Interleukin 1 is more than an interleukin

Dextran sulfate-mediated enhancement of mitogen-induced B-cell proliferation

We have studied lipopolysaccharide (LPS)-induced proliferation of rat lymphocytes and have found that a serum-free tissue culture medium supports significant cell division. When the compound dextran sulfate (DxS), which itself is not mitogenic, is added to LPS-stimulated cultures, significant augmentation of proliferation results. DxS will significantly enhance anti-immunoglobulin-induced proliferation as well. An intact T-cell compartment is not required for DxS-mediated enhancement of LPS-induced cell division, in that lymphocytes derived from athymic rats proliferate and respond to the influence of DxS to the same degree as euthymic derived lymphocytes. A "DxS-free" supernatant from DxS-stimulated spleen cell cultures is able to substitute for DxS in all stimulatory activity. This supernatant possesses interleukin 1 (IL-1) activity. However, purified recombinant IL-1 does not cause enhanced proliferation when added to LPS-stimulated cultures as is seen with DxS or the "DxS-free" supernatant.

The role of lymphocytes, macrophages and interferon in the depression of drug metabolism by dextran sulfate

Cytochrome P-450-mediated drug biotransformation is depressed by many immune stimulants. We have shown that such depression caused by the immune stimulant dextran sulfate is mediated by Kupffer cells. The purpose of this study is to determine if other cells of the immune system or a cellular product such as interferon are involved in the depressive action of dextran sulfate on drug metabolism. Plasma samples taken from mice treated with dextran sulfate contained no detectable interferon, yet hepatic cytochrome P-450 was significantly depressed, suggesting that interferon did not mediate the depression of drug metabolism by dextran sulfate. Administration of cyclophosphamide or antilymphocyte serum to mice prior to dextran sulfate to markedly decrease lymphocyte populations did not prevent the depressive actions of dextran sulfate on cytochrome P-450, suggesting that the lymphocyte population was not involved in the dextran sulfate mediated depression. Preincubation of dextran sulfate with peritoneal macrophages prior to incubation with hepatocytes significantly depressed hepatocyte cytochrome P-450 content, while dextran sulfate alone had no direct effect on hepatocyte cytochrome P-450 content. These results further support the hypothesis that macrophages play a major role in the depression of cytochrome P-450 by dextran sulfate.

Dietary fat and neoplasia--the role of net energy in enhancement of carcinogenesis: effects of fat and calories on the immune system

The mechanism by which carcinogenesis is enhanced by dietary fat is not understood. We know that a minimum level of essential fatty acids (EFA) is necessary for mammary tumor development and that this level probably exceeds the normal requirements of rats. Once the minimum level of EFA has been supplied, the calorie contribution of dietary fat may account for its enhancement of carcinogenesis. In this regard, we must recognize that the efficiency with which dietary energy is utilized is known to increase as the fat content of the diet is raised. Hence even when fed isocalorically to low fat diets, high fat diets will provide more net energy. Modulation of host immunity has been proposed as a mechanism of action of both fat and calorie intake on neoplasia. We review the literature examining the effects of fat and calories on the cell-mediated immune system, that arm of the immune system most directly responsible for the killing of neoplastic cells.

Increase in proliferation and cytotoxic cell development in human mixed lymphocyte cultures in the presence of very low concentrations of LPS: role of IL-1 and prostaglandin E2

Lipopolysaccharide (LPS) added to human allogeneic mixed lymphocyte cultures (MLC), even at very low concentrations, increased the level of specific cytotoxicity that developed. Proliferation was also increased by LPS in MLC but no increase was detectable when the allogeneic stimulus was absent. LPS enhanced only low cytotoxic responses while having little effect on naturally high responses. Significant enhancement in cytotoxic response was found within the picogram-nanogram per milliliter range of concentrations of LPS and only when it was added at the initiation of cultures. This early action of low concentrations of LPS suggested that IL-1 was involved. Indeed, a supernatant from silica-treated human mononuclear cells containing IL-1 activity also enhanced cytotoxic and proliferative responses. Aside from increasing IL-1 secretion we also found that LPS significantly increased synthesis and secretion of PGE2 which had a selective inhibitory effect. Namely, addition of indomethacin or flurbiprofen to MLC further enhanced the cytotoxicity of LPS-treated but not that of untreated cultures without increasing the proliferative response. These results suggest a key role for macrophage-derived IL-1 and PGE2 in the regulation of proliferative and cytotoxic responses of T cells. They also suggest that very low amount of LPS may reach the immune system and contribute to the expression of cell-mediated immune responses.

