Using machine learning to improve the accuracy of patient deterioration predictions: Mayo Clinic Early Warning Score (MC-EWS)

OBJECTIVE

We aimed to develop a model for accurate prediction of general care inpatient deterioration.

MATERIALS AND METHODS

Training and internal validation datasets were built using 2-year data from a quaternary hospital in the Midwest. Model training used gradient boosting and feature engineering (clinically relevant interactions, time-series information) to predict general care inpatient deterioration (resuscitation call, intensive care unit transfer, or rapid response team call) in 24 hours. Data from a tertiary care hospital in the Southwest were used for external validation. C-statistic, sensitivity, positive predictive value, and alert rate were calculated for different cutoffs and compared with the National Early Warning Score. Sensitivity analysis evaluated prediction of intensive care unit transfer or resuscitation call.

RESULTS

Training, internal validation, and external validation datasets included 24 500, 25 784 and 53 956 hospitalizations, respectively. The Mayo Clinic Early Warning Score (MC-EWS) demonstrated excellent discrimination in both the internal and external validation datasets (C-statistic = 0.913, 0.937, respectively), and results were consistent in the sensitivity analysis (C-statistic = 0.932 in external validation). At a sensitivity of 73%, MC-EWS would generate 0.7 alerts per day per 10 patients, 45% less than the National Early Warning Score.

DISCUSSION

Low alert rates are important for implementation of an alert system. Other early warning scores developed for the general care ward have achieved lower discrimination overall compared with MC-EWS, likely because MC-EWS includes both nursing assessments and extensive feature engineering.

CONCLUSIONS

MC-EWS achieved superior prediction of general care inpatient deterioration using sophisticated feature engineering and a machine learning approach, reducing alert rate.

An Investigation of Healthcare Worker Perception of Their Workplace Safety and Incidence of Injury

Background: Managing the safety climate in health care is a promising tool for improving employee and patient safety in the health care work environment. Gaps in the theoretical and conceptual underpinnings of safety climate, as well as the evidence base for its practical application in health care remain. The purpose of this study was to evaluate the number of work injuries occurring in health care work units and associated safety climate beliefs. Methods: A retrospective analysis was conducted utilizing organizational staff survey data collected by a large medical hospital in the Midwest in 2015. Employees (n = 32,327) were invited to identify safety climate perceptions via survey. Injuries, days restricted, and days absent were identified through the Hospital's Occupational Safety and Health Administration (OSHA) log. Zero inflated negative binomial regressions used injuries as dependent variables and safety climate perceptions as independent variables. Findings: In all, 23,599 employees completed the survey (73% response rate) across 1,805 employee work units which were defined as groupings of employees reporting to a single supervisor. We found that there was an association between fewer injuries and health care workers indicating that they share responsibility for compliance with safety rules and procedures (relative risk [RR] = 0.98, 95% confidence interval [CI] = [0.98, 0.99]). Conclusion/Application to Practice: This study supports the use of a safety climate measure to assess working units' perceptions of employee safety. A continued focus on the health and safety of employees who interact directly with patients is warranted, as well as employees who do not provide direct patient care.

Identifying the Most Costly Patients in Radiation Oncology and Predicting the Top Spenders

PURPOSE:

Quality payment programs aim to adjust payments on the basis of quality and cost; however, few quality metrics exist in radiation oncology. This study evaluates and predicts the top spenders (TS) after radiation therapy (RT).

MATERIALS AND METHODS:

Patient characteristics, cancer details, treatments, toxicity, and survival data were collected for patients treated with RT at Mayo Clinic from 2007 to 2016. Standardized costs were obtained and adjusted for inflation. TSs were identified as those with greater than 93rd percentile costs (≥ $120,812). Prediction models were developed to predict TSs using training and validation sets using information available at consultation, after RT, and at last follow-up.

RESULTS:

A total of 15,131 patients were included and 1,065 TSs identified. Mean cost overall was $55,290 (median, $39,996) for all patients. Prediction models 1, 2, and 3 had concordance statistics of 0.83 to 0.83, 0.85 to 0.85, and 0.87 to 0.88, respectively in training and validation, indicating excellent prediction of TSs. Factors that were most predictive of TSs included stage N/A and stage 4 ( v stage 0; odds ratio [OR], 18.23 and 8.44, respectively; P < .001); hematologic, upper GI, skin and lung cancers ( v breast; OR, 11.45, 7.69, 3.81, and 2.43, respectively; P < .01); immunotherapy, surgery, and chemotherapy use (OR, 4.36, 2.51, and 1.61, respectively; P < .01); hospitalizations within 90 days of RT (OR, 2.26; P < .01); or death during the episode (OR, 1.56; P < .01).

