicken splenocyte preparations using anti-CD3, CD4, and CD8 monoclonal antibodies and secondary complement-fixing polyclonal antibodies. The remaining cells were incubated overnight with in vitro treatments of thymulin and IFN-gamma, either separately or together, followed by an assay for cytotoxicity. Although the control K-strain had higher overall NK cell-mediated cytotoxicity than the thymulin-deficient SLD-strain, the following trends were seen in both strains. Thymulin continued to enhance NK activity following CD4 or CD3 cell depletion, but not after CD8 or CD8 and CD4 cell depletion. Since avian NK cells express CD8 alpha, but not CD3 or CD4 on their surface, these results suggest that the ability of in vitro thymulin treatments to enhance NK activity is not mediated by T-cells but may be due to direct effects on NK cells.

Cell cycle control in cellular homeostasis during the immune response: interactions between TH1, TH2 cytokines, and Bcl2 and p53 molecules

Cytokine regulation of lymphocyte survival may play an important role in the control of the cell cycle during the immune response both in health and disease. Expression of the Bcl2 gene promotes cell survival by countering apoptosis stimuli. The p53 protein has been implicated in the control of the cell cycle, in the synthesis and repair of DNA and in programmed cell death. TH1 and TH2 cytokines exert a mutual cross-regulation on the precursors of TH1- or TH2-type effector cells which are important mediators in directing the immune system towards the appropriate response. TH1 and TH2 cytokines have also been implicated in the modulation of the expression of cell cycle regulator genes. Therefore, the study of the relationships between TH1 and TH2 cytokines and Bcl2 and p53 molecules in healthy subjects could lead to a better understanding of the physiological regulation of the immune response and identify markers for prognostic and diagnostic indices and biotherapeutic treatment. We determined the serum levels of cytokines (IL2, IFN gamma, IL4, IL10, IL5, IL6, IL1 beta, TNF alpha, IL8), soluble receptors (sIL2R, sIL6R), Bcl2-protein and p53-antibody in a group of healthy subjects. Multivariate statistical analyses were used to study the cytokine network relationships with Bcl2-protein and p53-antibody, as they allow a simultaneous evaluation of all variables which reflects the physiological situation. Our overall results suggest that relationships exist between TH1 and TH2 cytokines and the Bcl2-protein and p53-antibody in physiological conditions. This information could now be used in experimental studies to create diagnostic and prognostic indices for the monitoring of health and disease.

Influence of cytokines, monoclonal antibodies and chemotherapeutic drugs on epithelial cell adhesion molecule (EpCAM) and LewisY antigen expression

MoAbs against tumour-associated antigens (TAA) may be useful for the treatment of colorectal cancer. Since an increased expression of TAA may lead to enhanced antibody-dependent cellular cytotoxicity we examined whether the cytokines IL-2, IL-4, IL-6, IL-10, IL-12, interferon-alpha (IFN-alpha), IFN-gamma, granulocyte-macrophage colony-stimulating factor, macrophage colony-stimulating factor and tumour necrosis factor-alpha can influence EpCAM and LewisY expression on the surface of the colorectal carcinoma cell lines HT29, LoVo and SW480. We found that only IFN-alpha increased significantly whereas IL-4 decreased both EpCAM and LewisY expression. IFN-gamma significantly increased LewisY expression only. When tumour cells were treated with MoAb, the LewisY-specific MoAb BR55-2 down-regulated LewisY antigen expression, whereas MoAb 17-1A, which binds to EpCAM, up-regulated this TAA after 3 days of culture. The cytokines IFN-alpha or IFN-gamma combined with MoAb 17-1A enhanced further slightly the expression of EpCAM. In additional experiments with chemotherapeutic drugs commonly used for the treatment of colorectal cancer, we found that 5-fluorouracil, mitomycin-C and oxaliplatin up-regulated EpCAM and LewisY antigen expression. Raltitrexed enhanced LewisY and down-regulated EpCAM expression, whereas CPT-11 had no influence at all. The highest expression for EpCAM on HT29 cells was achieved by the combination of IFN-alpha, 5-fluorouracil and MoAb 17-1A. Our results may be useful for defining combinations of biological and chemotherapeutic drugs for the treatment of colorectal cancer. Further trials should evaluate to what extent these combinations enhance antibody-dependent cellular cytotoxicity.