Discrepancy between the production of interleukin 1, alpha-interferon and granulocytic colony-stimulating activity of human monocytes stimulated by a partially purified human urinary colony-stimulating factor

A partially purified human urinary colony-stimulating factor (pp-CSF), with a specific activity of 1.0 X 10(6) U/mg protein, was purified by using a stepwise DEAE-cellulose anion exchange chromatography and a molecular sieve high performance liquid chromatography (TSK gel G3000SW) sequentially. Production of three kinds of monokines by human peripheral blood monocytes was tested in vitro, which contained granulocytic colony-stimulating activity (G-CSA), interleukin 1 (IL-1) and interferon alpha (IFN-alpha). Human peripheral blood mononuclear cells were separated by Ficoll-Hypaque density gradient centrifugation, and monocytes were obtained by adherence to dishes. Although pp-CSF stimulated monocytes to produce G-CSA in vitro, it failed to stimulate the IL-1 or IFN-alpha production. The discrepancy between production or release of these three kinds of monokines by human monocytes stimulated with pp-CSF suggests that pp-CSF preferentially stimulates human monocytes to produce G-CSA. To test the effects of pp-CSF on human monocytes in vivo, we performed i.v. infusions of pp-CSF to four volunteers, and we then took peripheral blood monocytes. Compared to before the infusion of pp-CSF, G-CSA production by monocytes was enhanced, while production of IL-1 and IFN-alpha was not enhanced after the infusion of pp-CSF. These results suggest that pp-CSF stimulates monocytes to produce G-CSA but not to produce IL-1 nor IFN-alpha.

The influence of antibiotics on the immune system. III. Investigations on the cellular functions of chicken leukocytes in vitro

Tetracyclines are bacteriostatic antibiotics widely used in veterinary medicine. It is reported here that the tetracycline analogue oxytetracycline (OxyTC) interferes with the mitogenic response of chicken leukocytes. A dose-dependent suppression of lectin stimulation of peripheral blood and spleen leukocytes was observed. The kinetics of the DNA-synthetic activity were seriously affected. The antimicrobial agent does not seem to have any effect on interleukin 2 (IL-2) production, whereas the uptake of 3H-thymidine by IL-2-dependent T cell blasts was severely reduced. It is concluded that the T cell blast is the target for OxyTC.

Differences between intra- and extracellular interleukin-1

The intracellular (IC) and extracellular (EC) pools of interleukin 1 (IL-1) of human monocyte cultures were found to differ in their molecular size and charge characteristics. EC activity was found by Sephadex G-75 chromatography to consist mainly of a single peak in the 15,000-17,000 mol. wt range. In contrast, IC activity was distributed in four peaks (mol. wts of approx. 15,000, 26,000, 45,000 and greater than 70,000). Treatment of a pool of the IC 26,000, 45,000 and greater than 70,000 mol. wt species with CHAPS, a zwitterionic detergent, yielded a large amount of the 15,000 mol. wt species, thus suggesting that a portion of the larger species consists of aggregates of the 15,000 mol. wt molecule. Both IL-1 pools were found by isoelectrofocusing to be composed of three molecular species with pIs of 5.5, 6.7. However, the proportions of these species differed markedly between the EC and IC pools. The large majority of IC activity (approximately 90%) was found at pI 5.5, while 55-60% of EC activity had a pI of 6.7 and 35-40% had a pI of 5.5. The differences in their biophysical properties support the notion that the IC and EC pools of IL-1 also differ in their functions.

The pituitary-adrenocortical axis and the immune system

Recent findings indicate that interactions between the pituitary-adrenocortical axis and the immune system involve more than simply the effects of glucocorticoid hormones. This altered view has resulted from the observations that: 1) cells of the immune system have receptors for and are directly acted upon by ACTH and endorphins, and 2) the immune system is an important non-pituitary source of these peptide hormones. In this chapter, while we review in a cursory way the older findings with glucocorticoid hormones, we concentrate on the newer developments which suggest that leukocyte- and pituitary-derived ACTH and endorphins perform regulatory functions within and between the immune system and the pituitary-adrenocortical axis.

Cytokines regulating acute inflammation and synthesis of acute phase proteins

The acute phase response to injury includes metabolic alterations, such as fever, leucocytosis, enhanced uptake of some metals and amino acids by liver, and changes in the synthesis of certain plasma proteins. Many of these effects can be elicited either in vivo or in tissue culture by monocyte- and keratinocyte-derived cytokine interleukin 1 (IL-1), which had earlier been variably termed leucocytic endogenous mediator, lymphocyte activating factor, or endogenous pyrogen. Although recombinant murine IL-1 was shown to induce hepatic synthesis of acute phase proteins other authors demonstrated that hepatocyte stimulating factor (HSF) is distinct from IL-1. Possible relationships between HSF und IL-1 and the molecular mechanisms of action of these cytokines on the synthesis of acute phase proteins are briefly discussed.

