Serum markers of immune activation and liver allograft rejection

Biomarkers for the diagnosis of acute cellular rejection in liver transplant recipients: A review

The gold standard for the diagnosis of acute cellular rejection (ACR) is a liver biopsy. The quest for an alternative non-invasive biomarkers has been long and is ongoing. However, an efficient and useful biomarker has not been developed yet. In this manuscript, we review all possible candidate biomarkers that have been studied in recent years, starting with cytokines and ending with an overview of different newly discovered "omics". Promising paths are being explored but a valid non-invasive biomarker has not been discovered yet.

Diagnostic value of peripheral blood T-cell activation and soluble IL-2 receptor for acute rejection in liver transplantation

BACKGROUND

T-cells play an important role in the pathogenesis of rejection. Monitoring T-cells activation markers in peripheral blood may contribute to diagnosis of acute rejection after liver transplantation (LTX).

METHODS

Lymphocyte subset distribution, expression of T-cell activation markers (flow cytometry), concentration of soluble (s) interleukin-2 receptor (IL-2R) (solid phase chemiluminescence immunoassay), and liver enzymes as well as bilirubin were prospectively tested in peripheral blood samples of LTX patients with (n=69) and without acute rejection (n=50). Acute rejection was assessed by standard criteria including liver biopsies.

RESULTS

Intra-individual monitoring of immune parameters revealed an up-regulation of IL-2 receptor (CD25) expression on CD4 and CD8 T-cells together with increases in sIL-2R levels in patients with acute rejections. Measuring sIL-2R levels resulted in highest diagnostic efficiency (>85%). This level of diagnostic efficiency was not reached by any other marker tested. From all conventional markers of hepatocellular integrity and function, alkaline phosphatase reached the highest level of diagnostic efficiency with 70%.

CONCLUSIONS

Monitoring of up-regulation of the IL-2/IL-2R pathway represents a useful tool for assessment of acute rejection after LTX.

Serum amyloid A versus C-reactive protein in acute pancreatitis: clinical value of an alternative acute-phase reactant

OBJECTIVES

The acute-phase reactant C-reactive protein (CRP) is currently the serum variable of choice for an early, accurate, and cost-effective severity assessment of acute pancreatitis in the daily clinical routine. Serum amyloid A (SAA) proteins comprise a family of apolipoproteins that constitute another major acute-phase reactant and thus could be a potential alternative to CRP assessment. In the present study we investigated the clinical usefulness of SAA determinations in acute pancreatitis using an automated immunoassay technique.

DESIGN

Cohort study, comparing patients with complicated and mild acute pancreatitis; control groups included individuals with further abdominal disorders and healthy volunteers.

SETTING

A collaborative study between the department of general surgery and the routine laboratory of the department of clinical chemistry/pathobiochemistry.

PATIENTS

We enrolled 66 patients with acute pancreatitis in the present study. Control groups consisted of healthy subjects (n = 30), patients with chronic pancreatitis (n = 20), patients with pancreatic carcinoma (n = 20), and patients with acute appendicitis (n = 20).

INTERVENTIONS

Blood samples were collected during 14 consecutive days in patients with acute pancreatitis. A single blood specimen was taken in all control groups after the diagnosis was established.

MEASUREMENTS AND MAIN RESULTS

SAA concentrations were 3 mg/L (median; range, 3-93) in healthy subjects. Although SAA and CRP both reached their maximum within 4 days after onset of symptoms in patients with acute pancreatitis, SAA concentrations rose faster above normal ranges and reached 676 mg/L (median; range, 12-1880), higher than CRP, which reached 313 mg/L (median; range, 29-613). As observed for CRP, SAA was significantly higher in patients who developed complications such as necrosis, infection of necrosis, or multiple organ dysfunction syndrome or in patients who died. SAA achieved best results in discriminating between necrotizing pancreatitis and interstitial edematous pancreatitis. However, CRP provided an earlier differentiation between both entities and a significantly better overall accuracy, as shown by receiver operating characteristics analysis. SAA concentrations in patients with chronic pancreatitis were 6 mg/L (median; range, 3-756). In patients with pancreatic carcinoma, SAA concentrations were 7 mg/L (median; range, 3-492), and in patients with acute appendicitis, they were 50 mg/L (median; range, 3-2140).

CONCLUSION

SAA is a nonspecific and rapidly produced variable in inflammatory abdominal disorders with a wider dynamic range than CRP. The current assay technique renders SAA an applicable and readily available variable under clinical routine conditions. In cases of acute pancreatitis, however, CRP is still superior to SAA for early and accurate stratification of patients with a complicated course.

Increased plasma concentrations of serum amyloid A: an indicator of the acute-phase response after cardiopulmonary bypass

OBJECTIVES

To assess the expression of mixed and hepatic venous serum amyloid A (SAA) concentrations and its relationship to plasma concentrations of C-reactive protein, interleukin-6 (IL-6), and endotoxin during and after cardiopulmonary bypass (CPB).

