The cytokine wall chart

Influence of Polysulphone-Derived Dialysis Membranes on the Interaction of Circulating Mononuclear Cells with the Endothelium

Purpose

Cardiovascular morbidity in hemodialysis (HD) patients may be influenced by the activation of circulating mononuclear cells (MCs) with subsequently increased endothelium interaction. The use of more biocompatible membranes would reduce this monocyte activation. We compare monocyte activation after using two different high-flux polymers, polysulphone and polyethersulphone.

Methods

The first part of the study was done with 10 patients who successively received dialysis for 2 weeks with polysulphone and polyethersulphone. The second part with 30 patients dialyzed for 3 months with polysulphone or polyethersulphone. Blood samples were taken before (pre-HD) and after (post-HD) the first HD session with each membrane to evaluate the effect of a single HD session. To assess acute and chronic effects of membranes, blood samples were taken pre-HD, after 2 weeks (first part of study) and after 3 months (second part of study). MCs were isolated from blood and then incubated with cultured human endothelial cells to evaluate MC adhesion, MC-dependent endothelial toxicity, and endothelial protein expressions of nitric oxide synthase and endothelin-converting enzyme-1 (ECE-1).

Results

One single HD session did not induce any changes. Dialysis for 2 weeks (first part of study) with polyethersulphone reduced MC adhesion to endothelium, cellular toxicity, and ECE-1 protein expression compared to polysulphone or basal conditions. Dialysis for 3 months (second part of study) increased MC adhesion to endothelium, whereas cellular toxicity was decreased with both dialyzers compared to the basal situation.

Conclusions

Although polyethersulphone HD decreased the interaction of MC with the endothelium in short-term experiments, both membranes were comparable in the long-term.

Relationships between Helicobacter pylori infection status, endoscopic, histopathological findings, and cytokine production in the duodenum of Crohn's disease patients

BACKGROUND

The chronic inflammatory process in patients with Crohn's disease (CD) may affect any part of the gastrointestinal (GI) tract. The pathogenesis of CD involves immunological abnormalities, including deficient or excessive expression of cytokines. We examined Helicobacter pylori infection status, endoscopic and histopathological findings, and cytokine production in the duodenum of CD patients in comparison with controls.

METHODS

Thirty-eight CD patients underwent diagnostic upper GI endoscopy. Twelve age- and sex-matched health checkup examinees were used as controls. H. pylori infection status was assessed by the (13)C-urea breath test. At the time of endoscopy, two biopsy specimens each were obtained from the second portion of the duodenum, one for hematoxylin-eosin staining and immunohistochemical analysis with anti-CD68 antibody, and one for in vitro organ culture. Interleukin (IL)-6 and -8 levels were measured in organ culture supernatant by enzyme-linked immunosorbent assay.

RESULTS

H. pylori infection was significantly (P<0.05) more frequent in controls (42%) than in CD patients (8%). In the duodenum, erosions or ulcers were more frequent in CD patients (53%) than in controls (8%). Mononuclear cell infiltration in the duodenum was more severe in CD patients than in controls and IL-6 production was higher, whereas IL-8 production showed no significant difference. CD68+ cells in the duodenum were more prominent in CD patients than in controls.

CONCLUSIONS

H. pylori infection is unlikely in CD patients, but they show immunological abnormalities in the duodenum, possibly from innate immune responses.

Characteristics of bone marrow cells under conditions of impaired innervation in patients with spinal trauma

We studied quantitative and functional parameters of bone marrow stem cells and mature lymphocyte population under conditions of impaired innervation in patients with injuries to the cervical and thoracic portions of the spinal cord. Our findings indicated the absence of deficiency of quantitative and proliferative potentials of stem cells and demonstrated intact subpopulation structure of mature lymphocytes and T-cell proliferative activity similar to that in donors. The content of CD34+ cells in patients did not differ from that in donors. The percentage of CD34+CD38- hemopoietic stem cells was elevated in patients, presumably due to increased proliferative activity of hemopoietic stem cells. The possibility of derivation and in vitro culturing of fibroblast-like cells with mesenchymal stem cell phenotype was demonstrated.

