Accessory cells and T cell activation. The relationship between two components of macrophage accessory cell function: I-A and IL1

What Is IL-1 for? The Functions of Interleukin-1 Across Evolution

Interleukin-1 is a cytokine with potent inflammatory and immune-amplifying effects, mainly produced by macrophages during defensive reactions. In mammals, IL-1 is a superfamily of eleven structurally similar proteins, all involved in inflammation or its control, which mainly act through binding to specific receptors on the plasma membrane of target cells. IL-1 receptors are also a family of ten structurally similar transmembrane proteins that assemble in heterocomplexes. In addition to their innate immune/inflammatory effects, the physiological role of IL-1 family cytokines seems to be linked to the development of adaptive immunity in vertebrates. We will discuss why IL-1 developed in vertebrates and what is its physiological role, as a basis for understanding when and how it can be involved in the initiation and establishment of pathologies.

From Antigen Delivery System to Adjuvanticy: The Board Application of Nanoparticles in Vaccinology

In the last years, nanotechnologies have raised great interest because of the potential applications of engineered nanoparticles in nanomedicine (i.e., in vaccination, in diagnostic imaging procedures, and as therapeutic drug delivery systems). The use of nanoparticles in medicine has brought about the issue of their interaction with the immune system for two main reasons: first, understanding how long nanomedicines could persist in the organism and exert their beneficial effects before being recognized and eliminated by our defensive systems; second, understanding how the immune responses can be modulated by nanoparticles in order to obtain optimal effects. This issue is crucial in vaccine formulations based on the use of nanoparticles, which can operate both as a delivery system to enhance antigen processing and as an immunostimulatory adjuvant to induce and amplify protective immunity, in part because of their ability to activate the inflammasome and induce the maturation of interleukin 1β. Nanoparticles can be excellent adjuvants due to their biocompatibility and their physicochemical properties (e.g., size, shape, and surface charge), which can be tailored to obtain different immunological effects. This review provides an overview of recent strategies for the use of nanoparticles as promising/attractive adjuvants for novel prophylactic and therapeutic vaccines. The use of nanovaccines, with their practically infinite possibilities of specific design, could open the way to precision vaccinology, i.e., vaccine formulations tailored on the individual immune reactivity status.

There is more than one interleukin 1

In 1972, Gery and co-workers(1) detected a factor that promotes murine thymocyte proliferation in culture supernatants of human peripheral blood adherent leukocytes. This factor is active across species lines, does not support the growth of interleukin 2 (IL-2)-dependent lymphocyte lines, is produced by monocytic rather than lymphocytic leukocytes, and has subsequently been termed interleukin 1 (IL- 1)(2). More recently, it has become evident that IL-1 activities can be produced by virtually every nucleated cell type and, in addition, IL-1 has been reported to have stimulatory effects on the growth and differentiation of numerous cell types. In this review, Joost Oppenheim and his colleagues discuss the biochemical characteristics, gene cloning, cell sources, biological properties and actions of IL-1, and give reasons why this pleitotropic, nonspecific hormone-like cytokine is of considerable concern to immunologists.

Laser modulation of angiogenic factor production by T-lymphocytes

BACKGROUND AND OBJECTIVE

In previous investigations, small variations in the energy densities of low level light therapy (LLLT) were found to produce significant differences in the proliferation of resting T-lymphocytes in vitro. Pulsing these cells with mitogen in addition to laser therapy produced inhibitory effects regardless of the amplitude of the energy density used. In the current study, the effect of LLLT on the production of angiogenic factor(s) by T-lymphocytes was investigated in vitro.

STUDY DESIGN/MATERIALS AND METHODS

Human T-cells isolated from peripheral blood were prepared in suspension either with or without addition of mitogen. Cell suspensions were irradiated with laser by using the following energy densities: 1.2, 3.6, 6.0, and 8.4 J/cm(2). Wavelength, pulsing frequency, and power output were kept constant at 820 nm, 5,000 Hz, and 50 mW, respectively. After either 3 or 5 days of incubation, lymphocyte supernatants were collected and added as conditioned media to cultured endothelial cells (ECs). The effect on the proliferation of these ECs was assessed over a 72-hour period by using a methylene blue assay.