Monocyte-derived inhibitor of interleukin 1 induced by human cytomegalovirus

It has previously been shown that human cytomegalovirus (HCMV) can exert immunosuppressive effects, and it has been suggested that these may be mediated by monocytes, although the mechanism is unclear. We showed that infection of human monocytes with the AD169 strain of HCMV abrogates their production of interleukin 1 (IL-1) activity. This was associated with the release from infected monocytes of an inhibitor of IL-1 activity which was also released after HCMV infection of the U937 macrophage-like cell line. The inhibitor of IL-1 activity is a protein with an apparent molecular weight of ca. 95,000. This action of HCMV strain AD169 was virus specific and required infectious virus but occurred without virus replication or detectable expression of viral proteins. This effect may account, at least in part, for the previously observed immunosuppressive properties of HCMV.

Human lymphocytes induce a differential release of prostaglandin E2 and interleukin 1-like mononuclear cell factor from normal blood monocytes

Lymphocytes influence the production of both prostaglandin E2 (PGE2) and interleukin 1 (IL 1) by monocytes. We have examined whether these two products are released concomitantly or not under identical culture conditions using monocyte- and lymphocyte-enriched populations obtained on Percoll gradient. IL 1 was measured as mononuclear cell factor (IL 1/MCF). When incubated with concanavalin A, the monocyte-enriched fraction (MF; 80-91% monocytes), but not the lymphocyte-enriched fraction (LF; 95% lymphocytes) produced increasing amounts of PGE2 and MCF. However, when LF cells were added to MF cells in culture, a 40% to 60% decrease of PGE2 secretion was observed whereas the MCF production remained unchanged or increased up to 26-fold. Such a dissociation between IL 1 and PGE2 production by monocytes indicates independent regulation mechanisms in controlling the immune response under the influence of lymphocytes.

Interleukin 2 production by peripheral blood lymphocytes in allograft recipients during acute rejection episodes

In this study we investigate the relationship between the Interleukin 2 (IL-2) yield produced by kidney allograft recipient's peripheral blood lymphocytes (PBL) under lectin stimulation and the occurrence of acute rejection episodes. PBL were harvested prospectively before grafting, after grafting in steady-state period, and at the onset of acute rejection episodes. In addition, we tested retrospectively the ability of PBL of recipients engrafted for more than 1 yr to produce IL-2. IL-2 levels were assessed on the IL-2-dependent CTL-L2 murine cell line. Our data show: 1) before grafting, hemodialysed patients (N = 14) produced normal IL-2 yield compared with healthy donors (N = 21); 2) the IL-2 secretion of PBL of recipients with good graft function (N = 18) is decreased markedly during roughly the first 12 months following transplantation (P less than 0.01); 3) when acute rejection crisis occurred during this time period (N = 24), a sharp and highly significant increment (P less than 0.01) in lectin-induced IL-2 production of recipient's PBL was seen. After 1 yr, the capacity to secrete IL-2 upon lectin stimulation tends to be restored. Finally, our data correlate rejection and high PBL-IL-2 secretion clearly at a time when recipients with well-functioning grafts have markedly impaired IL-2 secretion.

Activation of human eosinophils by monokines and lymphokines: source and biochemical characteristics of the eosinophil cytotoxicity-enhancing activity produced by blood mononuclear cells

We and others have previously reported that human blood mononuclear cells release in culture certain substances that enhance the capacity of purified human blood eosinophils to kill the antibody-coated larvae of Schistosoma mansoni. The present study shows that this eosinophil cytotoxicity-enhancing activity (ECEA) is released by monocytes and T lymphocytes. Monocytes produce ECEA in resting and in LPS-stimulated cultures; T lymphocytes release such activity when stimulated by mitogens such as concanavalin A. Furthermore, the human monocytic line U-937 also releases ECEA-like activity when stimulated by LPS. The enhancing activity produced by monocytes has been partially characterized: it is sensitive to proteolysis by trypsin, relatively heat stable, and associated with molecules that have an apparent molecular weight of 14,000 to 65,000 daltons and isoelectric points of 3.8-3.9, 4.2, 4.5, 4.8-4.9. This shows that while ECEA produced by monocytes is heterogeneous in size and charge, it is probably different from interleukin 1.

B-cell-derived interleukin 1 (IL-1)-like factor. I. Relationship of production of IL-1-like factor to accessory cell function of Epstein-Barr virus-transformed human B-lymphoblast lines