Regulation of immunity to malaria: valuable lessons learned from murine models

A major advance in immunology has been the establishment of a framework for analysing how certain immune responses dominate following exposure to a particular pathogen or antigen. CD4(+) T helper (Th) cells can be separated into two major subsets which mediate qualitatively distinct cell-mediated (Th1) and humoral (Th2) immune responses. Immunity to most pathogens can be broadly categorized into a predominant protective response of either type. A characteristic of murine malarias is that primary infections with asexual erythrocytic parasites (the pathogenic stage of the malaria life cycle) generate a host protective immune response with a broad spectrum of Th1- and Th2-type CD4(+) T-cell involvement and so can be examined as models of the interaction of Th1 and Th2 cells during an immune response to an infectious agent. Andrew Taylor-Robinson here describes recent events in the dissection of the mechanisms responsible for the generation of protective immunity to Plasmodium chabaudi chabaudi and other experimental malarias in mice.

Depressed immunity and impaired proliferation of hematopoietic progenitor cells in patients with complete spinal cord injury

The bone marrow is supplied with both sensory and autonomic neurons, but their roles in regulating hematopoietic and immunocompetent cells are unknown. Leukocyte growth and activity in patients with stable and complete spinal cord injuries were studied. The innervation of the bone marrow below the injury level lacked normal supraspinal activity, that is, a decentralized bone marrow. Lymphocyte functions were markedly decreased in injured patients. Long-term colony formation of all hematopoietic cell lineages, including dendritic cells, by decentralized bone marrow cells was substantially reduced. It was concluded that nonspecific and adaptive lymphocyte-mediated immunity and growth of early hematopoietic progenitor cells are impaired in patients with spinal cord injuries. Possibly, this reflects cellular defects caused by the malfunctioning neuronal regulation of immune and bone marrow function.

Depressed immunity and impaired proliferation of hematopoietic progenitor cells in patients with complete spinal cord injury

The bone marrow is supplied with both sensory and autonomic neurons, but their roles in regulating hematopoietic and immunocompetent cells are unknown. Leukocyte growth and activity in patients with stable and complete spinal cord injuries were studied. The innervation of the bone marrow below the injury level lacked normal supraspinal activity, that is, a decentralized bone marrow. Lymphocyte functions were markedly decreased in injured patients. Long-term colony formation of all hematopoietic cell lineages, including dendritic cells, by decentralized bone marrow cells was substantially reduced. It was concluded that nonspecific and adaptive lymphocyte-mediated immunity and growth of early hematopoietic progenitor cells are impaired in patients with spinal cord injuries. Possibly, this reflects cellular defects caused by the malfunctioning neuronal regulation of immune and bone marrow function.

Role of different dialysis membranes in the release of interleukin-6-soluble receptor in uremic patients

BACKGROUND

Interleukin-6 (IL-6) exerts its actions through a cell-surface receptor system that consists of two transmembrane subunits: the IL-6 binding glycoprotein gp 80 (IL-6R) and the signal-transducing component (gp 130). Soluble forms of the IL-6R (sIL-6R) are generated by shedding of the membrane-associated proteins. The sIL-6R binds the ligand IL-6 with comparable affinity as the membrane-associated IL-6R and enhances the actions of IL-6.

METHODS

Our aim was to evaluate the role of both uremia and different dialysis membranes on peripheral blood mononuclear cell (PBMC) release (either in absence or in presence of mitogen stimulation) and plasma levels of sIL-6R. Ten patients chronically dialyzed with cuprophan membranes (CU), eight patients on regular dialysis treatment with polymethylmethacrylate (PMMA) membranes, 11 uremic nondialyzed patients (UR), and 12 healthy subjects (CON) were included in the study.

RESULTS

PBMCs harvested from CU spontaneously released significantly (P < 0.01) greater amounts of sIL-6R (881.8 +/- 80.1 pg/mL), as compared with CON (267.5 +/- 26.5 pg/mL), UR (258.4 +/- 38.1 pg/mL), and PMMA (288.4 +/- 24.6 pg/mL). Under mitogenic stimulation, the sIL-6R release was significantly (P < 0.01) increased in all groups. The greater PBMC production of sIL-6R in CU was followed by significantly (P < 0.01) higher levels of circulating soluble receptors (48.7 +/- 2.5 ng/mL, 60%), as compared with CON (30.5 +/- 1.9 ng/mL). UR also showed high circulating levels of sIL-6R (53.3 +/- 5.9 ng/mL), probably secondary to an impaired urinary excretion. Circulating levels of sIL-6R in PMMA were comparable to CON (30.3 +/- 3.3 ng/mL). Either the absence of monocyte activation or the adsorption of sIL-6R on the hydrophobic PMMA surface could explain this finding.