CONCLUSION:

This is the first study of its kind to predict with high accuracy the highest spenders in radiation oncology. These patients may benefit from pre-emptive management to mitigate costs, or may require exclusion or adjustment from quality payment programs.

Qualitative study of implementation of patient self-reported measures in a consultation-liaison psychiatry practice

RATIONAL, AIMS, AND OBJECTIVES

Understanding of barriers and successes associated with the implementation of electronic patient self-reported measures (ePSRMs) within clinical settings are limited and have not been pursued utilizing implementation science frameworks. This qualitative study is designed to assess staff perceptions of an ePSRM implementation.

METHODS

The study took place in an academic hospital's Consultation Liaison Psychiatry practice. Qualitative interviews were conducted with the staff and clinicians from the practice. Participants were directly involved with the implementation and use of the ePSRM system within the Psychiatry practice. Interviews were structured around the Reach, Effectiveness, Adoption, Implementation, Maintenance (RE-AIM) framework.

RESULTS

Participants reported increased patient engagement as well as efficiency and time savings. The intervention was perceived to be more challenging for older patients. Facilitators include communicating the ePSRM to patients prior to the care visit, having enough trained staff or super-users who can assist with technical problems, and having a shorter questionnaire.

CONCLUSIONS

Overall, assessment of the ePSRM implementation was positive. Staff and clinicians indicated benefits in time, effectiveness, and improvements in patient treatment. Results indicate that defining how the system would fit within the clinical workflow was key, as was a flexible and user-friendly technology platform. The ePSRM implementation was dependent upon clinical involvement and interest in adoption, while barriers were associated with technical challenges as well as some patient difficulties, such as cognitive impairment. The use of the RE-AIM framework is valuable as it allows for systematic assessment of the implementation and identifies areas in that implementation has succeeded or is lacking.

Identifying and predicting the most costly patients in oncology

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Background: Quality based payment programs in medicine are currently being introduced nationally, aimed to improve care and reduce cost. This study aimed to evaluate the top spenders (TS) after cancer diagnosis and predict TS at two separate time points using predictive analytics. Methods: Patient characteristics, cancer details, treatments, adverse events, and outcomes were collected for patients treated for cancer at Mayo Clinic from 2007 - 2017. Standardized costs over a 2 year period after first treatment were obtained from the Mayo Clinic Cost Data Warehouse with Medicare reimbursements assigned to all services and adjusted to the 2017 GDP Implicit Price Deflator for inflation. TS were identified as those with greater than 93rd percentile costs (≥$113,158) due to a sharp rise in cost at that level. Descriptive statistics and univariate analysis were used for comparison. A prediction model with a training (80%) and validation set (20%) using multivariate selection was used to predict TS and was repeated using information available at 1) the time of consultation and 2) at last follow-up. Results: A total of 80,385 patients were included and 5,626 TS were identified. Mean cost (25th, 75th percentile) overall was $44,953 ($16,776, $51,889). Prediction models at time 1 and 2 had ROC AUC statistics of 0.82 and 0.89 in training and 0.82 and 0.88 in the validation indicating good prediction of high costs. Factors most predictive of TS included need for blood transfusions within 90 days of treatment (OR 5.3), bone marrow transplant (OR 4.0), mild liver disease (OR 3.5), hemiplegia (OR 3.4), weight loss > 10% within 90 days of treatment (OR 3.3), upper GI cancer (OR 3.0), ‘other’ cancer type (OR 2.8), immunotherapy use (OR 2.7), and hospitalizations within 90 days (OR 2.4), all p < 0.001, among others. The largest costs were due to hospital services in the TS and non-TS groups, mean costs $114,258 and $13,185 respectively. Conclusions: This is the first study to predict with high accuracy the top spenders in Oncology. Patient comorbidities and toxicities were among the strongest predictors of high costs, along with certain treatments (bone marrow transplant and immunotherapy). Our findings suggest that quality payment programs should adjust for comorbidities, and that reducing toxicity may be an effective method at reducing costs.

