Tired and stressed: direct holographic quasi-static stretching of aging echinocytes and discocytes in plasma using optical tweezers [Invited]

Red blood cells (RBCs) undergo a progressive morphological transformation from smooth biconcave discocytes into rounder echinocytes with spicules on their surface during cold storage. The echinocytic morphology impacts RBCs' ability to flow through narrow sections of the circulation and therefore transfusion of RBC units with a high echinocytic content are thought to have a reduced efficiency. We use an optical tweezers-based technique where we directly trap and measure linear stiffness of RBCs under stress without the use of attached spherical probe particles or microfluidic flow to induce shear. We study RBC deformability with over 50 days of storage performing multiple stretches in blood plasma (serum with cold agglutinins removed to eliminate clotting). In particular, we find that discocytes and echinocytes do not show significant changes in linear stiffness in the small strain limit (∼ 20 % change in length) up to day 30 of the storage period, but do find differences between repeated stretches. By day 50 the linear stiffness of discocytes had increased to approximately that measured for echinocytes throughout the entire period of measurements. These changes in stiffness corresponded to recorded morphological changes in the discocytes as they underwent storage lesion. We believe our holographic trapping and direct measurement technique has applications to directly control and quantify forces that stretch other types of cells without the use of attached probes.

Intraoperative cell salvage: The impact on immune cell numbers

BACKGROUND

Patient outcomes are influenced by many confounding factors peri-operatively, including the type of surgery, anaesthesia, transfusion, and immune competence. We have previously demonstrated (in-vitro) that compared to allogeneic blood transfusion (ABT), intraoperative cell salvage (ICS) improves immune competence. The peri-operative immune response is complex. Altered or impaired immune responses may predispose patients to develop adverse outcomes (i.e., post-operative wound infection, pneumonia, urinary tract infection etc.) Surgical patients may develop infection, even without the confirmed presence of a definite microbiological pathogen. With all these factors in mind it is important to consider changes in immune cell numbers (and sub-populations) and functional capacity during peri-operative transfusion.

METHODS

In this TRIMICS-Cell (Transfusion Related Immune Modulation and Intraoperative Cell Salvage-Cell numbers) study (n = 17, October 2018-November 2019) we prioritized and analysed peri-operative changes in the number and proportions of immune cell populations and sub-populations (B cells (CD20+), NK (natural killer) cells (CD56+), monocytes (CD14+), T cells (total CD3+ and sub-populations: T helper cells (CD4+), cytotoxic T cells (CD8+), effector T cells (CD4+ CD127+), activated effector T cells (CD4+ CD25+ CD127+) and regulatory T cells (CD4+ CD25+ CD127-)), plasmacytoid dendritic cells (pDC; Lineage-, HLA-DR+, CD11c-, CD123+), classical dendritic cell (cDC) (Lineage-, HLA-DR+, CD11c+), and cDC activation (Lineage-, HLA-DR+, CD11c+), co-stimulatory/adhesion molecules and pDC (CD9+, CD38+, CD80+, CD83+, CD86+, CD123+). Firstly we analysed the whole cohort of study patients and secondly according to the relevant transfusion modality (i.e., three study groups: those who received no transfusion, received ICS only (ICS), or both ICS and allogeneic packed red blood cells (pRBC) (ICS&RBC)), during major orthopaedic surgery.

RESULTS

For the whole study cohort (all patients), changes in immune cell populations were significant: leucocytes and specifically neutrophils increased post-operatively, returning towards pre-operative numbers by 48h post-operatively (48h), and lymphocytes reduced post-operatively returning to pre-operative numbers by 48h. When considering transfusion modalities, there were no significant peri-operative changes in the no transfusion group for all immune cell populations studied (cell numbers and proportions (%)). Significant changes in cell population numbers (i.e., leucocytes, neutrophils and lymphocytes) were identified in both transfused groups (ICS and ICS&RBC). Considering all patients, changes in immune cell sub-populations (NK cells, monocytes, B cells, T cells and DCs) and functional characteristics (e.g., co-stimulation markers, adhesion, activation, and regulation) were significant peri-operatively and when considering transfusion modalities. Interestingly DC numbers and functional capacity were specifically altered following ICS compared to ICS&RBC and pDCs were relatively preserved post-operatively following ICS.