RESULTS

Endothelial cell proliferation increased significantly when incubated with conditioned media collected from resting T-cells exposed to 1.2 and 3.6 J/cm(2). Day 5 conditioned media produced similar patterns of EC proliferation to that of day 3 but at lower magnitude. Pulsing of T-lymphocytes with mitogen in addition to laser irradiation significantly lessened their angiogenic capability. Conditioned media from 3.6 J/cm(2) laser-treated T-cells induced the maximal EC proliferation in all groups studied.

CONCLUSION

It would seem that laser therapy stimulates lymphocytes to produce factor(s) that can modulate EC proliferation in vitro; this effect on the lymphocytes is influenced by (1) the amplitude of energy density used for T-cell irradiation, (2) exposing T-cells to both mitogen and laser, and (3) the duration of T-cell incubation in culture.

Mechanisms of immune activation of human immunodeficiency virus in monocytes/macrophages

Monocytes/macrophages (M/M) are the major host of human immunodeficiency virus (HIV) in solid tissues. However, blood monocytes are nonpermissive for HIV infection, indicating that M/M activation or differentiation is necessary for HIV replication. Since M/M are activated during immune responses, we investigated the effect of T-cell activation on HIV expression in M/M derived from peripheral blood of HIV-infected individuals. Previously, we reported that coculture of monocytes from HIV-infected donors with T cells and mitogens resulted in M/M differentiation and HIV expression. Production of HIV by M/M from infected donors required direct contact between monocytes and T cells (for the first 24 h), and the response to alloantigens, but not mitogens, was restricted to HLA-DR. In this study, we found that HIV was more readily recovered from M/M of asymptomatic HIV seropositive donors (69%) than from M/M of symptomatic donors (57%). Viral antigens (e.g., inactivated herpes simplex virus) could initiate the immune response and HIV expression. The ability of noninfected T cells to activate HIV expression in M/M and observations that treatments of M/M with antibodies to deplete T cells did not reduce HIV expression suggested that the monocytes were endogenously infected. To define the aspects of immune activation specifically involved in initiating HIV expression in M/M, interactions of M/M and T cells and participation of cytokines were investigated. The T cell which activated M/M was CD4+ CD8-. Fixed allogeneic cells are known to induce T-cell activation but were not able to serve as antigen for M/M differentiation, suggesting that M/M may need to function as antigen-presenting cells to receive the signal to differentiate and express HIV. Blocking of M/M-T-cell interaction with antibodies directed against LFA-1 or interleukin-1 prevented HIV expression. However, inhibition of later stages of T-cell activation, such as blocking of interleukin-2 receptors, did not diminish HIV expression in M/M. Consistent with the requirement for cell-cell contact between M/M and T cells, a variety of cytokines were unable to initiate HIV replication in M/M. The ability of T cells to induce cellular differentiation and HIV replication in M/M in vitro suggests that initiation of an immune response to an antigen, such as an opportunistic pathogen, could be a mechanism by which HIV disseminates to tissues in vivo.

Involvement of dendritic cells in early insulitis of BB rats

In this study, subsets of mononuclear infiltrates in pancreatic islets of BB rats at different stages of insulitis were determined by various monoclonal antibodies against rat lymphoid cells, including a mouse monoclonal IgM antibody that distinguishes between macrophages and dendritic cells (mAb 1F119). 1F119+ dendritic cells were absent in and around islets of Wistar control rats. In BB rats, the first alteration of islets detectable by immunohistochemistry when compared with normal islets was the enhanced expression of 1F119 antigen around and in the islets (17% 1F119+ islets). At disease stage 1 (i.e. no leukocyte infiltration after HE staining), lymphocytes and macrophages were almost absent. At disease stage 2 (leukocyte infiltration < 20 cells), a more intense form of dendritic cell infiltration was seen (stage 1 versus stage 2, P < 0.0001). In addition, ED2+ and ED3+ cells were present around the islets (50% of islets were infiltrated with 1F119+ cells versus 16% with ED2+, 19% with ED3+, 11% with W3/25+ cells, and 11% with OX8+ cells, P < 0.0001). At disease stage 3 (> 20 cells), a clear increase of ED2+ and ED3+ macrophages and of W3/25+ and OX8+ T-lymphocytes in the infiltrates was observed. These observations suggest a role for antigen presenting dendritic cells in the initiation of immune reaction in type 1 diabetes of BB rats.