Augmentation of 17-1A-induced antibody-dependent cellular cytotoxicity by the triple cytokine combination of interferon-alpha, interleukin-2, and interleukin-12

Previously, interferon-alpha (IFN-alpha), interleukin-2 (IL-2), and interleukin-12 (IL-12) were shown to increase the antibody-dependent cellular cytotoxicity (ADCC) induced by the murine monoclonal antibody 17-1A, which recognizes the tumor-associated antigen EpCAM. In this study, the authors wanted to determine whether the combination of these three cytokines would yield greater cytotoxicity than the single cytokines. For cytotoxicity assessment, a new flow cytometric assay was used that allows the analysis of long-term ADCC exerted by macrophages. Peripheral blood mononuclear cells from healthy donors were used as effector cells against the colorectal carcinoma cell line HT29 at a low effector-to-target ratio of 4.5:1. With this test, the effectiveness of the combinations IL-2 and IFN-alpha, IL-2 and IL-12, and IL-12 and IFN-alpha were compared with each other. The combinations IL-2 plus IL-12 and IFN-alpha plus IL-12 were more potent at the concentrations tested. Furthermore, the triple cytokine combination of IFN-alpha, IL-2, and IL-12 revealed significantly greater ADCC than dual cytokine combinations. Next, CD14+, CD4+, and CD4- cells were isolated by paramagnetic beads and magnetic activated cell sorter (MACS) columns. The CD14+ and CD4- cell populations contained the ADCC effectors. The addition of CD4+ cells to CD14+ or CD4- cells resulted in augmented ADCC, indicating that cooperation between immune cells occurs. These results suggest that multiple cytokine combinations with monoclonal antibodies may be more effective for cancer immunotherapy.

The TH1 and TH2 cytokine network in healthy subjects: suggestions for experimental studies to create prognostic and diagnostic indices for biotherapeutic treatments

In vivo and in vitro studies have demonstrated the selective regulatory effect that TH1 and TH2 cytokines reciprocally exert in the regulation of the polarization of precursor cells into TH1 or TH2 types. The study of the network relationships between TH1 and TH2 (TH1/TH2) cytokines in healthy subjects could lead to a better understanding of how the physiological network of cytokines regulates the immune response. Such study could lead to gain suggestions for follow-up experiments to create prognostic and diagnostic indices for biotherapeutic treatments of patients. Hence we determined serum levels (environment network) and PBMC production (cellular network) of IL2, IFN gamma, IL4, IL6 and IL10 in the peripheral blood of healthy subjects; these cytokines made up our networks under basic conditions. Both men and women were studied as hormones can influence the polarization of TH1 and TH2 cells. Cytokines within the physiological network function simultaneously so multivariate statistical methods were used to study TH1/TH2 relationships. The use of mathematical modelling is the only effective way of studying the immune system as a whole. The physiological TH1/TH2 network under activation conditions was evaluated by incorporating: sIL2R and sIL6R into the basic environment network model and the production levels of cytokines by PBMC after PHA stimulus, into the basic cellular network model. The influence of APC was evaluated by adding: serum levels of TNF alpha and IL1 beta to the environment network model, and production levels of IFN gamma, IL10 and IL6, after stimulus with LPS, to the cellular network model. Our results led us to hypothesize that the physiological network of TH1/TH2 cytokines regulates TH polarization by means of specific relationships between TH1 and TH2 cytokines, which may be different in men and women. These relationships could be studied experimentally to create prognostic and diagnostic indices for more efficient prevention programs and biotherapeutic treatments of patients.

