Production of transforming growth factor beta by human T lymphocytes and its potential role in the regulation of T cell growth

Association of circulating receptor Fc gamma RIII-positive monocytes in AIDS patients with elevated levels of transforming growth factor-beta

Monocytes in the circulation of normal individuals express two receptors for the constant region of immunoglobulin, Fc gamma RI and Fc gamma RII. In contrast, we have observed that AIDS monocytes express significant levels of a third Fc gamma R, Fc gamma RIII (CD16), which is normally associated with activation or maturation of the monocyte population. By dual-fluorescence analysis using a monoclonal antibody specific for Fc gamma RIII (MAb 3G8), 38.5 +/- 3.2% of the LeuM3 (CD14)-positive monocytes in AIDS patients were CD16 positive as compared to 10.4 +/- 1.0% for healthy individuals (n = 29; P less than 0.005). Furthermore, AIDS monocytes expressed Fc gamma RIII-specific mRNA which is expressed minimally or not at all in control monocytes. As a recently identified inducer of Fc gamma RIII expression on blood monocytes, transforming growth factor-beta (TGF-beta) was found to be elevated in the serum and/or plasma of AIDS patients. Moreover, incubation of normal monocytes with AIDS serum or plasma induced CD16 expression which correlated with serum TGF-beta levels (r = 0.74, P less than 0.001) and was inhibited with a neutralizing antibody to TGF-beta. Thus, the increased CD16 expression on peripheral blood monocytes in AIDS patients may be the consequence of elevated circulating levels of the polypeptide hormone TGF-beta.

Effect of recombinant human transforming growth factor beta and tumor necrosis factor alpha on bone marrow progenitor cells of HIV-infected persons

With progressive disease, the majority of patients with human immunodeficiency virus (HIV) infection develop bone marrow failure with anemia, leukopenia, and thrombocytopenia, the cause of which has not yet been clarified. Besides direct infection of bone marrow progenitor cells and immune-mediated cytolysis, the action of inhibitory cytokines, like transforming growth factor beta (TGF-beta) and tumor necrosis factor alpha (TNF-alpha), has to be discussed with regard to their pathophysiological role in HIV-induced bone marrow failure. Therefore, the influence of recombinant human TGF-beta and TNF-alpha on colony growth of pluripotent (CFU-GEMM), erythroid (BFU-E), and granulocyte-macrophage (CFU-GM) progenitor cells from the bone marrow of HIV-1-infected persons and normal controls was assessed in methylcellulose cultures. Both cytokines inhibited the colony formation of hematopoietic progenitor cells from HIV-positive persons. When added to unseparated bone marrow cells from HIV-infected persons and normal controls, the 50% inhibition (ID50) of BFU-E by TGF-beta occurred at 1.3 ng/ml and 3.7 ng/ml, respectively, while the ID50 of CFU-GM occurred at 15.5 ng/ml and 142.7 ng/ml. Concentrations of TNF-alpha, causing 50% inhibition of colony formation by bone marrow cells from HIV-infected or noninfected individuals were 6.3 U/ml and 17.0 U/ml for BFU-E, and 24.4 U/ml and greater than 3,000 U/ml for CFU-GM, respectively. The ID50 of the CFU-GEMM growth was below the lowest concentration of both cytokines tested. The suppressive effects were specifically abolished by antibodies against TGF-beta and TNF-alpha, thus confirming that the inhibitory activities were due to the cytokine preparation used.

Identification of a gene family regulated by transforming growth factor-beta

We have identified two related genes whose mRNAs are increased after treatment with transforming growth factor-beta (TGF-beta 1). Mouse AKR-2B cells were treated with TGF-beta 1 in the presence of cyclohexamide and a cDNA library was subjected to differential screening. Several TGF-beta-induced genes (beta IG) were isolated and two of these, beta IG-M1 and beta IG-M2, were characterized. beta IG-M1 and beta IG-M2 RNAs were significantly increased after TGF-beta 1 treatment and both were superinduced in the presence of cyclohexamide. cDNA sequence analysis of beta IG-M1 showed that it encoded a 379-amino-acid protein which was 81% homologous to CEF-10, a v-src and TPA-inducible gene, and identical to cyr61, a gene induced by serum in growth-arrested BALB-3T3 cells. cDNA sequence analysis of beta IG-M2 showed that it encoded a 348-amino-acid protein that was 50% homologous to beta IG-M1. Thirty-eight cysteine residues are conserved between beta IG-M1 and beta IG-M2, which are clustered at the amino and carboxy ends: The middle regions of the two proteins are cysteine free and display the highest degree of nonhomology. Both proteins contain an amino-terminal cysteine-rich motif common to insulin-like growth factor binding proteins and a carboxy-terminal domain with strong homology to a motif found near the carboxy-terminal of the malarial circumsporozoite protein which may be involved in cell adhesion. The regulation of mRNA encoding these proteins by TGF-beta 1 suggests that they may be involved in mediating some of the pleiotropic effects of this multipotent modulator of cell growth and differentiation.

Isolation and characterisation of milk growth factor, a transforming-growth-factor-beta 2-related polypeptide, from bovine milk

A strategy was developed for the purification of a biologically active polypeptide growth and migration factor from skimmed bovine milk. This 25-kDa dimeric molecule, termed milk growth factor (MGF), was isolated by a method consisting of a combination of strong cation-exchange chromatography, low-pressure hydrophobic-interaction chromatography, hydrophobic-interaction HPLC and size-exclusion HPLC steps, which separated the protein according to its properties of charge, hydrophobicity and size, respectively. On average, a total purification of 10(6)-10(7)-fold and a yield of approximately 115 +/- 78 ng/MGF/milk was obtained using the method described. All purification steps were performed with novel combinations of ethanol and volatile acidic salt (ammonium acetate) solutions in order to retain biological activity of the protein. These conditions, together with the easy removal of salt by lyophilization, facilitated the detection of biological activity in fractions collected at each step of the purification by means of a sensitive in vitro fibroblast-migration assay in which the half-maximal activity was obtained at a concentration of approximately 17 +/- 4 pg/ml (i.e. approximately 1 pM) of the pure protein. Biological activity of the dimeric protein was unaffected by heat treatment or exposure to acid (pH 2.0), but was lost upon reduction to its monomeric form. Amino acid composition and sequence analyses demonstrate that MGF is related to transforming growth factor type beta 2.

Regulation of transforming growth factor beta 1 gene expression by the product of the retinoblastoma-susceptibility gene

Transforming growth factor beta (TGF-beta) isoforms inhibit the growth of many cell types and block progression of the cell cycle by inhibiting events in late G1 phase. The retinoblastoma gene product, RB, also has properties of a cell-cycle regulatory factor. It remains underphosphorylated in the presence of TGF-beta and has been shown to repress the activity of the c-fos promoter, resulting in inhibition of transit through the cell cycle. These observations led us to examine effects of human RB on the expression of the human TGF-beta 1 gene. Using chimeric TGF-beta 1 promoter-chloramphenicol acetyltransferase gene constructs, we show that RB induces TGF-beta 1 gene expression in CCL-64 mink lung epithelial cells and A-549 human lung adenocarcinoma cells but represses its expression in NIH 3T3 and AKR-2B mouse cells. Several sequences homologous to the c-fos RB control element were identified in the TGF-beta 1 promoter. These results demonstrate that human RB can regulate TGF-beta 1 gene expression negatively or positively depending on the cell type.