The relationship of production of interleukin 1 (IL-1)-like factor to accessory function of Epstein-Barr virus (EBV)-transformed B lymphocytes was examined. Six of eight human EBV-B cell lines spontaneously produced and released detectable levels of thymocyte comitogenic factor in vitro, but no interleukin 2 (IL-2) activity. Eight of eight produced fibroblast proliferation activity. Culture supernatants from the two apparent nonproducers of thymocyte comitogenic activity induced the proliferation of the IL-1-dependent murine helper-T-cell clone D10G4.1 in the presence of concanavalin A (Con A). One of the EBV-B cell lines produced a potent inhibitory factor in addition to IL-1-like thymocyte comitogenic and fibroblast proliferation factors. The inhibitory factor inhibited mouse thymocyte proliferative response to Con A, and the proliferation of the IL-2-dependent CT6 cell line, but not human fibroblast growth. All but one of the eight EBV-B cell lines tested, the exception being the line that produced an inhibitory factor, were able to serve as antigen-presenting cells that enabled purified human T lymphocytes to proliferate in one-way mixed lymphocyte reactions (MLR) and in response to Con A. The supernatants of 14 of 16 clones derived from two of the EBV-B cell line cells contained thymocyte comitogenic activity and all 16 stimulated fibroblast proliferation. The phenotypic characteristics of the EBV-B cell lines were heterogeneous, but there was no clear-cut relationship between the cell surface phenotypes of either the cloned or uncloned EBV-B cells and their ability to produce these factors. These studies show that all of the EBV-B cell lines that can function as accessory cells have the capacity to produce an IL-1-like factor.

Defect in lectin-induced interleukin 2 (IL-2) production by peripheral blood lymphocytes of patients with Hodgkin's disease

Peripheral blood lymphocytes (PBL) of patients with Hodgkin's disease were studied for their capacity to produce interleukin 2 upon in vitro phytohemaglutinin stimulation in the presence or absence of either interleukin 1 or indomethacin (2 micrograms/ml); eight patients were studied at the discovery of their disease before receiving any therapy (onset HD; OHD). Seventeen patients were tested in long-term (greater than 3 yr) remission (remission HD; RHD); most RHD were treated with both chemotherapy and irradiation. Fourteen healthy individuals served as controls. PBL from OHD have a significant (P less than 0.01) defect in the production of PHA-induced IL-2. Indomethacin and IL-1 had no effect on IL-2 yield. PBL from RHD yield intermediate levels of IL-2, which are nevertheless significantly lower (P less than 0.02) than control values. RHD recover the capacity of normal PBL to increase their production of IL-2 in indomethacin-supplemented culture medium. Interestingly, PHA responsiveness was significantly decreased only in RHD, thus not explaining the low IL-2 yield obtained in supernatants. In addition, 4-day PHA-blasts from both HD patients and control individuals increase their thymidine incorporation in the presence of purified lectin-free IL-2 to a similar degree, suggesting that their IL-2 receptors are unimpaired. Finally, OHD sera significantly inhibit PHA-induced IL-2 yield of normal PBL, suggesting that a seric component(s) may play a role in some cases. We conclude that defective IL-2 production may play a role in the well-documented deficient cellular immunity seen in Hodgkin's disease.

High level human interleukin 1 production by a hepatoma cell line

The human hepatic adenocarcinoma cell line, SK-hep-1, was found to constitutively produce Interleukin 1. Addition of the ionophore A23187 and lipopolysaccharide resulted in a 30-fold enhancement in the release of biological activity. Serum supplementation did not affect the level of production. Interleukin 1 from these cells had a molecular weight of 10-20,000 daltons on gel exclusion chromatography. Polyadenylated RNA, when fractionated on sucrose density gradients and injected into Xenopus laevis oocytes, produced high levels of biological activity in the 14-16s region. An oligonucleotide probe, complementary to the coding sequence of the Interleukin 1 cDNA isolated from human monocytes, hybridized specifically to this part of the gradient. These results demonstrate that SK-hep-1 cells are a valuable source of material for studying the polypeptide and messenger RNA of Interleukin 1.

The immunophysiological basis for vaccinating ruminants against mastitis

The roles of humoral and cellular defence mechanisms in protection of the mammary gland against bacterial infection are reviewed. Effective protection depends on opsonisation of pathogens and subsequent phagocytosis by neutrophils. A concomitant requirement for protection is the rapid infiltration of neutrophils into the infected gland. Immunological studies have shown the need to prime animals against antigens expressed by bacteria when they grow in vivo. Vaccination procedures which promote these mammary defence mechanisms are discussed.

Human endothelial cell cultures: phenotypic modulation by leukocyte interleukins

We report here that soluble factors from activated mononuclear leukocytes have a dramatic effect on cultured endothelial cells. While human umbilical vein endothelial cells grown under standard conditions show a polygonal, epithelial-like morphology, cells exposed to culture media conditioned by lectin-activated human mononuclear leukocytes become extremely elongated and/or send out numerous cytoplasmic processes, assuming a dendritic configuration. This effect cannot be mimicked by exogenous cyclic AMP, is reversible upon interruption of the treatment, and appears specific for endothelial cells, since it has not been observed so far with other cell types. The shape changes are accompanied by a reorganization of the endothelial cell cytoskeleton: actin microfilament bundles tend to be disposed in parallel arrays, while intermediate filaments and microtubules penetrate up to the extremity of the cytoplasmic processes. Colchicine prevents endothelial cell elongation but only slightly impairs the formation of lateral cell processes ("dendritic configuration"). Purified interleukins were tested for their ability to induce these changes of cell shape. Escherichia coli-recombinant human interleukin 2 had no effect, and gamma-interferon only a slight effect on endothelial cell morphology. Interleukin 1 induced moderate cell elongation, while combined treatment with both interleukin 1 and gamma-interferon resulted in shape changes indistinguishable from those elicited by supernatants of activated mononuclear leukocytes. The possible relevance of the observed endothelial cell changes to the reported angiogenic activity of mononuclear cell products is discussed.