Trends in the Use of Laparoscopy and Robotics for Colorectal Cancer in Florida

Background: Laparoscopy and more recently robotics are increasingly used for colorectal cancer surgery in the United States. We examined the current trends of minimally invasive surgical resections for colorectal cancer in Florida. Methods: The Florida Inpatient Discharge Dataset was used to examine the clinical data of patients who underwent elective surgery for colorectal cancer during 2013-2015. Multivariate analyses were performed to compare patient characteristics associated with the use of open and minimally invasive surgeries. Results: A total of 10,513 patients were analyzed; 5451 (52%) had open surgery, 4403 (42%) laparoscopy, and 659 (6%) robotic surgery. The rates of minimally invasive surgery (MIS) increased from 46.95% in 2013 to 48.72% in 2015. Among minimally invasive surgical procedures, the use of robotics increased from 9.82% in 2013 to 15.48% in 2015. Metastatic cancer (odds ratio [OR] 0.61, confidence interval [CI] 0.55-0.67), Elixhauser score of 3-5 (OR 0.85, CI 0.76-0.95) or more than 5 (OR 0.78, CI 0.63-0.97), Medicaid insurance (OR 0.73, CI 0.6-0.89), Black race (OR 0.88, CI 0.77-0.99), and rural residence (OR 0.83, CI 0.69-0.99) were associated with lower odds of MIS than open surgery. Conclusions: This study demonstrates that the overall rates of MIS for colorectal cancer in Florida increased from 2013 to 2015. Socially deprived and very sick patient populations with colorectal cancer are less likely to undergo MIS.

Cost of Acute and Follow-Up Care in Patients With Pre-Existing Psychiatric Diagnoses Undergoing Radiation Therapy

PURPOSE

The impact of psychiatric comorbidities on the cost of cancer care in radiation oncology practices is not well studied. We assessed the acute and 24-month follow-up costs for patients with and without pre-existing psychiatric comorbidities undergoing radiation therapy.

METHODS AND MATERIALS

Patients with cancer undergoing radiation therapy at our institution from 2009 to 2014 were denoted as having pre-existing psychiatric conditions (Psych group) if they had associated billing codes for any of the 422 International Classification of Diseases, 9th revision psychiatric conditions during the 12 months before their cancer diagnosis. The Elixhauser comorbidity index was calculated, excluding psychiatric categories. Medicare reimbursement was assigned to professional services, and Medicare departmental cost-to-charge ratios were applied to service line hospital charges and adjusted for inflation to create 2017 standardized costs. Acute (0-6 month) and follow-up (6-24 month) costs were subcategorized into clinic, emergency department, hospital inpatient, and outpatient costs.

RESULTS

Among 1275 patients, 126 (9.9%) had at least 1 pre-existing psychiatric diagnosis. On univariate analysis, both acute and long-term costs were higher in the Psych group. The largest significant differences in costs were follow-up hospital inpatient costs ($5861 higher; 95% confidence interval [CI], $687-$11,035; P = .002), follow-up hospital outpatient costs ($2086 higher; 95% CI, -$142 to $4,314; P = .040), and follow-up emergency department costs ($396 higher; 95% CI, $149-$643; P < .001). Age, race, sex, and treatment modalities were comparable, but the Psych group patients had more median comorbidities (2 vs 1) and had more respiratory cancer diagnoses than the nonpsychiatric group (31% vs 17%). On multivariate analysis adjusted for age, sex, cancer diagnosis, and comorbidities, global follow-up costs remained 150% higher in the Psych group (P < .001). Acute costs were similar after adjustment (P = .63).

CONCLUSIONS

Psychiatric comorbidities independently predict elevated healthcare costs in patients treated for cancer. Radiation oncology payment models should consider adjustments to account for psychiatric comorbidities because addressing these may mitigate cost differential.

The cost implications of palliative radiation therapy dose and fractionation for painful metastatic bone lesions