Repertoire development and ligand specificity of murine TCR gamma delta cells

During the past several years, we have been studying the circulating TCR gamma delta cells expressed in peripheral lymphoid tissues. Biochemical and molecular characterization of the TCR gamma delta heterodimers present on these TCR gamma delta cells identified 3 TCR gamma proteins, V gamma 2-C gamma 1, V gamma 1.2-C gamma 2, and V gamma 1.1-C gamma 4. In addition, at least 6 different V delta gene products (V delta 2,4,5,6,V alpha 10, V alpha 11) are expressed in peripheral lymphoid tissue. Nucleotide sequence analysis has revealed a great deal of junctional diversity present among the different V gamma and V delta proteins. Thus, compared to other nonlymphoid tissues (e.g., skin), this population of TCR gamma delta cells appears quite extensive. The development and specificity of TCR gamma delta cells has been pursued by two approaches. First, different TCR gamma delta cells clones were generated which recognize MHC-encoded gene products. One clone recognizes an unconventional TL-encoded antigen, whereas others have been shown to recognize either classical MHC class I or class II antigens. The TCR gamma delta receptor genes have been cloned from the TL-specific TCR gamma delta cell and used to construct transgenic mice to examine the development of TCR gamma delta cells. Although the Tg+ TCR gamma delta cells are tolerized by thymic clonal tolerance similar to TCR alpha beta cells, the epithelial Tg+ TCR gamma delta cells are subjected to non-deletional tolerance (anergy). A second approach towards examining the development of TCR gamma delta cells has been to compare the repertoire of TCR gamma delta splenocytes in a variety of inbred and MHC-congenic strains of mice using subset-specific anti-murine TCR gamma delta mAb. The percentage of individual subsets of splenic TCR gamma delta cells differ widely between different inbred strains of mice due to both MHC- and TCR-encoded genetic differences. In summary, these studies provides a basis for understanding and determining the ligand(s) of the TCR gamma delta heterodimer and the factors which shape the peripheral TCR gamma delta repertoire.

Transforming growth factor beta 1 is implicated in the failure of tamoxifen therapy in human breast cancer

Transforming growth factor-beta 1 (TGF-beta 1) is inhibitory for breast epithelial cells in vitro and treatment of breast cancer cell lines with tamoxifen results in a rise in TGF-beta 1 mRNA expression with associated inhibition of cell growth. To study whether these findings apply in vivo we examined TGF-beta 1 mRNA expression in an oestrogen-dependent mouse xenograft system following systemic treatment of the mice with tamoxifen. In agreement with in vitro studies. TGF-beta 1 mRNA expression was sustained at high levels and associated with a reduction in tumour size. A subsequent study of breast tumour tissue from 56 patients demonstrated high levels of TGF-beta 1 mRNA in 45 of the tumours. High expression was found to correlate with premenopausal status, but not with tumour oestrogen receptor content or other parameters. In a subgroup of 11 patients who had received tamoxifen therapy for 3 to 6 months prior to surgery, unexpectedly high levels of TGF-beta 1 mRNA were demonstrated in tumours increasing in size and unresponsive to tamoxifen. Data from this study indicate that in patients with breast cancer, TGF-beta 1 in the tumour may not behave as in vitro and xenograft studies have suggested. We speculate that failure of tamoxifen therapy may be due to failure of the autocrine inhibitory functions of TGF-beta 1 either alone or in combination with paracrine stimulation of stromal cells or angiogenesis and localised immunosuppression. Further studies of active TGF-beta 1, TGF-beta receptors and the interactions with other growth factors will be required to elucidate the precise role of TGF-beta 1 in human breast cancer and in the failure of tamoxifen therapy.

Comparison of effects of transforming growth factor-beta and cyclosporin A on antigen-presenting cells of blood and epidermis

The antigen-processing and -presenting functions of freshly obtained epidermal Langerhans cells (fresh LC) and 72-h cultured Langerhans cells (cultured LC) differ remarkably. It has been proposed that the disparate functional programs revealed in vitro may correspond directly with distinct in vivo physiologic functions--fresh LC are the in vitro equivalent of intraepidermal LC and cultured LC are equivalent to LC that have migrated from skin to the draining lymph node. As an approach to studying this proposal, we have compared the effects of two immunosuppressive agents, cyclosporin A (CsA) and transforming growth factor-beta (TGF beta), on the alloantigen-presenting capabilities of fresh LC, cultured LC, and peripheral blood mononuclear cells (PBMC). CsA pretreatment (1 and 10 mu/ml x 2 h) profoundly inhibited alloantigen presentation by fresh LC, cultured LC, and PBMC. By contrast, TGF beta pretreatment (1 and 10 ng/ml x 2 h) inhibited presentation by PBMC and cultured LC, but not by fresh LC. The resistance of fresh LC to the deleterious effects of TGF beta is discussed in terms of the possibility that TGF beta may inhibit antigen processing following conventional endocytosis. We suggest that fresh, but not cultured, LC escape TGF beta effects because they possess an "alternative" endocytic pathway, marked by the presence of Birbeck granules.

Protective effect of transforming growth factor beta 1 on experimental autoimmune diseases in mice

Interleukin 1 (IL-1) and tumor necrosis factor alpha are thought to contribute to the inflammatory response associated with autoimmune diseases. Transforming growth factor beta 1 (TGF-beta 1) counteracts many effects of these cytokines and has various immunosuppressive properties. In the present study, it is shown that microgram amounts of TGF-beta 1, injected daily for 1-2 weeks, protect against collagen-induced arthritis (CIA) and relapsing experimental allergic encephalomyelitis (REAE), the animal models for rheumatoid arthritis and multiple sclerosis, respectively. When administered during induction of the disease, TGF-beta 1 prevents CIA but only delays the onset of REAE by 2-3 days. However, when administered during a remission. TGF-beta 1 prevents the occurrence of relapses in REAE. The results suggest that TGF-beta 1 has powerful anti-inflammatory effects, mimicking in some respects the beneficial effects of immunosuppressive drugs in these experimental models of autoimmune disease, but without discernable adverse effects.

Transforming growth factor beta suppresses human immunodeficiency virus expression and replication in infected cells of the monocyte/macrophage lineage

The pleiotropic immunoregulatory cytokine transforming growth factor beta (TGF-beta) potently suppresses production of the human immunodeficiency virus (HIV), the causative agent of the acquired immunodeficiency syndrome, in the chronically infected promonocytic cell line U1. TGF-beta significantly (50-90%) inhibited HIV reverse transcriptase production and synthesis of viral proteins in U1 cells stimulated with phorbol myristate acetate (PMA) or interleukin 6 (IL-6). Furthermore, TGF-beta suppressed PMA induction of HIV transcription in U1 cells. In contrast, TGF-beta did not significantly affect the expression of HIV induced by tumor necrosis factor alpha (TNF-alpha). These suppressive effects were not mediated via the induction of interferon alpha (IFN-alpha). TGF-beta also suppressed HIV replication in primary monocyte-derived macrophages infected in vitro, both in the absence of exogenous cytokines and in IL-6-stimulated cultures. In contrast, no significant effects of TGF-beta were observed in either a chronically infected T cell line (ACH-2) or in primary T cell blasts infected in vitro. Therefore, TGF-beta may play a potentially important role as a negative regulator of HIV expression in infected monocytes or tissue macrophages in infected individuals.

