Activation of macrophages for ADCC in vitro: effects of IL-4, TNF, interferons-alpha/beta, interferon-gamma, and GM-CSF

Engineered biological nanoparticles as nanotherapeutics for tumor immunomodulation

Biological nanoparticles, or bionanoparticles, are small molecules manufactured in living systems with complex production and assembly machinery. The products of the assembly systems can be further engineered to generate functionalities for specific purposes. These bionanoparticles have demonstrated advantages such as immune system evasion, minimal toxicity, biocompatibility, and biological clearance. Hence, bionanoparticles are considered the new paradigm in nanoscience research for fabricating safe and effective nanoformulations for therapeutic purposes. Harnessing the power of the immune system to recognize and eradicate malignancies is a viable strategy to achieve better therapeutic outcomes with long-term protection from disease recurrence. However, cancerous tissues have evolved to become invisible to immune recognition and to transform the tumor microenvironment into an immunosuppressive dwelling, thwarting the immune defense systems and creating a hospitable atmosphere for cancer growth and progression. Thus, it is pertinent that efforts in fabricating nanoformulations for immunomodulation are mindful of the tumor-induced immune aberrations that could render cancer nanotherapy inoperable. This review systematically categorizes the immunosuppression mechanisms, the regulatory immunosuppressive cellular players, and critical suppressive molecules currently targeted as breakthrough therapies in the clinic. Finally, this review will summarize the engineering strategies for affording immune moderating functions to bionanoparticles that tip the tumor microenvironment (TME) balance toward cancer elimination, a field still in the nascent stage.

Susceptibility of rhabdomyosarcoma cells to macrophage-mediated cytotoxicity

The prognosis of advanced stage rhabdomyosarcoma (RMS) is still sobering. In recent years, outcome has not been further improved by conventional therapy. Therefore, novel treatment options such as macrophage-directed immunotherapy have to be investigated. The aim of this study was to analyze the phagocytosis of RMS cells by macrophages and to modulate the susceptibility using monoclonal antibodies and cytotoxic drugs.   Expression of the macrophage activating ligand calreticulin and CD47, the counterpart of the inhibitory receptor SIRPα, was analyzed with Affymetrix mRNA expression arrays and immunohistochemistry on 11 primary RMS samples. Results were verified in two RMS cell lines using flow cytometry and immunocytochemistry. Macrophage cytotoxic activity was quantified by a MTT colorimetric assay in co-culture experiments of RMS cells with monocyte-derived, GM-CSF stimulated macrophages. Gene expression analysis and immunohistochemistry revealed a high expression of CD47 and calreticulin in alveolar and embryonal RMS tissue specimens. Extracellular expression of CD47 on RMS cell lines was confirmed by flow cytometry, whereas calreticulin was exclusively detected in the endoplasmatic reticulum. After co-culturing of RMS cells with macrophages, viability dropped to 50-60%. Macrophage-mediated cytotoxicity was not influenced by a blocking antibody against CD47. However, susceptibility was significantly enhanced after pre-treatment of RMS cells with the anthracycline drug doxorubicin. Furthermore, translocation of calreticulin onto the cell surface was detected by flow cytometry. The immunologic effect of doxorubicin may improve the efficacy of adoptive cellular immunotherapy and chemotherapy of childhood RMS.

Tumor-Specific Antibody, Cetuximab, Enhances the In Situ Vaccine Effect of Radiation in Immunologically Cold Head and Neck Squamous Cell Carcinoma