Accessory function of human leukemic cell lines: properties of B and B-K562 hybrid cell lines

The accessory function (AF) of various B cell lines has been investigated by studying their ability to replace monocytes inducing the proliferation of highly purified T lymphocytes in the presence of phytohemagglutinin. AF could be exerted by B cells from different origin, including Epstein-Barr virus (EBV) transformed lymphoblastoid cell lines (LCL), Burkitt's lymphoma (BL)-derived lines, either EBV-positive or not, pre-B and B leukemias and lymphomas. The EBV-converted BJAB-B95 BL cells could exert an AF as efficient as BJAB cells, their EBV-negative counterparts, which demonstrates that EBV itself does not play any role in this function. The HLA-DR antigen-negative BL-K562 hybrids PUTKO and DUTKO, T51.4.1.6 cells which derived from an HLA-DR-negative variant of the T51 LCL and 721.84.5 cells from a mutagenically dissected HLA-DR-negative clone of the 721 LCL, also exerted very efficient AF. 721 LCL, PUTKO and DUTKO hybrids could produce interleukin 1 activity when triggered with 12-O-tetradecanoyl-phorbol 13-acetate (TPA). Furthermore, addition of anti-DR monoclonal antibodies which blocked completely the AF of the B cell lines in mixed lymphocyte-tumor cell reaction did not affect the mitogen-triggered AF exerted by the same B cell lines. The induction of cellular differentiation with TPA markedly reduced the AF exerted by all B cell lines studied as well as by the hybrid cells DUTKO. By contrast, the PUTKO hybrid was unsensitive to sodium butyrate and TPA treatments, which were unable to abrogate its AF. Taken together, these data indicate that the AF in mitogen-induced T lymphocyte responses is dependent upon some precise maturational stages of accessory cells and HLA-DR antigen expression is not required for AF in mitogen-induced proliferation assays.

A simple bioassay for monocyte-derived hepatocyte stimulating factor: increased synthesis of alpha 2-macroglobulin and reduced synthesis of albumin by cultured rat hepatocytes

Cytokines released from monocytes upon stimulation by lipopolysaccharide cause a number of cells to undergo proliferative and synthetic changes. At least one of these cytokines affects hepatocytes in vivo causing increased synthesis of a series of acute-phase proteins. We have established an in vitro micro-assay for hepatocyte stimulating factor (HSF) using primary cultures of normal rat hepatocytes. Measurement of increased synthesis of alpha 2-macroglobulin and decreased synthesis of albumin caused by exogenously added factor constitute a sensitive parameter for quantifying HSF. For comparing various cytokines preparations, we have defined a unit of HSF activity in terms of a stimulation index. We have used this assay to follow some preliminary attempts to isolate the factors responsible for stimulation of synthesis of acute-phase reactant by the liver.

A study of angiogenesis factors from five different sources using a radioimmunoassay

The use of a radioimmunoassay (RIA) demonstrated that angiogenic factors from human and animal tumours, normal bovine retinas, myocardial infarcts, synovial fluid from patients with joint diseases and wound fluid shared common antigenic determinants. Values for angiogenesis factors expressed as microgram Walker tumour TAF/mg protein varied from 0.8 (wound fluid) to 207 (myocardial infarct). Activated macrophages produced an angiogenic factor which did not cross-react. Normal tissue extracts which were non-angiogenic by the chicken chorioallantoic membrane assay also failed to cross-react in the RIA. The antigenic similarity of angiogenic factors from such a wide variety of sources suggests that, in order to minimize therapeutic side effects, it would be best to use angiogenic agonists and antagonists locally.

Pig interleukin 1 (catabolin) is a potent stimulator of bone resorption in vitro

A homogeneous form of pig interleukin 1 (catabolin) stimulates the resorption of mouse bones in culture. Concentrations as low as 25 pM are effective, demonstrating that it is more potent than 1,25-dihydroxy-vitamin D3 in our assay system. Catabolin was originally defined by its ability to stimulate glycosaminoglycan release from cartilage in culture and purified from pig mononuclear leucocyte supernatants. It also augments lectin-induced thymocyte proliferation, indicating that it is a form of pig interleukin 1. Bone resorbing factors are synthesized by other cell types, including fibroblasts and osteoblasts; we suggest that such cytokines are important in mediating the action of systemic hormones on bone.

