The role of interleukin-18 in the diagnosis and monitoring of hemophagocytic lymphohistiocytosis/macrophage activation syndrome - a systematic review

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening, hyperinflammatory disorder, characterized by multiorgan failure, fever and cytopenias. The diagnosis of HLH and its subtype Macrophage Activation Syndrome (MAS) remains a challenge. Interleukin 18 (IL-18) is emerging as a potential biomarker for HLH/MAS but is currently not a part of diagnostic criteria. This systematic review aimed to assess the potential role of IL-18 in the diagnosis and monitoring of HLH and MAS, and was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed and Embase were searched on 30 January 2020. Studies included all subtypes of HLH and a range of underlying disorders in both children and adults. A total of 14 studies were included. Generally, serum IL-18 was elevated in both primary and secondary HLH (> 1000 pg/ml) compared with other inflammatory conditions and with healthy individuals; thus, serum IL-18 may be able to discriminate between HLH and other inflammatory conditions. Significantly increased IL-18 (> 10 000 pg/ml) was also consistently described in MAS compared with other subtypes of HLH. The ability of IL-18 to distinguish MAS from systemic juvenile idiopathic arthritis (JIA) is less unambiguous, as IL-18 levels > 100 000 pg/ml were described in sJIA patients both with and without MAS. IL-18 may help to differentiate between HLH subtypes and other inflammatory conditions. As HLH and MAS are rare disorders, only few and relatively small studies exist on the subject. Larger, prospective multi-center studies are called for to assess the diagnostic precision of IL-18 for HLH and MAS.

Short-term transcutaneous non-invasive vagus nerve stimulation may reduce disease activity and pro-inflammatory cytokines in rheumatoid arthritis: results of a pilot study

Objective: Rheumatoid arthritis (RA) is a chronic, autoimmune, inflammatory disease. Studies suggest that pro-inflammatory cytokines may be attenuated by the vagus nerve through the cholinergic anti-inflammatory pathway. We aimed to evaluate the anti-inflammatory effects of short-term transcutaneous non-invasive vagus nerve stimulation (n-VNS) applied to the cervical vagus nerve in patients with RA. Method: We conducted a single-centre, open-label, preliminary proof-of-concept study of n-VNS in two cohorts of participants with RA: one with high disease activity (n = 16) and one with low disease activity (n = 20). Disease Activity Score based on 28-joint count-C-reactive protein (DAS28-CRP), cardiac vagal tone, and pro-inflammatory cytokines were measured at baseline and after 1 and 4 days of n-VNS. Results: In the high disease activity group, n-VNS resulted in reductions in DAS28-CRP (4.1 to 3.8, p = 0.02), CRP (8.2 to 6 mg/mL, p = 0.01), and interferon-γ (29.8 to 22.5 pg/mL, p = 0.02). In the low disease activity group, there was no effect on DAS28-CRP, and n-VNS was associated with a decrease in cardiac vagal tone (p = 0.03) and a reduction in interleukin-10 (0.8 to 0.6 pg/mL, p = 0.02). Participants with high disease activity had lower baseline cardiac vagal tone than those with low disease activity (3.6 ± 2 vs 4.9 ± 3 linear vagal scale, p = 0.03). Cardiac vagal tone was negatively associated with DAS28-CRP (r = -0.37, p = 0.03). Overall, n-VNS was well tolerated. Conclusion: This study provides preliminary support for an anti-inflammatory effect of n-VNS in patients with RA. These findings warrant further investigation in larger placebo-controlled trials.

Soluble CD163 and soluble mannose receptor predict survival and decompensation in patients with liver cirrhosis, and correlate with gut permeability and bacterial translocation

BACKGROUND

Activated hepatic macrophages play a key role in inflammation and fibrosis progression in chronic liver disease.

AIM

To assess the prognostic value of soluble (s)CD163 and mannose receptor (sMR) in cirrhotic patients and explore associations with markers of intestinal permeability (lactulose-mannitol ratio, diamine oxidase), bacterial translocation (endotoxin, lipopolysaccharide-binding protein) and markers of systemic immune activation (interleukin-6, interleukin-8, sCD14).

METHODS

We prospectively investigated 101 cirrhotic patients (Child-Pugh class A: n = 72, Child-Pugh classes B and C: n = 29) and 31 healthy controls. Patients were observed for a median follow-up of 37 months.

RESULTS

Median plasma levels of sCD163 and soluble mannose receptor were significantly elevated in cirrhotic patients (P < .001) and increased with disease severity (sCD163 in healthy controls = 1.3, Child-Pugh class A = 4.2, Child-Pugh classes B and C = 8.4 mg/L; sMR in healthy controls = 15.8, Child-Pugh class A = 36.5, Child-Pugh classes B and C = 66.3 μg/dL). A total of 21 patients died during the observation period. Patients with sCD163 levels above 5.9 mg/L showed significantly reduced survival (survival rate after 36 months: 71% versus 98%, P < .001). Patients with soluble mannose receptor levels above 45.5 μg/dL developed significantly more complications of cirrhosis within 12 months (73% versus 9%, P < .001). Furthermore, both variables correlated with the lactulose-mannitol ratio, diamine oxidase, lipopolysaccharide and interleukin-8.

