Electrolysis products, reactive oxygen species and ATP loss contribute to cell death following irreversible electroporation with microsecond-long pulsed electric fields.

Membrane permeabilization and thermal injury are the major cause of cell death during irreversible electroporation (IRE) performed using high electric field strength (EFS) and small number of pulses. In this study, we explored cell death under conditions of reduced EFS and prolonged pulse application, identifying the contributions of electrolysis, reactive oxygen species (ROS) and ATP loss. We performed ablations with conventional high-voltage low pulse (HV-LP) and low-voltage high pulse (LV-HP) conditions in a 3D tumor mimic, finding equivalent ablation volumes when using 2000 V/cm 90 pulses or 1000 V/cm 900 pulses respectively. These results were confirmed by performing ablations in swine liver. In LV-HP treatment, ablation volume was found to increase proportionally with pulse numbers, without the substantial temperature increase seen with HV-LP parameters. Peri-electrode pH changes, ATP loss and ROS production were seen in both conditions, but LV-HP treatments were more sensitive to blocking of these forms of cell injury. Increases in current drawn during HV-LP was not observed during LV-HP condition where the total ablation volume correlated to the charge delivered into the tissue which was greater than HV-LP treatment. LV-HP treatment provides a new paradigm in using pulsed electric fields for tissue ablation with clinically relevant volumes.

Non-Contact Irreversible Electroporation in the Esophagus With a Wet Electrode Approach.

Our objective was to develop a technique for performing irreversible electroporation (IRE) of esophageal tumors while mitigating thermal damage to the healthy lumen wall. We investigated noncontact IRE using a wet electrode approach for tumor ablation in a human esophagus with finite element models for electric field distribution, joule heating, thermal flux, and metabolic heat generation. Simulation results indicated the feasibility of tumor ablation in the esophagus using an catheter mounted electrode immersed in diluted saline. The ablation size was clinically relevant, with substantially lesser thermal damage to the healthy esophageal wall when compared to IRE performed by placing a monopolar electrode directly into the tumor. Additional simulations were used to estimate ablation size and penetration during noncontact wet-electrode IRE (wIRE) in the healthy swine esophagus. A novel catheter electrode was manufactured and wIRE evaluated in seven pigs. wIRE was performed by securing the device in the esophagus and using diluted saline to isolate the electrode from the esophageal wall while providing electric contact. Computed tomography and fluoroscopy were performed post-treatment to document acute lumen patency. Animals were sacrificed within four hours following treatment for histologic analysis of the treated esophagus. The procedure was safely completed in all animals; post-treatment imaging revealed intact esophageal lumen. The ablations were visually distinct on gross pathology, demonstrating full thickness, circumferential regions of cell death (3.52 ± 0.89 mm depth). Acute histologic changes were not evident in nerves or extracellular matrix architecture within the treatment site. Catheter directed noncontact IRE is feasible for performing penetrative ablations in the esophagus while avoiding thermal damage.

sCD25 as an independent adverse prognostic factor in adult patients with HLH: results of a multicenter retrospective study.

Hemophagocytic lymphohistiocytosis (HLH) is a rare but often fatal hyperinflammatory syndrome caused by an inborn or acquired error of immunity. In adults, the underlying immunodeficiency generally arises alongside severe infections, malignancies, autoimmune diseases, and immunosuppressive treatment. To analyze risk factors and outcome in adults, we conducted a multicenter retrospective study. A total of 62 adult (age ≥18 years) patients met at least one of the following inclusion criteria: (1) ≥5 of 8 HLH-2004 criteria, (2) HScore ≥ 200 plus 4 HLH-2004 criteria, or (3) mutation compatible with an HLH diagnosis. Most patients (65%) were male, and the median age at diagnosis was 53.5 years (range, 19-81 years). All patients were assigned to 4 etiologic subgroups based on their most likely HLH trigger. The survival probability of the 4 etiologic subgroups differed significantly (P = .004, log-rank test), with patients with an underlying malignancy having the worst clinical outcome (1-year survival probability of 21%). The parameters older age, malignant trigger, elevated serum levels of aspartate transferase, creatinine, international normalized ratio, lactate dehydrogenase, sCD25, and a low albumin level and platelet count at treatment initiation were significantly (P < .1) associated with worse overall survival in the univariate Cox regression model. In multivariate analysis, sCD25 remained the only significant prognostic factor (P = .005). Our results suggest that sCD25 could be a useful marker for the prognosis of patients with HLH that might help to stratify therapeutic interventions.