Characterization and purification of an immunosuppressive factor produced by a small cell lung cancer cell line

The present study was undertaken to determine whether small cell lung cancer (SCLC) cell lines produce immunosuppressive factors and, if they do, to characterize the factors. The supernatants of SCLC cell lines, H69 and N857, inhibited not only the blastogenic response of human peripheral blood lymphocytes (PBL) to phytohemagglutinin or concanavalin A, but also the cytotoxic activity of lymphokine-activated killer cells. Neither was inhibited by supernatants from non-SCLC cell lines PC9, QG56, and A549. The immunosuppressive activity of H69 supernatant was stable upon heating to 56 degrees C for 60 min, but labile when heated to 70 degrees C for 10 min. The activity was abolished after dialysis at pH 2.0 or pH 11.0, but not at pH 4.5 or pH 9.0. Digestion with trypsin or proteinase eliminated the immunosuppressive activity, whereas treatment with neuraminidase, mixed glycosidase, DNase or RNase had no effect, suggesting that the immunosuppressive activity in H69 supernatant is due to a protein factor. This H69-derived immunosuppressive factor was isolated by ion exchange chromatography using a gradient of 0.04 to 0.08 M NaCl solution. Gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed the factor to have molecular weights of 98 kD and 102 kD, respectively. These results suggest that SCLC cells produce a potent immunosuppressive factor which may account for the immune deficiency in SCLC patients.

Transforming growth factor beta expression in human marrow stromal cells

The effects of hematopoietic cytokines on the expression of transforming growth factors (TGF beta) mRNA and the effect of TGF beta on cytokine and on a major extracellular matrix protein, collagen I, mRNA expression was studied in human marrow stromal cells. As with other cultured mesenchymal cells, stromal cells constitutively express TGF beta 1 but not TGF alpha mRNA. In simian virus 40 (SV40)-transformed stromal cells downregulation of TGF beta 1 expression was observed 2 hours after incubation with recombinant human (rh) tumor-necrosis factor alpha (TNF alpha) and 144 h after addition of rh granulocyte macrophage colony-stimulating factor (GM-CSF). Neither interleukin-1 (IL-1)beta nor IL-6 had an observable effect on TGF beta 1 mRNA expression. TGF beta upregulated collagen I mRNA expression. These data suggest that cytokines may influence TGF beta mRNA expression.

Transforming growth factor beta 1 suppresses acute and chronic arthritis in experimental animals

Systemic administration of the cytokine, TGF beta 1, profoundly antagonized the development of polyarthritis in susceptible rats. TGF beta 1 administration (1 or 5 micrograms/animal), initiated one day before an arthritogenic dose of streptococcal cell wall (SCW) fragments, virtually eliminated the joint swelling and distortion typically observed during both the acute phase (articular index, AI = 2.5 vs. 11; P less than 0.025) and the chronic phase (AI = 0 vs. 12.5) of the disease. Moreover, TGF beta 1 suppressed the evolution of arthritis even when administration was begun after the acute phase of the disease. Histopathological examination of the joint revealed the systemic TGF beta 1 treatment greatly reduced inflammatory cell infiltration, pannus formation, and joint erosion. Consistent with the inhibition of inflammatory cell recruitment into the synovium, TGF beta 1 reversed the leukocytosis associated with the chronic phase of the arthritis. Control animals subjected to the same TGF beta 1 dosing regimen displayed no discernable immunosuppressive or toxic effects even after 4 wk of treatment. These observations not only provide insight into the immunoregulatory effects of TGF beta, but also implicate this cytokine as a potentially important therapeutic agent.

The pattern of myocardial fibrosis in chronic Chagas' heart disease

Observations are described on the fibrillar nature and structural features of the collagenous interstices of the human myocardium in chronic chagasic cardiomyopathy, comparing them with similar observations in normal hearts, using the picrosirius red technique and polarization microscopy. A total of 28 adult hearts obtained at autopsy were used: 5 control without evidence of cardiac disease, and 23 with chronic Chagas' heart disease. The findings in the myocardium of those without Chagas' disease were in keeping with those reported in the literature. In those with Chagas' disease diffuse interstitial fibrosis could be observed in all cases, albeit to varying degree. The pattern was that of a diffuse increase in the amount of thick collagen fibers surrounding bundles of muscle fibers (perimysial matrix), varying in intensity from one area to another, and around the intramyocardial coronary vessels, combined with a less pronounced increase in the matrix of endomysial collagen. The relationship between the observed myocardial fibrosis and cardiac function, and the potential mechanisms for its production, are discussed. Further research is needed into the patterns and pathogenesis of myocardial fibrosis in order to offer possibilities for prevention and development of corrective forms of therapy for the fibrotic process.

Interferon-gamma reverses the stimulation of collagen but not fibronectin gene expression by transforming growth factor-beta in normal human fibroblasts

It has recently become apparent that several cytokines and growth factors are capable of modulating fibroblast proliferation and biosynthetic activity. To understand the role of these factors in connective tissue regulation, we examined the effects of the simultaneous addition of interferon-gamma (IFN-gamma) and transforming growth factor-beta (TGF-beta) on normal human dermal fibroblast collagen and fibronectin production. In addition, in vitro transcription rates and steady-state mRNA levels for these molecules were determined by nuclear run-off assays and Northern and dot-blot hybridization using specific human cDNA probes. Treatment of cultures with TGF-beta caused stimulation of collagen and fibronectin production. Addition of IFN-gamma to the TGF-beta-treated cultures abrogated the stimulatory effects of TGF-beta on collagen production in a dose-dependent manner and resulted in a net inhibition of collagen production. In contrast, the increase in fibronectin synthesis induced by TGF-beta was augmented further by IFN-gamma. These changes in collagen and fibronectin production were accompanied by parallel changes in the steady-state mRNA levels for these proteins. The effects of TGF-beta plus IFN-gamma on fibronectin gene expression appeared to be mediated entirely by transcriptional mechanisms, whereas the effects on collagen gene expression resulted from a combination of transcriptional and post-transcriptional events.

Cytotoxic potential despite impaired activation pathways in T lymphocytes infiltrating nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is an epithelial tumor consistently associated with EBV. The histological picture is characterized by a strikingly abundant lymphocytic infiltrate. Furthermore, the epithelial tumor cells present several immunological characteristics which suggest an important role for tumor-infiltrating lymphocytes (TIL) in the biology of this tumor. The present study reports the phenotypic and functional characterization of TIL from NPC obtained after enzymatic digestion of 15 NPC biopsies. Flow cytometric analysis of TIL suspensions indicated that most TIL were mature CD3+ T lymphocytes (mean = 60%) with a variable CD4/CD8 ratio. Most TIL were TCR alpha/beta-positive (mean = 55%) and only a few TCR gamma-delta-positive cells could be identified. A small percentage (mean = 9%) displayed an activated phenotype (CD25+, HLA class II+). Using limiting dilution analysis, we found that the average frequency of proliferative T-lymphocyte precursors (PTL-P) is lower among TIL (1/40) than in autologous (1/7) or normal PBL (1/1.4). Moreover, sorting experiments have shown that this defect is significantly more pronounced in the CD8+ than in the CD4+ TIL subset. Accordingly, the TCR and the CD2-mediated antigen-independent pathways of activation were impaired. Different types of cytotoxic precursor could be detected. These included lectin-dependent cell cytotoxicity (LDCC) and NK-like or lymphokine-activated killer (LAK) activity. Interestingly, some TIL from NPC were able to lyse an NPC tumor (C15) maintained in nude mice. Thus, despite impaired activation pathways, the cytolytic potential of proliferating TIL in NPC is preserved.