CONCLUSION

Our data demonstrate the prognostic value of sCD163 in predicting long-term survival in patients with liver cirrhosis and identify soluble mannose receptor as a prognostic marker for occurrence of cirrhosis-associated complications. The correlation between gut barrier dysfunction and activation of macrophages points towards a link between them.

Transcutaneous cervical vagal nerve stimulation modulates cardiac vagal tone and tumor necrosis factor-alpha

The vagus nerve is a central component of cholinergic anti-inflammatory pathways. We sought to evaluate the effect of bilateral transcutaneous cervical vagal nerve stimulation (t-VNS) on validated parameters of autonomic tone and cytokines in 20 healthy subjects. 24 hours after t-VNS, there was an increase in cardiac vagal tone and a reduction in tumor necrosis factor-α in comparison to baseline. No change was seen in blood pressure, cardiac sympathetic index or other cytokines. These preliminary data suggest that t-VNS exerts an autonomic and a subtle antitumor necrosis factor-α effect, which warrants further evaluation in larger controlled studies.

Single-centre experience of the macrophage activation marker soluble (s)CD163 - associations with disease activity and treatment response in patients with autoimmune hepatitis

BACKGROUND

Autoimmune hepatitis (AIH) is characterised by liver inflammation with reversibility upon anti-inflammatory treatment. Soluble (s)CD163, a specific macrophage activation marker, is associated with inflammation in other liver diseases, but never investigated in AIH.

AIM

To investigate sCD163 in patients with acute AIH and in complete and incomplete responders to standard anti-inflammatory pharmacotherapy, and during follow-up in treatment naive patients.

METHODS

In a cross-sectional design, we studied 121 AIH patients (female/male 89/32, median age 49 years); of these, we prospectively studied 10 treatment naïve AIH patients during prednisolone treatment and tapering. Twenty patients had variant syndromes of AIH and primary biliary cholangitis or primary sclerosing cholangitis. sCD163 was compared with markers of disease activity, severity and treatment response.

RESULTS

In the patients with acute AIH (n = 21), sCD163 was sixfold increased compared with the normalised levels in patients (n = 32) with complete response to standard treatment [9.5 (3.3-28.8) vs. 1.6 (0.8-3.2) mg/L, P < 0.01)], while the patients (n = 27) with incomplete response had higher sCD163 [2.2 (1.3-7.9), P < 0.05] than the complete responders. sCD163 was positively associated with ALAT, IgG and bilirubin (rho: 0.45-0.59, P < 0.001, all), and negatively to external coagulation factors (rho:-0.34, P < 0.001). In the treatment naïve patients, sCD163 fell during high-dose prednisolone treatment and tapering. Immunohistochemical staining confirmed increased CD163 expression in liver biopsies from patients with acute AIH.

CONCLUSIONS

sCD163 was markedly elevated in AIH in the acute phase, normalised by successful treatment in complete responders, but remained higher in the incompletely responding cases. Our results demonstrate macrophage activation in AIH paralleling disease activity, severity and treatment response, suggesting a role for macrophage activation in AIH.

The macrophage activation marker sCD163 combined with markers of the Enhanced Liver Fibrosis (ELF) score predicts clinically significant portal hypertension in patients with cirrhosis

BACKGROUND

Noninvasive identification of significant portal hypertension in patients with cirrhosis is needed in hepatology practice.

AIM

To investigate whether the combination of sCD163 as a hepatic inflammation marker and the fibrosis markers of the Enhanced Liver Fibrosis score (ELF) can predict portal hypertension in patients with cirrhosis.

METHODS

We measured sCD163 and the ELF components (hyaluronic acid, tissue inhibitor of metalloproteinase-1 and procollagen-III aminopeptide) in two separate cohorts of cirrhosis patients that underwent hepatic vein catheterisation. To test the predictive accuracy we developed a CD163-fibrosis portal hypertension score in an estimation cohort (n = 80) and validated the score in an independent cohort (n = 80). A HVPG ≥10 mmHg was considered clinically significant.

RESULTS

Both sCD163 and the ELF components increased in a stepwise manner with the patients' Child-Pugh score (P < 0.001, all), and also with increasing HVPG (P < 0.001). receiver operator characteristics (ROC) analyses showed that each one of the individual components predicted a HVPG >10 mmHg with AUROC's of approximately 0.80. The combined score optimised by logistic regression analyses improved the AUROC to 0.91 in the estimation cohort and 0.90 in the validation cohort. Furthermore, a high value of the combined score was associated with a high short-term mortality.

CONCLUSIONS

The combination of the macrophage activation marker sCD163 and the fibrosis markers predicted significant portal hypertension in patients with cirrhosis. This score may prove useful for screening purposes and highlights the importance of both the inflammatory and the fibrotic components of cirrhotic portal hypertension.