In head and neck squamous cell carcinoma (HNSCC) tumors that over-expresses huEGFR, the anti-EGFR antibody, cetuximab, antagonizes tumor cell viability and sensitizes to radiation therapy. However, the immunologic interactions between cetuximab and radiation therapy are not well understood. We transduced two syngeneic murine HNSCC tumor cell lines to express human EGFR (MOC1- and MOC2-huEGFR) in order to facilitate evaluation of the immunologic interactions between radiation and cetuximab. Cetuximab was capable of inducing antibody-dependent cellular cytotoxicity (ADCC) in MOC1- and MOC2-huEGFR cells but showed no effect on the viability or radiosensitivity of these tumor cells, which also express muEGFR that is not targeted by cetuximab. Radiation enhanced the susceptibility of MOC1- and MOC2-huEGFR to ADCC, eliciting a type I interferon response and increasing expression of NKG2D ligands on these tumor cells. Co-culture of splenocytes with cetuximab and MOC2-huEGFR cells resulted in increased expression of IFNγ in not only NK cells but also in CD8+ T cells, and this was dependent upon splenocyte expression of FcγR. In MOC2-huEGFR tumors, combining radiation and cetuximab induced tumor growth delay that required NK cells, EGFR expression, and FcγR on host immune cells. Combination of radiation and cetuximab increased tumor infiltration with NK and CD8+ T cells but not regulatory T cells. Expression of PD-L1 was increased in MOC2-huEGFR tumors following treatment with radiation and cetuximab. Delivering anti-PD-L1 antibody with radiation and cetuximab improved survival and resulted in durable tumor regression in some mice. Notably, these cured mice showed evidence of an adaptive memory response that was not specifically directed against huEGFR. These findings suggest an opportunity to improve the treatment of HNSCC by combining radiation and cetuximab to engage an innate anti-tumor immune response that may prime an effective adaptive immune response when combined with immune checkpoint blockade. It is possible that this approach could be extended to any immunologically cold tumor that does not respond to immune checkpoint blockade alone and for which a tumor-specific antibody exists or could be developed.

Chronic lung inflammation primes humoral immunity and augments antipneumococcal resistance

Airway epithelial cells (AECs) display remarkable plasticity in response to infectious stimuli and their functional adaptations are critical for antimicrobial immunity. However, the roles of AECs and humoral mediators to host defense in non-communicable lung inflammation remain elusive. We dissected pulmonary defense against Streptococcus pneumoniae in hosts with pre-existing inflammatory conditions (SPC-HAxTCR-HA mice). Lung tissue transcriptomics and bronchoalveolar lavage fluid (BALF) proteomics revealed an induction of humoral defense mechanisms in inflamed lungs. Accordingly, besides antibacterial proteins and complement components being overrepresented in inflamed lungs, elevated polymeric immunoglobulin receptor (pIgR)-expression in AECs correlated with increased secretory immunoglobulin (SIg) transport. Consequently, opsonization assays revealed augmented pneumococcal coverage by SIgs present in the BALF of SPC-HAxTCR-HA mice, which was associated with enhanced antipneumococcal resistance. These findings emphasize the immunologic potential of AECs as well as their central role in providing antibacterial protection and put forward pIgR as potential target for therapeutic manipulation in infection-prone individuals.

Morphological and Functional Alterations of Alveolar Macrophages in a Murine Model of Chronic Inflammatory Lung Disease

Purpose

Chronic lung inflammation commonly induces a multitude of structural and functional adaptations within the lung tissue and airspaces. Yet the impact of a persistent inflammatory environment on alveolar macrophages is still incompletely understood. Here, we examined morphology and function of alveolar macrophages in a transgenic mouse model of chronic lung disease.

Methods

Imaging flow cytometry, flow cytometry, and microscopic evaluation of alveolar macrophages isolated from healthy and inflamed lungs were performed. Gene expression of polarization markers was compared by quantitative real-time RT-PCR. The pro-inflammatory immune response of alveolar macrophages toward bacterial ligands was assessed in in vivo clodronate-liposome depletion studies.

Results

Chronic lung inflammation is associated with a substantially altered, activated alveolar macrophage morphology, and blunted TNF-α response by these cells following stimulation with ligands derived from the respiratory pathogen Streptococcus pneumoniae.

Conclusions

These results demonstrate pleiotropic effects of pulmonary inflammation on alveolar macrophage phenotype and function and suggest a functional impairment of these cells during infection with airborne pathogens.