Different susceptibilities to cyclosporin A of the mitogenic and potentiating activities of interleukins

A dissociation was observed between the mitogenic and potentiating activities of interleukins (ILs)-1 or -2 in murine thymocyte cultures treated with drugs. The direct mitogenic effects of the ILs were unaffected by cyclosporin A (CsA) at concentrations which abolished the potentiating activities of these mediators, i.e. their synergy with lectins. Conversely to CsA, dexamethasone was more inhibitory to the mitogenic activity of the ILs than to their synergistic reactions with the lectins. The resistance to CsA of the mitogenic activity of IL-1 was unexpected since this response is assumed to be mediated by newly formed IL-2 and CsA inhibits IL-2 production. This resistance was further tested by coculturing thymocytes with the IL-2-dependent CT6 cells; net gains of thymidine uptake by the cocultures were attributed to IL-2 release. Such net gains were observed in cocultures stimulated with IL-1 alone and were relatively resistant to CsA. On the other hand, net gains stimulated by mitogenic lectins, alone or with IL-1, were eliminated by CsA. These results support the notion that IL-1 direct activity on thymocytes is mediated by newly released IL-2 and show that this IL-1 activity is unusual in being resistant to CsA. Low levels of protection against CsA were also observed in cultures potentiated by IL-1: lymphocytes stimulated by lectins or antigens and IL-1 were inhibited by CsA less than lymphocytes stimulated without IL-1. Yet, this partial protection by IL-1 was achieved only at CsA concentrations about 100 fold lower than those resisted by thymocytes directly stimulated by IL-1.

Interleukin 1, a mediator of immunoadjuvant peptidoglycans

Bacterial peptidoglycans and the synthetic analog muramyl dipeptide possess various immunomodulating properties (adjuvant effect, increase of resistance to infectious agents and to tumor growth). They are able to induce B cell activation and to stimulate macrophages to produce monokines such as Interleukin 1 (IL 1). IL 1 plays an essential role in immune response. It promotes thymocytes maturation and Interleukin 2 secretion by antigen sensitive T cells, which in turn triggers regulatory T cells. Moreover, it is involved in the proliferation and differentiation of B cells. There is a correlation between the immunoenhancing effect of PG of a definite structure and their ability to induce IL 1 secretion. Non-adjuvant PG were inactive. This suggests that one of the major mechanisms of action of adjuvant PG could be the stimulation of IL 1 synthesis.

Interspecies cross-reactivity of Class II antigen of MHC determined by syngeneic, allogeneic and xenogeneic B and T cells

Although this chapter ought to summarize the role of MHC antigens in T cell activation, the immunobiological meaning of the polymorphism of Class II antigens, as well as that of Class I antigens, is still unresolved. The antigen-presenting ability of human APC is dominant over that of murine APC in the stimulation of antigen-specific xenogeneic T cells. In addition, xenoreactive murine T cells specific for human PBL failed to recognize the polymorphic determinant of Class II antigens of human MHC. On the basis of the data, Class II antigens may be seen to have some role as antigen-presenting molecules rather than as restricting molecules, at least, in the xenogeneic APC-T cell interaction or the xenogeneic MLR responses. These data together with the fact that the linkage disequilibrium found among the various groups of alleles encoding Class I and II antigens making up an MHC haplotypes suggest that the MHC may play a key role during evolution. These studies using xenogeneic cell interaction may shed some light on the immunobiological function of polymorphism of MHC antigens in the mechanisms of T cell activation, and the evolutional history of the polymorphism of the NHC in self or not-self recognition by T cells.

Structural analysis of the charge heterogeneity of human interleukin 1

Human peripheral blood monocytes stimulated with lipopolysaccharide (LPS) produced two major proteins which enhanced the proliferative response of thymocytes to mitogenic stimulation (IL-1 activity). These proteins were of the same molecular weight (about 14,000) but had different ionization properties (pI 5.1 and 6.8). Treatment with neuraminidase did not alter the pI or the activity of either species, indicating that they did not differ solely in their extent of sialyation. Tunicamycin, at levels which markedly inhibited the incorporation of carbohydrate into proteins secreted by LPS-stimulated macrophages, failed to affect the two forms of IL-1. IL-1 also did not bind to concanavalin A-Sepharose. Thus, carbohydrate groups did not appear to play an important role in the structure or activity of the two species of IL-1. However, the biological activity of these two species of IL-1 was dissociated by treatment with N-ethylmaleimide (NEM), iodoacetamide (IAA), and heat. The protein with a pI of 6.8 was significantly inactivated by NEM, IAA, and heat, whereas the IL-1 with a pI of 5.1 was minimally affected. It appears that the two species of IL-1 differ in the availability of reactive groups, which are most probably sulfhydryls, and, consequently, also in tertiary structure.