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Background: Palliative radiation treatment (pRT) is used for symptomatic bone metastases (mets). Several fractionation schedules show equal efficacy for pain relief, and ASTRO’s Choosing Wisely recommends 8Gy x1, 4Gy x5, or 3Gy x10. This study aims to investigate the cost implications of pRT for bone mets. Methods: Patients (Pts) treated with pRT for bone mets at Mayo Clinic from 2007 - 2016 were included in this study. Costs for all services were subdivided into RT and total costs at 30 & 90 days (30D & 90D). Standardized costs were obtained from the Mayo Clinic Cost Data Warehouse and Medicare reimbursements were assigned to all services with cost to charge adjustments and 2017 GDP Implicit Price Deflator for inflation. Cost means were compared via the Kruskal-Wallis test. Results: 538 pts were treated with pRT, 124 receiving 8Gy x1, 204 receiving 4Gy x5, and 210 receiving 3Gy x10. Pts with breast and prostate cancer were most likely to be treated with 3Gy x10 and pts with GI and lung cancer were most likely to be treated with 8Gy x1. RT costs at 30D were $1,497, $1,891, and $1,982 (p=0.03) and RT costs at 90D were $2,602, $2,753, and $3,032 (p=0.08) for initial RT regimens of 8Gy x1, 4Gy x5, and 3Gy x10. Total costs of care at 30D were similar from $15,969 - 17,687 (p=0.6) and total costs at 90D were similar from $22,361 - 23,219 (p=0.7) between arms. A total of 23%, 28%, and 39% of pts were alive 2 years following pRT from each arm (p=0.07). Conclusions: This is the first study of its kind to analyze actual treatment costs for the three most common pRT regimens in bone mets. Single fraction RT was most used for pts with poor prognoses and was associated with lower RT costs at 30D, but similar RT costs at 90D, possibly due to retreatment. RT choice had no impact on overall costs of care at 30D or 90D. pRT remains of high value, representing only 11-13% of total costs.[Table: see text]

Toxicity following palliative radiation therapy for painful metastatic bone lesions

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Background: Palliative radiation treatment (pRT) is a common and effective treatment for patients with symptomatic bone metastases. However, patients receiving RT for bone metastases often may have a poor performance status and are more likely to experience toxicity during or after treatment. This study aims to investigate the number and type of toxicity event occurring during or after pRT for bone metastases. Methods: Patients treated with RT for bone metastases at Mayo Clinic from 2007 to 2016 were included in this study. Demographic, disease, treatment, and toxicity information were collected. Specifically, toxicity events were identified as emergency department (ED) visits and inpatient hospitalization (IH) within 90 days, breaks in treatment >4 days, and excessive 30 day financial toxicity defined as standardized Medicare costs >1 standard deviation above the mean. RT treatment was compared by dose and fractionation via descriptive statistics. Results: A total of 538 patients treated with pRT were identified, 124 receiving 8Gy x1, 204 receiving 4Gy x5, and 210 receiving 3Gy x10. Patients with breast and prostate cancer were most likely to be treated with 3Gy x10 and patients with GI and Lung cancer were most likely to be treated with 8Gy x1. A description of the patient characteristics and toxicities are shown in Table 1. For 8Gy x1, 4Gy x5, and 3Gy x10 breaks in treatment were rare (0%, 2%, and 3.3%), ED visits (15%, 24%, & 28%), IH (12%, 23%, & 19%), and financial toxicity (13%, 18%, & 21%) were common. A total of 22.6%, 27.5%, and 38.6% of patients were alive two years following pRT from each group. Conclusions: Toxicity during or shortly after pRT of bone metastases is common. This study confirms that additional steps should be taken to monitor and mitigate toxicity in this vulnerable patient group. [Table: see text]

Patient portal adoption and use by hospitalized cancer patients: a retrospective study of its impact on adverse events, utilization, and patient satisfaction

BACKGROUND

Portal use has been studied among outpatients, but its utility and impact on inpatients is unclear. This study describes portal adoption and use among hospitalized cancer patients and investigates associations with selected safety, utilization, and satisfaction measures.

METHODS

A retrospective review of 4594 adult hospitalized cancer patients was conducted between 2012 and 2014 at Mayo Clinic in Jacksonville, Florida, comparing portal adopters, who registered for a portal account prior to hospitalization, with nonadopters. Adopters were classified by their portal activity during hospitalization as active or inactive inpatient users. Univariate and several logistic and linear regression models were used for analysis.

RESULTS

Of total patients, 2352 (51.2%) were portal adopters, and of them, 632 (26.8%) were active inpatient users. Portal adoption was associated with patients who were young, female, married, with higher income, and had more frequent hospitalizations (P < .05). Active inpatient use was associated with patients who were young, married, nonlocals, with higher disease severity, and were hospitalized for medical treatment (P < .05). In univariate analyses, self-management knowledge scores were higher among adopters vs nonadopters (84.3 and 80.0, respectively; P = .01) and among active vs inactive inpatient users (87.0 and 83.3, respectively; P = .04). In regression models adjusted for age and disease severity, the association between portal behaviors and majority of measures were not significant (P > .05).