Large extracellular loop of tetraspanin as a potential vaccine candidate for filariasis

Lymphatic filariasis affects nearly 120 million people worldwide and mass preventive chemotherapy is currently used as a strategy to control this infection. This has substantially reduced the incidence of the infection in several parts of the world. However, a prophylactic vaccine would be more effective in preventing future infections and will supplement the mass chemotherapy efforts. Unfortunately, there is no licensed vaccine available currently to prevent this infection. Molecules expressed on the surface of the parasite are potential candidates for vaccine development as they are exposed to the host immune system. In this study we show that the large extracellular loop of tetraspanin (TSP LEL), a protein expressed on the cuticle of Brugia malayi and Wuchereria bancrofti is a potential vaccine candidate. Our results showed that BmTSP LEL is expressed on the surface of B. malayi infective third stage larvae (L3) and sera from human subjects who are putatively immune to lymphatic filariasis carry high titer of IgG1 and IgG3 antibodies against BmTSP LEL and WbTSP LEL. We also showed that these antibodies in the sera of human subjects can participate in the killing of B. malayi L3 in an antibody dependent cell-mediated cytotoxicity mechanism. Vaccination trials in mice showed that close to 64% protection were achieved against challenge infections with B. malayi L3. Immunized animals showed high titer of anti-WbTSP LEL IgG1, IgG2a and IgG2b antibodies in the sera and IFN-γ secreting cells in the spleen. Onchocerca volvulus another filarial parasite also expresses TSP LEL. Cross-reactivity studies showed that IgG1 antibody in the sera of endemic normal subjects, recognize OvTSP LEL. Similarly, anti-OvTSP LEL antibodies in the sera of subjects who are immune to O. volvulus were also shown to cross-react with rWbTSP LEL and rBmTSP LEL. These findings thus suggested that rTSP LEL can be developed as a potential vaccine candidate against multiple filarial infections.

A potential role of macrophage activation in the treatment of cancer

One of the functions of macrophages is to provide a defense mechanism against tumor cells. In the last decades the mechanism of tumor cell killing by macrophages have been studied extensively. The tumor cytotoxic function of macrophages requires stimulation either with bacterial cell wall products such as lipopolysaccharide (LPS) or muramyldipeptide (MDP) or with cytokines such as interferon-gamma (IFN-gamma) and granulocyte-macrophage colony-stimulating factor (GM-CSF). Activated macrophages secrete several substances that are directly involved in tumor cell killing i.e. tumor necrosis factor (TNF) and nitric oxide (NO). On the other hand, substances are secreted that are able to stimulate tumor cell growth, depending on the stage and the nature of the tumor. Several clinical trials have been performed aiming at the activation of macrophages or dendritic cells, a subpopulation of the macrophages. In this review we will summarize and discuss experimental studies and clinical trials based on the activation of macrophages.

Vaccine-induced serum immunoglobin contributes to protection from herpes simplex virus type 2 genital infection in the presence of immune T cells

Herpes simplex type virus 2 (HSV-2) is a sexually transmitted pathogen that causes genital lesions and spreads to the nervous system to establish acute and latent infections. Systemic but not mucosal cellular and humoral immune responses are elicited by immunization of mice with a replication-defective mutant of HSV-2, yet the mice are protected against disease caused by subsequent challenge of the genital mucosa with virulent HSV-2. In this study, we investigated the role of immune serum antibody generated by immunization with a replication-defective HSV-2 vaccine prototype strain in protection of the genital mucosa and the nervous system from HSV-2 infection. Passive transfer of replication-defective virus-immune serum at physiologic concentrations to SCID or B-cell-deficient mice had no effect on replication of challenge virus in the genital mucosa but did significantly reduce the incidence and severity of genital and neurologic disease. In contrast, B-cell-deficient mice immunized with replication-defective HSV-2 were able to control replication of challenge virus in the genital mucosa, but not until 3 days postchallenge, and were not completely protected against genital and neurologic disease. Passive transfer of physiologic amounts of immune serum to immunized, B-cell-deficient mice completely restored their capacity to limit replication of challenge virus in the genital mucosa and prevented signs of genital and systemic disease. In addition, the numbers of viral genomes in the lumbosacral dorsal root ganglia of immunized, B-cell-deficient mice were dramatically reduced by transfer of immune serum prior to challenge. These results suggest that there is an apparent synergism between immune serum antibody and immune T cells in achieving protection and that serum antibody induced by vaccination with replication-defective virus aids in reducing establishment of latent infection after genital infection with HSV-2.