IA antigen-positive epithelioid cells in experimentally induced granulomatous inflammation

IA antigens on the cell membrane of inflammatory macrophages and epithelioid cells were investigated with immunoelectron microscopic method during development of granulomas induced by subcutaneous inoculation of 10(7) Mycobacterium lepraemurium into mice with and without hypersensitivity. In C57BL/6N (H-2b) immunogenetic high responder mice 6 weeks after infection majority (87%) of infiltrated cells were IA-positive. Two types of the staining reaction, strong and weak reactivity, were recognized among the positive cells. Strongly IA-positive cells showed lower phagocytosis (0.9/cell section) of mycobacteria than the weakly reacted cells (4.9/cell section). The strongly positive cells underwent morphological differentiation into large epithelioid cells during development of the hypersensitivity-type murine lepromas after 10 or more weeks of infection. Types of granulomas and IA-positive cells in C57BL/6N (nu/+) mice were identical to those found in C57BL/6N. In C57BL/6N (nu/nu) athymic nude mice initial infiltrating cells contained 38% of weakly IA-positive macrophages and a small number (7%) of strongly IA-positive macrophages. But the reactivity was lost later and only 4% of IA-positive cells remained in the granulomas without hypersensitivity. CBA/J (H-2k) low responder mice did not show IA-positive cells in either initial or late stage during the development of nonhypersensitivity-type murine lepromas. We suggest that the presence of IA-positive cells, particularly IA-positive epithelioid cells, in the lesions modulates the course of granulomatous tissue reaction in murine lepromas.

HLA class II molecules on monocytes regulate T cell proliferation through physical interaction in the CD3 activation pathway

HLA class II molecules are involved in the OKT3-induced T cell activation, since monoclonal antibodies (mAb) to monomorphic determinants of class II antigens are able to inhibit T cell proliferation. This effect involves several of the events leading to T cell activation and proliferation, i.e. interleukin (IL) 1, IL 6 and IL2 secretion and IL2 receptor expression. The main target of the inhibition is represented by monocytes, and the interference of anti-class II mAb in the direct interaction of monocytes with T cells is likely to play a relevant role in the inhibition mechanism. To test this hypothesis, we investigated in the present study the effect of anti-class II mAb on the proliferation of T cells stimulated with mAb OKT3 in the presence of paraformaldehyde-treated monocytes. We show that the inhibition of proliferation is specific and dose dependent, and seems to involve particular class II epitopes. Addition of fixed monocytes to inhibited T cell cultures restores proliferation to a moderate extent, only if monocytes are added within the first 12 h of culture, suggesting that class II antigens or spatially related molecules deliver signals concurrently with the mitogenic stimulus. The blocking capability of anti-class II mAb was not restricted to the CD4+ or the CD8+ T cell subsets, suggesting that, under inhibitory conditions, these mAb affect other structures on the T cell surface, relevant to the monocyte-T cell interaction.

Interleukin-1-induced promotion of T-cell differentiation in mice immunized with killed Listeria monocytogenes

We studied the effects of administration of recombinant interleukin-1 alpha (rIL-1 alpha) to mice after immunization with killed Listeria monocytogenes cells on the promotion of the functional differentiation of T cells in vivo. Mice immunized with killed L. monocytogenes were unable to express cell-mediated immunity to specific antigen in vivo, as determined by delayed-type hypersensitivity (DTH) and acquired cellular resistance (ACR), and splenic T cells obtained from such mice were unable to respond to rIL-2 and specific antigen and to produce IL-2 after antigenic restimulation in vitro. When rIL-1 alpha was given to mice after immunization with killed bacteria. T cells became capable of responding to rIL-2 and specific antigen in vitro. These functions of T cells were similar to those from mice immunized with viable listeriae. Moreover, using a local passive transfer system, it was found that effector T cells mediating DTH but not ACR to L. monocytogenes were generated in mice treated with rIL-1 alpha after immunization with killed bacteria. These T cells were able to produce macrophage chemotactic factor but not macrophage-activating factor or gamma interferon in vitro in response to stimulation with specific antigen. These results suggest that in vivo administration of rIL-1 alpha facilitates the maturation of antigen-specific T cells mediating DTH and that different effector T cells mediating DTH or ACR are involved in cell-mediated immunity to L. monocytogenes.

