Surprises from Intravital Imaging of the Innate Immune Response

Successful immune responses depend on the spatiotemporal coordination of immune cell migration, interactions, and effector functions in lymphoid and parenchymal tissues. Real-time intravital microscopy has revolutionized our understanding of the dynamic behavior of many immune cell types in the living tissues of several species. Observing immune cells in their native environment has revealed many unanticipated facets of their biology, which were not expected from experiments outside a living organism. Here we highlight both classic and more recent examples of surprising discoveries that critically relied on the use of live in vivo imaging. In particular, we focus on five major cell types of the innate immune response (macrophages, microglia, neutrophils, dendritic cells, and mast cells), and how studying their dynamics in mouse tissues has helped us advance our current knowledge of immune cell-mediated tissue homeostasis, host defense, and inflammation. Expected final online publication date for the Annual Review of Cell and Developmental Biology Volume 38 is October 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Macrophage network dynamics depend on haptokinesis for optimal local surveillance

Macrophages are key immune cells with important roles for tissue surveillance in almost all mammalian organs. Cellular networks made up of many individual macrophages allow for optimal removal of dead cell material and pathogens in tissues. However, the critical determinants that underlie these population responses have not been systematically studied. Here, we investigated how cell shape and the motility of individual cells influences macrophage network responses in 3D culture settings and in mouse tissues. We show that surveying macrophage populations can tolerate lowered actomyosin contractility, but cannot easily compensate for a lack of integrin-mediated adhesion. Although integrins were dispensable for macrophage chemotactic responses, they were crucial to control cell movement and protrusiveness for optimal surveillance by a macrophage population. Our study reveals that β1 integrins are important for maintaining macrophage shape and network sampling efficiency in mammalian tissues, and sets macrophage motility strategies apart from the integrin-independent 3D migration modes of many other immune cell subsets.

Macrophages are immune cells in the body that remove dying cells and debris from tissues. They live in almost all the body’s organs, surveilling for signs of infection and destroying microbes. They also migrate to wound sites, where they can eliminate foreign particles and stop microbes from entering the body.

To perform their surveillance role, macrophages need to work together as a team. They form a network, coordinating their movements to optimise the removal of particles and dead cells. How this happens is something of a mystery. As individuals, cells travel through tissues using a balance of several activities: they change their shape, they contract and relax, and they grab hold of their surroundings using proteins called integrins. It is thought that the choice between these types of movement may affect the rest of the network.

To investigate, Paterson and Lämmermann genetically engineered mouse macrophages grown in the laboratory so they would not produce working integrins. These macrophages were able to contract and relax, but they could not attach to the proteins in the structures they were exploring.

Paterson and Lämmermann then placed these macrophages in gels studded with proteins that mimic a biological matrix to observe their behaviour. When these macrophages were exposed to the chemicals that indicate the presence of a wound, they moved normally, changing shape and contracting and relaxing. Paterson and Lämmermann confirmed this normal behaviour for macrophages moving to sites of injuries in the tissue of living mice. However, when it came to surveillance, the macrophages’ abilities were seriously diminished, and they were unable to form an effective network to take up particles and dead cells.

This work sheds light on how the movement of individual cells affects the entire immune surveillance network. A deeper understanding could lead to new insights into how to prevent inflammation. The next step is to map macrophage networks in healthy and diseased tissues to understand how cell movement affects surveillance under different conditions.

Upregulation of VCAM-1 in lymphatic collectors supports dendritic cell entry and rapid migration to lymph nodes in inflammation

Dendritic cell (DC) migration to draining lymph nodes (dLNs) is a slow process that is believed to begin with DCs approaching and entering into afferent lymphatic capillaries. From capillaries, DCs slowly crawl into lymphatic collectors, where lymph flow induced by collector contraction supports DC detachment and thereafter rapid, passive transport to dLNs. Performing a transcriptomics analysis of dermal endothelial cells, we found that inflammation induces the degradation of the basement membrane (BM) surrounding lymphatic collectors and preferential up-regulation of the DC trafficking molecule VCAM-1 in collectors. In crawl-in experiments performed in ear skin explants, DCs entered collectors in a CCR7- and β1 integrin–dependent manner. In vivo, loss of β1-integrins in DCs or of VCAM-1 in lymphatic collectors had the greatest impact on DC migration to dLNs at early time points when migration kinetics favor the accumulation of rapidly migrating collector DCs rather than slower capillary DCs. Taken together, our findings identify collector entry as a critical mechanism enabling rapid DC migration to dLNs in inflammation.