CONCLUSION

A transient peri-operative alteration with recovery towards pre-operative numbers by 48h post-surgery was demonstrated for many immune cell populations and sub-populations throughout. Immune cell sub-populations and functional characteristics were similar peri-operatively in those who received no transfusion but changed significantly following ICS and ICS&RBC. Interesting changes that require future study are a post-operative monocyte increase in the ICS&RBC group, changes in cDC considering transfusion modalities, and possibly preserved pDC numbers post-operatively following ICS. Future studies to assess changes in immune cell sub-populations, especially during peri-operative transfusion, while considering post-operative adverse outcomes, is recommended.

The role of non-invasive prenatal testing (NIPT) for fetal blood group typing in Australia

Maternal alloimmunisation against red blood cell antigens can cause haemolytic disease of the fetus and newborn (HDFN). Although most frequently caused by anti-D, since the implementation of rhesus D (RhD) immunoglobulin prophylaxis, other alloantibodies have become more prevalent in HDFN. Recent advances in non-invasive prenatal testing (NIPT) have allowed early prediction of HDFN risk in alloimmunised pregnancies and allow clinicians to focus health resources on those pregnancies that require intervention. This article aims to provide updates on the current status of NIPT in Australia as both a diagnostic and screening tool in pregnancy.

Computational modeling - an approach to the development of blood grouping reagents

Introduction: Blood group antigens are defined by an immune response that generates antibodies against a red blood cell molecule. Antibodies against these antigens can be associated with hemolytic transfusion reactions. However, difficulties can arise when developing antibodies against antigens through the use of peptide sequences alone. Three-dimensional representations (models) of the molecular structure of antigen-bearing proteins can provide valuable insights into tertiary structures and their consequent antigenicity. This can be achieved through predictive computational modeling to produce both structural and molecular dynamics models of blood group proteins.Areas covered: Authors discuss the use of molecular dynamic simulations on existing structures, as well as the use of computational modeling techniques in the development of protein models lacking preexisting data. Finally, the authors discuss specific examples of the use of computationally derived models of the MNS blood group system and its use in attempts to produce antibodies against MNS proteins.Expert opinion: Although in silico techniques have limitations, computer-based predictive models can inform the direction of research into blood group proteins. It is to be expected that as computer-based techniques grow more powerful these contributions will be even more significant.

Neonatal Outcomes From Arboviruses in the Perinatal Period: A State-of-the-Art Review

Since the 2016 Zika outbreak and the understanding of the teratogenic effect of this infection, there has been a newfound interest in arbovirus infections and their effects on pregnancy, resulting in numerous publications in the last 5 years. However, limited literature focuses on arbovirus infection in different stages of pregnancy and their effect on the neonate. There is currently no consensus management of perinatal acquisition of arboviruses, and current evidence is largely anecdotal observational reports. Teratogens can have different effects on the developing fetus depending on the time of infection, so infections during pregnancy should be analyzed by trimester. A better understanding of arbovirus infection in the perinatal period is required to assist obstetric, neonatal, and pediatric clinicians in making decisions about the management of mother and neonate. Our objective was to assess the evidence of adverse neonatal outcomes for several arboviral infections when contracted during the perinatal period to guide clinicians in managing these patients. There are 8 arboviruses for which neonatal outcomes from maternal acquisition in the perinatal period have been reported, with the most data for dengue and Chikungunya virus infections. The evidence reviewed in this article supports the adoption of preventive strategies to avoid ticks and mosquitoes close to the date of delivery. For the other arbovirus infections, further community-based cohort studies during outbreaks are required to evaluate whether these infections have a similar teratogenic impact.

Understanding occult hepatitis C infection

BACKGROUND

Occult hepatitis C infection (OCI) is a type of hepatitis C virus (HCV) infection, defined as the presence of HCV RNA in hepatocytes or peripheral blood mononuclear cells (PBMCs) and the absence of HCV RNA in serum.

STUDY DESIGN AND METHODS

A literature review was conducted to identify articles that characterized OCI as a disease, including its epidemiology, mode of transmission, pattern of infection, progression, and treatment.

RESULTS

OCI patients experience a milder degree of inflammatory and cirrhotic changes than patients with chronic hepatitis C. OCI is transmissible parenterally both in vivo and in vitro, however the duration and outcome of OCI remains unclear. OCI is most consistently found in patients with previous hepatitis C disease and hemodialysis patients. Beyond the at-risk populations, OCI has also been demonstrated among healthy individuals and blood donors.