Immunomodulating activity of ginsenoside Rg1 from Panax ginseng

The immunomodulatory activity of ginsenoside Rg1 from Panax ginseng was studied in mice using sheep red cells as the antigen. It was found that ginsenoside Rg1 at a dose of 10 mg/kg administered for three consecutive days before immunization increased the number of spleen plaque-forming cell, the titers of sera hemagglutinins as well as the number of antigen-reactive T-cells. Ginsenoside Rg1 also increased the number of T-helper cells with respect to the whole T-cell number and the splenocyte natural killer activity. Ginsenoside Rg1 induced an augmentation of the production of IL-1 by macrophages and exerted a direct mitogenic effect on microcultured thymus cells. Ginsenoside Rg1 also partly restored the impaired immune reactivity by cyclophosphamide treatment.

Accessory cells in normal human and rodent lymph nodes: morphology, phenotype, and functional implications

This chapter provides a brief review of the professional accessory cells present in normal human and rodent lymph nodes. When dealing with the function of accessory cells in the immune system it has to be borne in mind that in principle all cells may possess or acquire the capability of antigen presentation, which is the decisive initiating step in the specific host defense bound to the lymphoid cells. Professional accessory cells are arrayed at the afferent limb of the immune response. The majority of them have a typical dendritic morphology, so that the term "dendritic cells" is widely used instead of the term "accessory cells," and has replaced the traditional terms "reticulum cells" and "reticular cells." Professional accessory cells are characterized by: 1. The capability to stimulate specific T- or B-cell response following antigen pulsing 2. A dendritic morphology 3. Expression of major histocompatibility glycoproteins, complement, and Fc receptors as well as of various adhesion molecules. 4. Presentation of processed or unprocessed native antigens 5. Production and secretion of interleukin-1 and interleukin-6 The bimodal differentiation of lymphocytes seems to be reflected in the occurrence of two types of dendritic accessory cell: accessory cells involved in cellular (T accessory cells) and humoral (B accessory cells) immunity. T accessory cells of the lymph node comprise: 1. The lymphoid dendritic cell of Steinman, which probably represent a subset of blood monocytes with possible terminal differentiation into other T accessory cells 2. Veiled cells, which have been shown to represent Langerhans cells of the epidermal covering on their way to thymus-dependent areas of lymph node, probably giving rise to interdigitating dendritic (reticulum) cells 3. Interdigitating dendritic (reticulum) cells as the typical accessory cells of lymphoid T zone The T accessory cells share morphological, ultrastructural, immunophenotypic, and functional properties, are myeloid in origin, and very probably derive from monocyte lineage. As immune stimulatory cells they present processed antigen only and initiate T-cell proliferation and differentiation by interleukin-1 and -6 secretion. Accessory cells involved in the initiation of a primary humoral immune reaction have not been convincingly characterized. Accessory cells responsible for a secondary B-cell response, however, are the so-called follicular dendritic (reticulum) cells constituting the typical web-like structure of the primary and secondary lymphoid follicles. Unlike T accessory cells, follicular dendritic (reticulum) cells are distinguished by accentuated membrane desmosomes and extensive anastomosing branches of dendrites.(ABSTRACT TRUNCATED AT 400 WORDS)

In vivo stimulation and restoration of the immune response by the noninflammatory fragment 163-171 of human interleukin 1 beta

The synthetic nonapeptide VQGEESNDK, corresponding to the fragment 163-171 of human IL-1 beta, showed in vivo immunomodulatory capacities qualitatively and quantitatively comparable to those of the mature human IL-1 beta protein. In fact, both IL-1 beta and the 163-171 fragment stimulated the immune response of normal mice and restored immune reactivities of immunocompromised animals. In addition, the synthetic IL-1 peptide was as efficient as the entire protein in inducing tumor rejection and radioprotection. On the other hand, the 163-171 fragment did not cause any of several inflammation-associated metabolic changes inducible by the whole IL-1 beta molecule in vivo: hypoferremia, hypoglycemia, hyperinsulinemia, increase in circulating corticosterone, SAA and fibrinogen, decrease in hepatic drug-metabolizing enzymes. Furthermore, at variance with IL-1 beta, the 163-171 peptide did not show the toxic effects causing shock and death in adrenalectomized mice. Thus, these results confirm our previous in vitro observations that functional domains are identifiable within the multipotent cytokine IL-1 beta, and demonstrate the biological relevance of this finding in a variety of in vivo systems. The identification of a selectively active fragment of a cytokine may thus represent a significant step towards a better directed and more rational immunotherapeutic approach.