Induction of human interleukin 1 mRNA measured by collagenase- and prostaglandin E2-stimulating activity in rheumatoid synovial cells

Human blood peripheral monocyte/macrophages release in culture a mononuclear cell factor (MCF) which stimulates the production of collagenase and prostaglandin E2 by human rheumatoid synovial cells and dermal fibroblasts. These two products play a role in connective tissue destruction. MCF has an apparent molecular weight of approximately 15 000 and is biologically and biochemically indistinguishable from interleukin 1. MCF therefore belongs to the well-documented nonimmune biological activities attributed to interleukin 1. Studies on the mechanisms of production and action of such monokine(s) have been difficult in view of the minute quantities produced by freshly isolated cells or from human monocytic lines. Starting from lectin-stimulated human blood mononuclear cells, we have isolated poly(A)+ RNA and studied its translation following microinjection into Xenopus laevis oocytes. The mRNA translation products stimulated collagenase and prostaglandin E2 production in human rheumatoid synovial cells and dermal fibroblasts. The size of MCF-mRNA was estimated to be 10 S. The mRNA of a member of the interleukin 1 family can now be studied in a system based on a specific and direct relevant biological assay and eventually compared with those of other monokines.

The effects of monocyte-conditioned medium and interleukin 1 on the synthesis of collagenous and non-collagenous proteins by mouse bone and human bone cells in vitro

Cultured adherent human mononuclear cells produce factor(s) which stimulate the release of calcium from new-born mouse calvaria in organ culture. This stimulation of bone resorption is accompanied by an inhibition of the incorporation of [3H]proline into collagen which is independent of increased prostaglandin production by the bone. When human osteoblast-like cells are treated with conditioned medium from human mononuclear cells, collagen accounts for a decreased proportion of the protein synthesised. This effect on matrix synthesis is not accompanied by an inhibitory action of the monocyte-conditioned medium preparations on net cell proliferation. In human osteoblast-like cell cultures, partially purified human interleukin 1 also inhibits the production of the bone-specific protein osteocalcin in a dose-dependent fashion. These observations are consistent with the hypothesis that products of human monocytes similar to, or identical with, human interleukin 1 may be important regulators of bone metabolism and may contribute to the bone loss seen in diseases such as chronic rheumatoid arthritis.

Impaired IL2 production by lymphocytes of patients with systemic lupus erythematosus

The aim of this study was to define as possible abnormality of interleukin 2 (IL2) production by PHA-stimulated peripheral blood lymphocytes (PBL) in systemic lupus erythematosus (SLE). Thirty-four SLE PBL samples were stimulated to produce IL2 and compared with PBL from healthy (age- and sex-matched) controls. A significant defect in IL2 production was observed in SLE patients. This defect was not restricted to corticosteroid-treated patients and was not correlated with the presence of lymphotoxic antibodies or with clinical disease activity. Although 5-day responsiveness to phytohaemagglutinin (PHA) decreased in SLE, the SLE PHA-blasts responded as well as control blasts to semipurified IL2, suggesting that the receptor for IL2 was normally expressed on SLE blasts. In 9 cases, the effect of addition of indomethacin (2 micrograms/ml) or of an optimal amount of IL1 on PHA-induced IL2 production was studied. Indomethacin increased (22%) the IL2 yield of healthy individual PBL. In SLE, indomethacin (but not IL1) was able to completely restore (41% increase) the IL2 production of lectin-stimulated PBL (P less than 0.01). These data suggest that, in SLE, the inhibition of IL2 production is mediated by prostaglandin, possibly produced by monocytes.

Serological and biological cross-reactivity of class II antigens between mice and humans in antigen-specific T-cell proliferative responses

Many studies have already been reported with regard to the serological cross-reactivities between the polymorphic determinants of murine Ia antigens and human HLA-DR antigens. In this paper, we examined the biological cross-reactivity of the polymorphism of Class II antigens in the xenogeneic antigen-presenting cell (APC)-T-cell interaction. The data indicate that purified protein derivative (PPD)-specific human T cells were not stimulated by PPD-pulsed murine APC from B10.S(9R) which possess I-As and I-Ek molecules serologically cross-reacting with human Class II antigens. On the contrary, B10.S(9R) T cells primed to PPD were stimulated by PPD-pulsed human APC. The failure of the murine APC-human T-cell interaction was not caused by the suppressive effect in culture with ongoing xenogeneic mixed lymphocyte reactions (MLR) or other cell culture conditions. Thus, a hierarchy of antigen-presenting ability in the xenogeneic APC-T-cell interaction was shown to exist.