Effects of interferons alpha and gamma on cytokine production and phenotypic pattern of human bronchial epithelial cells

Human bronchial epithelial cells are involved in airway immune mechanisms through secretion of cytokines and through cell-cell contacts with immunocompetent cells. The aim of our study was to assess the ability of interferon (IFN) alpha and gamma alone and in combination to modulate human bronchial epithelial cell (HBECs) release of the inflammatory cytokines IL-8 and IL-6 and fibronectin and to induce the surface expression of HLA-DR and ICAM-1 molecules involved in immune interactions with other cells. HBECs spontaneously secreted a limited amount of IL-8, which was significantly increased by IFN gamma. IFN alpha inhibited IFN gamma stimulated IL-8 secretion in a concentration-dependent manner. Further, IFN gamma induced IL-6 and fibronectin secretion, and this was also inhibited by IFN alpha. The expression of HLA-DR antigens was significantly increased by IFN gamma and partially inhibited by co-stimulation with IFN alpha. In contrast, IFN gamma also induced ICAM-1 expression by HBECs but co-stimulation with IFN alpha had no significant effect on the expression of this surface antigen. IFN alpha modulation of HBEC functions does not seem to be restricted to IFN gamma stimulation since either stimulatory or inhibitory effects of INF alpha on IL-8 production have been found in pilot experiments using IL-1 beta, TNF alpha, and TGF beta as stimuli. In summary, IFN-gamma induces a number of responses in HBECs including increased secretion of IL-6, IL-8 and fibronectin and increased expression of HLA-DR and ICAM-1. IFN alpha can inhibit all these except expression of ICAM-1 which is unaffected. IFN alpha can also interact with other inflammatory cytokines, but whether the effects are inhibitory or augmentive depends on the cytokines.

Lipopolysaccharide enhances FcgammaR-dependent functions in vivo through CD11b/CD18 up-regulation

Fc receptors for immunoglobulin G (IgG) (FcgammaR) mediate several defence mechanisms in the course of inflammatory and infectious diseases. In Gram-negative infections, cellular wall lipopolysaccharides (LPS) modulate different immune responses. We have recently demonstrated that murine LPS in vivo treatment significantly increases FcgammaR-dependent clearance of immune complexes (IC). In addition, we and others have reported the induction of adhesion molecules on macrophages and neutrophils by LPS in vivo and by tumour necrosis factor-alpha (TNF-alpha) in vitro. The aim of this paper was to investigate CD11b/CD18 participation in LPS enhancing effects on Fcgamma-dependent functionality of tissue macrophages. Our results have demonstrated that LPS can enhance antibody-dependent cellular cytotoxicity (ADCC) and IC-triggered cytotoxicity (IC-Ctx), two reactions which involve the Fcgamma-receptor but different lytic mechanisms. In vitro incubation of splenocytes from LPS-treated mice with anti-CD11b/CD18 abrogated ADCC and IC-Ctx enhancement, without affecting FcgammaR expression. Similar results were obtained with physiological concentrations of fibrinogen. In this way cytotoxic values of LPS-splenocytes decreased to the basal levels of control mice. Time and temperature requirements for such inhibition strongly suggested that anti-CD11b/CD18 could modulate intracellular signals leading to downregulation of FcgammaR functionality. Data presented herein support the hypothesis that functional and/or physical associations between integrins and FcgammaR could be critical for the modulation of effector functions during an inflammatory response.

Mainstream and sidestream cigarette smoke condensates suppress macrophage responsiveness to interferon gamma

