A. Michael Peters

Neutrophil kinetics in health and disease

Neutrophils play a key role in the elimination of pathogens. They are remarkably short-lived with a circulating half life of 6–8 h and hence are produced at a rate of 5 × 1010–10 × 1010 cells/day. Tight regulation of these cells is vital because they have significant histotoxic capacity and are widely implicated in tissue injury. This review outlines our current understanding of how neutrophils are released from the bone marrow; in particular, the role of the CXC chemokine receptor 4/stromal-derived factor 1 axis, the relative size and role of the freely circulating and marginated (i.e. slowly transiting) pools within the vascular compartment, and the events that result in the uptake and removal of circulating neutrophils. We also review current understanding of how systemic stress and inflammation affect this finely balanced system.

Pulmonary retention of primed neutrophils: a novel protective host response, which is impaired in the acute respiratory distress syndrome

Rationale Acute respiratory distress syndrome (ARDS) affects over 200 000 people annually in the USA. Despite causing severe, and often refractory, hypoxaemia, the high mortality and long-term morbidity of ARDS results mainly from extra-pulmonary organ failure; however the mechanism for this organ crosstalk has not been determined. Methods Using autologous radiolabelled neutrophils we investigated the pulmonary transit of primed and unprimed neutrophils in humans. Flow cytometry of whole blood samples was used to assess transpulmonary neutrophil priming gradients in patients with ARDS, sepsis and perioperative controls. Main results Unprimed neutrophils passed through the lungs with a transit time of 14.2 s, only 2.3 s slower than erythrocytes, and with <5% first-pass retention. Over 97% of neutrophils primed ex vivo with granulocyte macrophage colony-stimulating factor were retained on first pass, with 48% still remaining in the lungs at 40 min. Neutrophils exposed to platelet-activating factor were initially retained but subsequently released such that only 14% remained in the lungs at 40 min. Significant transpulmonary gradients of neutrophil CD62L cell surface expression were observed in ARDS compared with perioperative controls and patients with sepsis. Conclusions We demonstrated minimal delay and retention of unprimed neutrophils transiting the healthy human pulmonary vasculature, but marked retention of primed neutrophils; these latter cells then ‘deprime’ and are re-released into the systemic circulation. Further, we show that this physiological depriming mechanism may fail in patients with ARDS, resulting in increased numbers of primed neutrophils within the systemic circulation. This identifies a potential mechanism for the remote organ damage observed in patients with ARDS.

Doubts concerning the recently reported human neutrophil lifespan of 5.4 days

To the editor: Using orally administered deuterium-labeled water to label neutrophils in vivo, Pillay et al measured urinary and blood deuterium-to-proton enrichment ratios at intervals of ∼ 12 days over several weeks before and after termination of intake.[1][1] From mathematical modeling they

Comparison of GFR Measurements Assessed From Single Versus Multiple Samples

BACKGROUND Many previous studies have evaluated single-sample glomerular filtration rate (GFR) against multisample GFR, of which the single sample was a member, but none have compared single and multisample GFRs against an independent reference method. We therefore performed this comparison by using simultaneous independent multisample GFR measured with a different indicator. SETTING & PARTICIPANTS University hospital: patients and healthy volunteers (95 studies in 60 patients and 20 healthy participants). Healthy volunteers were studied fasting and after food; 10 of them had a repeated fasting study. STUDY DESIGN Diagnostic test study. INDEX TEST Single-sample GFR. REFERENCE TEST Multisample GFR with a different indicator. MEASUREMENTS GFR was measured by using chromium-51 ((51)Cr)-EDTA and iohexol, injected into opposite arms and scaled to 1.73 m(2). Blood samples, obtained bilaterally 20, 40, 60, 120, 180, and 240 minutes after injection, were assayed for indicator injected contralaterally. Single-sample GFR (Jacobsson method) was calculated from indicator concentrations at 3 and 4 hours. Single-sample GFR from 1 indicator was compared with multisample GFR from the other and vice versa, as well as from the same indicator. Differences were expressed as limits of agreement between paired measurements in Bland-Altman plots. Precision was expressed as the SD of the mean difference between paired measurements. RESULTS Limits of agreement between multisample GFRs measured by using (51)Cr-EDTA and iohexol (-12 to 20 mL/min) were similar to the corresponding limits for single-sample GFR at 3 (-16 to 17 mL/min) and 4 hours (-11 to 17 mL/min). The precision of single-sample GFR at 4 hours by using (51)Cr-EDTA for predicting iohexol multisample GFR (6.9 mL/min) was better than that of multisample GFR with (51)Cr-EDTA (7.9 mL/min). When analysis was limited to patients with GFR less than 60 mL/min, single-sample GFR was slightly inferior to multisample GFR. In healthy participants, single-sample GFR with (51)Cr-EDTA at 3 and 4 hours showed repeatability (SD of change, 9.4 and 9.3 mL/min) similar to multisample GFR with (51)Cr-EDTA (10.7 mL/min). Single-sample GFR at 4 hours by using (51)Cr-EDTA detected a food-induced increase in GFR (4.4 +/- 5.9 mL/min; P < 0.001) with more confidence than multisample GFR by using (51)Cr-EDTA (4.6 +/- 7.5 mL/min; P < 0.01). LIMITATIONS No separate gold standard (eg, inulin) to facilitate interpretation of observed differences between 2 markers. CONCLUSIONS Single-sample GFR is as reliable as multisample GFR for measuring GFR, especially when GFR is greater than 60 mL/min.