Sonographic and 3T-MRI-based evaluation of the tongue in ALS.

A few systematic imaging studies employing ultrasound (HRUS) and magnetic resonance imaging (MRI) have suggested tongue measures to aid in diagnosis of amyotrophic lateral sclerosis (ALS). The relationship between structural tongue alterations and the ALS patients' bulbar and overall motor function has not yet been elucidated. We here thus aimed to understand how in-vivo tongue alterations relate to motor function and motor function evolution over time in ALS. Our study included 206 ALS patients and 104 age- and sex-matched controls that underwent HRUS and 3T MRI of the tongue at baseline. Sonographic measures comprised coronal tongue echointensity, area, height, width and height/width ratio, while MRI measures comprised sagittal T1 intensity, tongue area, position and shape. Imaging-derived markers were related to baseline and longitudinal bulbar and overall motor function. Baseline T1 intensity was lower in ALS patients with more severe bulbar involvement at baseline. Smaller baseline coronal (HRUS) and sagittal (MRI) tongue area, smaller coronal height (HRUS) and width (HRUS) as well as more rounded sagittal tongue shape predicated more rapid functional impairment - not only of bulbar, but also of overall motor function - in ALS. Our results suggest that in-vivo sonography und MRI tongue measures could aid as biomarkers to reflect bulbar and motor function impairment.

The upper cervical spinal cord in ALS assessed by cross-sectional and longitudinal 3T MRI.

The upper cervical spinal cord is measured in a large longitudinal amyotrophic lateral sclerosis (ALS) cohort to evaluate its role as a biomarker. Specifically, the cervical spinal cord´s cross-sectional area (CSA) in plane of the segments C1-C3 was measured semi-automatically with T1-weighted 3T MRI sequences in 158 ALS patients and 86 controls. Six-month longitudinal follow-up MRI scans were analyzed in 103 patients. Compared to controls, in ALS there was a significant mean spinal cord atrophy (63.8 mm² vs. 60.8 mm², p = 0.001) which showed a trend towards worsening over time (mean spinal cord CSA decrease from 61.4 mm² to 60.6 mm² after 6 months, p = 0.06). Findings were most pronounced in the caudal segments of the upper cervical spinal cord and in limb-onset ALS. Baseline CSA was related to the revised ALS functional rating scale, disease duration, precentral gyrus thickness and total brain gray matter volume. In conclusion, spinal cord atrophy as assessed in brain MRIs in ALS patients mirrors the extent of overall neurodegeneration and parallels disease severity.

A Comparative Study of Ablation Boundary Sharpness After Percutaneous Radiofrequency, Cryo-, Microwave, and Irreversible Electroporation Ablation in Normal Swine Liver and Kidneys.

PURPOSE: To compare ablation boundary sharpness after percutaneous radiofrequency ablation (RFA), cryoablation (CA), microwave ablation (MWA) and irreversible electroporation (IRE) ablation in normal swine liver and kidney. MATERIALS AND METHODS: Percutaneous CT-guided RFA (n = 5), CA (n = 5), MWA (n = 5) and IRE (n = 5) were performed in the liver and kidney of four Yorkshire pigs. Parameters were chosen to produce ablations 2-3 cm in diameter with a single ablation probe. Contrast-enhanced CT imaging was performed 24 h after ablation, and animals were killed. Treated organs were removed and processed for histologic analysis with hematoxylin and eosin, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL). Three readers independently analyzed CT, H&E and TUNEL stained images of the ablation boundary to delineate regions of (1) viable cells, (2) complete necrosis or (3) mixture of viable and necrotic cells which was defined as the transition zone (TZ). The width of TZ was compared across the techniques and organs. RESULTS: Ablations appeared as non-contrast-enhancing regions on CT with sharp transition to enhancing normal tissue. On TUNEL stained slides, the mean width (µm) of the TZ after MWA was 319 ± 157 in liver and 267 ± 95 in kidney, which was significantly lower than RFA (811 ± 477 and 938 ± 429); CA (452 ± 222 and 700 ± 563); and IRE (1319 ± 682 and 1570 ± 962) (all p < 0.01). No significant differences were observed between the organs. CONCLUSION: Under similar conditions, the width of the TZ at the ablation boundary varies significantly between different ablation techniques.

Normal Porcine Ureter Retains Lumen Wall Integrity but Not Patency Following Catheter-Directed Irreversible Electroporation: Imaging and Histologic Assessment over 28 Days.