Mechanisms of bleomycin-induced lung damage

Bleomycins are a family of compounds produced by Streptomyces verticillis. They have potent tumour killing properties which have given them an important place in cancer chemotherapy. They cause little marrow suppression, but pulmonary toxicity is a major adverse effect. The mechanisms of cell toxicity are well described based on in vitro experiments on DNA. The bleomycin molecule has two main structural components: a bithiazole component which partially intercalates into the DNA helix, parting the strands, as well as pyrimidine and imidazole structures, which bind iron and oxygen forming an activated complex capable of releasing damaging oxidants in close proximity to the polynucleotide chains of DNA. This may lead to chain scission or structural modifications leading to release of free bases or their propenal derivatives. The mechanisms are well described based on in vitro experiments on DNA, but how they relate to intact cells in whole animals is more tenuous. Bleomycin is able to cause cell damage independent from its effect on DNA by induction lipid peroxidation. This may be particularly important in the lung and in part account for its ability to cause alveolar cell damage and subsequent pulmonary inflammation. The lung injury seen following bleomycin comprises an interstitial oedema with an influx of inflammatory and immune cells. This may lead to the development of pulmonary fibrosis, characterized by enhanced production and deposition of collagen and other matrix components. Several polypeptide mediators capable of stimulating fibroblasts replication or excessive collagen deposition have been implicated in this, but the precise role of these in bleomycin-induced fibrosis is yet to be demonstrated. Current therapy for bleomycin-induced lung damage is inadequate, with corticosteroids most often used. Given the mechanism of action described above, antioxidants and iron chelators might be beneficial. Although, studies to date are equivocal and there is insufficient evidence to promote their use clinically. Novel drugs are currently being developed and it is hoped these may be more useful.

IGG-stimulated and LPS-stimulated monocytes elaborate transforming growth factor type beta (TGF-beta) in active form

Mononuclear cells (MNC) stimulated either with lipopolysaccharide (LPS) or with surface-adsorbed IgG elaborated significant amounts of tumor necrosis factor (TNF) bioactivity, as well as immunoenzymatically detectable TNF-alpha and interleukin-1 beta. (IL1-beta). In contrast, IgG-stimulated cells released little IL1 bioactivity, but released an IL1 inhibitor, as determined by the thymocyte costimulatory assay (LAF assay). This inhibition was not due to an inhibitory effect of cyclooxygenase products, e.g. prostaglandin-E2 in the LAF assay. In contrast, antibodies against transforming growth factor type beta (TGF-beta), which is an important inhibitor of the LAF assay, augmented the LAF activity of supernatants from LPS-stimulated and IgG-stimulated MNC. Anti-TGF-beta-modulated LAF inhibition was enhanced by acid treatment of supernatants from mononuclear cells, but not of those from purified monocytes. Antibody blocking experiments point for the first time to a TGF-beta species other than type 1 as a monocyte-derived TGF-beta activity. Thus, TGF-beta released in active form from monocytes may be the more important antagonist of IL1 than cyclooxygenase-derived mediators. It implies that the LAF assay, in the absence of anti-TGF-beta antibodies, is an inadequate indicator of IL1 activity.

Altered regulation of TGF-beta 1 and TGF-alpha in primary keratinocytes and papillomas expressing v-Ha-ras

The influence of an oncogenic v-Ha-ras gene on the expression of TGF-beta and TGF-alpha by mouse keratinocytes and derived tumors has been investigated. Normal mouse keratinocytes cultured as basal cells in 0.05 mM Ca2+ secreted low levels of TGF-beta 2 peptide, and this increased markedly following culture in 1.4 mM Ca2+, retinoic acid, or phorbol esters. In contrast, introduction of a v-Ha-ras gene into normal keratinocytes increased basal expression and secretion of TGF-beta 1 (rather than TGF-beta 2) in response to all three agents. The selective secretion of TGF-beta 1 in v-Ha-ras keratinocytes in response to 1.4 mM Ca2+ occurred even though the four TGF-beta 2 transcripts were induced and the TGF-beta 1 transcript decreased, suggesting that the activated v-Ha-ras gene product regulates expression of the TGF-beta isoforms at the posttranscriptional level. Immunohistochemical analysis of papillomas formed following skin grafting of v-Ha-ras keratinocytes onto nude mice indicated that TGF-beta 1 was abundant in the basal and spinous layers, while there was no expression of TGF-beta 1 in normal skin. In contrast, both normal and neoplastic tissues expressed TGF-beta 2 and TGF-beta 3 in the granular layers. Furthermore, TGF-alpha mRNA expression was also elevated fivefold in cultured v-Ha-ras keratinocytes, and TGF-alpha protein was overexpressed in the grafted papillomas, but there was no detectable expression in normal skin. Elevated expression of both TGF-beta 1 and TGF-alpha in the basal and spinous layers of benign tumors may be important for the high proliferation rate in these tumors as well as for increased proliferation in the suprabasal layer.

Mammalian ciliary-body epithelial cells in culture produce transforming growth factor-beta

Transforming growth factor-beta (TGF-beta) has recently been found in the aqueous humor. The present study was initiated to test whether the ciliary-body epithelium, the site of aqueous humor formation, is capable of producing TGF-beta. Human, rat and bovine ciliary epithelial cells were grown in tissue culture and their supernatants were tested for TGF-beta using a bioassay. After acid activation of the samples, TGF-beta activity was found in the supernatants of all three mammalian ciliary epithelial cells. Most of this activity could be blocked by a neutralizing antibody against TGF-beta type 2. Native supernatants did not contain detectable TGF-beta activity. Thus, the ciliary epithelium is capable of producing the inactive form of TGF-beta (mainly type 2) and may be a source of TGF-beta in the aqueous humor.

Transforming growth factor-beta and the immune system

It is now apparent that the transforming growth factor beta (TGF-beta) family of proteins has potent immunoregulatory properties ranging from effects on the growth and differentiation of primitive stem cells to the differentiated functions of immune effector cells. Although most reports have described the immunosuppressive activities of TGF-beta, recent evidence supports the concept that TGF-beta can have both inhibitory and stimulatory actions on these systems. Recently, it has been found that TGF-beta can have autocrine as well as paracrine effects on the immune system, indicating that immune cells can activate the inactive secreted form of TGF-beta. Furthermore, TGF-beta has differential intracellular effects on cell surface receptor modulation, tyrosine phosphorylation, and cytokine gene transcription as well as cell-mediated cytotoxicity. Importantly, the administration of TGF-beta has proven beneficial in several animal disease models such as septic shock, allograft rejection, and autoimmunity. Moreover, the increased levels of TGF-beta found in several disease states associated with immunosuppression such as different forms of malignancy, chronic degenerative diseases, and AIDS implicate the involvement of TGF-beta in the pathogenesis of some diseases. Ultimately, well designed clinical trials will determine whether the exciting potential of TGF-beta can be used to treat or prevent disease.

Interleukin-1 corrects the defective autologous mixed lymphocyte response in multiple sclerosis

Patients with chronic progressive multiple sclerosis (MS) have alterations of T cell regulation that can be measured by in vitro assays and include decreases of the autologous mixed lymphocyte reaction (AMLR). Whether a defect in cytokine secretion was involved in the altered AMLR was investigated in 29 MS patients and 13 age- and sex-matched controls. The response of CD4+ T cell populations to irradiated non-T cells was decreased in MS as compared to control subjects. As previously reported, decreases in the AMLR were similarly observed with whole T cells of MS subjects as compared to controls. The addition of recombinant interleukin (IL)-1 to cultures of either whole T cells or CD4+ T cells with irradiated non-T cells in the AMLR corrected the immune defect in subjects with MS but had no effect on the AMLR in control subjects. In contrast, addition of rIL-2 or rIL-4 to the AMLR did not correct the decreased AMLR in MS patients as compared to controls. The lymphokines IFN-gamma and TGF-beta 2 both decreased the AMLR in MS patients and controls while TNF had no effect. Further, the magnitude of the AMLR response corresponded to IL-1 secretion induced by LPS in the non-T cell population. These studies indicate that defects in IL-1 may be related to immune defects of suppression in MS patients. Selective correction of immunoregulatory defects using lymphokines or their inducers in subjects with autoimmune diseases such as MS may be possible.