The macrophage activation marker sCD163 is associated with changes in NAFLD and metabolic profile during lifestyle intervention in obese children

BACKGROUND

Obesity is associated with metabolic derangement and non-alcoholic fatty liver disease (NAFLD). Macrophages are involved in liver inflammation and fibrosis, and soluble (s)CD163 is a macrophage activation marker.

OBJECTIVES

To associate sCD163 with parameters of paediatric obesity and NAFLD, as well as changes in these parameters during lifestyle intervention.

METHODS

We studied 117 obese children during a 10-week lifestyle intervention; 71 completed the 12-month follow-up. We recorded clinical and biochemical data, and performed liver ultrasonography.

RESULTS

Baseline sCD163 was higher in children with elevated alanine transaminase (ALT) (2.3 ± 0.7 vs. 2.0 ± 0.6 mg L(-1), P = 0.03), steatosis (2.3 ± 0.7 vs. 2.0 ± 0.6 mg L(-1), P = 0.01) and high paediatric NAFLD fibrosis index (2.3 ± 0.7 vs. 1.9 ± 0.6 mg L(-1) , P = 0.03). Baseline sCD163 was independently associated with ALT, cholesterol and high-sensitivity C-reactive protein (hs-CRP). The change in sCD163 during lifestyle intervention was associated with changes in ALT, homeostatic model assessment of insulin resistance (HOMA-IR), hs-CRP and cholesterol, and inversely associated with the change in high-density lipoprotein cholesterol.

CONCLUSION

sCD163 was associated with markers of liver injury and metabolic parameters in obese children, and changes in these parameters during lifestyle intervention. This may suggest that activated macrophages play a role in NAFLD and sCD163 may serve as a marker of liver disease severity and treatment effect.

Soluble CD163, a specific macrophage activation marker, is decreased by anti-TNF-α antibody treatment in active inflammatory bowel disease

Activated macrophages shed the haemoglobin-haptoglobin scavenger receptor CD163 into the circulation as soluble(s)-CD163. We measured sCD163 as an in vivo macrophage activation marker in patients with Crohn's disease (CD) or ulcerative colitis (UC) receiving antitumour necrosis factor (TNF)-α antibody or prednisolone treatment. We also investigated the CD163 expression on circulating monocytes. 58 patients with CD, 40 patients with UC and 90 healthy controls (HC) were included. All patients had active disease at inclusion and were followed for 6 weeks of anti-TNF-α antibody or prednisolone treatment. We measured plasma sCD163 levels at baseline, 1 day, 1 week and 6 weeks after initiating treatment. CD163 expression on circulating CD14(+) monocytes was measured in 21 patients with CD receiving anti-TNF-α antibody treatment. Baseline sCD163 levels were elevated in patients with CD [1.99 (1.80-2.18) mg/l] and in patients with UC [2.07 (1.82-2.32) mg/l] compared with HC [1.51 (1.38-1.63) mg/l] (P < 0.001). Anti-TNF-α antibody treatment induced a rapid decrease in sCD163 levels in patients with CD and in patients with UC 1 day after treatment initiation (P < 0.05). One week of prednisolone treatment did not induce a reduction in sCD163 levels. Anti-TNF-α treatment normalized sCD163 levels in patients with UC, whereas patients with CD exhibited sustained increased sCD163 levels. In patients with CD, CD163 expression on CD14(+) monocytes was increased compared with HC. This study highlights that active CD and UC are associated with increased macrophage activation, as indicated by elevated sCD163 levels and monocytic CD163 expression. Anti-TNF-α antibody treatment induced a rapid decrease in sCD163 levels, suggesting a specific effect on macrophage activation in inflammatory bowel diseases.

Soluble CD163 levels are elevated in cerebrospinal fluid and serum in people with Type 2 diabetes mellitus and are associated with impaired peripheral nerve function

AIMS

To measure soluble CD163 levels in the cerebrospinal fluid and serum of people with Type 2 diabetes, with and without polyneuropathy, and to relate the findings to peripheral nerve function.

METHODS

A total of 22 people with Type 2 diabetes and 12 control subjects without diabetes were included in this case-control study. Participants with diabetes were divided into those with neuropathy (n = 8) and those without neuropathy (n = 14) based on clinical examination, vibratory perception thresholds and nerve conduction studies. Serum and cerebrospinal fluid soluble CD163 levels were analysed using an enzyme-linked immunosorbent assay.

RESULTS

Soluble CD163 levels were significantly higher in the cerebrospinal fluid and serum of the participants with Type 2 diabetes compared with the control participants [cerebrospinal fluid: median (range) 107 (70-190) vs 84 (54-115) μg/l, P < 0.01 and serum: 2305 (920-7060) vs 1420 (780-2740) μg/l, P < 0.01). Cerebrospinal fluid soluble CD163 was positively related to impaired peripheral nerve conduction (nerve conduction study rank score: r = 0.42; P = 0.0497) and there was a trend for higher levels of soluble CD163 in the cerebrospinal fluid and serum in participants with neuropathy than in those without neuropathy [cerebrospinal fluid: median (range) 131 (86-173) vs 101 (70-190) μg/l, P = 0.08 and serum: 3725 (920-7060) vs 2220 (1130-4780), P = 0.06).

