Ovarian production of IL6 and its potential inhibitory effect on progesterone secretion in Cynomolgus fascicularis.

We explored the potential relevance of interleukin-6 (IL6) to ovarian function in cynomolgus monkey females which were treated to induce multiple follicular growth. Present work gave evidences that IL6 was produced in the ovulatory follicle after hCG administration by using anti-IL6 monoclonal antibody and immunohistochemical techniques. IL6 was produced by granulosa cells in cultures. However, this production was not stimulated by adding to cultures FSH or Bt2cAMP, known to induce IL6 production in various cell types. IL6 was shown to antagonize luteinizing FSH effects. Inhibitory IL6 effect was probably mediated at a site distal to cAMP generation since it had no effect on progesterone production induced by dibutyryl cAMP treatment. The presence of IL6 in the ovulatory follicle show that inflammatory cytokines may play a role at ovulation. On the other hand, its inhibitory effect on progesterone production by granulosa cells could not likely affect the process of luteinization which is controlled by LH/hCG.

In situ production of interleukin-6 within human lung allografts displaying rejection or cytomegalovirus pneumonia.

Interleukin-6 (IL-6) is a pleiotropic cytokine that is a regulator of inflammation and immunity. As production of IL-6 may be an important mechanism by which local and systemic inflammatory processes are regulated during lung transplantation, we measured this cytokine concentration in the serum and bronchoalveolar lavage fluid (BALF) collected in 27 lung recipients. IL-6 bioactivity was analyzed using a B cell hybridoma proliferation assay (B9 cell line). Three groups of clinical situations were analyzed: control lung recipients, rejections, and CMV pneumonia. Serum IL-6 concentrations (mean +/- SEM) were 24.2 +/- 3.3 U/ml in the 26 control samples. In 20 allograft rejection episodes, the serum IL-6 concentration was higher than in control samples but the difference was not significant (59.3 +/- 20.5 U/ml, P > 0.05). IL-6 serum levels were significantly increased during the 14 CMV pneumonias (61.2 +/- 11.5 U/ml, P < 0.01). In BALF, IL-6 levels were increased during CMV pneumonia (52.4 +/- 21.9 U/ml BALF), and to a lesser extent during rejection events (14.1 +/- 3.7 U/ml BALF), as compared with controls (5.6 +/- 1.6 U/ml BALF, P < 0.005, and P < 0.05, respectively). Similar results were observed when IL-6/albumin and IL-6/urea ratios were determined so as to compensate for possible dilution effects in BALF. IL-6 in BALF was produced in situ during CMV pneumonia as shown by in situ hybridization experiments that revealed a significant number of IL-6 gene-expressing alveolar cells in this condition. IL-6 concentrations in the serum and in the BALF were compared. There was no correlation between serum and BALF IL-6 concentrations, showing that serum IL-6 levels do not accurately reflect intrapulmonary IL-6 levels do not accurately reflect intrapulmonary IL-6 production. Thus IL-6 is produced within lung transplants during CMV pneumonia, and to a lesser extent during allograft rejection.

Interleukin-6 overproduction by cultured thymic epithelial cells from patients with myasthenia gravis is potentially involved in thymic hyperplasia.

Most patients with Myasthenia Gravis (MG) present a thymic hyperplasia characterized by the presence of lymphoid follicles. The acetylcholine receptor autoantigen, as well as autoantigen specific activated T and B cells found in the thymus, strongly suggest that auto-sensitization could take place in this organ. Since IL-6 is involved in T and B cell growth and differentiation, we thought that abnormal IL-6 expression by thymic epithelial cells (TEC) could be related to thymic hyperplasia in MG. In this paper, IL-6 protein and gene expression by cultured TEC from patients with MG were examined. TEC from patients presented a dramatic IL-6 hyperproduction phenotype as compared to controls when stimulated by exogenous signals such as LPS and cytokines (IL-1 beta, TNF-alpha) alone or in combination. Moreover, we observed a similar effect with a physiological signal such as the syngeneic lympho-epithelial cell contact. Autologous thymocytes stimulated normal and MG TEC IL-6 production in a time- and dose- dependent way, and with a higher magnitude in MG TEC compared to controls. In all stimulation conditions, induction of IL-6 production required protein synthesis and was associated with increased IL-6 mRNA level expression as assessed by computer-aided quantification after in situ mRNA hybridization. In addition, recombinant IL-6 induced in vitro growth of TEC, demonstrating that IL-6 is a possible autocrine growth factor for these cells. This deregulated IL-6 production as well as the ability of TEC to use it as a growth factor may be of pathophysiological relevance in MG. It provides an explanation for morphological changes of the thymus and may have a key role in initiation, exacerbation and ongoing of the autoimmune response in MG. Therefore this study extends our current understanding of the molecular pathophysiology of MG.

Serum neopterin after lung transplantation.