Sidestream smoke evolves from the smoldering end of a cigarette while the smoker is not puffing, and contributes substantially to environmental tobacco smoke (ETS). In contrast, main stream smoke emerges from the butt end of the cigarette and is mainly inhaled by the smoker. This study was performed to compare the effects of short-term exposure to cigarette smoke condensates prepared from sidestream (CSC-SS) and mainstream cigarette smoke (CSC-MS) on macrophage basal metabolism and responsiveness to two different stimuli, bacterial lipopolysaccharide (LPS) and interferon gamma (IFNgamma). Despite their generation at different temperatures and their different chemical composition, CSC - SS and CSC - MS had similar effects on macrophages. Both enhanced macrophage basal metabolism and responsiveness to LPS. Macrophage responsiveness to IFNgamma, assessed by their expression of four functional capacities, was suppressed by both CSC-SS and CSC-MS. The four assessed IFNgamma-inducible functional capacities were: enhanced phagocytosis of immuoglobulin-opsonized sheep red blood cells, TPA-induced peroxide production, class II major histocompatibility complex expression, and nitric oxide synthesis with LPS co-stimulation. The effects of CSC - SS and CSC - MS were similar qualitatively; they differ quantitatively in some cases, with CSC-MS generally effective at lower concentrations (expressed as cigarette-equivalents) than CSC-SS. Considering dilution of sidestream smoke in room air and loss during passage through the respiratory system, we expect to deliver the maximal dose to lung macrophages in situ only in rooms dense with smokers. However, only a fraction of the maximal dose can partially suppress induction of some functions, such as nitric oxide production and MHC expression. Macrophages play critical roles in tissue modeling during development. Of particular concern are neonates, whose organs are still undergoing growth and development, and are therefore susceptible to impaired development. If involuntary exposure to ETS hinders induction of macrophage functional capacities by cytokines, then development of the lungs and perhaps other organs would be impaired. In general, since macrophages are potent effectors and regulators of immunity, impairment of their responsiveness to cytokine must disrupt the proper functioning of the immune system.

Immunotoxicology of cigarette smoke condensates: suppression of macrophage responsiveness to interferon gamma

We have investigated systematically the effects of short-term exposure to main stream cigarette smoke condensates (CSC-MS) on basal and inducible functional capacities of murine peritoneal exudate macrophages. Macrophages treated with CSC-MS form granules that fluoresce orange under blue excitation, consistent with the speculation that they are polycyclic aromatic hydrocarbons (PAH). CSC-MS selectively suppressed interferon gamma (IFN gamma) induction of four macrophage functional capacities: enhanced phagocytosis of immunoglobulin-opsonized sheep red blood cells, TPA-induced H2O2 production, class II major histocompatibility complex expression, and nitric oxide synthesis. In contrast, two macrophage functions that are not induced by IFN gamma, basal electron transport and LPS-induced TNF alpha production, were enhanced by treatment with CSC-MS. These results suggest that the suppressive effects of CSC-MS on macrophage responsiveness were selective and were not due to nonspecific inhibition of general functions such as RNA or protein synthesis. Since macrophage responsiveness to IFN gamma can result in induction of functional capacities that are fundamental to immunity, the data suggest that CSC-MS maybe deleterious to the general health of the smoker.

Fc gamma receptor-dependent clearance is enhanced following lipopolysaccharide in vivo treatment

Lipopolysaccharides (LPS) occupy centre stage in the pathogenesis of gram-negative sepsis. Although LPS are potent stimulators of the mononuclear phagocyte system (MPS), their effects on immune complex (IC)-specific clearance have not yet been reported. In order to evaluate this issue, we examined the MPS function after LPS treatment by measuring intravascular removal rate of syngeneic erythrocytes sensitized with specific immunoglobulin G (IgG) (EA). Our findings showed that LPS, directly or through the release of endogenous cytokines, enhance Fc gamma receptor (Fc gamma R)-dependent clearance. The EA uptake by liver, spleen and bone marrow was significantly increased leading to an effective clearance of immune complexes. Splenic antibody-dependent cellular cytotoxicity (ADCC), an in vitro indicator of Fc gamma R functionality, was also increased after in vivo LPS treatment. However, cytometric studies showed that endotoxin did not modify Fc gamma R expression on splenocytes, but markedly enhanced the expression of CD11b/CD18 (Mac-1), an adhesion molecule closely related to Fc gamma R activity. We conclude that LPS enhance Fc gamma R-dependent effector functions and suggest that this effect is mediated through alterations in adhesion molecules.