CONCLUSIONS

Cerebrospinal fluid soluble CD163 level is associated with impaired peripheral nerve function. Higher levels of soluble CD163 in people with diabetic polyneuropathy suggest that inflammation plays a role in the development of neural impairment. The relationship between cerebrospinal fluid soluble CD163 level and peripheral nerve conduction indicates that soluble CD163 may be a potential biomarker for the severity of diabetic polyneuropathy.

Macrophage-related serum biomarkers soluble CD163 (sCD163) and soluble mannose receptor (sMR) to differentiate mild liver fibrosis from cirrhosis in patients with chronic hepatitis C: a pilot study

Macrophages regulate the fibrotic process in chronic liver disease. The aim of the present pilot study was to evaluate two new macrophage-specific serum biomarkers [soluble CD163 (sCD163) and soluble mannose receptor (sMR, sCD206)] as potential fibrosis markers in patients chronically infected with hepatitis C virus (HCV). Forty patients with chronic hepatitis C were included from two hospital clinics. On the day of inclusion, transient elastography (TE) was performed to assess the fibrosis stage, and blood samples were collected for the measurement of sCD163 and sMR. The plasma concentrations of both biomarkers were significantly higher in patients infected with HCV and with cirrhosis compared to those with no/mild liver fibrosis (5.77 mg/l vs. 2.49 mg/l and 0.44 mg/l vs. 0.30 mg/l for sCD163 and sMR, respectively). The best separation between groups was obtained by sCD163 [area under the receiver operating characteristic curve (AUC) 0.89 (95 % confidence interval [CI] 0.79-0.99)] as compared to sMR [AUC 0.75 (95 % CI 0.61-0.90)]. sCD163 and sMR correlated significantly (r (2) = 0.53, p < 0.0001). Interestingly, sCD163 also correlated significantly with TNF-α (presented in a previous publication), which is shed to serum by the same mechanism as sCD163 (r (2) = 0.40, p < 0.0001). In conclusion, the macrophage-related markers sCD163 and sMR are significantly higher in patients chronically infected with HCV and with cirrhosis than in those with no/mild fibrosis. sCD163 is a promising new fibrosis marker in patients infected with HCV.

Soluble CD163, a marker of Kupffer cell activation, is related to portal hypertension in patients with liver cirrhosis

BACKGROUND

Activation of Kupffer cells may be involved in the pathogenesis of portal hypertension by release of vasoconstrictive substances and fibrosis due to co-activation of hepatic stellate cells.

AIM

To study soluble plasma (s) CD163, a specific marker of activated macrophages, as a biomarker for portal hypertension in patients with liver cirrhosis.

METHODS

We measured sCD163 concentration and the hepatic venous pressure gradient (HVPG) by liver vein catheterisation in 81 cirrhosis patients (Child-Pugh CP-A: n = 26, CP-B: n = 29, CP-C: n = 26) and 22 healthy subjects. We also measured their cardiac output (CO), cardiac index and systemic vascular resistance (SVR). Liver status was examined by Child-Pugh and MELD-score.

RESULTS

In cirrhosis, sCD163 concentration was nearly three times higher than in controls (4.7 ± 2.5 vs. 1.6 ± 0.5 mg/L, P < 0.001). sCD163 was also higher, as measured in steps by CP-score (P < 0.001). The HVPG rose steeply to an asymptote of 22 mmHg with sCD163 up to about 5 mg/L and not to higher values with higher sCD163. In a multivariate analysis, sCD163 was the only independent predictor of the HVPG but did not predict any of the systemic circulatory findings. sCD163 > 3.95 mg/L (upper normal limit) predicted HVPG ≥ 10 mmHg with a positive predictive value of 0.99.

CONCLUSIONS

Circulating sCD163 originating from activated Kupffer cells is increased in cirrhosis with increasing Child-Pugh score and with increasing HVPG, and it is an independent predictor for HVPG. These findings support a primary role of macrophage activation in portal hypertension, and may indicate a target for biological intervention.

Soluble CD163: a biomarker linking macrophages and insulin resistance

AIMS/HYPOTHESIS

Soluble CD163 (sCD163) was recently identified as a strong risk marker for developing type 2 diabetes. We hypothesised that sCD163 independently associates with insulin resistance.

METHODS

This cross-sectional study includes 234 participants: 96 with type 2 diabetes, 34 with impaired glucose tolerance (IGT) and 104 with normal glucose tolerance (NGT), matched for sex and BMI. Glucose-lowering medication was paused for 1 week before plasma samples were obtained for determination of sCD163 and other inflammatory and metabolic variables. Insulin resistance was estimated by homeostasis model assessment of insulin resistance (HOMA-IR).