PURPOSE: To evaluate the effect of catheter-directed irreversible electroporation (IRE) on the integrity, patency, and function of the normal porcine ureter. MATERIALS AND METHODS: A catheter-mounted electrode was used to perform fluoroscopy-guided IRE in 8 healthy pigs. Two unilateral ablations (90 pulses at 2,000 V, 100 µs) were performed in each animal in the proximal and distal ureter. Serum creatinine measurements and contrast-enhanced computed tomography imaging were performed at 1, 7, 14, 21, and 28 days after IRE, and findings were compared with baseline values by Student t test. Two animals each were euthanized at 1, 7, 14, and 28 days after IRE for histologic assessment of treatment effects. Quantitative histologic analysis of regeneration and healing of the ureteral wall was graded on a five-point scale. RESULTS: IRE was successfully performed in all animals. Preservation of ureteral wall integrity was confirmed by the leakage-free passage of contrast medium in the treated ureter of all animals through the observation period. Ureteral strictures and associated renal pelvicaliceal dilation were observed in all animals by study days 7 (P = .005) and 14 (P = .007) and did not resolve by day 28. Urothelial recovery was observed in tissue samples from day 7, with progressive replacement of the tunica muscularis with granulation tissue. Despite extensive scarring of the tunica muscularis, full recovery of the urothelium was observed by day 28. CONCLUSIONS: The normal porcine ureter retains lumen wall integrity and function following catheter-directed IRE. Scarring of the tunica muscularis in the treated ureter results in stricture formation and reduction of lumen patency.

Computed Tomography Perfusion Following Transarterial Chemoembolization of Hepatocellular Carcinoma: A Feasibility Study in the Early Period.

OBJECTIVES: The aim of this study was to assess the feasibility of computed tomography (CT) perfusion in early follow-up after transarterial chemoembolization (TACE) of hepatocellular carcinoma (HCC). METHODS: Fifteen patients with a total of 16 HCC who were referred to our institution for TACE were included in the study. Computed tomography perfusion was performed within 1 to 3 days before and 4 to 7 days after TACE. Multiphase contrast-enhanced CT was performed 35 (SD, 20) days after TACE. Hepatic arterial blood flow and portal venous blood flow, as well as the perfusion index (PI), were calculated for each HCC using the dual input maximum slope method. Visual grading of the PI and visual grading of the amount of deposition of embolic material within the HCC were performed using a 6-step scale. Differences in perfusion before and after TACE and correlation of perfusion before TACE with the amount of embolization material depositions 1 week and 1 month after TACE were tested. RESULTS: No statistically significant correlation was found between pre-TACE perfusion parameters and the amount of embolization material deposition in the post-TACE studies. There was no statistically significant difference between pre- and post-TACE arterial blood flow and portal venous blood flow, whereas PI was significantly lower after TACE. Congruently, visual grading of PI was statistically significantly lower after TACE. There was no statistically significant difference in quantitative pre-TACE and post-TACE PI between tumors, which showed hypervascularization in the multiphase follow-up CT and tumors that did not show hypervascularization. However, tumors that showed hypervascularization in the multiphase follow-up CT had significantly higher visual grading of PI after TACE than tumors that did not show hypervascularization. CONCLUSIONS: Our findings indicate that visual interpretation of the PI of HCC derived from dual-input maximum slope CT perfusion may be an early predictor of response to TACE.

Acute and delayed bleeding requiring embolization after image-guided liver biopsy in patients with cancer.

PURPOSE: To report incidence of acute versus delayed presentations of bleeding requiring embolization after focal liver biopsy, in correlation with angiographic findings and treatment success rates. The available literature will be reviewed as well. MATERIALS AND METHODS: Health Insurance Portability and Accountability Act-compliant institutional review board approved retrospective review of 2180 consecutive patients undergoing 2335 targeted liver biopsies at a tertiary-care cancer center. Hepatic arterial embolization episodes within 30days from biopsy were identified via radiology PACS. Electronic medical record review was performed for indication of embolization and postembolization clinical course. RESULTS: The incidence of postbiopsy bleeding requiring embolization was 0.5% (12/2335 biopsies). In those with bleeding, 1/12 (8%) had no hepatic arterial findings at angiography. Angiographic hepatic arterial findings resolved after embolization in 11/11 patients (100% technical success). Bleeding ceased after embolization in 10/12 patients (83% clinical success). Complications were seen in 2/12 (17%) patients: cholecystitis and hepatic infarct, respectively. Delayed presentation of bleeding (defined as >24h postbiopsy) occurred in 5/12 (42%) patients; the longest latency was 12days. CONCLUSION: The overall incidence of bleeding requiring embolization in our population was 0.5%. This complication rate compares favorably to the 0-4.2% (median: 0.29%) rate quoted in the available, heterogeneous, literature on this topic. Delayed presentation occurred in almost half of patients. Arterial embolization carries excellent technical and clinical success rates.

