The role of cortisol in immunosuppression in subarachnoid haemorrhage.

BACKGROUND: We sought to determine the extent to which cortisol suppressed innate and T cell-mediated cytokine production and whether it could be involved in reducing peripheral cytokine production following subarachnoid haemorrhage (SAH). METHODS: Whole blood from healthy controls, patients with SAH and healthy volunteers was stimulated with lipopolysaccharide (LPS), to stimulate innate immunity, or phytohaemagglutinin (PHA), to stimulate T cell-mediated immunity. Varying concentrations of cortisol were included, with or without the cortisol antagonist RU486. Concentration of interleukin-6 (IL-6), IL-1ß and tumour necrosis factor-alpha) TNFα were determined as a measure of innate immunity. IL-6, IL-17 (interferon gamma) IFNƔ and IL-17 were determined as an indicator of T cell-mediated immunity. RESULTS: Suppression of innate responses to LPS was apparent in whole blood from SAH patients, relative to healthy controls, and TNFα production was inversely correlated with plasma cortisol concentration. Cytokine production in whole blood from healthy volunteers was inhibited by cortisol concentrations from 0.33 µM, or 1 µM and above, and these responses were effectively reversed by the cortisol antagonist RU-486. In SAH patients, RU-486 reversed suppression of innate TNF-α and IL-6 responses, but not IL-1ß or T cell-mediated responses. CONCLUSION: These data suggest that cortisol may play a role in reducing innate, but not T cell-mediated immune responses in patients with injuries such as SAH and that cortisol antagonists could be effective in boosting early innate responses.

Overcoming matrix matching problems in multiplex cytokine assays.

Failure to match assay matrices with samples in immunoassays can result in incorrect sample values being reported. For multiplex assays this presents particular problems, due to the need to find a matrix suitable for all the analytes. Here, we describe strategies adopted to overcome matrix problems identified in establishing a cytokine multiplex assay in human plasma. Standard analytes were diluted in plasma samples to identify representative plasma for assay development. Horse sera were screened to evaluate potential interference before using to adjust a matrix to match plasma samples. Suitability of the matrix match was confirmed by evaluating recovery of known concentrations of analytes from plasma. Individual plasmas modified the assay signal for some analytes to a variable extent, particularly for IL-1α and IL-1ß. Addition of horse serum to assay buffer improved matching to plasma samples, although endogenous MCP-1 activity was apparent in one sample. Matching of plasma and assay matrices allowed recoveries within 10% to 20% of the expected values, unless the samples contained atypical interfering activity. Attention to choice of samples and diluent used for assay development is particularly important for measurement of sample analytes in cytokine multiplex assays.

Interleukin-1 receptor antagonist reverses stroke-associated peripheral immune suppression.

INTRODUCTION: Infections are common following stroke and adversely affect outcome. Cellular immune suppression associated with acute stroke may increase susceptibility to infection. Cytokines are important contributors to both stroke pathology and the response to infection. Since interleukin (IL)-1 blockade is a candidate treatment for cerebral ischemia, we examined whether administration of interleukin-1 receptor antagonist (IL-1Ra) to patients with acute stroke affected innate cellular immune responses in a phase II placebo-controlled trial. METHODS: Venous blood samples were taken prior to treatment initiation, at 24h and 5 to 7d. Blood was also drawn from stroke-free controls. Lipopolysaccharide (LPS) stimulation of whole-blood cultures assessed the potential of leukocytes to produce cytokines. RESULTS: Induction of tumor necrosis factor (TNF)-α, IL-1ß, IL-6, IL-8 and IL-10 by LPS was significantly reduced in patients at admission, compared to controls. At 24h, cytokine induction remained suppressed in the placebo group. In contrast, for patients treated with IL-1Ra, induction of TNF-α, IL-6 and IL-10 was similar to controls and IL-1ß induction was significantly greater than in the placebo group. At 5 to 7d, TNF-α and IL-1ß induction remained suppressed only in the placebo group (p<0.05). Plasma cortisol concentrations, elevated at admission in patients compared to controls, were substantially reduced at 24h in the patients receiving IL-1Ra (p<0.05) and inversely correlated (p<0.001) with either TNF-α (r=-0.71) or IL-1ß induction (r=-0.67) at admission. CONCLUSION: Treatment with IL-1Ra reverses peripheral innate immune suppression in the acute phase of stroke, which is associated with attenuated cortisol production. The mechanisms underlying these observations, including the potential impact of IL-1Ra on stroke severity and the clinical significance of immune suppression, require further evaluation in larger studies.