RESULTS

Concentrations of sCD163 were 1.95 mg/l (0.63-6.97) in individuals with type 2 diabetes, 1.64 mg/l (0.58-4.19) in those with IGT, and 1.48 mg/l (0.48-4.11) (median [range]) in those with NGT (p < 0.0001). In univariate analyses, sCD163 correlated significantly with HOMA-IR (R = 0.44), insulin (R = 0.41), glucose (R = 0.30), triacylglycerol (R = 0.29) and HDL-cholesterol (R = -0.34) (all p < 0.0001). All but glucose remained significant when adjusting for age, sex, BMI and glycaemic group. In univariate regression analyses, HOMA-IR was associated with sCD163, C-reactive protein (CRP), TNF-α and IL-6 (all p ≤ 0.0001). An increase of 50% in sCD163 resulted in an estimated increase in HOMA-IR of 36% (95% CI 26, 48; p < 0.0001). In multiple linear regression analyses, sCD163 (p = 0.001) and CRP (p = 0.01) remained independent predictors of HOMA-IR, whereas TNF-α and IL-6 did not.

CONCLUSIONS/INTERPRETATION

Macrophage-specific sCD163 was strongly associated with insulin resistance independently of TNF-α and other predictors. Moreover, sCD163 was associated with well-known variables of the metabolic syndrome.

New immunological serum markers in bacteraemia: anti-inflammatory soluble CD163, but not proinflammatory high mobility group-box 1 protein, is related to prognosis

High mobility group-box 1 protein (HMGB1) is a late-onset proinflammatory cytokine. Soluble haemoglobin scavenger receptor (sCD163) is a specific marker of anti-inflammatory macrophages. The study purpose was to relate the levels of these new markers in bactaeremic patients to levels of well-known pro- and anti-inflammatory markers [procalcitonin, lipopolysaccharide (LPS)-binding protein, interleukin (IL)-6, IL-10] and to evaluate the levels in relation to disease severity and aetiology. A total of 110 patients with bacteraemia were included in a prospective manner from the medical department at a large Danish university hospital. Levels of HMGB1 and sCD163 were higher in patients with bacteraemia compared to controls (P < 0.001). HMGB1 correlated with proinflammatory molecules [procalcitonin (PCT)] and traditional infectious parameters [C-reactive proteins (CRP), white blood cells (WBC) and neutrophils], whereas sCD163 correlated with levels of IL-6, IL-10 but not to lipopolysaccharide-binding protein (LBP), PCT or CRP. Levels of sCD163 and IL-6 were significantly higher among non-survivors compared to survivors (P < 0.05). Neither HMGB1 nor any of the proinflammatory markers were elevated in fatal cases compared to survivors. There was no statistically significant difference in HMGB1 and sCD163 levels in Gram-negative versus Gram-positive bacteraemia. HMGB1 reflects proinflammatory processes, whereas sCD163 reflects anti-inflammatory processes as judged by correlations with traditional marker molecules. sCD163 and IL-6, but not HMGB1, were prognostic markers in this cohort pointing to an anti-inflammatory predominance in patients with fatal disease outcome.

Differential expression of monocyte CD163 in single- and dual-asthmatic responders during allergen-induced bronchoconstriction

BACKGROUND

Mononuclear phagocytes play an important role in modulating inflammatory reactions in response to antigen challenge.

OBJECTIVE

To investigate the regulation of CD163, a marker of anti-inflammatory macrophages, during Dermatophagoides pteronyssinus (Dp)-induced bronchoconstriction.

METHODS

Among 110 Dp-sensitive patients who underwent bronchial challenge with Dp, there were 51 dual responders (DR), 32 single responders (SR) and 27 non-responders (NR). Monocyte expression of CD14 and CD163 was evaluated by flow cytometry. Exhaled NO (eNO) concentration was determined on-line using a chemiluminescence analyser. In 21 DR, nine SR and 13 NR-soluble CD163 in plasma was measured by ELISA before, 1, 8 and 24 h after the challenge.

RESULTS

In DR, the baseline expression of monocyte CD163 and eNO were significantly greater than in SR and NR. A pattern of (1) decreased monocyte CD163 expression, (2) unchanged sCD163 and (3) increased eNO in DR was contrasted by a pattern of (1) increased CD163 expression, (2) increased sCD163 and (3) unchanged eNO in SR. During allergen challenge, the changes in monocyte CD163 expression and sCD163 inversely correlated with the changes in eNO.

CONCLUSION

Both pro-inflammatory and anti-inflammatory responses to allergen challenge are uniquely expressed among SR and DR.