A factor synthesized by rabbit periosteal fibroblasts stimulates bone resorption and collagenase production by connective tissue cells in vitro

Unstimulated monolayer cultures of confluent rabbit periosteal fibroblasts synthesize a factor that stimulates bone resorption in vitro. Furthermore it stimulates rabbit chondrocytes and mouse osteoblasts to synthesize collagenase. The factor has no effect on dead bone in culture, and its activity on live bone is mediated principally by osteoclasts, since it is 75% inhibited by salmon calcitonin. Characterization of the factor by gel filtration and isoelectric focusing indicates an Mr in the range 15000-25000 and a pI corresponding to approx. pH 4.7. These biological and physiochemical properties are similar to those reported for a factor released by peripheral blood monocytes. However, whereas human monocyte factor in both the crude and partially-purified state exhibits interleukin-1 activity, crude and fractionated periosteal fibroblast-conditioned medium does not. This is the first report of a conditioned medium containing a molecule like the monocyte-factor which appears to have no interleukin 1 activity. The factor may be synthesized by a wide range of cell types, and could have an important role in mediating connective tissue degradation during both physiological and pathological resorption.

Purification of human interleukin 1 by high-performance liquid chromatography

The utility of high-performance liquid chromatography (HPLC) in the purification of Interleukin 1 (IL 1, lymphocyte-activating factor) has been investigated Human IL 1-containing supernatants were concentrated by lyophilization and desalted using Bio-Gel P-6 DG desalting gel. Subsequently, the sample containing IL 1 activity was subjected to HPLC with a novel HPHT hydroxylapatite column. Using a sodium phosphate gradient, IL 1 was eluted as a single peak of activity separated from the major protein contaminant, yielding 90% recovery and a specific activity of 6.3 X 10(4) U/mg. Pooled fractions from Bio-Gel HPHT were concentrated and subjected either to Bio-Sil IEX 540 DEAE anion-exchange or Bio-Sil TSK 125 size exclusion chromatography. From DEAE the IL 1 activity was eluted before a linear sodium chloride gradient was started, whereas the protein contaminant was eluted at 110 mM NaCl. When TSK was used IL 1 activity was eluted within a molecular weight range of 20,000-10,000. Fractions from the DEAE or TSK columns that were positive for IL 1 activity did not contain detectable protein, suggesting a good resolution. Furthermore, the recovery from DEAE was 26% whereas TSK 125 yielded 119% of the original activity. The specific activities were 6 X 10(7) and 2.5 X 10(8) U/mg, respectively. Thus, this method provides a rapid and reproducible procedure for the purification if IL 1 for further biological characterization.

Human large granular lymphocytes are potent producers of interleukin-1

Natural killer (NK) activity against tumour and virus-infected target cells is shown by a subpopulation of peripheral blood mononuclear leukocytes with the morphological features of large granular lymphocytes (LGL). The lineage of human LGL is still controversial, as they display surface markers of both T lymphocytes and myelomonocytic cells. LGL have recently been reported to produce lymphokines such as interleukin-2 (IL-2) and alpha- as well as gamma-interferons, functions associated mainly with T cells. To determine whether cytokines associated with other cell lineages are also produced by LGL, we examined whether they might produce a myelomonocyte -associated cytokine such as interleukin-1 (IL-1). IL-1 is a 12-18,000 molecular weight (MW) lymphokine produced by a variety of cell types such as monocytes, keratinocytes and a human dendritic cell line, which plays a crucial role in immunoregulation and inflammation. Moreover, IL-1 has recently been reported to act synergistically with IL-2 and interferons in boosting LGL-mediated NK activity. We now show that a subset of highly purified human LGL with NK activity can be stimulated to secrete a soluble factor with the biochemical and biological characteristics of human IL-1.

Production of intra- and extracellular interleukin-1 (IL-1) by human monocytes

Human monocytes, separated by adherence and cultured in plastic wells, produced "spontaneously" high levels of intracellular interleukin-1 (IL-1) during the first 20 hr in culture while releasing in most cases less than 10% of it into the medium. The addition of bacterial lipopolysaccharides (LPS), quartz silica particles, zymosan, or phorbol myristate acetate (PMA) enhanced 3 to 50 times the overall production and 25 to 2000 times the release of IL-1. From 24 to 44 hr of culture, the "spontaneous" production and release of IL-1 decreased to negligible amounts. During the same period of time, the addition of silica particles or PMA had clearly less effect while the addition of LPS or zymosan produced high levels of intracellular IL-1 but only a modest release of it. When any of the stimuli was added after the first 48 hr and up to 6 days of culture, no release of IL-1 was detected and only a small amount of the intracellular fraction was seen when using LPS or zymosan. These results were not due to cell death prior to the addition of the stimuli but rather to a decrease in the responsiveness of the mononuclear phagocytes that coincides with their transformation into macrophages. The different patterns of production and release observed with time suggest that synthesis and secretion of IL-1 by human monocytes are two distinct biological events.