Role of chicken IL-2 on gammadelta T-cells and Eimeria acervulina-induced changes in intestinal IL-2 mRNA expression and gammadelta T-cells

Continuous culture of concanavalin A (Con A)-activated spleen cells in the presence of chicken recombinant IL-2 (rIL-2) promoted preferential growth of gammadelta T-cells. These cells displayed a high level of spontaneous cytotoxicity against LSCC-RP9 tumor cells, an avian NK cell target. Stimulation of IL-2-dependent gammadelta T-cells with Con A induced IFN-gamma and IL-2 mRNA transcripts, whereas stimulation with rIL-2 induced only IFN-gamma mRNA. Subcutaneous injection of 3-week-old chickens with IL-2 DNA increased splenic cells, expressing the CD8 and gammadelta TCR antigens. To investigate the role of IL-2 and gammadelta T-cells in parasitic infection, chickens were orally infected with Eimeria acervulina and the expression of IL-2 mRNA transcripts in the spleen and duodenum and the percentage of gammadelta T-cells in the duodenum were examined. Following both, the primary and secondary infections, a significant enhancement of IL-2 mRNA transcripts in the spleen and intestine and increased percentage of intraepithelial gammadelta T-cells in the duodenum were observed. These results indicate that host immune responses to E. acervulina involve an up-regulation of IL-2 secretion and an increased duodenum gammadelta T-cells.

Improvement of murine immune functions in vitro by thioproline

Previous studies have shown that several immune functions were improved in mice after the ingestion of a thioproline (thiazolidine-4-carboxylic acid) enriched diet. In the present work, we have studied the in vitro effects of several concentrations of this thiol compound (0.1, 0.5, 1, 2.5 and 5 mM) on the most relevant functions of three pivotal immune cells, namely, macrophages, lymphocytes, and natural killer (NK) cells from BALB/c mice. The results show that thioproline stimulates the phagocytic process of macrophages, increasing the mobility directed to the inflammatory focus (chemotaxis) and the phagocytosis of inert particles. It increases the adherence and the chemotaxis capacities of lymphocytes, their proliferative activity and favours the natural cytotoxic activity that could improve the capacity to destroy malignant cells. Thioproline concentrations of 0.5 and 1 mM were the most effective regarding the different functions analysed. These results suggest that the improvement of immune functions, observed in previous work, after thioproline-enriched diet ingestion is due to a direct action of this thiol compound on immune cells.

Immunostimulatory effects of human recombinant interleukin-12 on peripheral blood mononuclear cells from normal dogs

Interleukin-12 (IL-12) plays a pivotal role in regulating cellular immune responses involving autoimmunity, infectious disease, and cancer. Human recombinant (hr) IL-12 is being evaluated for therapy of human cancer. We investigated the potential of hrIL-12 to activate canine peripheral blood mononuclear cells (PBMC) using proliferation and cytotoxicity as readouts. Human rIL-12 caused increased proliferation of PBMC, and enhanced lysis of allogeneic canine tumor targets mediated by PBMC from normal dogs in vitro. In addition, antibody-dependent cellular cytotoxicity (ADCC) mediated by canine PBMC was enhanced by hrIL-12. These results indicate that hrIL-12 is recognized by canine immune cells, triggering a number of immune responses in canine PBMC, that may be important for immunotherapy of canine cancer. Information from this investigation provides impetus for evaluation of the effects of hrIL-12 on PBMC from tumor-bearing dogs and should be helpful in the development of hrIL-12 as an immune cell activator in vivo in the dog.

Effects in vitro of several antioxidants on the natural killer function of aging mice

The aim of the present work is to study the change with aging in the effect in vitro of several antioxidants: thiazolidine-4-carboxylic acid or thioproline, N-acetylcysteine (NAC), ascorbic acid (AA), and alpha-tocopherol (vitamin E, VE) on the natural killer (NK) activity in mononuclear cells from axillary nodes, spleen, thymus and peritoneal leukocytes from BALB/c male mice. Young (8+/-2 weeks), adult (24+/-2 weeks). mature (48+/-2 weeks), and old (72+/-2 weeks) animals were studied. A nonradioactive cytotoxic assay with cells from the murine lymphoma YAC-1 as target cells and a relation effector cells/target cells of 10/1 were used. The concentrations of the different antioxidants were: 1 mM for thioproline and N-acetylcysteine and 5 microM for ascorbic acid and alpha-tocopherol, which induced a maximum effect in our previous dose-response experiments. The results show that, in general, the above antioxidants cause an enhancement of the NK activity at all ages studied, this stimulation being higher with thioproline and N-acetylcysteine than with ascorbic acid and alpha-tocopherol. The effects were similar for the three lymphoid organs and the peritoneum. This stimulation of the NK activity by antioxidants is an important favorable response, especially in old mice, in which age results in a decrease in NK function and, therefore, in a higher incidence of neoplasia.