CONCLUSIONS

These results suggest an important role for poor dialysis biocompatibility of CU on the release of sIL-6R, which increases sIL-6R plasma levels, thereby enhancing the inflammatory effects of IL-6.

Cytokine production in haemodialysis

Many aspects regarding morbidity and mortality of dialysis patients are related to the production of cytokines by peripheral blood mononuclear cells. Clinical alterations resulting from cytokine production and release may include dialysis amyloidosis, malnutrition and atherogenesis. Cytokine release may also play a relevant role in immunodeficiency of dialysis patients by inducing alterations in immune and host-defense system. Interleukin-1, interleukin-6 and tumor necrosis factor are three pro-inflammatory cytokines, mainly produced by monocytes, and involved in pathogenetic aspects of hemodialysis-related diseases. In this review we analyse the mechanisms underlying monocyte activation and describe the different modalities for studying cytokine production and release. Clinical implications of cytokine production are also discussed.

Dysregulated hematopoiesis and a progressive neurological disorder induced by expression of an activated form of the human common beta chain in transgenic mice

Previously we described activating mutations of hbetac, the common signaling subunit of the receptors for the hematopoietic and inflammatory cytokines, GM-CSF, IL-3, and IL-5. The activated mutant, hbetacFIDelta, is able to confer growth factor-independent proliferation on the murine myeloid cell line FDC-P1, and on primary committed myeloid progenitors. We have used this activating mutation to study the effects of chronic cytokine receptor stimulation. Transgenic mice were produced carrying the hbetacFIDelta cDNA linked to the constitutive promoter derived from the phosphoglycerate kinase gene, PGK-1. Transgene expression was demonstrated in several tissues and functional activity of the mutant receptor was confirmed in hematopoietic tissues by the presence of granulocyte macrophage and macrophage colony-forming cells (CFU-GM and CFU-M) in the absence of added cytokines. All transgenic mice display a myeloproliferative disorder characterized by splenomegaly, erythrocytosis, and granulocytic and megakaryocytic hyperplasia. This disorder resembles the human disease polycythemia vera, suggesting that activating mutations in hbetac may play a role in the pathogenesis of this myeloproliferative disorder. In addition, these transgenic mice develop a sporadic, progressive neurological disease and display bilateral, symmetrical foci of necrosis in the white matter of brain stem associated with an accumulation of macrophages. Thus, chronic hbetac activation has the potential to contribute to pathological events in the central nervous system.

Cytokines and food intake: the relevance of the immune system to the student of ingestive behavior

The aims of this paper are to provide a selective review of the literature relating immune system mediators, especially cytokines, to the control of eating and to indicate why this literature is particularly relevant to the student of ingestive behavior. Four reasons are given. Firstly, many immune system mediators influence eating, providing excellent examples of neuroimmunological controls of behaviour. Secondly, the immune system appears to be involved in the profound eating pathology associated with several clinical conditions. Thirdly, cytokines affect both energy intake and energy expenditure. Fourthly, the anorexia typically associated with activation of the immune system provides an informative model for the analysis of gut-brain communication in the control of eating.

Cutaneous reactions to recombinant cytokine therapy

Cytokines are critical to several fundamental homeostatic mechanisms such as fever, acute phase reactions, wound healing, hematopoiesis, inflammation, cellular and humoral immune responses, and tumor regression. As a result of advances in recombinant DNA technology, recombinant cytokines are available as therapeutic agents. They have been used for metastatic cancers and immunodeficiencies, as a therapy for naturally occurring or drug-induced anemias or leukopenias, and they have also been applied to some cutaneous disorders. Cytokine therapy can result in toxic reactions that affect many organ systems, especially the skin. These reactions are common and diverse, ranging from minor injection site reactions, pruritus, and flushing to life-threatening autoimmune disorders, severe erythroderma, or bullous skin reactions. This review focuses on the major cytokines that are in current clinical use or under investigation and describes the cutaneous complications of these agents.