CONCLUSIONS

This review summarises our current understanding of OCI and suggests areas for further research to improve our understanding of this phenomenon, including a better understanding of its epidemiology and full clinical course. The current understanding of OCI and its clinical implications remain limited. Further standardized detection methods, ongoing surveillance, and investigation of its potential transmissions are required.

Targeted exome sequencing designed for blood group, platelet, and neutrophil antigen investigations: Proof-of-principle study for a customized single-test system

BACKGROUND

Immunohematology reference laboratories provide red blood cell (RBC), platelet (PLT), and neutrophil typing to resolve complex cases, using serology and commercial DNA tests that define clinically important antigens. Broad-range exome sequencing panels that include blood group targets provide accurate blood group antigen predictions beyond those defined by serology and commercial typing systems and identify rare and novel variants. The aim of this study was to design and assess a panel for targeted exome sequencing of RBC, PLT, and neutrophil antigen-associated genes to provide a comprehensive profile in a single test, excluding unrelated gene targets.

STUDY DESIGN AND METHODS

An overlapping probe panel was designed for the coding regions of 64 genes and loci involved in gene expression. Sequencing was performed on 34 RBC and 17 PLT/neutrophil reference samples. Variant call outputs were analyzed using software to predict star allele diplotypes. Results were compared with serology and previous sequence genotyping data.

RESULTS

Average coverage exceeded 250×, with more than 94% of targets at Q30 quality or greater. Increased coverage revealed a variant in the Scianna system that was previously undetected. The software correctly predicted allele diplotypes for 99.5% of RBC blood groups tested and 100% of PLT and HNA antigens excepting HNA-2. Optimal throughput was 12 to 14 samples per run.

CONCLUSION

This single-test system demonstrates high coverage and quality, allowing for the detection of previously overlooked variants and increased sample throughput. This system has the potential to integrate genomic testing across laboratories within hematologic reference settings.

A coarse-grained red blood cell membrane model to study stomatocyte-discocyte-echinocyte morphologies

An improved red blood cell (RBC) membrane model is developed based on the bilayer coupling model (BCM) to accurately predict the complete sequence of stomatocyte-discocyte-echinocyte (SDE) transformation of a RBC. The coarse-grained (CG)-RBC membrane model is proposed to predict the minimum energy configuration of the RBC from the competition between lipid-bilayer bending resistance and cytoskeletal shear resistance under given reference constraints. In addition to the conventional membrane surface area, cell volume and bilayer-leaflet-area-difference constraints, a new constraint: total-membrane-curvature is proposed in the model to better predict RBC shapes in agreement with experimental observations. A quantitative evaluation of several cellular measurements including length, thickness and shape factor, is performed for the first time, between CG-RBC model predicted and three-dimensional (3D) confocal microscopy imaging generated RBC shapes at equivalent reference constraints. The validated CG-RBC membrane model is then employed to investigate the effect of reduced cell volume and elastic length scale on SDE transformation, to evaluate the RBC deformability during SDE transformation, and to identify the most probable RBC cytoskeletal reference state. The CG-RBC membrane model can predict the SDE shape behaviour under diverse shape-transforming scenarios, in-vitro RBC storage, microvascular circulation and flow through microfluidic devices.

Modeling the parvovirus B19 blood safety risk in Australia

BACKGROUND

Three probable cases of transfusion-transmitted (TT) parvovirus B19 (B19V) occurred in Australia between 2014 and 2017. This study aimed to determine the B19V DNA prevalence among blood donors, to model the risk to recipients of fresh components, and to assess risk management options.

STUDY DESIGN AND METHODS

Plasma samples from 4232 donors were tested for B19V DNA by polymerase chain reaction. Reactive samples were confirmed and viral load determined. A transmission-risk model was used to estimate recipient risk, and the risk from community exposure was estimated using seroprevalence data.

RESULTS

Two samples (0.0473%, 95% confidence interval [CI] 0.0130-0.172) confirmed positive for B19V DNA had a potentially infectious viral load of 10⁵ IU/mL or higher. The estimated risk of a TT-B19V-associated significant complication was low overall at approximately 1 in 300,000 (95% CI, 1 in 82,000 to 1 in 1 million) fresh components transfused, with 3.1 (95% CI, 0.85-11.3) complications modeled per year. Among vulnerable recipient groups, the risk was higher than 1 in 15,000 patients, but the risk from community exposure far exceeded the transfusion risk for all patient and age groups.