Predictive value of soluble haemoglobin scavenger receptor CD163 serum levels for survival in verified tuberculosis patients

Pre-treatment serum levels of sCD163 were measured in a cohort of 236 suspected tuberculosis (TB) cases from Guinea-Bissau, with a median follow-up period of 3.3 years (range 0-6.4 years). In 113 cases, the diagnosis of TB was verified by positive sputum microscopy and/or culture. Among the verified TB cases, a decreased survival rate was found in 27 patients with sCD163 levels above the upper reference limit (3.95 microg/mL). The difference in survival was significant during TB treatment (log rank, p<0.02) and after long-term follow-up (log rank, p<0.001). The decrease in survival rate during TB treatment remained significant in a multivariate Cox model controlling for human immunodeficiency virus (HIV) status, age and gender, with a mortality increase of 1.19 (95% CI, 1.04-1.36) per microg of sCD163, and a hazard ratio (HR) for sCD163 levels above the upper reference limit of 4.18 (95% CI, 1.06-16.4). The difference was not significant after excluding patients with concomitant HIV-1 and HIV-2 infection in Kaplan-Meier analyses (log rank, p 0.11). In contrast, the difference in survival remained significant in Kaplan-Meier analyses after long-term follow-up, even after excluding patients with concomitant HIV-1 and HIV-2 infection (log rank, p 0.002). In the Cox model, the mortality increase per microg of sCD163 was 1.27 (95% CI, 1.14-1.40), with an HR for elevated sCD163 levels of 2.85 (95% CI, 1.44-5.63). The HRs for concomitant HIV-1 and HIV-2 infection were 6.92 (95% CI, 3.28-14.58) and 2.48 (95% CI, 1.09-5.67), respectively. Thus, sCD163 levels appeared to be an independent predictor of survival in verified TB patients.

Biological variation of soluble CD163

A soluble plasma form of CD163 (sCD163) was recently identified. The protein has anti-inflammatory effects in vitro and is elevated in patients with myelo-monocytic leukaemia and infection. For rational use and evaluation of this potential new quantity it is important to have knowledge of its biological variability and to use a methodology that has a sufficiently analytical quality. The day-to-day and diurnal biological variabilities of sCD163 were studied in 12 healthy people using a sandwich ELISA. The within-run-, between run- and total analytical coefficients of variation were estimated to 3.6%, 4.8% and 6.0%, respectively. The day-to-day within-subject biological variation was estimated to 9.0%, and the between-subject biological variation to 35.9%. A diurnal variation in sCD163 concentrations with 14% lower values in the night (supine position) was observed. The ratio between total analytical variation and within-subject biological variation was 0.67. The index of individuality, calculated as the ratio between within-subject biological variation and between-subject biological variation, was low and similar to complement factors and immunoglobulins. A low index of individuality is important in a monitoring situation where small changes from the set point of the individual can be detected in serial measurements. For this purpose, the critical difference for a series of results in the same patient (significant at p < 0.05) was calculated to 30% for samples taken on different days and measured in separate runs.

Soluble CD163: a marker molecule for monocyte/macrophage activity in disease

By immunoprecipitation we have identified a soluble plasma form of CD163 (sCD163), the IL-6 inducible macrophage-receptor for clearing haptoglobin-haemoglobin complexes. A sandwich ELISA for measuring sCD163 was established and used to determine the sCD163 levels in normal subjects and patients with inflammatory and myeloproliferative diseases. In normal subjects, the concentration of sCD163 was high (median 1.9 mg/l) with low intra-individual variation. Highly increased levels were seen in patients with sepsis, myeloid leukaemia and in patients with Gaucher disease characterized by accumulation of tissue macrophages. Although the physiological role of sCD163 remains unknown, our present data suggest that sCD163 might prove to be a valuable marker molecule in infectious and myeloproliferative diseases.

Characterization of an enzyme-linked immunosorbent assay for soluble CD163

We have recently identified a soluble plasma form of CD163 sCD163, the macrophage receptor for clearance of haptoglobin-haemoglobin complexes, and we have observed highly elevated levels of sCD163 in subgroups of haematological patients. In the present study, we describe the optimization and characterization of a sandwich ELISA for the determination of the concentration of sCD163 in plasma and serum. The optimal concentrations of antibodies were determined systematically and the assay was calibrated by CD163 purified from human spleen membranes. The minimum detection limit was below 6.25 microg/L. Recovery of CD163 added to plasma samples was 106%. The concentration of sCD163 in paired serum and plasma samples correlated well (r2=0.99); however, serum levels were 1.1 times higher than the plasma levels. The addition of haptoglobin-haemoglobin complexes did not influence the assay. A very high stability of sCD163 was measured in whole blood and in plasma subjected to different temperatures and after repeated freezing and thawing.

[Biochemical changes in fibromyalgia. Can serum hyaluronic acid be used diagnostically?]

AIM

To assess the levels of hyaluronic acid (HA) in Danish patients with fibromyalgia (FM).

METHODS

Serum levels of HA were determined in 53 patients with established FM and 55 control samples with a radiometric assay (Pharmacia). Values were correlated to clinical parameters of disease severity (duration of disease, tender point scales, visual analogue scales).

RESULTS

There were no differences in the HA levels of patients and controls. In all the patients, except one, values were within the reference intervals. Nor was there an association between HA levels and clinical findings.

CONCLUSIONS

Patients with FM do not generally have increased serum levels of HA, and other serum measurements have not been helpful in the diagnosis of FM. Some biochemical changes have been described in FM, however, and these have mainly been observed in the spinal fluid.

Evaluation of potential organ culture media for eye banking using human donor corneas

AIM

To evaluate the ability of different commercially available cell culture solutions to preserve human donor corneas during 3 weeks of "closed system" organ culture at physiological temperature. This screening was performed in an attempt to establish a rational basis for the development of a serum-free organ culture medium for eye banking.