DESIGN

Prospective, consecutive sample with repeated measurements.

SETTING

Surgical intensive care unit (ICU) in a university hospital.

PATIENTS

Twenty patients who underwent elective coronary bypass grafting.

INTERVENTIONS

A radial artery catheter, pulmonary artery catheter, and right hepatic vein catheter were inserted. Blood samples were collected to determine the different mediators, lactate concentrations, and oxygen saturations.

MEASUREMENTS AND MAIN RESULTS

After induction of anesthesia, baseline values were obtained and the following parameters were determined 20 mins after onset of CPB, 20 mins after termination of CPB, at admission to the ICU, and 6, 8, 12, and 24 hrs later: hemodynamics, body core temperature, hepatic venous oxygen saturation, and mixed and hepatic venous lactate, endotoxin, interleukin (IL)-6, C-reactive protein (CRP), and SAA concentrations. Endotoxin and IL-6 plasma concentrations increased during CPB, peaked 6 hrs after admission to the ICU (endotoxin: 23.1 +/- 6.2 pg/mL; IL-6: 646 +/- 104 pg/mL), and decreased thereafter; SAA and CRP concentrations began to increase after 6 and 8 hrs, respectively, with the highest concentrations reached 24 hrs postoperatively (CRP: 14 +/- 3.6 mg/L; SAA: 668 +/- 114 micrograms/mL). Lactate concentrations began to increase 20 mins after CPB, and continued to increase until 12 hrs postoperatively. There were no significant differences between mixed and hepatic venous values of endotoxin, IL-6, CRP, SAA, and lactate (p < .05). Body core temperature, which was < 37.5 degrees C before surgery for all patients, increased 6 hrs after admission to the ICU and peaked 12 hrs postoperatively (38.3 +/- 1.1 degrees C). Hepatic venous oxygen saturation did not change. Correlations were obtained between IL-6 values and heart rate (r2 = .20; p < .005), and endotoxin concentrations and systemic vascular resistance (r2 = .18; p < .001). Body core temperature correlated significantly closer with SAA (r2 = .52; p < .0001) values than with IL-6 (r2 = .27; p < .0001) or CRP (r2 = .16; p < .001) values (p < .05).

CONCLUSIONS

SAA is an additional and sensitive marker of the acute-phase response following CPB; the increase in SAA concentrations parallels the temporary increase in body core temperature and is preceded by endotoxemia and IL-6 secretion.

Artificial liver support: the pipe dream of today should be the reality of the near future

The title of this article is taken from an interesting Letter to the Editor entitled 'Artificial liver support-Pipe dream or reality' by Cattral and Levy of the Toronto Hospital, Canada, published in the New England Journal of Medicine 1994, in which the authors persuasively propose possibilities of artificial liver support and suggest its advantages. We find that their suggestions agree with the core of our thoughts on this subject. The present article deals with the concept of implanting livers taken from humans, primates or non-primates (e.g. hog) into patients in parallel with their own metabolically fatigued or cirrhotic livers, with minimal surgical manipulation, as a prelude to total artificial liver support via a liver dialysis device. While the possibility exists that the host liver may recover function, a donor liver, whether implanted into the patient's abdomen or connected in vitro to the patient's circulatory system extracorporeally, may provide the host liver respite and a period for recovery and proliferation, if possible. Once recovery is under way, the donor liver may be removed and the patient will not experience the usual risks of rejection and the necessary side-effects of immunosuppression associated with conventional full hepatectomy and donor transplantation. The viability of a liver implantation model in rats is correlated in this article with hepatic acute phase response.

Acute cellular rejection after liver transplantation: variability, morbidity, and mortality