Upregulation of tumor necrosis factor alpha and interleukin-1 beta in Q fever endocarditis

The occurrence of Q fever endocarditis likely involves some alterations in the responses of monocytes, the in vivo targets of Coxiella burnetii. To test this hypothesis, the production of the inflammatory cytokines tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6 was assessed in monocytes from patients with Q fever endocarditis. Spontaneous transcription and secretion of tumor necrosis factor and interleukin-1 were significantly higher in patient monocytes than in healthy controls. The interleukin-6 transcripts were also upregulated in patient cells. Moreover, in patients with recent endocarditis exhibiting high titers of immunoglobulin G directed to C. burnetii in phase I, monocytes released significantly higher levels of tumor necrosis factor and interleukin-1 than in patients with stabilized endocarditis. Immunoglobulin G titers and the overproduction of tumor necrosis factor and interleukin-1 were significantly correlated. Hence, the overproduction of inflammatory cytokines might be a marker of disease activity.

A possible role for lysozyme in determining acute exacerbation in chronic bronchitis

The aggregation of non-serotypable Haemophilus influenzae (NTHI) by whole saliva from patients with chronic obstructive lung disease (COLD) was investigated. Significant differences were observed between salivary aggregating activity of a control and COLD population (P < 0.001). Saliva from patients less prone to acute exacerbations had a greater capacity to aggregate bacteria compared with saliva from patients with a predilection to infection. The mechanism of saliva-mediated aggregation of NTHI was investigated and shown to be related to lysozyme content. Lysozyme activity in saliva was measured by the turbidimetric technique and results showed that patients with chronic bronchitis had increased levels of salivary lysozyme, with a subpopulation within the non-infection-prone group having greater amounts. A significant difference was observed in salivary lysozyme between controls and non-infection-prone (P < 0.005) and infection-prone (P < 0.05) patients, respectively: the non-infection-prone patients having significantly (P < 0.005) more than the infection-prone patients. There was significant correlation (r = 0.742, P < 0.001) between salivary aggregation of NTHI and lysozyme activity. Chromatographically purified human lysozyme had a similar aggregation profile to that of saliva. There was no difference in serum and saliva lactoferrin concentrations between groups, but there was a significant increase (P < 0.05) in serum lysozyme concentration in the non-infection-prone group. This study suggests that the level of salivary lysozyme derived from macrophages may play an important role in determining resistance or susceptibility to acute bronchitis.

Pulmonary immunity to Pseudomonas aeruginosa in intestinally immunized rats roles of alveolar macrophages, tumor necrosis factor alpha, and interleukin-1 alpha

The aims of this study were to assess the role played by alveolar macrophages, tumor necrosis factor alpha (TNF-alpha), and interleukin-1 alpha (IL-1 alpha) in pulmonary immunity against Pseudomonas aeruginosa in animals that have been immunized via the gut-associated lymphoid tissue. Following intra-Peyer's patch immunization and subsequent intratracheal challenge with live bacteria, significantly enhanced bacterial clearance from the lungs correlated with an increase in bronchoalveolar neutrophils, increased recruitment and phagocytic activity of alveolar macrophages, and accelerated production of TNF-alpha in the bronchoalveolar space, while levels of IL-1 alpha remained low. Administration of recombinant TNF-alpha in physiological concentrations did not affect the proliferation of P. aeruginosa in vitro, but when given intratracheally to rats at the time of infection, recombinant TNF-alpha significantly increased bacterial clearance from the lungs. In these animals, phagocytic activity of bronchoalveolar neutrophils was enhanced, while the recruitment of alveolar macrophages and neutrophils remained unchanged. In acutely infected nonimmune animals, bronchoalveolar concentrations of soluble IL-1 alpha and TNF-alpha increased until the time of death. Levels of prostaglandin E2 and thromboxane B2 were similar in each experimental group. These results indicate that infection in immune animals enhanced both recruitment and phagocytic activity of alveolar macrophages as well as induced an accelerated production of TNF-alpha. In immune challenged animals, this cytokine enhanced the phagocytic activity of neutrophils and improved bacterial clearance from the lung. Levels of soluble IL-1 alpha and TNF-alpha in nonimmune rats increased consistently following infection until the time of death, thus implicating these cytokines in the pathogenesis of acute P. aeruginosa pneumonia.