A comparison of anesthetic protective barriers for the management of COVID-19 pediatric patients

BACKGROUND

Barrier techniques, such as plastic sheets or intubation boxes, are purported to offer additional protection for healthcare workers.

AIMS

To assess the functionality, perceived safety, droplet protection, and aerosol protection of several barrier techniques.

METHODS

Firstly, a simulation study with 12 different laryngoscopists was conducted to assess the time taken to perform an intubation (via direct laryngoscopy, via video laryngoscopy, and via a bougie) with four different barrier techniques (personal protective equipment only, a plastic sheet, a tented plastic sheet, and an intubation box). Secondly, a cough at the time of intubation was simulated using ultraviolet dye to assess the spread of droplets; and thirdly, smoke was used to assess the spread of aerosols.

RESULTS

Intubation time using the box was noninferior to using no barrier. Based on subjective ratings by the laryngoscopists, the most functional technique was no barrier followed by the intubation box, then the tented sheet, and then the plastic sheet. The technique that conferred the highest feeling of safety to the laryngoscopists was the intubation box, followed by the tented sheet, then no barrier, and then the plastic sheet. All the barriers prevented the ultraviolet dye contaminating the head and torso of the laryngoscopist. Smoke remained within the intubation box if plastics sheets were used to cover the openings and suction was ineffective at clearing it. With no barrier in place, smoke was effectively cleared away from the patient in a theater with laminar flow but tended to spread up toward the laryngoscopist in a room without laminar flow.

CONCLUSIONS

A well-designed intubation box is an effective barrier against droplets and is noninferior to no barrier in relation to intubation time. However, a box interferes with laminar flow in theaters with formal ventilation systems and may result in accumulation of aerosols if it is completely enclosed.

Reduced-Nicotine Cigarettes in Young Smokers: Impact of Nicotine Metabolism on Nicotine Dose Effects

The use of cigarettes delivering different nicotine doses allows evaluation of the contribution of nicotine to the smoking experience. We compared responses of 46 young adult smokers to research cigarettes, delivering 0.027, 0.110, 0.231, or 0.763 mg nicotine, and conventional cigarettes. On five separate days, craving, withdrawal, affect, and sustained attention were measured after overnight abstinence and again after smoking. Participants also rated each cigarette, and the nicotine metabolite ratio (NMR) was used to identify participants as normal or slow metabolizers. All cigarettes equally alleviated craving, withdrawal, and negative affect in the whole sample, but normal metabolizers reported greater reductions of craving and withdrawal than slow metabolizers, with dose-dependent effects. Only conventional cigarettes and, to a lesser degree, 0.763-mg nicotine research cigarettes increased sustained attention. Finally, there were no differences between ratings of lower-dose cigarettes, but the 0.763-mg cigarettes and (even more so) conventional cigarettes were rated more favorably than lower-dose cigarettes. The findings indicate that smoking-induced relief of craving and withdrawal reflects primarily non-nicotine effects in slow metabolizers, but depends on nicotine dose in normal metabolizers. By contrast, relief of withdrawal-related attentional deficits and cigarette ratings depend on nicotine dose regardless of metabolizer status. These findings have bearing on the use of reduced-nicotine cigarettes to facilitate smoking cessation and on policy regarding regulation of nicotine content in cigarettes. They suggest that normal and slow nicotine metabolizers would respond differently to nicotine reduction in cigarettes, but that irrespective of metabolizer status, reductions to <0.763 mg/cigarette may contribute to temporary attentional deficits.