TGF-beta 1, beta 2, beta 1.2 and the bone morphogenetic protein BMP2: members of the transforming growth factor type beta supergene family with different morphogenetic effects on rat astrocyte cultures

The transforming growth factors type beta (TGF-beta) are immunoregulatory cytokines with pronounced effects on tissue homeostasis and repair. We observed that TGF-beta 1, TGF-beta 2, and the heterodimeric TGF-beta 1.2 induced astrocyte hyperplasia and strongly affected monolayer formation. After confluent growth, astrocytes are contact inhibited and form a dense monolayer. Addition of TGF-beta induced migration of cells to local centers, the formation of foci, followed by detachment of these aggregates from the cell culture surface. This effect was unique and could neither be induced by BMP2, a member of the decapentaplegic subfamily of type beta transforming growth factors nor by other cytokines or interleukins. Thus TGF-beta secreted by activated leukocytes might be a local regulator of astrocyte function during regenerative processes in inflammatory demyelinating brain disease.

The role of transforming growth factor-beta in hematopoiesis. A review

The role of TGF beta hematopoiesis is currently being defined. It does appear that TGF beta and related polypeptides can modulate and regulate bone marrow and thymic-derived cells throughout their functional life span. The effects of TGF beta are pleiotropic and may depend on (a) cell lineage, (b) specific cellular phenotype, (c) stage of differentiation, (d) immediate microenvironment, (e) other cytokines and (f) cellular function. The understanding of TGF beta and its relationship to other cytokines should not only increase our understanding of hematopoiesis but may also have therapeutic implications.

Transforming growth factor-beta receptor profiles of human and murine embryonic palate mesenchymal cells

Cell signalling in the developing mammalian palate appears to involve various growth factors and hormones. An important developmental role for the transforming growth factor-beta (TGF-beta) class of growth factors is suggested by the immunolocalization of TGF-beta 1 in the palate during its ontogeny. This study examined the effects of TGF-beta stimulation of, as well as TGF-beta receptor profiles in, murine embryonic palate mesenchymal (MEPM) and human embryonic palate mesenchymal (HEPM) cells. Results showed that TGF-beta 1 (1 ng/ml) stimulated proliferation of HEPM cells and inhibited proliferation of MEPM cells in a dose-dependent manner. The time course of 125I-TGF-beta 1 binding to specific receptors was determined by incubating cells in the presence of 170 pM 125I-TGF-beta 1 for up to 4 h. In both cell types, at 37 degrees C, the binding of 125I-TGF-beta decreased linearly over 4 h, while at 4 degrees C, binding increased with time of incubation. Incubation of both cell types at 4 degrees C for 4 h, with increasing concentrations of 125I-TGF-beta 1, resulted in binding which demonstrated saturation kinetics. Scatchard analyses revealed one class of receptors for HEPM (K 32.3 pM) and MEPM (K 26.3 pM). However, SDS-PAGE analyses of 125I-TGF-beta chemically crosslinked to specific receptor sites revealed that both cell types contained the types I (65,000 Mr) and III (230,000 Mr) TGF-beta receptors while MEPM also contained the type II (86,000 Mr) receptor. Binding studies further demonstrated the ability of platelet-derived growth factor to transmodulate TGF-beta binding. These results indicate that the HEPM cell line and primary cultures of MEPM cells, although obtained from palates at similar developmental stages, are dramatically different in their responsiveness to TGF-beta and have disparate TGF-beta receptor profiles.

Effect of transforming growth factor-beta 1 and -beta 2 on the proliferation of Burkitt lymphoma and lymphoblastoid cell lines

We tested the effect of transforming growth factor (TGF)-beta 1 and TGF-beta 2 on the proliferation of human B cell lines. The panel was selected to give information whether (1) their origin, (2) their phenotype, (3) their Epstein-Barr virus (EBV) carrier state, influence their responsiveness. The growth of lymphoblastoid cell lines (LCL) was not inhibited by TGF-beta 1. The EBV-carrying Burkitt lymphoma (BL) lines, Daudi, Jijoye, Rael but not Raji were inhibited. Three EBV-negative BL lines and the majority of their converted sublines were sensitive. The cell lines tested expressed TGF-beta receptors and TGF-beta 1 transcripts. The proliferation of EBV-infected B cells was inhibited by TGF-beta, their sensitivity decreased, however, after 3 days. The results suggest that the activation state of the B cells is decisive for TGF-beta sensitivity and EBV influences it indirectly by changing the cell phenotype.

The effect of macrophage activation state on antigen presenting capability as defined by helper T-cell function

Resident peritoneal cells were obtained from BALB/c mice and enriched for cells of the macrophage lineage by adherence onto 96 well tissue culture plates. Adherent cells were then exposed to various recombinant cytokines or supernatants from cell cultures, for 24 h. The ability of such adherent antigen presenting cells (APC) to support proliferation and development of helper function in T-lymphocyte populations, primed with sheep erythrocytes (SRBC), was examined. The addition of cytokines to the APC population did not enhance either proliferation of the T-cells nor helper function, assessed by assay of polyclonal IgG secretion in second cultures, beyond that obtained with control APC. The potent macrophage activators interferon-gamma and lipopolysaccharide caused a significant decrease in both parameters of T-cell activity. This effect was caused by a prostaglandin-mediated pathway inasmuch as indomethacin (1-5 microM) prevented it. Further analysis showed that this negative signal predominated until macrophages were diluted below 5% of the total cell population. At 0.5% macrophages, interferon-gamma stimulated APC function of these cells compared with untreated macrophages. Despite the relative difficulty in manipulating the T-cell response by attempted modulation of the APC with cytokines, the simple manoeuvre of incubation of otherwise responsive, primed T-cells with a high dose (10%) of SRBC during in vitro restimulation, caused the proliferation and helper function of these T-cells to be markedly decreased. This phenomenon was seen regardless of the cytokine used to stimulate the APC population. These studies further clarify the dual role the macrophage in regulation of T-cell responses.

Comparison of transforming growth factor beta and a human tumour-derived suppressor factor

Serum-free supernatants from the human melanoma cell line G361 contain a factor that can potently suppress the generation of tumouricidal lymphokine-activated killer (LAK) cells in response to interleukin-2. To characterise the suppressive factor of tumour origin we performed a number of physicochemical and functional comparisons with another immunosuppressive protein, transforming growth factor beta (TGF beta). The bioactivity of tumour-derived suppressor factor (TDSF), assayed by suppression of LAK cell generation, was unaffected by a reducing agent but lost when denatured with a chaotropic agent. In contrast, TGF beta was inactivated by reduction but not denaturation. TDSF lost bioactivity in conditions of pH less than 4, whereas TGF beta showed no loss of activity. The TDSF moiety has an estimated pI of 4.3 and a molecular mass of 69-87 kDa. This differs from published values of pI 9.5, and 25 kDa molecular mass for TGF beta. Anti-TGF beta antiserum reversed the effects of TGF beta but did not affect the suppression of LAK cell generation caused by TDSF. These findings provide compelling evidence that the TDSF moiety is not TGF beta, and may be a novel immunoregulatory cytokine.