Immunoprinting reveals different genetic bases for (auto)immuno diseases

The genetic basis of complex (auto)immune diseases has been studied for an ovine nematode infection, human rheumatoid arthritis (RA), early onset pauciarticular arthritis (EOPA) and multiple sclerosis (MS). Immunoprinting combines the powerful simplicity of polymerase chain reaction (PCR)-based amplification of discrete, highly informative microsatellite loci with the principle of genetic associations. This approach has allowed us to define novel genetic risk factors in adult RA patient categories whereas EOPA forms in juveniles display other prominent genetic contributions. Differentially regulated tumor necrosis factor (TNF) expression may lead to a better understanding of the causal pathogenesis of EOPA while T cell receptor (TCR) gene polymorphisms appear crucial for RA manifestations in certain patient groups. Statistically significant marker associations have still to be defined for MS in larger panels of patient and control cohorts. The clinical course of the disease will probably have to be taken into account when associations with lymphokine levels are evaluated. In essence a convoluted myriad of negative and a few positive disease association data have been generated efficiently by immunoprinting. As expected, the interrelationships are truly complicated between the polymorphic genetic instances predisposing to autoimmune disease. Nevertheless, risk factors may be defined on an individualized basis by indirect gene diagnosis revealing predispositions and providing a more solid basis for differential diagnosis and treatment.

The inhibitory activity of human interleukin-1 receptor antagonist is enhanced by type II interleukin-1 soluble receptor and hindered by type I interleukin-1 soluble receptor

Interleukin-1 (IL-1) is a major proinflammatory cytokine produced by monocytes/macrophages. At the inflammatory site, IL-1 is a potent inducer of the production of prostaglandin E2 (PGE2) and metalloproteinases on fibroblast-like cells, thus triggering tissue damage. The biological activity of IL-1 is counterbalanced by two types of inhibitors: the IL-1 receptor antagonist (IL-1Ra) which competitively binds IL-1 receptor without inducing signal transduction; and IL-1 soluble receptors (IL-1sR) which bind IL-1 and diminish the free concentration of soluble cytokine, thus hampering its binding to the cell surface receptor. Since IL-1sR can also bind IL-1Ra, we studied the simultaneous effects of both inhibitors on the production of interstitial collagenase (C'ase) and PGE2 by human dermal fibroblasts and synovial cells stimulated by either IL-1 alpha or IL-1 beta. IL-1Ra inhibited fibroblast and synovial cell stimulation by approximately 90%, with the exception of C'ase production by synovial cells which was inhibited by approximately 55%. Type I IL-1sR (IL-1sRI) preferentially inhibited IL-1 alpha, whereas type II IL-1sR (IL-1sRII) mainly inhibited IL-1 beta. When IL-1Ra was used simultaneously with IL-1sRI, the final inhibition was lower than that of either of the inhibitors. The simultaneous presence of IL-1Ra and IL-1sRII abolished the IL-1-induced production of PGE2 and C'ase on both dermal fibroblasts and synovial cells, demonstrating that concurrently these two inhibitors are able to abolish most of the inflammatory response. To our knowledge, this is the first example of two types of inhibitors that abolish each other's effects, one of which acts at the receptor level and the other at the ligand level, thus leaving ligand activity unimpaired.

Indirect gene diagnoses for complex (multifactorial) diseases--a review

The analysis of multifactorial diseases requires the efficient investigation of large numbers of (gene) loci and patient (family) samples. Since simple repetitive DNA markers are dispersed all over the chromosomes, molecular techniques employing these tools render most conventional screening procedures obsolete. Examples of tumors, autoimmune diseases and infections are presented to validate concepts of indirect gene diagnoses via simple, tandemly arranged, repetitive DNA sequences. The salient advantages of microsatellite technologies vs. those of multilocus DNA fingerprinting are weighed.

Indirect DNA/gene diagnoses via electrophoresis--an obsolete principle?