CONCLUSION

In the context of the small contribution of transfusion to the burden of B19V disease, the significant costs that would be incurred by any strategy to reduce the risk, and given the significant uncertainties and likely overestimation of the risk, we conclude TT-B19V is a tolerable risk to blood safety, despite being high for some vulnerable recipient groups.

Investigation of red blood cell mechanical properties using AFM indentation and coarse-grained particle method

Background

Red blood cells (RBCs) deform significantly and repeatedly when passing through narrow capillaries and delivering dioxygen throughout the body. Deformability of RBCs is a key characteristic, largely governed by the mechanical properties of the cell membrane. This study investigated RBC mechanical properties using atomic force microscopy (AFM) with the aim to develop a coarse-grained particle method model to study for the first time RBC indentation in both 2D and 3D. This new model has the potential to be applied to further investigate the local deformability of RBCs, with accurate control over adhesion, probe geometry and position of applied force.

Results

The model considers the linear stretch capacity of the cytoskeleton, bending resistance and areal incompressibility of the bilayer, and volumetric incompressibility of the internal fluid. The model’s performance was validated against force–deformation experiments performed on RBCs under spherical AFM indentation. The model was then used to investigate the mechanisms which absorbed energy through the indentation stroke, and the impact of varying stiffness coefficients on the measured deformability. This study found the membrane’s bending stiffness was most influential in controlling RBC physical behaviour for indentations of up to 200 nm.

Conclusions

As the bilayer provides bending resistance, this infers that structural changes within the bilayer are responsible for the deformability changes experienced by deteriorating RBCs. The numerical model presented here established a foundation for future investigations into changes within the membrane that cause differences in stiffness between healthy and deteriorating RBCs, which have already been measured experimentally with AFM.

Electronic supplementary material

The online version of this article (10.1186/s12938-017-0429-5) contains supplementary material, which is available to authorized users.

SPH-DEM approach to numerically simulate the deformation of three-dimensional RBCs in non-uniform capillaries

Background

Blood continuously flows through the blood vessels in the human body. When blood flows through the smallest blood vessels, red blood cells (RBCs) in the blood exhibit various types of motion and deformed shapes. Computational modelling techniques can be used to successfully predict the behaviour of the RBCs in capillaries. In this study, we report the application of a meshfree particle approach to model and predict the motion and deformation of three-dimensional RBCs in capillaries.

Methods

An elastic spring network based on the discrete element method (DEM) is employed to model the three-dimensional RBC membrane. The haemoglobin in the RBC and the plasma in the blood are modelled as smoothed particle hydrodynamics (SPH) particles. For validation purposes, the behaviour of a single RBC in a simple shear flow is examined and compared against experimental results. Then simulations are carried out to predict the behaviour of RBCs in a capillary; (i) the motion of five identical RBCs in a uniform capillary, (ii) the motion of five identical RBCs with different bending stiffness (K_b) values in a stenosed capillary, (iii) the motion of three RBCs in a narrow capillary. Finally five identical RBCs are employed to determine the critical diameter of a stenosed capillary.

Results

Validation results showed a good agreement with less than 10% difference. From the above simulations, the following results are obtained; (i) RBCs exhibit different deformation behaviours due to the hydrodynamic interaction between them. (ii) Asymmetrical deformation behaviours of the RBCs are clearly observed when the bending stiffness (K_b) of the RBCs is changed. (iii) The model predicts the ability of the RBCs to squeeze through smaller blood vessels. Finally, from the simulations, the critical diameter of the stenosed section to stop the motion of blood flow is predicted.

Conclusions

A three-dimensional spring network model based on DEM in combination with the SPH method is successfully used to model the motion and deformation of RBCs in capillaries. Simulation results reveal that the condition of blood flow stopping depends on the pressure gradient of the capillary and the severity of stenosis of the capillary. In addition, this model is capable of predicting the critical diameter which prevents motion of RBCs for different blood pressures.