Acute cellular rejection of the allograft is a potentially serious complication after liver transplantation, yet its true incidence is unknown. We therefore investigated the frequency of acute cellular rejection reported by transplant centers and its impact on morbidity and mortality. Morbidity was defined as duration of hospitalization. Of 200 articles screened, 18 were selected for inclusion in the study database, in which there was a total of 1,437 patients who received transplants. All contained more than 20 patients and invariably used histopathology for diagnosis of acute cellular rejection. These reports included all transplant patients within a fixed period and sufficient data to determine the incidence of acute cellular rejection. Morbidity data were obtained from our previous series. The mean incidence of acute cellular rejection in all centers was 49.8% (range between centers, 24% to 80%). Two immunosuppressive cohorts were identified: high-dose cyclosporine induction (> or = 5 mg/kg/d) and low-dose cyclosporine induction (< or = 4 mg/kg/d). Acute cellular rejection was reported in 27.0% of the high-dose group and 63.6% of the low-dose group, P = .0001. Strict adherence to Snover's histological criteria for acute cellular rejection did not alter the reported mean incidence. Frequency of acute cellular rejection was 45.2% (range between centers, 24% to 80%) in 8 studies that used Snover's criteria, and 51.6% (range between centers, 37% to 80%) in 10 studies that did not. There was no correlation between mortality and incidence of acute cellular rejection in the 9 studies that reported survival (R2 = .105). Morbidity data showed that the average length of initial hospitalization after transplantation for patients with acute cellular rejection was 52.4 +/- 8.3 (range, 14 to 124) days, in contrast to 28.3 +/- 2.3 (range, 9 to 87) days for patients with no rejection. P = .0008. The total number of hospital days in the first 6 months for patients with acute cellular rejection was 55.6 +/- 8.6 (range, 14 to 124) days and with no rejection, was 37.7 +/- 3.1 (range, 9 to 99) days. P = .0232. The incidence of acute cellular rejection varies widely among transplant centers, regardless of the use of Snover's criteria. Acute cellular rejection appeared to be less frequent in programs using high-dose cyclosporine induction regimens. The presence of acute cellular rejection seemed to have no correlation with mortality but significantly increased morbidity and therefore the cost of transplantation.

Soluble T lymphocyte markers in the diagnosis of cellular rejection and cytomegalovirus hepatitis in liver transplant recipients

Hepatic dysfunction following liver transplantation is often caused by cellular rejection or infection with cytomegalovirus. These etiologies can at times be difficult to differentiate. We measured the levels of soluble T lymphocyte markers sIL2R, sCD4, and sCD8 in serum as possible diagnostic indicators of cellular rejection and cytomegalovirus hepatitis. Pretransplant levels, and serial post-transplant levels of soluble T lymphocyte markers were measured in five control patients without cellular rejection or cytomegalovirus infection, ten patients with cellular rejection, and six patients with cytomegalovirus hepatitis. In all cases, cellular rejection and cytomegalovirus hepatitis were documented with liver histology. For each group of patients, we calculated the mean ratio of the post-transplant marker level divided by the pre-transplant level. We found an elevation in the mean ratio of sIL2R in patients with cellular rejection shortly before or at the time of diagnosis of rejection as compared to the transplant control group. Levels of sCD8 were not significantly increased in patients with cellular rejection. We found a more pronounced elevation in the mean marker ratios of both sIL2R and sCD8 in patients with cytomegalovirus hepatitis which were higher compared not only to the transplant control group but also compared to the cellular rejection group. The rise of serum levels preceded the histologic diagnosis of cytomegalovirus hepatitis and detection of cytomegalovirus in blood cultures. Increased serum levels of sIL2R with concomitant elevation of sCD8 suggest the diagnosis of cytomegalovirus hepatitis over cellular rejection.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum amyloid A: an acute phase apolipoprotein and precursor of AA amyloid

Serum amyloid A is an acute phase protein complexed to HDL as an apoprotein. The molecular weight is 11.4-12.5 kDa in different species and the protein has from 104 to 112 amino acids, without or with an insertion of eight amino acids at position 72. The protein is very well conserved throughout evolution, indicating an important biological function. The N-terminal part of the molecule is hydrophobic and probably responsible for the lipid binding properties. The most conserved part is from position 38 to 52 and this part is therefore believed to be responsible for the until now unknown biological function. The protein is coded on chromosome 11p in man, and chromosome 7 in mice, and found in all mammals until now investigated, and also in the Peking duck. In the rat a truncated SAA mRNA has been demonstrated, but no equivalent serum protein has been reported. Acute phase SAA is first of all produced in hepatocytes after induction by cytokines, but extrahepatic expression of both acute phase and constitutive SAA proteins have been demonstrated. Several cytokines, first of all IL-1, IL-6 and TNF are involved in the induction of SAA synthesis, but the mutual importance of these cytokines seems to be cell-type specific and to vary in various experimental settings. The role of corticosteroids in SAA induction is somewhat confusing. In most in vitro studies corticosteroids show an enhancing or synergistic effect with cytokines on SAA production in cultured cell. However, in clinical studies and in vivo studies in animals an inhibitory effect of corticosteroids is evident, probably due to the all over anti-inflammatory effect of the drug. Until now no drug has been found that selectively inhibits SAA production by hepatocytes. Effective anti-inflammatory or antibacterial treatment is the only tool for reducing SAA concentration in serum and reducing the risk of developing secondary amyloidosis. The function of SAA is still unclear. Interesting theories, based on current knowledge of the lipid binding properties of the protein and the relation to macrophages, in the transportation of cholesterol from damaged tissues has been advanced. A putative role in cholesterol metabolism is supported by the findings of SAA as an inhibitor of LCAT. The potential that SAA is a modifying protein in inflammation influencing the function of neutrophils and platelets is interesting and more directly related to the inflammatory process itself.(ABSTRACT TRUNCATED AT 400 WORDS)