Difference in response of NK cell activity in newborns and adult to IL-2, IL-12 and IL-15

The killing activity of cord blood mononuclear cells (cMNC) against cytomegalovirus (CMV)-uninfected and -infected fibroblasts was comparable to that of adult peripheral blood mononuclear cells (aPBMC). The killing activity of cMNC against K562 cells was significantly lower compared with that of aPBMC. Treatment of cMNC and aPBMC with interleukin-2 (IL-2), IL-12 or IL-15 significantly enhanced killing activity against K562 cells and CMV-uninfected and -infected cells. By comparison of cMNC with aPBMC, killing activity against the K562 cells of cMNC was augmented to the level of aPBMC when cultured with IL-2, IL-12 or IL-15. The killing activity of cMNC against CMV-uninfected and -infected fibroblasts did not increase to the level of adult PBMC by treatment with IL-2, IL-12 or IL-15. These data suggest that cord blood contains a functionally different NK cell subpopulation than that among adult NK cells.

Effect of interleukin (IL)-12 and IL-15 on activated natural killer (ANK) and antibody-dependent cellular cytotoxicity (ADCC) in HIV infection

The ability of IL-12 and IL-15 to enhance natural killer (NK) activity and antibody-dependent cellular cytotoxicity (ADCC) of mononuclear cells (MNCs) from HIV+ children and their mothers was investigated. MNCs from HIV+ patients were deficient in NK and ADCC activity compared to control MNCs against several target cells. Overnight incubation with IL-15 or IL-12 augmented NK activity of MNCs from both patients and controls, and the combination of IL-12 and IL-15 resulted in the greatest enhancement. ADCC in HIV+ patients against gp120-coated CEM.NKR cells or chicken erythrocytes could also be enhanced by IL-2 or IL-15 in overnight cultures. Culturing MNCs with either IL-2 or IL-15 for 1 week increased the NK activity in patients to levels of controls treated with these cytokines. However, the response to the combination of IL-12 and IL-15 was less than that to IL-15 alone in 1-week cultures. Culturing MNCs with IL-2 and IL-15 for 1 week also increased the percentage of CD16+/CD56+ cells in both patients and controls. Thus, IL-15 can restore the deficient NK activity in patients and may be a candidate for immunomodulative therapy in HIV+ patients.

Interleukin (IL)-15 enhances antibody-dependent cellular cytotoxicity and natural killer activity in neonatal cells

Interleukin (IL)-15 is a novel cytokine that is very similar to IL-2 in receptor specificity and biological activities. We compared the ability of IL-15 and IL-12 to enhance the cytotoxicity of neonatal (cord blood) and adult mononuclear cells (MNC) in both natural killer (NK) and antibody-dependent cellular cytotoxicity (ADCC) assays. Incubation with IL-15 (10 ng/ml) or IL-12 (1 ng/ml) for 18 h enhanced the NK activity (using K562 target cells) of both cord and adult MNC, increasing cord cell cytotoxicity threefold. Similar enhancement was seen in ADCC assays using erythrocyte targets and NK-resistant CEM cells coated with HIV gp-120 antigen. Incubation of cord cells with IL-15 or IL-12 for 1 week increased both NK and ADCC, although the combination produced less of an effect than either cytokine alone. IL-15 also increased the percentage of CD16+/CD56+ cells after 1 week incubation. This enhancement of NK and ADCC activities and the number of NK cells by IL-15 suggests it may be clinically useful in treating immunodeficient patients.