In principle, gene defects can be investigated directly or indirectly via informative polymorphisms in their vicinity. But because many defects are not yet defined molecularly, these inherited diseases can only be diagnosed indirectly via analysis of informative family situations. Since (multiple) mutation analyses, e.g. via DNA sequencing, are time-consuming and expensive, indirect analysis may still be performed initially--particularly in diseases caused by heterogenous mutations. We focus on diagnoses of neurological and (auto)immune diseases by polymerase chain reaction and separation of the DNA fragments via gel electrophoreses. Even after gene defects have been identified, indirect analysis might be necessary, for example in Huntington's chorea. Although this genetic defect has been characterized as a trinucleotide disease, indirect DNA diagnosis is still performed in particular cases for psychological reasons. The causes of autoimmune diseases are multifactorial and the inheritance is complex, involving several genes. Genome-wide screening programs may involve indirect approaches via analyses of polymorphic microsatellites. Large parts of the immunological genome can be covered when 20 or more genes are investigated simultaneously. Thus the genetic bases of autoimmune diseases are disclosed. Microsatellites themselves could have a biological meaning. We therefore discuss also DNA/protein interactions for simple tandem repeats, the major targets for indirect gene diagnoses. Only indirect evidence exists that certain simple repeats influence genomic (in)stability. Taken together, indirect gene diagnoses supplement direct approaches in a variety of different purposes and in combination with standard electrophoresis techniques.

CD38 ligation induces discrete cytokine mRNA expression in human cultured lymphocytes

Human CD38 is a surface glycoprotein expressed by different immuno-competent cells such as immature and activated lymphocytes, plasma cells and natural killer cells. It has recently been reported that the CD38 molecule exerts adenosine diphosphate ribosyl cyclase activity and is associated with distinct transmembrane signaling molecules. This study reports that ligation of CD38 by specific monoclonal antibodies (mAb) induces multiple cytokine mRNA expression in cultured peripheral blood mononuclear cells (PBMC). The mRNA for tumor necrosis factor-alpha, interleukin (IL)-1 beta, IL-6, granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-12 were always detected, whereas interferon-gamma and IL-10 mRNA expression were seen in most, but not all PBMC cultures. Low levels of IL-2, IL-4 and IL-5 mRNA were also found. The key observation of this work is that CD38 ligation in PBMC induces a large spectrum of cytokines, many of which overlap with those induced via CD3 activation. The main differences between CD38 and CD3 activation are the low to undetectable levels of IL-2 mRNA, and the sustained IL-1 beta and IL-6 mRNA accumulation found in PBMC cultures following treatment with anti-CD38 mAb. Furthermore, PBMC proliferation was not found to be a prerequisite for CD38-mediated cytokine induction. Together, these results suggest that human CD38 activates a signaling pathway which leads to the induction of a discrete array of cytokines, and that this pathway only partially overlaps with that controlled by T cell receptor CD3.

Purification and characterization of a pregnancy-associated protein: TJ6s

PROBLEM

Characterization of the soluble form of a novel protein, TJ6 (TJ6s) with immune suppressive activity from murine fetoplacental units.

METHOD

Preferential ammonium sulfate precipitation, gel filtration and ion-exchange chromatography were employed to purify the protein TJ6s from murine fetoplacental units using an anti-peptide antibody as a detection tool. Biological activity of the purified protein was studied in lymphocyte proliferation assays.

RESULTS

Purified TJ6s has a M(r) of approximately 18 kDa as evidenced by SDS-PAGE in both reducing and non reducing conditions. It exerted a strong anti-proliferative activity in both anti-CD3 and Con A proliferation lymphocyte proliferation assays but not in a PHA assay, suggesting that the anti-proliferative effects on T cells are exerted only on cells specifically activated directly through T cell receptor complex.

CONCLUSION

The results indicate that TJ6s is a novel anti-proliferative protein that has many of the characteristics that are considered necessary for survival of the fetal allograft.

Characterization of binding sites for neuropeptide FF on T lymphocytes of the Jurkat cell line

Neuropeptide FF (NPFF) is a neuropeptide with antiopiate properties able to antagonize the action of both endogenous and exogenous opiates. Because we have recently shown that NPFF modulates the proliferation of human T lymphocytes, we have searched for binding sites for this peptide on T lymphocytes. Our study shows that T lymphocytes of the Jurkat cell line express binding sites for [125I]YLFQPQRFamide, an iodinated analogue of NPFF. This binding is time and dose dependent, reversible, saturable, and may be resolved in two distinct components of high and low affinity. The opiate receptor agonists mu, delta, and kappa, as well the antagonist naloxone, were unable to affect binding. Beside the effects of opiates on immune cells, our results suggest that an antiopiate peptide, such as NPFF, could play a role in the modulation of the immune system.