Obesity-related health status is a better predictor of pregnancy with fertility treatment than body mass index: a prospective study

This study assessed whether an obesity-related health status instrument (Edmonton obesity scoring system - EOSS) or body mass index (BMI) better predicted pregnancy rates in overweight women undergoing fertility treatments. A prospective cohort study was conducted on patients with a BMI ≥ 25 kg m(-2) undergoing a fertility treatment cycle (ovulation induction, superovulation, or in vitro fertilization). Obesity-related health status including blood pressure, blood work, health history, and functional assessment were assessed. A total of 101 patients were included in the study with an average age of 36.3 ± 4.2 years and a mean BMI of 31.8 ± 5.2 kg m(-2) . EOSS was found to be statistically predictive of pregnancy rate/cycle (OR 0.51, 95% CI 0.27-0.94; P = 0.03), whereas BMI was not (OR 0.95, 95% CI 0.86-1.05). A similar trend was seen for clinical pregnancy rate/cycle started. However, the association between clinical pregnancy rates and EOSS or BMI did not reach statistical significance (OR 0.53, P = 0.06 and OR 0.98, P = 0.62 respectively). Our results demonstrated that EOSS better predicted pregnancy rates after fertility treatments than BMI. In fact, for every EOSS stage increased by one unit, the odds of pregnancy were approximately halved. A multi-centre study powered for live birth is warranted to establish effective pre-fertility management of overweight women.

Genetic deletion of transglutaminase 2 does not rescue the phenotypic deficits observed in R6/2 and zQ175 mouse models of Huntington's disease

Huntington's disease (HD) is an autosomal dominant, progressive neurodegenerative disorder caused by expansion of CAG repeats in the huntingtin gene. Tissue transglutaminase 2 (TG2), a multi-functional enzyme, was found to be increased both in HD patients and in mouse models of the disease. Furthermore, beneficial effects have been reported from the genetic ablation of TG2 in R6/2 and R6/1 mouse lines. To further evaluate the validity of this target for the treatment of HD, we examined the effects of TG2 deletion in two genetic mouse models of HD: R6/2 CAG 240 and zQ175 knock in (KI). Contrary to previous reports, under rigorous experimental conditions we found that TG2 ablation had no effect on either motor or cognitive deficits, or on the weight loss. In addition, under optimal husbandry conditions, TG2 ablation did not extend R6/2 lifespan. Moreover, TG2 deletion did not change the huntingtin aggregate load in cortex or striatum and did not decrease the brain atrophy observed in either mouse line. Finally, no amelioration of the dysregulation of striatal and cortical gene markers was detected. We conclude that TG2 is not a valid therapeutic target for the treatment of HD.

Exploiting fast detectors to enter a new dimension in room-temperature crystallography

A departure from a linear or an exponential intensity decay in the diffracting power of protein crystals as a function of absorbed dose is reported. The observation of a lag phase raises the possibility of collecting significantly more data from crystals held at room temperature before an intolerable intensity decay is reached. A simple model accounting for the form of the intensity decay is reintroduced and is applied for the first time to high frame-rate room-temperature data collection.

A mixed fixed ratio/progressive ratio procedure reveals an apathy phenotype in the BAC HD and the z_Q175 KI mouse models of Huntington's disease

Apathy, characterized by generally reduced interest in and likelihood to perform goal-directed actions, is a recognized symptom of Huntington's disease (HD), a devastating neurological disorder caused by a CAG repeat expansion of the Htt gene located on chromosome 4. The present experiments used a modified progressive ratio task that incorporated a fixed-ratio schedule of reinforcement component to assess consummatory behavior, and a progressive-ratio schedule component that required increasing numbers of lever-presses for successive reinforcers (0.01 ml of evaporated milk). The studies revealed an apathetic phenotype in two mouse models of HD, with decreased response rates either overall or only at higher ratio requirements in the progressive-ratio component relative to wild-type controls. Based on the procedure used (within-session fixed- and progressive-ratio components), it is proposed that an observed phenotype can be ascribed either specifically to reduced motivation to work for food reinforcement or more generally to deficits in consummatory behavior. This procedure provides a simple means to assess this type of phenotype in rodents, with issues in consummatory vs. incentive motivation reflected in general alterations in fixed- versus progressive alterations on an escalating-ratio schedules respectively, providing translational measures of the amotivation/apathy construct of the human realm to the homologous construct of incentive motivation in preclinical models of human disease.