METHODS

72 normal human donor corneas were organ cultured for 21 days at 31 degrees C in eight different test media (nine corneas in each group). The basic culture solutions included: minimal essential medium (MEM), MEM with stabilised L-glutamine, M199, DIF-1000, SFM, F99, and F99 with ascorbic acid, insulin, bFGF, transferrin, selenium, and lipids (termed F99-Sr). All media were supplemented with 2% fetal calf serum (FCS), except for MEM, which was also studied at 8% FCS. The evaluation parameters included: (1) the endothelial cell loss as evaluated using trypan blue staining; (2) the ability of keratocytes and endothelial cells to incorporate tritiated uridine into RNA as evaluated using autoradiography and digital image analysis; (3) the leakage of immunogenic keratan sulphate as assessed using ELISA; and (4) changes in storage medium pH, glucose, and lactate content.

RESULTS

SFM induced the lowest endothelial cell loss of 14% (SD 2%) and the highest RNA synthesis rates of all test solutions supplemented with 2% FCS. Corneas stored in SFM also showed the least leakage of keratan sulphate and the highest glucose consumption and lactate production. In five media (MEM with 2% FCS, MEM with stabilised L-glutamine, M199, F99, and F99-Sr), comparable and intermediate potentials for organ culture were observed with endothelial cell loss of 16-19%. By contrast, 29% (4%) of the endothelium was lost after storage in DIF-1000. Interestingly, the use of 8% FCS (in MEM) had a marked protective effect on the endothelium, which showed the highest RNA synthetic activity combined with a cell loss of only 11% (4%), compared with 19% (6%) at 2% FCS (p<0.05).

CONCLUSION

Among the present test solutions, SFM appears to be the most prominent candidate for a new corneal organ culture medium and should be further tested and possibly refined to effectively substitute serum addition.

Patients with fibromyalgia have normal serum levels of hyaluronic acid

OBJECTIVE

To investigate the levels of hyaluronic acid (HA) in Danish patients with fibromyalgia (FM).

METHODS

Serum levels of HA were determined in 53 patients with established FM and 55 control samples using a radiometric assay. Values were correlated to clinical disease severity variables (duration of disease, tender point scales, visual analog scales).

RESULTS

There were no differences in HA levels between patients and controls. HA levels of all patients except one were within the reference ranges. There was no association between HA levels and clinical findings.

CONCLUSION

Patients with FM do not generally have increased serum levels of HA.

Connective tissue markers of rheumatoid arthritis

Rheumatoid arthritis (RA) is a common systemic autoimmune disorder of unknown aetiology. The most common outcome of RA is a progressive development of joint destruction and deformity. Early introduction of disease-modifying antirheumatic drugs seems important for prevention of the long term injuries of articular cartilage and bone. Early diagnosis and selection of patients with rapidly progressive disease therefore is of clinical significance. Routine laboratory tests are valuable in monitoring for renal, hepatic and haematological side effects of medical treatment. Determination of rheumatoid factor contributes to the classification of arthritis as RA, and acute phase reactants are useful for quantifying and comparing the level of inflammatory activity in the course of a given patient. There is, however, a lack of sensitive and specific biochemical markers for RA, and frontline biochemical research is devoted to characterizing molecules which are of diagnostic and prognostic value, as well as molecules which are indicators of the degree of joint cartilage and bone destruction. The present survey summarizes current knowledge concerning possible tissue-specific marker molecules of RA.

Viability of human corneal keratocytes during organ culture

The viability of human corneal keratocytes was assessed during four weeks of 'closed system' organ culture at 31 degrees C. After 28 days of culturing, the entire keratocyte population was still alive and viable because all cells incorporated uridine; a parameter for RNA-synthesis. During the first 14 days, mitoses were found in the anterior half of the stroma (0.23% mitoses per 48 h), while only few keratocytes were able to divide at day 28 (0.01% mitoses per 48 h). Metabolic parameters revealed a progressing acidosis in the medium with oxygen and glucose depletion. Immunological measurements of keratan sulphate proteoglycan suggested that approximately 1% of the total content was lost during the period. In conclusion, our current organ culture technique can maintain a viable keratocyte population for four weeks; a viable stroma can be grafted within this period.

Demonstration of immunogenic keratan sulphate in commercial chondroitin 6-sulphate from shark cartilage. Implications for ELISA assays

The prototype monoclonal keratan sulphate (KS) antibody 5D4 that is widely used for detection of KS in tissues and biological fluids reacts strongly with commercial low grade shark cartilage chondroitin 6-sulphate. Characterization of the immunogenic material by chondroitinase ABC digestion, ELISA inhibition studies, immunoblotting and HPLC analyses confirmed the presence of substantial amounts of KS, probably as a large proteoglycan (> 120 kDa). Commercial and heterogenic glycosaminoglycan preparations therefore must be used with great caution in immunological analyses. On the other hand the shark cartilage chondroitin 6-sulphate is an easy accessible source of immunogenic KS that can be used as a reference standard and as coating antigen in KS-ELISAs. The concentration of immunogenic KS in synovial fluid measured with an ELISA based solely on reagents of shark cartilage chondroitin 6-sulphate correlated well (r = 0.90) with the concentrations obtained with a traditional KS-ELISA that uses purified aggrecan as standard and coating antigen, and KS in both serum and synovial fluid could be measured with sufficient linearity.