Removal of endotoxin from culture media by a polymyxin B sepharose column. The activity of contaminating endotoxin in culture media measured by the interleukin 1 inducing effect on human monocyte cultures and by the Limulus test

The in vitro study of monocytes (Mo) poses several problems. Minor contamination with endotoxin (ET) of media and utensils as well as adherence to glass or plastic surfaces may activate the cells and cause pronounced production of monokines. Many commercially liquid culture media were found to contain ET in concentrations above 25 X 10(-12) g/ml. A simple system for the removal of ET from media and solutions was established by use of a commercially available Polymyxin B Sepharose gel. To measure the lipopolysaccharide (LPS) binding capacity of the gel, known concentrations of LPS were added to culture media, which were passed through a column consisting of the Polymyxin B Sepharose gel. The content of ET and added LPS in media was measured by the Limulus amoebocyte lysate (LAL) test before and after passage of the column. The LPS-binding capacity of the gel was approximately 2.4 X 10(-6) g/10 ml. The biological activity of contaminating ET and added LPS in media, before and after passage of the column, was also characterized by the capacity of the media to induce interleukin 1 (IL-1) secretion in human Mo cultures. The content of IL-1 in Mo culture supernatants was determined by the mouse thymocyte costimulatory (LAF) assay. By comparison of the activity of ET in these different biological systems, it was demonstrated that 15-20 X 10(-12) g/ml of ET stimulate human Mo cultures to IL-1 secretion.

Inhibition by anti-HLA class II monoclonal antibodies of monocyte-dependent T cell proliferation induced by monoclonal antibody OKT3

The inhibitory effect of monoclonal antibodies (mAb) to monomorphic (locus-restricted and locus-shared) and polymorphic determinants of HLA class II antigens on the monocyte-dependent proliferation of T cells stimulated with mAb OKT3 has been studied. The effect appears to be specific, dose dependent, is not mediated by the Fc portion of mAb and reflects their interaction with the corresponding determinants. The anti-HLA class II mAb do not have to be present in the culture throughout the incubation period, but are essential in early phases of mAb OKT3 T cell activation. Both monocytes and T cells are the targets of the inhibition exerted by the anti-HLA class II mAb. Their inhibitory effect involves several steps in the sequence of events which leads to T cell proliferation, including interleukin (IL) 1 and 2 secretion, and IL2 receptor expression.

Recognition of rat dendritic cells by a monoclonal antibody

A mouse monoclonal IgM antibody reactive with dendritic cells (DC) from the Brown Norway (BN) rat was prepared. This antibody (1F119) binds to a membrane-bound antigen present on DC from thoracic duct lymph, spleen, thymus, and lymph node. The antigen is present only in low density on 5% of splenic macrophages (M phi) and absent from peritoneal M luminal diameter. In situ, the antibody exhibits a strong reactivity towards DC in the thymic medulla, whereas no reaction is observed with cortical cells. Furthermore, cells positive for 1F119 can be identified in T-cell areas of spleen, lymph node, and Peyers' patches. 1F119 was genetically restricted in that a strong reactivity was found with DC from rats of the RT1n and RT1u haplotypes, an intermediate reactivity with the RT1c haplotype, only a weak reactivity with the RT1l and RT1b haplotypes, and no reactivity with the RT1a and RT1k haplotypes. The relatively weak reactivity of 1F119 with respect to the RT1l haplotype also appeared from a weak binding of 1F119 to DC from Lewis rats, as was assessed by FACS analysis. This result was comparable to the binding of OX3 (RT1.Bl and RT1.Bu) to DC from BN rats. Studies performed on thymus sections of recombinant rat strains indicate that 1F119, despite its apparent specificity for DC, reacts with a polymorphic RT1.B product.