Risk in pediatric anesthesia

Risk in pediatric anesthesia can be conveniently classified as minor or major. Major morbidity includes cardiac arrest, brain damage and death. Minor morbidity can be assessed by clinical audits with small patient samples. Major morbidity is rare. It is best assessed by very large clinical studies and by review of closed malpractice claims. Both minor and major morbidity occur most commonly in infants and children under three, especially those with severe co-morbidities. Knowledge of risk profiles in pediatric anesthesia is a starting point for the reduction of risk.

An investigation into customer service policies and practices within the Scottish college library sector: A comparison between the customer service exemplars from the retail sector with current Scottish college library practice

The aim of this research project was to investigate the customer care methods within the Scottish college library sector.The researcher sought to compare examples of the customer care and service policies and practices from the sector with exemplars of good customer service from the retail sector. A qualitative, grounded theory approach was taken. Models of good practice were identified from published literature and from within the retail sector. Interviews were undertaken with a number of Scottish college librarians to determine if good practice existed already within the Scottish college sector. Analysis showed that high quality customer service models were present within the sector.

Predictors of pulmonary exacerbations in patients with cystic fibrosis infected with multi-resistant bacteria

BACKGROUND

This study examined characteristics of adult and adolescent patients with cystic fibrosis (CF) to determine factors associated with an increased risk of pulmonary exacerbations.

METHODS

249 patients with CF infected with multidrug resistant bacteria were recruited and prospectively followed for up to 4.5 years until they experienced a pulmonary exacerbation severe enough to require intravenous antibiotics. Multivariable regression analyses were used to compare the characteristics of patients who experienced an exacerbation with those who did not.

RESULTS

124 of the 249 patients (50%) developed a pulmonary exacerbation during the first year and 154 (62%) experienced an exacerbation during the 4.5 year study period. Factors predictive of exacerbations in a multivariable survival model were younger age (OR 0.98, 95% CI 0.96 to 0.99), female sex (OR 1.45, 95% CI 1.07 to 1.95), lower forced expiratory volume in 1 second (FEV(1)) (OR 0.98, 95% CI 0.97 to 0.99), and a previous history of multiple pulmonary exacerbations (OR 3.16, 95% CI 1.93 to 5.17). Chronic use of inhaled corticosteroids was associated with an increased risk of exacerbation (OR 1.92, 95% CI 1.00 to 3.71) during the first study year.

CONCLUSIONS

Patients who experience pulmonary exacerbations are more likely to be younger, female, using inhaled steroids, have a lower FEV(1), and a history of multiple previous exacerbations. It is hoped that knowledge of these risk factors will allow better identification and closer monitoring of patients who are at high risk of exacerbations.

Lithium monitoring before and after the distribution of clinical practice guidelines

OBJECTIVE

To determine whether distribution of clinical practice guidelines improves lithium monitoring and whether standards of monitoring differed between patients in psychiatric contact and those seen only in primary care.

METHOD

Standards of monitoring were assessed for patients on lithium in northeast Scotland throughout 1995 and/or throughout 1996. Guidelines were circulated in January 1996 to all local general practitioners and psychiatrists. Monitoring was compared between 1995 and 1996 and for patients with and without psychiatric contact.

RESULTS

Both primary care and psychiatric records were scrutinized for 422 and 403 patients prescribed lithium throughout 1995 and 1996, respectively. While monitoring was poor on several parameters during both years, frequency of measurement of both thyroid and renal function improved in 1996. Standards of monitoring were better for patients in psychiatric care.

CONCLUSION

Standards of lithium monitoring require further improvement. Locally agreed practice guidelines are helpful but patients on lithium should be in continuing contact with an experienced psychiatrist.

The effect of allowing clinical discretion in ordering biochemical tests. Evaluation by complementary methods

We describe the effects on costs, working patterns, and clinical behavior of installing a DAX "discretionary" biochemistry analyzer. Use of the new analyzer encouraged doctors to be more specific in requesting biochemical tests, which substantially reduced the number of tests requested and slightly reduced overall costs. Doctors preferred being able to order tests in this more specific way.

Effect of sepsis and surgery on trace minerals

The purpose of this study was to evaluate effect of infection and surgery on serum iron, zinc, and the copper simultaneously. Twenty patients who had emergency abdominal surgery for acute inflammatory conditions, and 15 controls who had elective abdominal surgery were studied. Preoperatively, serum iron levels were significantly decreased in the septic group compared to controls (p less than 0.001). Following surgery and removal of the septic focus, serum iron, ferritin, and zinc levels increased, while serum transferrin levels decreased significantly. Serum copper levels did not show any significant difference. It is concluded that serum iron, transferrin, ferritin, and zinc levels are affected profoundly by septic and the surgical stress.