Immunohistochemical localization of transforming growth factor-beta in human photoreceptors

Transforming growth factor-beta (TGF-beta) is a multifunctional growth factor that can either stimulate or inhibit cellular proliferation depending on cell type and culture conditions. The immunohistochemical localization of TGF-beta was investigated in human retinas and choroids using streptavidin peroxidase immunohistochemistry and a polyclonal rabbit antibody directed against the N-terminal 30 amino acids of TGF-beta 1. This antibody recognizes the beta 1 form of TGF-beta but not beta 2. TGF-beta localization was observed exclusively in photoreceptors in all adult non-diabetic and non-insulin dependent diabetic eyes, and 4 of 6 insulin dependent eyes. It was determined that TGF-beta was associated with both rods and cones using localization of peanut agglutinin (PNA), a lectin which binds to cone sheaths, on serial sections. Chondroitinase ABC digestion of sections prior to immunohistochemistry did not reduce TGF-beta immunoreactivity, suggesting that binding was not to glycosaminoglycans in the interphotoreceptor matrix. TGF-beta immunoreactivity was not observed in 2 premature human eyes in which photoreceptor outer segments had not yet developed. Localization in photoreceptors was also not observed in photocoagulation scars, in atrophic regions in a diabetic retina, nor in detached areas of retina from a young victim of head trauma. Based on PNA binding, succinate dehydrogenase enzyme histochemistry and phase contrast microscopy on adjacent sections, the TGF-beta negative areas of these retinas did not appear to have viable photoreceptors. This work demonstrates that TGF-beta is found exclusively in viable adult human retinal photoreceptors. It's function in these cells is currently not known.

Modulation of hematopoietic colony formation of stem cells in peripheral blood by anti-TGF-beta in patients with severe immunosuppression

The influence of transforming growth factor-beta (TGF-beta) on hematopoiesis has been evaluated by adding blocking antibodies against TGF-beta to colony forming assays (CFU-c). When optimum concentrations of recombinant growth factors, granulocyte-macrophage colony stimulating factor (GM-CSF), and interleukin-3 (IL-3) were added to stem cells from the peripheral blood of healthy individuals and certain patients with tumors or HIV infection, the anti-TGF-beta capable of blocking 5 ng/ml of active TGF-beta had no significant influence on erythroid or myeloid colony formation. However, in certain immunosuppressed individuals, anti-TGF-beta resulted in a significant decrease of erythroid colony formation and slight suppression of myeloid colony formation. The significant inhibition of hematopoiesis by plasma of HIV patients could be due to the presence of active forms of TGF-beta. The results of the blocking experiments are consistent with the concept that TGF-beta in low concentrations is essential for erythropoiesis and myelopoiesis but that higher levels of TGF-beta primarily inhibit erythropoiesis in vitro. TGF-beta serves as a coordinating factor when efficient recruitment of granulocytes and monocytes is more essential than erythropoiesis and stem cell growth.

A phorbol ester-regulated ribonuclease system controlling transforming growth factor beta 1 gene expression in hematopoietic cells

12-Tetradecanoylphorbol-13-acetate (TPA)-induced differentiation of U937 promonocytes leads to a 30-fold increase in transforming growth factor beta 1 (TGF-beta 1) gene expression, and this effect results from a stabilized mRNA. Similar up-regulation was detected in TPA-treated K562 erythroblasts but was absent from cell lines that do not differentiate in response to TPA. Related studies in vitro showed that postnuclear extracts of U937 promonocytes contain a ribonuclease system that degrades TGF-beta 1 mRNA selectively and that this system is completely blocked by prior treatment of the cells with TPA. These data identify a new mechanism for regulating TGF-beta 1 mRNA levels and allow us to establish the overall basis for control of TGF-beta 1 gene expression by activation of protein kinase C. Our results also provide a new basis for understanding the long-term up-regulation of TGF-beta 1 gene expression that can accompany hematopoietic cell differentiation.

Immunoregulatory role of transforming growth factor beta (TGF-beta) in development of killer cells: comparison of active and latent TGF-beta 1

Using recombinant DNA technology, we have generated Chinese hamster ovary (CHO) cell lines that synthesize latent transforming growth factor beta 1 (TGF-beta 1) to study immune regulation by TGF-beta 1. In vitro, latent TGF-beta 1 synthesized by transfectants or added exogenously as a purified complex after activation inhibited CTL generation to a similar extent as seen with acid-activated recombinant human (rHu) TGF-beta 1. In vivo, serum from nu/nu mice bearing CHO/TGF-beta 1 tumors contained significant levels of latent TGF-beta 1 in addition to depressed natural killer (NK) activity in spleens which paralleled that seen in C3H/HeJ mice treated with acid-activated rHuTGF-beta 1. rHuTGF-beta 1 treatment of mice receiving heart allografts resulted in significant enhancement of organ graft survival. Because of possible regulated tissue-specific activation, administration of latent rather than active TGF-beta may provide a better route to deliver this powerful immunosuppressive agent in vivo.

Suppression of lymphokine-activated killer (LAK) cell induction mediated by interleukin-4 and transforming growth factor-beta 1: effect of addition of exogenous tumour necrosis factor-alpha and interferon-gamma, and measurement of their endogenous production

Recombinant human interleukin-4 (rhIL-4) and transforming growth factor-beta 1 (TGF-beta 1) suppressed the induction of lymphokine-activated killer (LAK) activity induced by recombinant human interleukin-2 (rhIL-2) in peripheral blood lymphocytes. DNA synthesis and the expression of the p55 alpha chain of the IL-2 receptor (Tac antigen) were also inhibited. The inhibitory effect was greatest when these factors were added during the first 48 h of a 4-day culture, with reduced cytolytic activity against both natural killer (NK) resistant and NK-sensitive tumour cell line targets. The suppressive action of both cytokines was accompanied by a reduction in tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) levels in lymphocyte culture supernatants. Recombinant human IFN-gamma (rhIFN-gamma), but not recombinant human TNF-alpha (rhTNF-alpha) was able to overcome the inhibitory effect of recombinant human interleukin-4 (rhIL-4) on LAK induction and DNA synthesis but not Tac antigen expression. However, cytotoxicity induced by rhIFN-gamma alone was also suppressed by rhIL-4 and TGF-beta 1, inferring that rhIFN-gamma-mediated abrogation of rhIL4 suppression was not simply a direct IL-2-independent effect on cytotoxicity. In addition, rhIL-4 did not increase TGF-beta production from rhIL-2-activated peripheral blood mononuclear cells, suggesting that rhIL-4 did not mediate reduction of rhIL-2 responses through the induction of TGF-beta release.

A possible role for transforming growth factor-beta in systemic sclerosis

The cause of systemic sclerosis remains unknown, but cellular and molecular mechanisms possibly responsible for the characteristic clinical manifestations of fibrosis and vascular damage (Raynaud's phenomenon, telangiectasis, digital infection, and renal arteriopathy) are becoming understood in greater detail. One possibly important cytokine is transforming growth factor-beta (TGF-beta); its involvement is reviewed here. With regard to vascular lesions, TGF-beta has variably been shown to inhibit endothelial cell growth in vitro but to promote angiogenesis in vivo, a paradox that remains unresolved. Nonetheless, an injurious activity of TGF-beta on microvascular endothelial cells could help to explain the intimal proliferation and microvascular obliteration seen. Whether as a result of or as a cause of endothelial cell damage, platelet activation has been well documented in systemic sclerosis and the platelet alpha granule pool contains a large quantity of TGF-beta. TGF-beta is also produced by activated macrophages and T cells, both of which are known to occur within systemic sclerosis lesions. An important effect of TGF-beta is its stimulation of fibroblast collagen and fibronectin synthesis and their deposition into the extracellular matrix. Stimulation by TGF-beta may therefore account for the fibrosis seen in the dermis and in the internal organs. Direct evidence of TGF-beta involvement in systemic sclerosis is scanty, and awaits discovery of either an abnormal expression of or response to TGF-beta. The biologic effects of TGF-beta appear to be regulated at the level of activation from a latent polypeptide precursor form. Descriptions of the importance of this cytokine in pathologic conditions will need to account for this activation and its regulation. Nonetheless, the physiologic effects so far attributed to TGF-beta make its involvement in systemic sclerosis an attractive possibility to explain some of the manifestations of this enigmatic disease.