Genotyping confirms inheritance of the rare At(a-) type in a case of haemolytic disease of the newborn

The At(a) blood group antigen (now AUG2 in the Augustine system) is a high-frequency antigen with negative phenotype At(a-) found only in individuals of African ancestry. In a twin pregnancy, the fifth pregnancy in a woman of African origin, serological investigations confirmed that the mother was At(a-) and anti-At(a) was detected. DNA samples were exome sequenced and alignment was performed to allow variant calling. It was confirmed that the single nucleotide polymorphism, rs45458701, within the SLC29A1 gene encoding the ENT1 protein, recently reported to be a basis of the At(a-) phenotype was also the basis of the phenotype in this family. The reagents for serological analysis required to identify the rare blood type present in this mother are held in only a few reference laboratories worldwide. This case highlights the utility of genetic methods in resolving complex investigations involving blood grouping and demonstrates that genotyping of variants associated with blood types present in specific ethnic groups may be the fastest method available for identification of the basis of fetomaternal incompatibilities.

Seroprevalence of Antibodies to Ross River and Barmah Forest Viruses: Possible Implications for Blood Transfusion Safety After Extreme Weather Events

Climate change is predicted to increase the transmission of many vector-borne pathogens, representing an increasing threat to a safe blood supply. In early 2011, Australia experienced catastrophic rainfall and flooding, coupled with increased arbovirus transmission. We used Ross River (RRV) and Barmah Forest (BFV) viruses as test cases to investigate the potential risk posed to Australia's blood supply after this period of increased rainfall . We estimated the risk of collecting an infected donation as one in 2,500-58,000 for RRV and one in 2,000-28,000 for BFV. Climate change may incrementally increase the arbovirus threat to blood safety.

The RHD(1227G>A) DEL-associated allele is the most prevalent DEL allele in Australian D- blood donors with C+ and/or E+ phenotypes

BACKGROUND

Red blood cells (RBCs) with D antigen levels only detected by anti-D adsorption-elution and an antiglobulin test express a DEL phenotype. For two DEL types, including RHD(1227G>A), immunization of D- recipients has been reported. This study's aim was to measure the prevalence of DEL-associated RHD alleles in a cohort of Australian D- donors to develop a model to estimate alloimmunization risk.

STUDY DESIGN AND METHODS

D-, C+ and/or E+ blood donors were screened for RHD exons using quantitative polymerase chain reaction. Donors with RHD signals were DEL phenotyped with MCAD6 anti-D. RHD alleles were characterized via single-nucleotide polymorphism array or sequencing. Extended DEL phenotyping was performed with an anti-D panel.

RESULTS

Among 2027 donors, 39 carried RHD alleles that have been previously reported to associate with either the DEL or the weak D phenotype. An additional five donors carried previously unreported RHD alleles and exhibited the DEL phenotype: RHD(IVS2-2delA), RHD(IVS1+5G>C), RHD(ex9:del/CE), and RHD(ex8:del/CE) represented twice. In total, DEL/weak D-associated RHD alleles were detected in 44 of 2027 donors or 2.17% (95% confidence interval, 1.54%-2.81%). The RHD(1227G>A) DEL allele was the most frequent (n = 16). The risk of transfusing D- females not more than 40 years of age with an RHD(1227G>A) DEL RBC unit (when managed as D-) is estimated to be one in 149,109 transfusions (range, 100,680-294,490).

CONCLUSION

DEL/weak D-associated RHD alleles were found in 2.17% of Australian D-, C+ and/or E+ blood donors. This differs from previous European reports in that the clinically significant RHD(1227G>A) DEL allele is the most prevalent.

Plasma selenium status in a group of Australian blood donors and fresh blood components

The purpose of this study was to assess plasma selenium levels in an Australian blood donor population and measure extra-cellular selenium levels in fresh manufactured blood components. Selenium levels were measured using graphite furnace atomic absorption spectrometry with Zeeman background correction. The mean plasma selenium level in healthy plasmapharesis donors was 85.6±0.5 μg/L and a regional difference was observed between donors in South East Queensland and Far North Queensland. Although participants had selenium levels within the normal range (55.3-110.5 μg/L), 88.5% had levels below 100 μg/L, a level that has been associated with sub-optimal activity of the antioxidant enzyme glutathione peroxidase (GPx). Extra-cellular selenium levels in clinical fresh frozen plasma (cFFP) and apheresis-derived platelets (APH Plt) were within the normal range. Packed red blood cells (PRBC) and pooled buffy coat-derived platelets (BC Plt) had levels at the lower limit of detection, which may have clinical implications to the massively transfused patient.