Pulmonary permeability edema in a large animal model of nonpulmonary sepsis. A morphologic study

Morphologic studies were undertaken in a sheep model of pulmonary permeability edema (PPE) induced by cecal ligation and perforation. Biopsies taken every 24 hours through 96 hours following induction of sepsis showed, at 24 hours, interstitial edema accompanied by widespread aggregation of polymorphonuclear leukocytes. This was confirmed by electron microscopy, which also demonstrated endothelial cell swelling, platelet aggregation, and fibrin deposition. By 48 hours, a "thromboangiitis" had developed that persisted through 96 hours. In vitro pulmonary angiograms done at 60 and 96 hours showed multiple filling defects; it was possible to demonstrate that these defects corresponded to the "thromboangiitis." These thrombotic lesions, which were not the result of embolization from indwelling lines, closely resembled vascular changes described in the adult respiratory distress syndrome. It is believed that this is the first time that such lesions have been described in a model of PPE resulting from nonpulmonary sepsis.

Evaluation of a time-resolved immunofluorometric assay for serum thyroid stimulating hormone

The LKB 'Delfia, immunofluorometric assay for serum TSH has been evaluated. The assay is simple and rapid to perform and is capable of processing in excess of 100 specimens within a working day. The sensitivity of the assay is 0.05 microU/L, with a working range extending beyond 324 microU/L. The change in signal at each point over the standard curve approaches 1000-fold, significantly greater than that of a typical immunoradiometric assay. Mean figures for intra-assay and inter-assay precision were 4.7% and 8.6% CV, respectively. Mean recovery of added TSH was 98.3%, and samples containing high levels of endogenous TSH diluted parallel to the standard curve. The method showed good correlation with an immunoradiometric assay for TSH. The reference ranges for clinically defined groups of subjects were euthyroid 0.47-3.84 microU/L (n = 83); primary hypothyroidism 15--greater than 324 microU/L (n = 28); thyrotoxicosis less than 0.05 microU/L (n = 46). It is concluded that the 'Delfia' assay offers the clinical biochemistry laboratory an attractive and reliable alternative to a sensitive immunoradiometric assay for serum TSH.

The analysis of tricyclic antidepressant drugs at therapeutic blood levels by reversed-phase high-performance liquid chromatography using pairing and organic counter-ions

A serum assay method incorporating two internal standards suitable for routine clinical analysis of tricyclic antidepressant drugs at the therapeutic level is described. The method involves extraction and chromatography using a reversed-phase high-performance liquid chromatography system incorporating pairing and organic counter-ions. The quantitative characteristics of the method are reported and results are compared with consensus values for four commonly encountered drugs, amitriptyline, nortriptyline, imipramine and desipramine. The method is shown to be applicable to more recently developed antidepressants such as nomifensine and maprotiline and the flexibility of the chromatography is discussed. Sample chromatograms obtained from patient samples in the presence and absence of potentially interfering drugs and metabolites are discussed.

Incorporation of a SMAC analyzer into the data-processing procedures of a computer-assisted laboratory

This paper describes the incorporation of a SMAC (Technicon) analyzer into data-processing techniques that have been developed on existing computer hardware during several years. The SMAC system is interfaced directly to a small computer, and suitable peripherals produce a manageable form of result tabulation for subsequent reporting, as well as provide quality-control information to the SMAC operators in real time. The design is such as to facilitate the performance analysis of the SMAC system during its initiation period and during normal service operation.

Incorporation of a SMAC analyzer into the data-processing procedures of a computer-assisted laboratory

This paper describes the incorporation of a SMAC (Technicon) analyzer into data-processing techniques that have been developed on existing computer hardware during several years. The SMAC system is interfaced directly to a small computer, and suitable peripherals produce a manageable form of result tabulation for subsequent reporting, as well as provide quality-control information to the SMAC operators in real time. The design is such as to facilitate the performance analysis of the SMAC system during its initiation period and during normal service operation.