Feasibility of a Modified Biopsy Needle for Irreversible Electroporation Ablation and Periprocedural Tissue Sampling.

OBJECTIVES: To test the feasibility of modified biopsy needles as probes for irreversible electroporation ablation and periprocedural biopsy. METHODS: Core biopsy needles of 16-G/9-cm were customized to serve as experimental ablation probes. Computed tomography-guided percutaneous irreversible electroporation was performed in in vivo porcine kidneys with pairs of experimental (n = 10) or standard probes (n = 10) using a single parameter set (1667 V/cm, ninety 100 µs pulses). Two biopsy samples were taken immediately following ablation using the experimental probes (n = 20). Ablation outcomes were compared using computed tomography, simulation, and histology. Biopsy and necropsy histology were compared. RESULTS: Simulation-suggested ablations with experimental probes were smaller than that with standard electrodes (455.23 vs 543.16 mm2), although both exhibited similar shape. Computed tomography (standard: 556 ± 61 mm2, experimental: 515 ± 67 mm2; P = .25) and histology (standard: 313 ± 77 mm2, experimental: 275 ± 75 mm2; P = .29) indicated ablations with experimental probes were not significantly different from the standard. Histopathology indicated similar morphological changes in both groups. Biopsies from the ablation zone yielded at least 1 core with sufficient tissue for analysis (11 of the 20). CONCLUSIONS: A combined probe for irreversible electroporation ablation and periprocedural tissue sampling from the ablation zone is feasible. Ablation outcomes are comparable to those of standard electrodes.

Feasibility of catheter-directed intraluminal irreversible electroporation of porcine ureter and acute outcomes in response to increasing energy delivery.

PURPOSE: To evaluate the feasibility of focal intraluminal irreversible electroporation (IRE) in the ureter with a novel electrode catheter and to study the treatment effects in response to increasing pulse strength. MATERIALS AND METHODS: Five IRE treatment settings were each evaluated twice for the ablation of normal ureter in 5 Yorkshire pigs (n = 1-4 ablations per animal; total of 10 ablations) with the use of a prototype device under ultrasound and fluoroscopic guidance. Animals received unilateral or bilateral treatment, limited to a maximum of 2 ablations in any 1 ureter. Treatment was delivered with increasing pulse strength (from 1,000 V to 3,000 V in increments of 500 V) while keeping the pulse duration (100 µs) and number of pulses (n = 90) constant. Ureter patency was assessed with antegrade ureteropyelography immediately following treatment. Animals were euthanized within 4 hours after treatment, and treated urinary tract was harvested for histopathologic analysis with hematoxylin and eosin and Masson trichrome stains. RESULTS: IRE was successfully performed in all animals, without evidence of ureteral perforation. Hematoxylin and eosin analysis of IRE treatments demonstrated full-thickness ablation at higher field strengths (mucosa to the adventitia). Masson trichrome stains showed preservation of connective tissue at all field strengths. CONCLUSIONS: Intraluminal catheter-directed IRE ablation is feasible and produces full-thickness ablation of normal ureters. There was no evidence of lumen perforation even at the maximum voltages evaluated.

Planning irreversible electroporation in the porcine kidney: are numerical simulations reliable for predicting empiric ablation outcomes?