Annexin A1 modulates macula densa function by inhibiting cyclooxygenase 2

Annexin A1 (ANXA1) exerts anti-inflammatory effects through multiple mechanisms including inhibition of prostaglandin synthesis. Once secreted, ANXA1 can bind to G protein-coupled formyl peptide receptors (Fpr) and activate diverse cellular signaling pathways. ANXA1 is known to be expressed in cells of the juxtaglomerular apparatus, but its relation to the expression of cyclooxygenase 2 (COX-2) in thick ascending limb and macula densa cells has not been elucidated. We hypothesized that ANXA1 regulates the biosynthesis of COX-2. ANXA1 abundance in rat kidney macula densa was extensively colocalized with COX-2 (95%). Furosemide, an established stimulus for COX-2 induction, caused enhanced expression of both ANXA1 and COX-2 with maintained colocalization (99%). In ANXA1-deficient mice, COX-2-positive cells were more numerous than in control mice (+107%; normalized to glomerular number; P < 0.05) and renin expression was increased (+566%; normalized to glomerular number; P < 0.05). Cultured macula densa cells transfected with full-length rat ANXA1 revealed downregulation of COX-2 mRNA (−59%; P < 0.05). Similarly, treatment with dexamethasone suppressed COX-2 mRNA in the cells (−49%; P < 0.05), while inducing ANXA1 mRNA (+56%; P < 0.05) and ANXA1 protein secretion. Inhibition of the ANXA-1 receptor Fpr1 with cyclosporin H blunted the effect of dexamethasone on COX-2 expression. These data show that ANXA1 exerts an inhibitory effect on COX-2 expression in the macula densa. ANXA1 may be a novel intrinsic modulator of renal juxtaglomerular regulation by inhibition of PGE2 synthesis.

Observation of erythrocyte dynamics in the retinal capillaries and choriocapillaris using ICG-loaded erythrocyte ghost cells

PURPOSE

To find evidence of retinal vasomotion and to examine the relationship between erythrocyte dynamics and previously observed high-frequency pulsatile blood flow through the choriocapillaris.

METHODS

An osmotic shock technique was used to encapsulate indocyanine green (ICG) dye in erythrocyte ghost cells at a concentration that produced maximum cell fluorescence. By obviating the plasma staining that results from aqueous ICG's high affinity for plasma proteins, high contrast was maintained between reinjected ICG-loaded erythrocytes and their plasma background. High-speed, high-magnification ICG angiograms showing individual cell movement were recorded from the intact eyes of four monkeys and three rabbits for periods up to 30 seconds.

RESULTS

In monkey retinal perifoveal capillaries, numerous erythrocytes were seen to pause for as long as 20 seconds and then resume transit. Similar pausing behavior was observed in the subfoveal choriocapillaris. Individual erythrocytes also were seen to pause in the rabbits' choriocapillaries below the medullary rays, where visualization of the cells was uninhibited by overlying retinal vasculature or dense pigment.

CONCLUSIONS

Reinjected ICG-loaded erythrocytes permit routine visualization of retinal capillary and choriocapillaris hemodynamics of the intact eye. It is speculated that erythrocyte-pausing in both microcirculations facilitates metabolic exchange across capillary walls. In retinal capillaries, pausing is presumed to result from vasomotion-which has been postulated as necessary for the inhibition of retinal edema-and in choriocapillaries, to result from the shifting distributions of local perfusion pressures within the network of capillary vessel segments that comprise each lobular area of the choriocapillaris vascular plexus.

Up-regulation of production of TGF-beta and IL-4 and down-regulation of IL-6 by apoptotic human bronchial epithelial cells