Exploiting the informativity of 'meaningless' simple repetitive DNA from indirect gene diagnosis to multilocus genome scanning

Most eukaryotic genomes are characterized by excessively large amounts of non-coding DNA sequences among which redundant (repetitive) elements constitute a sizable portion. The functional role of an abundant subclass of repetitive sequences--simple, tandemly arranged repeats--remained mysterious so far. Even the biological meaning of most of these elements appears quite refractory to present-day techniques in molecular genetics. Notwithstanding simple repetitive sequences have been developed into superb tools for various aspects of eukaryotic genome research: Using oligonucleotide probes carrying simple repeat motifs multilocus DNA fingerprinting can be applied for individual identification and genetic relationship analyses in plants, animals and humans. Microsatellite analyses via polymerase chain reaction of simple repeat blocks allow for efficient investigations of such divers subject matters as criminal stains, detailed genome maps and indirect gene diagnoses.

Tumour necrosis factor-alpha and other cytokines in Guillain-Barré syndrome

The efficacy of plasma exchange implicates myelinotoxic humoral factors in the pathogenesis of Guillain-Barré syndrome. Candidate factors include autoantibodies to peripheral nerve myelin, which are not unique to Guillain-Barré syndrome; and cytokines such as tumour necrosis factor-alpha (TNF-alpha) which are T cell/macrophage products. Plasma cytokine concentrations were determined in 26 patients with Guillain-Barré syndrome undergoing plasma exchange, 25 with other acute neurological diseases, and 40 healthy controls. Raised TNF-alpha concentrations (> 25 pg/ml) were found in seven of 26 patients with Guillain-Barré syndrome v none of 23 disease controls (p = 0.001). The peak grade of clinical deficit correlated with TNF-alpha concentrations (r = 0.6, p < 0.01). There was no significant difference between interleukin-1 beta or interferon-gamma concentrations in patients and disease controls. The data suggest that TNF-alpha may be a critical factor in the pathogenesis of Guillain-Barré syndrome.

Cytokines and the immune response

The recent massive growth and development of clinical immunology has been enriched by the discovery of a new family of molecules, the cytokines, which consist of various groups of polypeptide mediators involved in the communication network of the cells of the immune system. This article provides an overview of the immune system and the current status of the cytokines and their clinical application.

Primate antibodies to components of the human immune system

The feasibility to raise nonhuman primate antibodies against selected components of the human immune system was tested. The immunogens were whole cells (human T lymphocytes) or purified, recombinant human proteins (cytokines: TNF alpha or GM-CSF; soluble forms of cell surface antigens: sCD4 or sCD25). Significant immunizations, yielding functionally relevant antibodies, were readily achieved in rhesus monkeys, but, not surprisingly, may be less frequent in chimpanzees. The results suggest a general strategy for production of therapeutically useful MAB.

Cytotoxicity of cytokine-induced killer cells coated with bispecific antibody against acute myeloid leukemia cells

Various types of cytokines have been used in in vitro experiments to generate cytokine-induced killer (CIK) cells that are reactive to patient acute myeloid leukemia (AML) cells. Of these CIK cells, interleukin-2 (IL-2)-activated peripheral blood mononuclear cells, i.e., lymphokine-activated killer (LAK) cells, with the initial addition of the anti-CD3 monoclonal antibody (T3 LAK cells), are the most potent cytotoxic lymphocytes, and have marked proliferative capacity. The cytotoxicity of such T3 LAK cells against CD13+ AML cells is further enhanced by the addition of anti-CD3 x anti-CD13 bispecific antibody (BsAb) during the cytotoxicity assay. The combined use of T3 LAK cells and the BsAb can be used for ex vivo purging of CD13+ AML cells in autologous bone marrow transplantation. Other cytokines, such as IL-7 or IL-7 in combination with IL-2, or newly identified cytokines, will also be tested in attempts to obtain more specific and more potent effector cells. Studies of methods to increase the susceptibility of AML cells to CIK are also required.

Immune mechanisms in atherogenesis

Research in recent years has resulted in an increased understanding of the molecular mechanisms in the development of inflammatory processes. In atherosclerosis, focal expression of key adhesion molecules has been detected which may mediate the recruitment of mononuclear cells to the plaque. Local cytokine production could account for further cell migration and proliferation. The presence of substantial numbers of T lymphocytes in the plaque and local and circulating autoantibodies to modified lipoproteins suggest that T and B lymphocyte responses may play important roles in these processes.