Side-to-side symmetry of radioprotein transfer from tissue space to systemic vasculature following subcutaneous injection in normal subjects and patients with breast cancer

Quantitative lymphoscintigraphy can be used for investigation of unilateral lymphatic disease of the limbs, such as breast cancer-related lymphoedema (BCRL). Previous studies have compared lymphatic function in the affected limb with that in the unaffected contralateral limb. This study aims to confirm that the assumption of pre-morbid symmetry, never previously demonstrated, is valid. A dual-isotope technique, with bilateral subcutaneous hand injection of polyclonal human immunoglobulin G (HIgG) labelled with either technetium-99m or indium-111, was performed on a total of 37 subjects. The use of two different labels, one for each limb, enabled comparison not only of the rate of clearance from the injection depot, but also of the rate of appearance in venous blood. Results demonstrate clear symmetry between the two arms with respect to both depot clearance and blood appearance rates, as well as the coupling between these two variables. In unilateral lymphatic disease, results of quantitative lymphoscintigraphy should be expressed in relation to the normal arm rather than to an independent control population.

Indirect radionuclide cystography: a sensitive technique for the detection of vesico-ureteral reflux

The detection or exclusion of vesico-ureteral reflux (VUR) has classically been by micturating cystourethrography (MCUG). Radionuclide cystography will detect VUR but fails to provide the same detailed anatomical informations as MCUG. This study allowed a comparison of indirect radionuclide cystography (IRC) and MCUG in 65 children. Renal reflux was detected by IRC in 32% of renal units, while VUR was seen in 36% by MCUG. When a comparison was made with MCUG, IRC had a sensitivity of 74.1% and a specificity of 90.5%. The markedly reduced radiation dose, avoidance of a bladder catheter plus the ability to monitor the urinary tract constantly during the entire procedure should ensure that IRC is the examination of choice in follow-up studies for VUR in all toilet-trained children.

Use of 111-Indium-labelled autologous eosinophils to establish the in vivo kinetics of human eosinophils in healthy subjects

Eosinophils are the major cellular effectors of allergic inflammation and represent an important therapeutic target. Although the genesis and activation of eosinophils have been extensively explored, little is known about their intravascular kinetics or physiological fate. This study was designed to determine the intravascular life span of eosinophils, their partitioning between circulating and marginated pools, and sites of disposal in healthy persons. Using autologous, minimally manipulated 111-Indium-labeled leukocytes with blood sampling, we measured the eosinophil intravascular residence time as 25.2 hours (compared with 10.3 hours for neutrophils) and demonstrated a substantial marginated eosinophil pool. γ camera imaging studies using purified eosinophils demonstrated initial retention in the lungs, with early redistribution to the liver and spleen, and evidence of recirculation from a hepatic pool. This work provides the first in vivo measurements of eosinophil kinetics in healthy volunteers and shows that 111-Indium-labeled eosinophils can be used to monitor the fate of eosinophils noninvasively.