OBJECTIVE: Neopterin (N), a marker for activated cell-mediated immunity, was assayed in the sera of 44 lung recipients early and late after transplantation. The study was a prospective, blind clinical trial designed to evaluate the following: (1) the daily dynamics of the serum neopterin/creatinine (N/C) ratio during the first 3 weeks after transplantation; (2) the correlation between changes in the serum N/C ratio and episodes of rejection or infection; (3) the correlation between the serum N/C ratio and the concentration of serum soluble interleukin 2 receptor (sIL-2R), a marker of T-cell activation; and (4) the potential value of monitoring the serum N/C ratio during noninvasive long-term follow-up of lung recipients. METHODS: Sera from lung recipients were collected every day or every 2 days for the first 3 weeks after transplantation (22 patients) and before fiberoptic bronchoscopy and routine consultation (44 patients). The N concentrations were determined by radioimmunoassay and sIL-2R levels were measured using a sandwich enzyme immunoassay. RESULTS: Serum N/C is an early and sensitive marker of immune activation in the 21 days following transplantation. The N/C ratios during early rejections (815 +/- 182 mumol/mol) and infections (677 +/- 75 mumol/mol) were higher than those in patients with no complications (160 +/- 32 mumol/mol). In contrast, the N/C ratio did not increase during rejection later after transplantation. More than 3 weeks after transplantation, an increase in the N/C ratio was specifically correlated with infections, mainly those due to cytomegalovirus (CMV) (control subjects, 132 +/- 12 mumol/mol; rejections, 163 +/- 25 mumol/mol; CMV pneumonia, 786 +/- 103 mumol/mol, p < 0.001). The N/C ratio correlated with sIL-2R serum levels (r = 0.625, p < 0.001). CONCLUSIONS: Our results indicate that more than 3 weeks after transplantation, the serum N/C ratio increases only in cases of infection, mostly CMV pneumonia. In contrast, both rejection and infectious complications are associated with an increased N production in the early postoperative period.

Synergistic induction of interleukin-6 production and gene expression in human thymic epithelial cells by LPS and cytokines.

We examined the ability of LPS and several cytokines (TNF-alpha, IL-1-beta, IFN-gamma, IL-4) to modulate IL-6 production by cultured human thymic epithelial cells (TEC). IL-6 activity was measured by the hybridoma growth factor biological activity. Moderate but detectable IL-6 activity was spontaneously produced in the presence of serum proteins. LPS as well as the cytokines TNF-alpha and IL-1-beta was a potent inducer of IL-6, increasing, respectively, IL-6 levels by 9-, 28-, and 75-fold (mean values) while IL-4 and IFN-gamma provoked no significant effect. Interestingly, clearly different kinetics were observed for IL-6 induction by the various activation agents, the maximal effect being reached at 24, 48, and 72 hr, respectively for LPS, TNF-alpha, and IL-1-beta. Moreover, a synergistic effect of TNF-alpha and either LPS or IL-1-beta was observed. Indeed, TEC incubated with the cytokines in combination at optimal doses produced 5- to 170-fold more IL-6 than TEC stimulated with the cytokines individually. Neutralizing anti-IL-6 polyclonal and monoclonal antibodies completely blocked hybridoma proliferation stimulating activity of TEC supernatants; thus, implying that this activity is essentially due to IL-6. In situ hybridization analysis of cytocentrifuged TEC with an mRNA antisense probe specific for human IL-6 and labeled with 35S demonstrated that up to 90% of TEC could be induced to express the IL-6 gene. Computer-aided quantification of IL-6 mRNA levels indicated that upon stimulation with TNF-alpha combined to LPS, both the numbers of cells expressing IL-6 mRNA and the amounts of cytoplasmic IL-6 mRNA per cell were increased. Taken altogether these results demonstrate that LPS and/or cytokines can modulate and synergistically stimulate IL-6 production. In addition to a possible role in regulating normal thymic T cell activation, the IL-6 produced by TEC could be of pathophysiological relevance in disregulated situations such as in hyperplastic thymuses from patients with myasthenia gravis.

Interleukin-6 production by tumor necrosis factor and lipopolysaccharide-stimulated rat renal cells.

Interleukin-6 (IL-6) is produced by various cell types, including monocytes, fibroblasts, and endothelial cells. IL-6 has also been detected in the urine of normal and renal transplant patients. Thus, the possible production of this cytokine by glomeruli and mesangial cells was investigated. Rat glomeruli were obtained by serial sieving of cortical homogenates of blood-free kidneys. Mesangial cells were obtained from the glomeruli and cultured under standard methods in RPMI 1640 medium containing 15% fetal calf serum. Glomeruli or confluent monolayers cells were then incubated in RPMI 1640 for 18 hr, in the presence or not of tumor necrosis factor-alpha (TNF alpha), lipopolysaccharide (LPS), or platelet-activating factor (PAF). IL-6 activity was measured using the IL-6-dependent cell line subclone (B 9-9) and expressed with respect to a standard curve established with recombinant IL-6. Glomeruli generate IL-6 upon TNF alpha (100 ng/ml) and LPS (1 microgram/ml), 11,500 +/- 3000 and 22,000 +/- 7500 U/ml, respectively. Nonstimulated mesangial cells produced 50 +/- 5 U/ml (mean +/- SEM, n = 4) of IL-6. TNF alpha (1 ng/ml) and LPS (1 microgram/ml) induced the production of 800 +/- 90 and 40,000 +/- 5000 U/ml, respectively (n = 4). In contrast, PAF (0.1 nM-1 microM) did not increase IL-6 production from glomeruli or mesangial cells. These results demonstrate that renal cells spontaneously generate minimal amounts of IL-6 and that this production is significantly increased by TNF alpha or LPS. A synergy between LPS and TNF alpha was induced in glomerular cells with 10 ng/ml of TNF alpha and graded concentrations of LPS. Thus, the production of IL-6 by glomerular cells and its modulation by other cytokines or endotoxins may play a role in the local immunological processes leading to immune glomerular diseases.