PURPOSE: Numerical simulations are used for treatment planning in clinical applications of irreversible electroporation (IRE) to determine ablation size and shape. To assess the reliability of simulations for treatment planning, we compared simulation results with empiric outcomes of renal IRE using computed tomography (CT) and histology in an animal model. METHODS: The ablation size and shape for six different IRE parameter sets (70-90 pulses, 2,000-2,700 V, 70-100 µs) for monopolar and bipolar electrodes was simulated using a numerical model. Employing these treatment parameters, 35 CT-guided IRE ablations were created in both kidneys of six pigs and followed up with CT immediately and after 24 h. Histopathology was analyzed from postablation day 1. RESULTS: Ablation zones on CT measured 81 ± 18 % (day 0, p ≤ 0.05) and 115 ± 18 % (day 1, p ≤ 0.09) of the simulated size for monopolar electrodes, and 190 ± 33 % (day 0, p ≤ 0.001) and 234 ± 12 % (day 1, p ≤ 0.0001) for bipolar electrodes. Histopathology indicated smaller ablation zones than simulated (71 ± 41 %, p ≤ 0.047) and measured on CT (47 ± 16 %, p ≤ 0.005) with complete ablation of kidney parenchyma within the central zone and incomplete ablation in the periphery. CONCLUSION: Both numerical simulations for planning renal IRE and CT measurements may overestimate the size of ablation compared to histology, and ablation effects may be incomplete in the periphery.

Percutaneous ablation of peribiliary tumors with irreversible electroporation.

PURPOSE: To assess biliary complications after irreversible electroporation (IRE) ablation of hepatic tumors located < 1 cm from major bile ducts. MATERIALS AND METHODS: A retrospective review was conducted of all percutaneous IRE ablations of hepatic tumors within 1 cm of the common, left, or right hepatic ducts at a single institution from January 2011 to September 2012. Computed tomography imaging performed before and after treatment was examined for evidence of bile duct dilatation, stricture, or leakage. Serum bilirubin and alkaline phosphatase levels were analyzed for evidence of biliary injury. RESULTS: There were 22 hepatic metastases in 11 patients with at least one tumor within 1 cm of the common, left, or right hepatic duct that were treated with IRE ablations in 15 sessions. Median tumor size treated was 3.0 cm (mean, 2.8 cm ± 1.2, range, 1.0-4.7 cm). Laboratory values obtained after IRE were considered abnormal after four treatment sessions in three patients (bilirubin, 2.6-17.6 mg/dL; alkaline phosphatase, 130-1,035 U/L); these abnormal values were transient in two sessions. Two patients had prolonged elevation of values, and one required stent placement; both of these conditions appeared to be secondary to tumor progression rather than bile duct injury. CONCLUSIONS: This clinical experience suggests that IRE may be a treatment option for centrally located liver tumors with margins adjacent to major bile ducts where thermal ablation techniques are contraindicated. Further studies with extended follow-up periods are necessary to establish the safety profile of IRE in this setting.

Comparison of simulation-based treatment planning with imaging and pathology outcomes for percutaneous CT-guided irreversible electroporation of the porcine pancreas: a pilot study.

PURPOSE: To investigate the reliability of simulations for planning pancreatic irreversible electroporation (IRE) ablations compared with computed tomography (CT) and pathology outcomes in an animal model. MATERIALS AND METHODS: Simulations were performed varying treatment parameters, including field strength (1.5-2.5 kV/cm), pulse number (70-90 pulses), and pulse length (70-100 µs). Pancreatic IRE was performed in six pigs under CT guidance. Two animals each were sacrificed for histology after 1 day, 14 days, and 28 days. Follow-up CT scans were performed on day 0, day 1, day 14, and day 28. Biochemical markers were collected before the procedure, 1 day after the procedure, and 14 days after the procedure. RESULTS: All ablation zones could be visualized on CT scan immediately after the procedure and on day 1 follow-up CT scan, and all animals survived until the designated endpoints. Histopathology revealed necrosis and edema on day 1 and fibrosis and glandular atrophy after 28 days. Blood vessels close to the ablation zone appeared normal. Laboratory analysis indicated mild to moderate amylasemia and lipasemia with normalization after 14 days. The ablation size on CT scan measured a mean (± SD) 146% ± 18 (day 0, P < .126) and 168% ± 18 (day 1, P < .026) of the simulation and on pathology measured 119% ± 10 (day 1, not significant) of the simulation. CONCLUSIONS: Results from simulations for planning IRE ablations, CT, and pathology may differ from each other. Ablation zones on CT and pathology appear larger than simulated, suggesting that clinically used treatment planning may underestimate the ablation size in the pancreas.

Evaluation of an endorectal electrode for performing focused irreversible electroporation ablations in the Swine rectum.