Human bronchial epithelial cells secrete cytokines that play a role in immune responses in the lung. However, the roles of these cytokines in regulating epithelial repair following acute lung injury are largely unknown. Responses to injury include hyperplasia of epithelial cells and squamous metaplasia. The resolution stage is characterized by discontinuation of hyperplasia. Apoptosis is considered to be the most efficient mechanism of removal of unwanted cells without causing inflammation. The presence of TGF-beta1 increases apoptosis, induces squamous metaplasia and inhibits proliferation of airway epithelial cells. Interleukin-4 increases the ability of macrophages to phagocytose epithelial cells and produce inflammatory cytokines. The purpose of this study was to investigate the hypothesis that apoptotic lung epithelial cells produce cytokines, which could act in an autocrine manner to control hyperplasia and induce squamous differentiation following acute lung injury. A bronchial epithelial cell line (16 HBE) was used as an in vitro model, to study the production of TGF-beta, IL-4 and IL-6 by lung epithelial cells undergoing apoptosis. Apoptotic and live cells were sorted on the basis of bright and negative staining with FITC-conjugated Annexin V, respectively. Intracellular IL-6, TGF-beta and IL-4 was measured using flow cytometric techniques. Electron microscopy, immunohistochemistry and ELISA were used as supportive techniques. Apoptotic cells produced significantly more TGF-beta and IL-4 (but less IL-6) than viable cells. Increased production of TGF-beta and IL-4 by epithelial cells undergoing apoptosis may contribute to the inhibition of proliferation, squamous metaplasia, and reduction of the inflammatory response in acute lung injury.

Interleukin-4 and tumour necrosis factor-alpha inhibit transforming growth factor-beta production in a human bronchial epithelial cell line: possible relevance to inflammatory mechanisms in chronic obstructive pulmonary disease

OBJECTIVE

Human bronchial epithelial cells are known to secrete an array of inflammatory cytokines including tumour necrosis factor-alpha (TNF-alpha) and interleukin (IL)-4, which may play a role in immune responses in lung diseases such as chronic obstructive pulmonary disease (COPD). However, the regulatory mechanisms governing cytokine production in bronchial epithelia in COPD are largely unknown. Transforming growth factor-beta (TGF-beta) is an anti-inflammatory cytokine and is involved in airway repair. The purpose of this study was to study the effect of TNF-alpha and IL-4 (pro-inflammatory cytokines known to be up-regulated in COPD), on the production of TGF-beta (a negative regulator of inflammation) by epithelial cells.

METHODOLOGY

A bronchial epithelial cell line was used as an in vitro culture model (16HBE). Cell cultures were stimulated with various combinations of TNF-alpha and IL-4 (20 ng/mL) for 24 h. Transforming growth factor-beta production was measured by flow cytometry, enzyme-linked immunosorbent assay and immunohistochemistry.

RESULTS

Exposure to TNF-alpha significantly up-regulated production of IL-4 from cultured epithelial cells. Unstimulated cells spontaneously released TGF-beta. Exposure to TNF-alpha and IL-4 significantly inhibited production of TGF-beta. The inhibitory effects of TNF-alpha and IL-4 on TGF-beta synthesis were summative.

CONCLUSIONS

The inhibitory effect of IL-4 and TNF-alpha on production of the regulatory cytokine TGF-beta in a bronchial epithelial cell line suggests that such mechanisms may contribute to the progression of the inflammatory response and compromise repair processes in inflammatory lung diseases such as COPD.

Cord blood leucocyte expression of functionally significant molecules involved in the regulation of cellular immunity

The cellular immune system of the newborn infant is immature and hypo-responsive when compared with adults. The extent to which immaturity of the leucocyte function underlies hyporesponsiveness in the newborn is incompletely understood. In this study flow cytometric techniques were applied to investigate the concurrent expression of a range of surface and intracellular leucocyte functional molecules and cytokines in resting and stimulated cord and adult blood. Production of interleukin (IL)-2 and expression of the components of its receptor, IL-2R alpha/beta/gamma, were investigated. No differences in the proportion of leucocytes producing IL-2R alpha and IL-2R gamma were observed for newborns and adults. A lower proportion of T cells and natural killer (NK) cells from newborns expressed IL-2R beta and upregulation of expression was slower. We hypothesize that reduced IL-2R beta may curtail early autocrine IL-2 activation of immune responses in the newborn. This hypothesis was supported by the observation that an increased proportion of stimulated T cells from newborns produced IL-2 at 4 h poststimulation, but at 24 h the proportion was lower than for adult T cells. The very low levels of interferon (IFN)-gamma produced by neonatal T cells and NK cells may also be partly explained by a curtailment of early autocrine activation of T cells. Expression and kinetics of upregulation for other functional molecules were studied. CD71, HLA-DR, tissue factor and CD152 levels were not significantly different for adults and newborns, suggesting that cord blood leucocytes, in some respects, may demonstrate functional maturity. IL-6 secretion by stimulated monocytes was also comparable in cord and adult blood. However, IL-1 alpha and IL-1 beta were produced by a lower proportion of monocytes from newborns than adults. Similarly, tumour necrosis factor (TNF)-alpha production for monocytes and T cells was lower in cord blood. The mean fluorescence intensity for IL-1 alpha, IL-1 beta and TNF-alpha was also lower for leucocytes from cord blood. These findings are significant in relation to the inability of newborn infants to mount a febrile response to infection. The findings of lower expression of IL-2R beta and lower production of inflammatory cytokines IL-1 alpha, IL-1 beta and TNF-alpha is a basis for improved understanding of the immunological immaturity of leucocytes in the newborn.