Effects of quinolones on interleukin 1 production in vitro by human monocytes

The new quinoline derivative antibiotics (quinolones), pefloxacin and ciprofloxacin at concentrations higher than 50 micrograms/ml inhibit the PHA response of the human mononuclear leukocytes in vitro. Since monocytes have been shown to be accessory cells for the activation of lymphocytes by mitogens, we investigated the effects of pefloxacin and ciprofloxacin on extracellular interleukin 1 (IL-1) and cell-associated IL-1 from lipopolysaccharide-stimulated human monocytes. Pefloxacin and ciprofloxacin decreased the extracellular IL-1 in a dose-dependent manner, while cell-associated IL-1 was not altered. These effects were observed even after a short period of incubation (1 or 2 h). No inhibitory activity against purified IL-1 or IL-2 could be demonstrated in the dialyzed supernatants from pefloxacin- or ciprofloxacin-treated monocytes. Neither pefloxacin nor ciprofloxacin modified the biological activity of preformed IL-1. The decrease of extracellular IL-1 induced by pefloxacin and ciprofloxacin could, in part, account for the observed decrease in the proliferative response of human mononuclear leukocytes to phytohemagglutinin, as extracellular IL-1 and proliferative response were positively correlated (at various concentrations of pefloxacin and ciprofloxacin). The decrease in extracellular IL-1 was not associated with any alteration in the expression of the HLA-DR antigen on the monocytes membrane. These data suggested that pefloxacin and ciprofloxacin could antagonize IL-1 production and release by lipopolysaccharide-stimulated monocytes. These quinolones could be interesting tools to study the production, processing, transport and release from the monocytes of IL-1.

On the role of astrocytes in polyclonal T cell activation

Murine astrocytes have been identified to possess accessory cell functions, which are thought to be regulated by the inducible expression of surface Ia molecules. The accessory cell functions include the induction of syngeneic and allogeneic T lymphocyte responses, the cytotoxic T cell activation towards haptens and the antigen-induced stimulation of helper T cell lines. In this report, astrocytes initially being Ia antigen-negative cells were found to restore the phytohaemagglutinin (PHA) response of mouse lymph node cells depleted of accessory cells by treatment with leucin methyl ester (Leu ME). Antisera against Ia determinants did not inhibit the PHA response or the release of interleukin-1 (IL-1) by activated astrocytes. Thus, the presence of Ia antigens is not required for mitogen-induced polyclonal T cell activation. In addition to IL-1 release, astrocytes may favour cell-cell contacts necessary for mitogen-induced polyclonal T cell response.

Immunization with antigen and interleukin 2 in vivo overcomes Ir gene low responsiveness

We studied the effect of purified interleukin 2 (IL-2), made by recombinant DNA techniques, on the serum antibody response to myoglobin in high- and low-responder mice. Previous studies (6, 7) have shown that this response is controlled by H-2-linked Ir genes. The IL-2 was emulsified with the antigen in complete Freund's adjuvant to provide a sustained high local concentration. In low-responder B10.BR mice, a single dose (optimum 50,000 U) resulted in a consistent 10-50-fold increase in specific serum antibody throughout the time course of the response, from 10 d to 46 d after immunization. In contrast, no effect of IL-2 was seen in congenic high-responder B10.D2 mice. With IL-2, the low-responder mice achieved specific antibody levels comparable to those of high responders. Vehicle alone had no effect, and IL-2 alone, without antigen, did not induce myoglobin-specific antibody. No effect of IL-2 was seen in athymic nude mice of high-responder H-2 haplotype. The effect of IL-2 may be on a small number of responding T cells in the low responder mice, but it is possible that IL-2 also acts directly on B cells in a response that remains T-dependent, and therefore is not observed in athymic mice. We suggest that IL-2 may enhance suboptimal T cell help in the low responder, whereas help is not limiting in the high responder. This approach may enable the study of antibody responses in low responders otherwise too weak to analyze, and may be useful in producing antibodies to poorly immunogenic antigens. Potential clinical uses include immunization with weak antigens in normal patients, or with any antigen in certain immunodeficient patients.