Role of Acetylsalicylic Acid in Cytokine Stimulation of Macrophages in Antibody-Dependent Cellular Cytotoxicity (ADCC)

In addition to the spectrum of biological action already known to be exhibited by acetylsalicylic acid (ASA) as an analgesic, anti-inflammatory and platelet aggregation inhibitor, there is growing evidence of a stimulatory effect on the immune system. ASA has been found to increase the production ofcytokines and to increase the activity of various leukocytes. The action of ASA on the activity of mouse peritoneal macrophages was therefore investigated in the present study. Therapeutically effective concentrations of ASA, which are known to decrease levels of prostaglandins, had neither a stimulating nor an inhibiting influence on antibody-dependent cellular cytotoxicity (ADCC) or on the binding capacity of macrophages with regard to SW 948 tumour cells. Likewise ASA had little or no adverse effect on the capacity of the macrophages for stimulation by interferon-gamma (IFN-gamma) and interleukin-4 (IL-4). Taken together, the immunostimulant effect of ASA shown in the literature as an increased production of interleukin-2 (IL-2) and IFN, could not be confirmed on the basis of the macrophage cytotoxiclty.

Modulation of macrophage function by transforming growth factor beta, interleukin-4, and interleukin-10

The findings reviewed above leave no doubt as to the complexity of actions of TGF-beta, IL-4, and IL-10 on monocytes/macrophages. Along with MDF, whose actions were recently reviewed elsewhere, TGF-beta, IL-4, and IL-10 are the only presently known, purified cytokines that have been shown to have strong macrophage-deactivating effects. However, none of them can be categorized as purely macrophage deactivating since they also exert macrophage-activating effects. In vitro, their effects, both in terms of extent and direction (activating vs. deactivating), are strongly influenced by the stimulation conditions (e.g., triggering signal, cytokine concentration, timing of cytokine addition), the species (mouse vs. human), the source (blood vs. peritoneal, alveolar, colostral) and the state of differentiation/activation of the macrophage (e.g., resting vs. inflammatory). In addition, TGF-beta, as well as IL-4 and IL-10, up- and/or downregulates the function of several cell types other than macrophages, which further hampers our ability to predict, on the basis of in vitro experiments with macrophages, possible effects during an immune response in vivo. Despite this complexity, the highly reductive approach of in vitro studies has revealed important differences in the ability of TGF-beta, IL-4, and IL-10 to modulate the phenotype of monocytes/macrophages. The disparities have been most striking with regard to the secretory function of monocytes/macrophages (see Table 2). First, TGF-beta, IL-4, and IL-10 have a different spectrum of activity. Thus, TGF-beta, but not IL-4 or IL-10, can induce resting human monocytes to produce TNF, IL-1, and IL-6. Second, they affect monokine and RNI and ROI production to a different extent. For example, IL-10 is an approximately 25-fold more potent suppressor of LPS-induced TNF production by mouse macrophages than is TGF-beta. Third, they differ in their ability to overcome additional activating stimuli, so that in the presence of LPS, IL-4, but not TGF-beta or IL-10 suppresses IFN gamma-induced RNI release. Fourth, their macrophage-deactivating effects require different stimulation conditions. Thus, IL-4, but not TGF-beta, interferes with RNI release strongly only after preincubation of the macrophages. Finally, these agents deactivate macrophages by distinct mechanisms. For example, IL-10 causes massive downregulation of TNF mRNA, whereas TGF-beta suppresses TNF release on a translational level. It will be a challenge to define clinical applications for these potent macrophage modulators on the basis of their different spectrum of activities. For TGF-beta and IL-4 such studies have already been initiated.

Neonatal pinealectomy impairs murine antibody-dependent cellular cytotoxicity

The pineal gland, through its principal hormone melatonin, is able to modulate different immune functions. We have previously demonstrated that exogenous melatonin induces a significant enhancement of murine antibody-dependent cellular cytotoxicity (ADCC). In order to determine whether the pineal gland plays a physiological role in ADCC regulation, we studied the influence of neonatal pinealectomy on this activity. The results presented here indicate that ablation of the pineal gland during the first week of life significantly reduces ADCC levels in adult mice. This impairment appears around 60 days of age, suggesting that sexual hormones may be involved in the pineal effect. Moreover, the administration of melatonin to pinealectomized mice restores ADCC levels regardless of the hour and seasonal time of injection. On the basis of the data reported here, a physiological regulation of ADCC by the pineal gland can be assumed.