Extracellular fluid volume and glomerular filtration rate in 1878 healthy potential renal transplant donors: effects of age, gender, obesity and scaling

UNLABELLED Aim. The aim of this study was to investigate the influence of age, gender, obesity and scaling on glomerular filtration rate (GFR) and extracellular fluid volume (ECV) in healthy subjects. METHODS This is a retrospective multi-centre study of 1878 healthy prospective kidney transplant donors (819 men) from 15 centres. Age and body mass index (BMI) were not significantly different between men and women. Slope-intercept GFR was measured (using Cr-51-EDTA in 14 centres; Tc-99m-DTPA in one) and scaled to body surface area (BSA) and lean body mass (LBM), both estimated from height and weight. GFR was also expressed as the slope rate constant, with one-compartment correction (GFR/ECV). ECV was measured as the ratio, GFR to GFR/ECV. RESULTS ECV was age independent but GFR declined with age, at a significantly faster rate in women than men. GFR/BSA was higher in men but GFR/ECV and GFR/LBM were higher in women. Young women (<30 years) had higher GFR than young men but the reverse was recorded in the elderly (>65 years). There was no difference in GFR between obese (BMI>30 kg/m2) and non-obese men. Obese women, however, had lower GFR than non-obese women and negative correlations were observed between GFR and both BMI and %fat. The decline in GFR with age was no faster in obese versus non-obese subjects. ECV/BSA was higher in men but ECV/LBM was higher in women. ECV/weight was almost gender independent, suggesting that fat-free mass in women contains more extracellular water. BSA is therefore a misleading scaling variable. CONCLUSION There are several significant differences in GFR and ECV between healthy men and women.

Lymphatic drainage pathways of the breast and the upper limb

ObjectiveTo determine how often the sentinel lymph node (SLN) draining the breast is the same node as the SLN draining the upper limb. A common SLN might increase the risk of upper limb breast cancer-related lymphoedema after SLN biopsy. MethodsPatients with invasive breast cancer, identified as being suitable for axillary lymph node dissection, were injected preoperatively with 40 MBq of technetium-99m (99mTc)-human polyclonal immunoglobulin G intradermally into the ipsilateral breast and 3 MBq of indium-111 (111In)-human polyclonal immunoglobulin G intradermally into the ipsilateral hand, or vice versa. Axillary lymph nodes were removed, separated and assayed in a well counter for 99mTc and 111In. ResultsFifteen patients entered the study. In 13 of 15 patients, the ‘hottest’ lymph node for 99mTc was separate from the ‘hottest’ lymph node for 111In. In two of 15 patients the ‘hottest’ lymph node for 99mTc was also the ‘hottest’ lymph node for 111In, suggesting a common drainage pathway from the ipsilateral breast and upper limb. ConclusionAlthough the majority of patients has different pathways of lymphatic drainage from the ipsilateral breast and upper limb, in a small minority of patients the drainage pathway is through a common SLN. Such patients may be at increased risk of developing upper limb breast cancer-related lymphoedema after SLN biopsy.

Reproducibilities and responses to food intake of GFR measured with chromium-51-EDTA and iohexol simultaneously and independently in normal subjects

BACKGROUND The aim was to evaluate the reproducibility of glomerular filtration rate (GFR) measured with iohexol and its response to food in a direct and independent comparison with Cr-51-ethylenediaminetetraacetic acid (EDTA), and examine the influence of two different whole body scaling parameters, body surface area (BSA) and extracellular fluid volume (ECV). METHODS Fasting and non-fasting GFR were measured in 20 normal volunteers using Cr-51-EDTA and iohexol, simultaneously injected into opposite arms. In 10, the fasting study was repeated. Venous samples obtained bilaterally 20, 40, 60, 120, 180 and 240 min after injection were assayed for indicator injected contralaterally-Cr-51-EDTA by well-counting and iohexol by X-ray fluorescence. GFR scaled to BSA was measured from six samples (GFR/BSA6) and from the last three (GFR/BSA3). GFR scaled to ECV was calculated as the mean transit time of marker using six samples (GFR/ECV6) or the last three (GFR/ECV3). RESULTS GFR/BSA3 was reproducible (coefficient of variations of 7.4% for Cr-51-EDTA and 7.6% for iohexol). Using Cr-51-EDTA, GFR/ECV3 (9.1%) and GFR/ECV6 (7.7%) were as reproducible as GFR/BSA3 and GFR/BSA6 (both 8.1%). However, GFR/ECV3 measured with iohexol had poorer reproducibility (16.8%). Food resulted in an increase in scaled GFR of about 5 ml/min but this was statistically significant only with respect to GFR/BSA (measured with Cr-51-EDTA or iohexol) and not GFR/ECV. CONCLUSIONS Measured with Cr-51-EDTA, but not iohexol, GFR/ECV was as reproducible as GFR/BSA. GFR/BSA, measured with Cr-51-EDTA or iohexol, but not GFR/ECV, significantly increased after food.