Intracellular Ca2+ stores of T lymphocytes: changes induced by in vitro and in vivo activation

Intracellular Ca2+ stores were investigated in resting and activated splenic T lymphocytes from Lewis rats. Activation was obtained either in vitro (spleen cells isolated from "naive" rats exposed to concanavalin A for 24 h) or in vivo (spleen cells from rats with fully developed symptoms of experimental allergic encephalomyelitis). In both experimental conditions several changes of Ca2+ homeostasis were observed with respect to resting lymphocytes: (1) a threefold increase of the total intracellular calcium (from 1.15 to 3.5 mmol/l); (2) a moderate increase of the pool sensitive to inositol 1,4,5-trisphosphate (IP3), investigated both in intact T lymphocytes (fura-2 and 45Ca(2+)-release techniques in cells challenged with phytohemagglutinin) and in T lymphocytes permeabilized with beta-escin (45Ca2+ release induced by saturating concentrations of IP3); and (3) the appearance of a pool released by the endoplasmic reticulum (ER) Ca2+ ATPase inhibitor thapsigargin (Tg), but insensitive to IP3, which, therefore, appears to be localized in areas of the ER devoid of the cognate receptor. The latter two findings were paralleled in activated lymphocytes by an increase of expression of ER markers, involved (calreticulin; Ca2+ ATPase) or not (protein disulfide isomerase) in the regulation of Ca2+ homeostasis. In contrast, calnexin (another ER marker) and the receptor for IP3 were increased to only a moderate extent. Finally, an enlargement of non-ER Ca2+ pools was observed in the cells pretreated with Tg in which 45Ca2+ release was induced by the Ca2+ ionophore ionomycin. Our results document structural and functional changes of intracellular Ca2+ stores which might play an important regulatory role in activated T lymphocytes.

In vitro cytokine production by HLA-B8,DR3 positive subjects

It is well known that healthy subjects carrying the HLA-B8,DR3 haplotype may show an impairment of immune system, the T cells being the most affected. To gain insight into the mechanism(s) of the impairment displayed by these subjects, efforts have been centered on the study of in vitro cytokine production because of the pivotal role played by these mediators in the activation and control of several immune functions. The available results indicate that the ability to several immune functions. The available results indicate that the ability to produce interleukin-1 (IL-1), IL-2 and the soluble form of its receptor (sIL-2R) is impaired in HLA-B8,DR3 positive healthy subjects. To better characterize the cytokine production capacity of HLA-B8,DR3 positive subjects, we have investigated the pattern of in vitro production of IL-2, sIL-2R, IL-4. IL-6 and gamma-interferon (gamma-IFN) by mononuclear cells from HLA-B8, DR3 positive subjects after phytohaemoagglutinin stimulation. A significant decrease of IL-2, sIL-2R and gamma-IFN production by HLA-B8,DR3 positive subjects was observed. No significant difference was instead found between the HLA-B8,DR3 positive subjects and the negative ones as regards IL-4 and IL-6 production. We suggest that this imbalanced cytokine production may well account for the pattern of immune response that may observed in HLA-B8,DR3 positive subjects, i.e. a normal or increased humoral response in face of a low T cell immune responsiveness.

CELL-SURFACE ANTIGENS

The cell surface is covered with protein molecules that are held in the membrane by hydrophobic transmembrane segments or glycosyl–phosphatidylinositol (GPI) anchors. Antigens found on cell surfaces comprise not only those encoded by the cell itself but also the products of intracellular parasites. Soluble ligands may be bound to receptor structures on the cell membrane or lectin-like molecules bound to cell-surface carbohydrate structures. The molecules that form an integral part of the cell surface may be proteins, glycoproteins, or glycolipids. They subserve one of three major functions: adhesion, antigen recognition, or receptors for soluble mediators. However, many cell-surface molecules possess more than one function—for example, molecules involved in cell–cell or cell–extracellular matrix adhesion can also themselves be involved in signal transduction. The cell-surface antigens of leukocytes have been intensively studied because of ease of access to this cellular compartment.

Development in the thymus: it takes two to tango

Intrathymic T-cell development is dependent upon signals provided by the thymic stromal cell microenvironment. However, loss of thymic T cells in natural and experimentally induced situations is associated with a reduction in the surrounding epithelium, suggesting an interdependence between thymocytes and their microenvironment. Here, the authors review the evidence in favour of this intrathymic symbiosis, and hypothesize that T cells may provide maturation and survival signals that are necessary for the development and maintenance of their microenvironment.