Role of endogenously produced interleukin-6 as a second signal in murine thymocyte proliferation induced by multiple cytokines: regulatory effects of transforming growth factor-beta

Previous studies have demonstrated that murine thymocytes proliferate in the presence of submitogenic concentrations of phytohemagglutinin-P (PHA-P) and various cytokines such as interleukin-1 (IL-1), interleukin-4 (IL-4), tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6). We report that C3H/HeJ thymocytes stimulated with PHA-P and IL-1, IL-4, or TNF-alpha secrete significant levels of IL-6 as determined on B9 hybridoma cells. The possibility that thymocyte proliferation induced by these cytokines was mediated through IL-6 was investigated utilizing a neutralizing monoclonal antibody against murine IL-6, MP5 20F3.1. The results demonstrate that MP5 20F3.1 inhibited the proliferative response of thymocytes and B9 hybridoma cells to recombinant MuIL-6 (but not HuIL-6) and neutralized the endogenous IL-6 produced in the thymocyte cultures, but did not have any measurable effects on the proliferative responses induced by IL-1, IL-4, or TNF-alpha. Although the level of endogeneously produced IL-6 did not play a measurable role in the proliferative response induced by TNF-alpha, the addition of higher concentrations of IL-6 augmented the proliferation of murine thymocytes induced by rMu TNF-alpha. In addition, recombinant human transforming growth factor-beta 1 (rHu TGF-beta 1) significantly inhibited thymocyte proliferation induced by HuIL-1, rMuIL-4, rMuIL-6, and rMuTNF-alpha. The studies suggest that IL-1, IL-4, or TNF-alpha mediate a proliferative signal on murine thymocytes independent of IL-6 and that the proliferative signals provided by these cytokines as well as IL-6 are inhibitable by rHu TGF-beta 1.

Expression of transforming growth factor-beta 1 mRNA in human hepatocellular carcinoma

We investigated the expression of transforming growth factor beta 1 (TGF-beta 1) mRNA in tumor tissues surgically removed from ten patients with hepatocellular carcinoma (HCC). All HCC tissues expressed TGF-beta 1 mRNA at different levels, indicating the presence of activated transcription of TGF-beta 1 gene in human HCC tissues in vivo. The level of TGF-beta 1 mRNA expression showed no relationship to main tumor size of plasma alpha-fetoprotein level. Some HCC tissues presenting a relatively low grade of histological differentiation showed the highest levels of TGF-beta 1 mRNA expression.

Distribution of immunoglobulins and secretory component in gastric cancer of the aged

The secretory immune system plays an important role in the local humoral immunity of the gastrointestinal tract. In order to evaluate humoral immunity in gastric cancer, distribution of immunoglobulins (Ig) and secretory component was immunohistochemically studied in 74 early and 15 advanced primary gastric cancers. In non-cancerous gastric mucosa, IgA and IgM, and secretory component were mainly identified in the cytoplasm of the intestinal metaplasia. In early gastric cancer of well-differentiated type, the localization of IgA and IgM, and secretory component was similar to that of intestinal metaplasia. In advanced gastric cancer, they were faintly observed and showed low positivity. The number of Ig-containing cells infiltrating cancerous stroma was enumerated. Immunoglobulin A-containing cells were dominant in the stroma of early gastric cancer. On the other hand, there were few Ig-containing cells in the stroma of advanced gastric cancer, and the number of IgA-containing and IgM-containing cells was also decreased. These results suggest that local humoral immunity is suppressed in gastric cancer, especially in advanced gastric cancer.

A phorbol ester-regulated ribonuclease system controlling transforming growth factor beta 1 gene expression in hematopoietic cells

12-Tetradecanoylphorbol-13-acetate (TPA)-induced differentiation of U937 promonocytes leads to a 30-fold increase in transforming growth factor beta 1 (TGF-beta 1) gene expression, and this effect results from a stabilized mRNA. Similar up-regulation was detected in TPA-treated K562 erythroblasts but was absent from cell lines that do not differentiate in response to TPA. Related studies in vitro showed that postnuclear extracts of U937 promonocytes contain a ribonuclease system that degrades TGF-beta 1 mRNA selectively and that this system is completely blocked by prior treatment of the cells with TPA. These data identify a new mechanism for regulating TGF-beta 1 mRNA levels and allow us to establish the overall basis for control of TGF-beta 1 gene expression by activation of protein kinase C. Our results also provide a new basis for understanding the long-term up-regulation of TGF-beta 1 gene expression that can accompany hematopoietic cell differentiation.

Differential modulation of the in vitro lymphocyte activation pathways by soluble and solubilized placental substances

Soluble and detergent-solubilized placental extracts were studied for their modulatory effects upon the proliferation of lymphocytes stimulated by various activating agents. It was shown that soluble placental extract (SPE) exerted an inhibitory effect on the lymphoproliferation triggered by alloantigen or LPS but not by Con A or the combined action of PMA + calcium ionophore A 23187. This effect was also observed with SPE precipitated by 30% of ammonium sulfate (SPE30). On the other hand, a solubilized placental extract (SzPE) that was obtained by using octyl-beta-D-glucopyranoside inhibited the stimulation triggered by alloantigen, LPS, and Con A but did not affect the protein kinase C pathway. The modulatory effects were observed not only when SPE (or SPE30) and SzPE were added at the time of culture initiation but also at 24 h before or after the activating agents. Preincubation with SPE30 or SzPE immobilized on plastic surface, however, transduced an enhanced lymphoproliferative response to alloantigen and mitogen Con A but not to LPS. The above results suggest that placental substances exerted their modulatory effects by interfering mainly with the antigen or mitogen lymphoproliferation pathways.

Transforming growth factor-beta 1 inhibits activation of macrophage cell line RAW 264.7 for cell killing

Transforming growth factor beta-1 (TGF-beta) is a multi-potent immunoregulatory peptide that has effects on numerous cell types. Here we report that human TGF-beta inhibits the activation of the macrophage cell line RAW 264.7 for killing of the L1210 tumour cell line. RAW 264.7 cells, like normal macrophages, require sequential interaction with priming and triggering stimuli for full activation of cytolytic activity. TGF-beta inhibits this cytotoxicity in a dose-dependent manner at both the priming and the triggering stage. Addition of as little as 1 ng/ml TGF-beta when added with either the priming signal, recombinant interferon-gamma (IFN-gamma), or the triggering signal, bacterial lipopolysaccharide (LPS), completely abrogated tumouricidal activity. Incubation with TGF-beta also inhibited the morphological changes normally observed in activated RAW 264.7 cells. However, TGF-beta was unable to inhibit the cytotoxic activity of RAW 264.7 cells against the target cell line WEHI 164, which is sensitive to tumour necrosis factor. In contrast to the effects on cytotoxic activity, the cytostatic activity of activated RAW 264.7 cells was not inhibited by TGF-beta at doses of up to 5 ng/ml. In addition, pretreatment of the L1210 target cells with TGF-beta made them refractory to both the cytostatic and cytotoxic effects of RAW 264.7 cells. These data suggest that TGF-beta may be an important mediator in the regulation of macrophage tumouricidal activity.