Improved method for silver staining of glycoproteins in thin sodium dodecyl sulfate polyacrylamide gels

A method for detection of glycoproteins in thin sodium dodecyl sulfate polyacrylamide gels was developed by a combination of (i) initial periodic acid oxidation/Alcian blue staining and (ii) subsequent staining with silver nitrate. The procedure allowed detection of as little as 1.6 ng of alpha 1-acid glycoprotein and 8-40 ng of a polydisperse mucin sample, which is at least 10 times more sensitive than previously published methods. The method should be very useful for assessment of sample purity and detection of glycoproteins in dilute mixed samples.

Effect of flunarizine and calcium on serotonin uptake in human and rat blood platelets and rat synaptosomes

Calcium and the calcium overload blocker flunarizine exert profound effects on mood. We therefore studied the effect of calcium and flunarizine on serotonin uptake in human and rat blood platelets and in rat synaptosomes. Calcium (1.3 mmol/L) had a weak inhibiting effect on serotonin uptake in blood platelets, whereas no effect was observed in synaptosomes. Flunarizine inhibited serotonin uptake in a concentration dependent manner with an IC50 value of 1 mumol/L in blood platelets and 5 mumol/L in synaptosomes. The inhibition did not depend on the presence of extracellular calcium indicating that the effect is not coupled to a blockade of cellular calcium influx. In human blood platelets, the inhibition was of the noncompetitive type. These results indicate that flunarizine interacts directly with the 5-HT uptake site. The relatively high concentration of flunarizine required to inhibit 5-HT uptake may question the clinical importance of this effect.

ELISA for the core protein of the cartilage large aggregating proteoglycan, aggrecan: comparison with the concentrations of immunogenic keratan sulphate in synovial fluid, serum and urine

Immunological assays for fragments of the cartilage large aggregating proteoglycan, aggrecan, have been widely used to monitor cartilage turnover. These assays have commonly employed the monoclonal keratan sulphate antibody, 5D4. Keratan sulphate, however, is present in many tissues and 5D4 affinity is critically dependent on antigen structure. We have therefore raised and characterized a monoclonal antibody (1-F21) that reacts with the core protein of aggrecan without interference from the glycosaminoglycan side chains and, using this antibody, we have optimized a sensitive, competitive ELISA. The within-assay and between-assay coefficients of variation were 4.9-8.9% and 11.1-13.0%, respectively. The mean concentrations of core protein in synovial fluid, serum and urine were 76.4 micrograms/ml, 104.0 ng/ml and 81.0 ng/ml, respectively. In synovial fluids the concentrations were closely correlated with the concentrations of keratan sulphate as determined by 5D4 (r = 0.94), whereas in serum and urine there was no obvious correlation between the determinations. These findings show that measurement of both core protein and keratan sulphate results in a more precise description of aggrecan turnover.

The epidermal growth factor-like domain of the human cartilage large aggregating proteoglycan, aggrecan: increased serum concentration in rheumatoid arthritis

The large aggregating proteoglycan from human cartilage, aggrecan, has recently been shown to possess an immunologically detectable domain with close homology to epidermal growth factor (EGF), that is variably expressed by alternative mRNA splicing. Using a competitive ELISA we detected this domain in sera from both patients with RA and normal controls. The EGF-like domain could only be detected after digestion of sera with chondroitinase ABC, which demonstrates its proteoglycan origin. The concentration of the aggrecan EGF-like domain was considerably elevated in sera from patients with RA as compared to the control sera (P < 0.001), and the concentration of the domain increased with age in both the patient (r = 0.58, P < 0.05) and the control (r = 0.66, P < 0.01) group. These results demonstrate that the EGF-like domain of aggrecan could be of value as a marker of RA.

Combined alcian blue and silver staining of subnanogram quantities of proteoglycans and glycosaminoglycans in sodium dodecyl sulfate-polyacrylamide gels

Proteoglycans stain weakly in polyacrylamide gels by traditional protein stains such as coomassie brilliant blue or silver. In the present work preparations of large aggregating proteoglycan from human articular cartilage were used to evaluate a convenient staining method based on successive staining with alcian blue and neutral silver. The method is developed for sodium dodecyl sulfate-polyacrylamide gel electrophoresis; with ultrathin minigels in a semiautomated electrophoresis system, takes 1 1/2 h, and uses stable reagents. Preparations, electrophoresis, and staining of up to 24 samples can be completed within 2 1/2 h. The method has a detection limit of 0.04-1 ng proteoglycan and less than 0.5 ng of glycosaminoglycan. In addition the method can be adjusted for selective staining of proteoglycans and glycosaminoglycans.