Reconstituting National Institute for Biological Standards and Control (NIBSC) chemokines.

We observed significant discrepancies between immunoassay results when using different internally prepared reference preparations for interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) from the National Institute for Biological Standards and Control (NIBSC). To evaluate the reasons for this we prepared the chemokines using diluents that incorporated protein at different steps. This showed that even brief addition of water to these preparations, in the absence of additional protein, resulted in loss of immunoreactivity in assays. The data obtained emphasise the importance of adding protein at an early stage of preparation to avoid loss of material and potential loss of activity.

Clinical outcome following acute ischaemic stroke relates to both activation and autoregulatory inhibition of cytokine production.

BACKGROUND: As critical mediators of local and systemic inflammatory responses, cytokines are produced in the brain following ischaemic stroke. Some have been detected in the circulation of stroke patients, but their role and source is unclear. Focusing primarily on interleukin(IL)-1-related mechanisms, we serially measured plasma inflammatory markers, and the production of cytokines by whole blood, from 36 patients recruited within 12 h and followed up to 1 year after acute ischaemic stroke (AIS). RESULTS: Admission plasma IL-1 receptor antagonist (IL-1ra) concentration was elevated, relative to age-, sex-, and atherosclerosis-matched controls. IL-1beta, soluble IL-1 receptor type II, tumour necrosis factor (TNF)-alpha, TNF-RII, IL-10 and leptin concentrations did not significantly differ from controls, but peak soluble TNF receptor type I (sTNF-RI) in the first week correlated strongly with computed tomography infarct volume at 5-7 days, mRS and BI at 3 and 12 months. Neopterin was raised in patients at 5-7 d, relative to controls, and in subjects with significant atherosclerosis. Spontaneous IL-1beta, TNF-alpha and IL-6 gene and protein expression by blood cells was minimal, and induction of these cytokines by lipopolysaccharide (LPS) was significantly lower in patients than in controls during the first week. Minimum LPS-induced cytokine production correlated strongly with mRS and BI, and also with plasma cortisol. CONCLUSION: Absence of spontaneous whole blood gene activation or cytokine production suggests that peripheral blood cells are not the source of cytokines measured in plasma after AIS. Increased plasma IL-1ra within 12 h of AIS onset, the relationship between sTNF-RI and stroke severity, and suppressed cytokine induction suggests early activation of endogenous immunosuppressive mechanisms after AIS.

Comparison of 'real-time' and immunometric RT-PCR: RNA interference of reverse transcriptase-PCR.

We measured interleukin-6 (IL-6) mRNA in whole blood, using an immunometric reverse transcriptase-polymerase chain reaction (IRT-PCR) method and 'real-time' RT-PCR using the Roche LightCycler. Both methods showed similar precision, in terms of inter- and intra-assay variation, where a lower total RNA concentration was used at a relatively high ratio of (IL-6) mRNA to total RNA. However, the 'real-time' RT-PCR method showed a greater loss of accuracy at higher concentrations of total RNA.

Simple, quantitative measurement of cytokine gene expression using an immunometric reverse transcriptase-polymerase chain reaction.

We have developed a novel system to quantify mRNA, using a coupled reverse transcriptase-polymerase chain reaction (RT-PCR) with RNA standards and an immunometric optical readout. Biotinylated RT-PCR products were captured onto avidin-coated microplates and hybridised to a dinitrophenol (DNP)-labelled oligonucleotide probe. Enzyme-linked anti-DNP antibodies were used to detect the product via a colorimetric enzyme assay. Unknown mRNA samples were quantified by interpolating the signal on a standard curve generated from dilutions of RNA (cRNA) standards for interleukin-6 (IL-6), tumour necrosis factor-alpha (TNFalpha), IL-1beta and actin mRNA. The assay for IL-6 mRNA was able to discriminate between samples with a two- to fourfold difference in concentration, had an intra-assay coefficient of variation (CV) of 17% and an inter-assay CV of 24%. The method was used to quantify IL-6 mRNA, relative to expression of IL-6 protein and biological activity, in human blood that had been activated by endotoxin. The IL-6 mRNA could be detected 1 h after endotoxin addition and peaked at 4 h. This paralleled the increase in protein production that followed approximately 1 h later.