PURPOSE: To study the feasibility of a novel endorectal electrode for the creation of focal ablations of the rectal wall with the use of irreversible electroporation (IRE). MATERIALS AND METHODS: A monopolar electrode with a grounding pad (10 ablations in five pigs) and a bipolar electrode (two ablations in one pig) were evaluated in healthy swine rectum. A two-dimensional model of the electrode in the rectum was created and used to solve the Laplace equation to determine field strength. Simulation was used to identify treatment settings for superficial ablation (mucosal layers) or transmural ablation of rectal wall. Animals were euthanized within 4 hours after treatment. RESULTS: Treatment was successfully completed without treatment-related complications. Eleven of 12 lesions were successfully located and extracted for pathologic analysis. All lesions were characterized by necrotic cell death with mild inflammation and hyperemia, with a sharp demarcation between ablated and adjacent normal tissue. Depth of lesions corresponded with numeric simulation. Histologic analysis and measurements indicated that lesion creation with the superficial treatment setting resulted in ablation of mucosal and submucosal layers with superficial or no injury to the muscularis propria (9.97 mm ± 0.31 length, 3.3 mm ± 2.92 depth), and that lesion creation with the transmural treatment setting resulted in full-thickness ablation (12.43 mm ± 3.85 length, 4.97 mm ± 2.89 depth) of the rectal wall. CONCLUSIONS: An endorectal electrode can be used to deliver IRE and create limited focal ablations in the rectal wall. Treatment parameters can be determined through numeric modeling to control the depth of penetration of ablation.

The uraemic retention solute para-hydroxy-hippuric acid attenuates apoptosis of polymorphonuclear leukocytes from healthy subjects but not from haemodialysis patients.

BACKGROUND: Disturbed polymorphonuclear leukocyte (PMNL) apoptosis contributes to the dysregulation of the non-specific immune system in uraemia. Intracellular Ca(2+) modulates PMNL apoptotic cell death. We investigated the effect of para-hydroxy-hippuric acid (PHA), an erythrocyte plasma membrane Ca(2+)-ATPase inhibitor accumulating in uraemic sera, and of cyclopiazonic acid (CPA), an inhibitor of the sarko/endoplasmatic Ca(2+)-ATPase, on PMNL apoptosis. METHODS: Apoptosis of PMNLs from healthy subjects and from haemodialysis (HD) patients was assessed after incubation for 20 h by evaluating morphological features under the fluorescence microscope and by measuring the DNA content and caspase activities by flow cytometry. The intracellular calcium concentration ([Ca(2+)](i)) was determined by measurement of fura-2 fluorescence using the 340/ 380 nm dual wavelength excitation. RESULTS: Spontaneous apoptosis of PMNLs from healthy subjects and from HD patients did not differ. PHA significantly attenuated, while CPA increased, the apoptotic cell death of PMNLs from healthy subjects. The PHA effect was not observed with PMNLs from HD patients, irrespective of whether the blood was drawn before or after HD treatment. Baseline [Ca(2+)](i) was increased in PMNLs obtained from HD patients before dialysis but reversed after dialysis. The PHA effects were not mediated via [Ca(2+)](i). The chemotactic peptide N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP) induced a [Ca(2+)](i) increase and reduced PMNL survival. Extracellular Ca(2+) did not affect CPA- and fMLP-induced apoptosis. CONCLUSIONS: PHA, without affecting [Ca(2+)](i), attenuates apoptosis of healthy but not of uraemic PMNLs. CPA and fMLP enhance PMNL apoptosis independently of Ca(2+) influx.

Effects of Tamm-Horsfall protein on polymorphonuclear leukocyte function.

BACKGROUND: Tamm-Horsfall protein (THP), a glycoprotein produced exclusively by renal tubular cells, is thought to be involved in several inflammatory disorders such as bacterial interstitial nephritis as well as in defence against uropathogenic microorganisms. The specific effects of THP on inflammatory cells, however, are not yet well known. Therefore, the present study investigates the effects of THP in its soluble form on distinct polymorphonuclear leukocyte (PMNL) functions. METHODS: PMNL were isolated from the venous blood of healthy adult donors and incubated at low THP concentrations (70-350 ng/ml), resembling plasma concentrations, and at high THP concentrations (1.75-8.75 micro g/ml), resembling urinary concentrations. RESULTS: High (urinary) THP concentrations inhibited PMNL apoptosis and chemotaxis and stimulated PMNL phagocytosis, while low (plasma) THP concentrations increased PMNL chemotaxis. CONCLUSIONS: These data indicate that THP influences several PMNL functions, suggesting a crucial immunomodulatory role for this glycoprotein in host defence mechanisms of the kidney and genitourinary tract.