Natural and synthetic agonists of the melanocortin receptor type 3 possess anti-inflammatory properties

The effects of the natural and synthetic ligands for the melanocortin receptor type 3 (MC3-R) have been evaluated in a murine model of experimental gout. Systemic treatment of mice with gamma2-melanocyte-stimulating hormone (gamma2-MSH) and the synthetic agonist MTII inhibited accumulation of KC, interleukin-1 beta (IL-1beta), and PMN elicited by urate crystals in the peritoneal cavity. In vitro, macrophage (Mø) activation, determined as release of KC and IL-1beta, was inhibited by gamma2-MSH and MTII. The mixed MC3/4-R antagonist SHU9119 prevented the inhibitory actions of gamma2-MSH and MTII in vitro and in vivo, whereas the selective MC4-R antagonist HS024 was without effect. Western blotting also showed the presence of MC3-R protein on murine peritoneal Mø. Furthermore, agonism at the MC3-R evoked accumulation of cAMP within the Mø, which was inhibited by SHU9119. Thus, naturally occurring melanocortins, as well as the synthetic long-acting compound MTII, activate MC3-R on peritoneal Mø to inhibit the experimental inflammatory response.

Surface and intracellular interleukin-2 receptor expression on various resting and activated populations involved in cell-mediated immunity in human peripheral blood

The kinetics of assembly of the high-affinity interleukin-2 receptor (IL-2R)alpha/beta/gamma were investigated by studying intracellular and surface expression of IL-2Ralpha, beta and gamma by T cells, monocytes and natural killer (NK) cells. IL-2Ralpha and IL-2Rgamma were expressed by small numbers of resting T cells. These numbers increased following stimulation, to maximal expression at 48 h and 72 h, respectively. This observation was consistent with de novo synthesis of the receptor protein in response to the stimulus. The proportion of T cells producing IL-2Rbeta was smaller and up-regulated later than the proportion of cells producing IL-2Ralpha or IL-2Rgamma. IL-2Rbeta may therefore slow the assembly of the high-affinity IL-2R on T cells. A small number of resting NK cells expressed IL-2Ralpha, both on the cell surface and intracellularly, but this increased over 72 h on stimulated NK cells. IL-2Rbeta was constitutively expressed, both on the cell surface and intracellularly, by monocytes and NK cells. An increased proportion of NK cells and monocytes produced IL-2Rbeta, 24 h and 4 h post-stimulation, respectively. Maximal or plateau expression occurred at 72 h and 24 h post-stimulation, for NK cells and monocytes, respectively. The early up-regulation of intracellular IL-2Rbeta for monocytes may facilitate the up-regulation of surface IL-2Rbeta, and early assembly of the high-affinity IL-2R, accelerating monocyte activation and function. High constitutive intracellular IL-2Rgamma expression (> 80%) in all types of leucocyte investigated, decreased over the 72 h following stimulation with a concurrent increase in surface expression. IL-2Rgamma was expressed by increased proportions of T cells, monocytes and NK cells, 4 h following stimulation. The intracellular storage of IL-2Rgamma may accelerate translocation to the cell surface after stimulation. The early translocation of IL-2Rgamma may reflect its usage as a signal transduction molecule by other cytokine receptors - IL-4, IL-7, IL-9 and IL-15. This study delineated the potential expression of the high-affinity IL-2Ralpha/beta/gamma on various stimulated leucocytes. The differential kinetics of assembly of the high-affinity IL-2Ralpha/beta/gamma on different leucocyte subsets suggests that IL-2 may regulate the inflammatory cellular responses in a sequential manner, paralleling the timed expression of IL-2Ralpha/beta/gamma on the monocytes, NK cells and T cells.