Transforming growth factor-beta activity in sheep lung lymph during the development of pulmonary hypertension

Chronic pulmonary hypertension is associated with extensive structural remodeling of the pulmonary arterial bed. The structural changes in the arterial walls include increased production of extracellular matrix components and smooth muscle cell hypertrophy, changes that have been similarly induced by transforming growth factor-beta (TGF-beta) in culture. In the present study, experiments were performed to determine whether TGF-beta is present in sheep lung lymph, and whether TGF-beta levels were altered in an animal model of chronic pulmonary hypertension induced by continuous air embolization. Several standard biological assays for TGF-beta activity were used for these determinations including soft agar assays, inhibition of epithelial cell proliferation, and a TGF-beta-specific radioreceptor assay. In each case, control lung lymph contained high concentrations of TGF-beta (100 ng/ml) which required transient acidification for detection. Samples of lung lymph from hypertensive sheep showed a transient and early two- to threefold increase in concentrations of latent TGF-beta. This activity could be partially blocked by TGF-beta antibodies. These studies indicate that sheep lung lymph contains TGF-beta and that the level of TGF-beta increases early during the development of pulmonary hypertension. Thus, TGF-beta may contribute to the development of the structural changes in the pulmonary arteries that occur during the onset of chronic pulmonary hypertension.

Dual effect of ciliary body cells on T lymphocyte proliferation

The interaction between organ-resident cells from the anterior uvea of the eye and T helper (Th) cells was investigated. Cells from Lewis rat ciliary body processes (CB cells), grown in tissue culture using an explant technique, could be induced to express major histocompatibility complex class II (Ia) antigens by incubation with rat interferon-gamma. Ia+ CB cells only poorly functioned as antigen-presenting cells (APC) for a syngeneic, uveitogenic Th cell line specific for the retinal soluble antigen (SAg). Moreover, if added to an Ag-driven lymphocyte proliferation assay in the presence of conventional APC, the rat CB cells had an inhibiting effect on Th proliferation. This inhibitory activity was not species specific, since similar effects were observed with bovine and human ciliary epithelial cells. The suppressive activity of CB cells was composed of a soluble factor, as well as a membrane-associated inhibitor. The soluble activity did not appear to be related to transforming growth factor-beta (TGF-beta), since no reversal of inhibition by a neutralizing antibody to TGF-beta was found. Part of the soluble inhibitory activity could be reversed by indomethacin treatment. The membrane-associated component was trypsin sensitive, suggesting a protein molecule. After abrogation of the inhibitory capacity by trypsin treatment and fixation by glutaraldehyde, CB cells effectively presented SAg to Th cells. These data suggest that CB cells are capable of mediating both Ag presentation and inhibition of Th cell proliferation.

Transforming growth factor beta and noncytopathic mechanisms of immunodeficiency in human immunodeficiency virus infection

This study examines the contribution of transforming growth factor beta (TGF beta), one of the most potent endogenous immunosuppressive factors, to the development of immunodeficiency in human immunodeficiency virus (HIV) infection. Increased titers of TGF beta were found in supernatants of peripheral blood mononuclear cells (PBMCs) from HIV-infected donors as compared to uninfected controls (P less than 0.001). This correlated closely with defective responses of CD4+ lymphocytes to the recall antigens tuberculin purified protein derivative or tetanus toxoid. The addition of TGF beta-neutralizing antibody to PBMCs partially restored these defective T-cell responses. Furthermore, purified TGF beta or HIV+ PBMC culture supernatants preferentially inhibited proliferation of CD4+ lymphocytes as compared to CD8+ cells. The increased expression of the TGF beta protein was associated with increased TGF beta mRNA as determined by a polymerase chain reaction assay. This increase in TGF beta protein and mRNA was due to a selective upregulation of the TGF beta 1 isoform. These results indicate that overexpression of TGF beta 1 occurs in HIV-infected individuals and that this cytokine can contribute to impaired immune functions and to depletion of CD4+ T lymphocytes.

A transforming growth factor beta 2 (TGF-beta 2)-like immunosuppressive factor in amniotic fluid and localization of TGF-beta 2 mRNA in the pregnant uterus

This report describes a murine amniotic fluid (MAF) immunosuppressive factor that has properties similar to transforming growth factor beta (TGF-beta). The MAF factor exhibits TGF-beta-like activity in stimulating soft agar colony formation by AKR-2B cells and inhibiting thymidine uptake by Mv1Lu cells. We demonstrate that both the immunosuppressive and TGF-beta-like activities of the MAF factor are completely neutralized by anti-TGF-beta 2-specific antibodies and not by anti-TGF-beta 1-specific antisera. The immunosuppressive factor in MAF is novel in that it appears to be identical or very closely related to TGF-beta 2 and is active in its native state. This active and anti-TGF-beta 2-neutralizable factor chromatographs at approximately 70 kD on Sephadex at neutral pH and appears to be able to complex with alpha-fetoprotein in native amniotic fluid. Chromatography of native MAF under acidic conditions demonstrates a lower molecular mass protein that chromatographs on BioGel in the same position as the mature 25-kD TGF-beta. This protein has the biological properties of TGF-beta and is immunosuppressive. Both of these activities are neutralizable with anti-TGF-beta 2 but not with anti-TGF-beta 1 or other antisera. By Northern analysis, we find high levels of TGF-beta 2 mRNA (with little or no TGF-beta 1) in the pregnant uterus that peak around day 15 of gestation and then fall rapidly by day 19 as birth approaches. The TGF-beta 2-like factor could possibly play a role in maternal immunity, in the retention of the fetal allograft, as well as in regulating fetal and neonatal immunological competence.

Transforming growth factor beta 1 influences glycosylation of alpha 1-protease inhibitor in human hepatoma cell lines

We have previously shown that changes in acute-phase protein glycosylation result from alterations occurring within hepatocytes as a result of regulation by cytokines, that the glycosylation patterns of proteins secreted by Hep 3B and Hep G2 cells respond differently to the crude mixtures of cytokines found in conditioned medium from LPS-stimulated monocytes, and that interleukin-6 (IL-6) causes increased concanavalin A (Con A) binding of alpha 1 protease inhibitor in Hep 3B cells and decreased Con A binding of this protein in Hep G2 cells. In the present study we found that transforming growth factor beta 1 (TGF-beta), like IL-6, led to secretion of forms of alpha 1-protease inhibitor with increased Con A binding in Hep 3B cells, and that IL-6 and TGF-beta in combination were additive. In contrast, in Hep G2 cells, TGF-beta had an effect opposite to that produced by IL-6, leading to secretion of forms of alpha 1-protease inhibitor with increased Con A binding. When employed in combination with IL-6. TGF-beta abolished the effect of that cytokine. These studies indicate that TGF-beta influences glycosylation of alpha 1-protease inhibitor in two human hepatoma cell lines in a manner that can be differentiated from that of IL-6. The identification of TGF-beta as a second defined cytokine capable of influencing glycoprotein glycosylation and the demonstration that the effect of one cytokine can be modulated by another cytokine support the view that changes in glycosylation of plasma proteins are mediated by combinations of cytokines.