CONCLUSIONS

Over half of our cancer inpatients adopted a portal prior to hospitalization, with increased adoption associated with predisposing and enabling determinants (eg: age, sex, marital status, income), and increased inpatient use associated with need (eg: nonlocal residence and disease severity). Additional research and greater effort to expand the portal functionality is needed to impact inpatient outcomes.

Explaining Obesity- and Smoking-related Healthcare Costs through Unconditional Quantile Regression

Background: This paper assesses obesity- and smoking-related incremental healthcare costs for the employees and dependents of a large U.S. employer. Objectives: Unlike previous studies, this study evaluates the distributional effects of obesity and smoking on healthcare cost distribution using a recently developed econometric framework: the unconditional quantile regression (UQR). Methods: Results were compared with the traditional conditional quantile regression (CQR), and the generalized linear modeling (GLM) framework that is commonly used for modeling healthcare cost. Results: The study found strong evidence of association of healthcare costs with obesity and smoking. More importantly, the study found that these effects are substantially higher in the upper quantiles of the healthcare cost distribution than in the lower quantiles. The insights on the heterogeneity of impacts of obesity and smoking on healthcare costs would not have been captured by traditional mean-based approaches. The study also found that UQR impact estimates were substantially different from CQR impact estimates in the upper quantiles of the cost distribution. Conclusions: These results suggest the potential role that smoking cessation and weight management programs can play in arresting the growth in healthcare costs. Specifically, given the finding that obesity and smoking have markedly higher impacts on high-cost patients, such programs appear to have significant cost saving potential if targeted toward high-cost patients.

Facilitating post-surgical complication detection through sublanguage analysis

Identification of postsurgical complications is the first step towards improving patient safety and health care quality as well as reducing heath care cost. Existing NLP-based approaches for retrieving postsurgical complications are based on search strategies. Here, we conduct a sublanguage analysis study using free text reports available for a cohort of patients with postsurgical complications identified manually to compare the keywords identified by subject matter experts with words/phrases automatically identified by sublanguage analysis. The results suggest that search-based approaches may miss some cases and the sublanguage analysis results can be used as a base to develop an information extraction system or support search-based NLP approaches by augmenting search queries.

IgG antibodies from dourine infected horses identify a distinctive Trypanosoma equiperdum antigenic pattern of low molecular weight molecules

Diagnosis and control of dourine is strongly based on serological evidence, but knowledge of the humoral response of horses during infection is limited. In this study we developed a chemiluminescent immunoblotting (cIB) assay to characterise the Trypanosoma equiperdum antigen pattern recognised by IgGs from naturally or experimentally dourine-infected horses and analyse the kinetics of IgG humoral response following the infection. One compounding factor is that sera from uninfected animals often cross-react with T. equiperdum antigens. Development of the cIB assay was based on the hypothesis that serum IgGs from healthy and infected animals recognise different T. equiperdum antigen patterns. We used sera from 8 naturally infected horses which had recovered from Italian outbreaks and 2 experimentally infected mares. In addition, sera from 10 healthy control animals, eight of which were CFT positive but IFA negative for dourine, were collected from disease free regions. Sera were compared by the complement fixation test (CFT), indirect immune fluorescence (IFA) and the cIB assay. cIB analysis revealed that IgGs from infected horses, in contrast to IgGs from healthy horses, specifically recognise a T. equiperdum antigenic profile with low molecular weight bands ranging between 16 and 35 kDa. A time course experiment indicated that IgGs specific for the 16-35 kDa parasite protein fraction appear 17 days post-infection. The cIB assay confirmed all ten infected animals as positive and all controls as negative. This study demonstrated that analysis of IgGs by cIB can provide clear confirmation of trypanosome infection in horses, suggesting that this technique can be applied as a confirmatory serological test for dourine infection.

What is preventable harm in healthcare? A systematic review of definitions

Background

Mitigating or reducing the risk of harm associated with the delivery of healthcare is a policy priority. While the risk of harm can be reduced in some instances (i.e. preventable), what constitutes preventable harm remains unclear. A standardized and clear definition of preventable harm is the first step towards safer and more efficient healthcare delivery system. We aimed to summarize the definitions of preventable harm and its conceptualization in healthcare.

Methods

We conducted a comprehensive electronic search of relevant databases from January 2001 to June 2011 for publications that reported a definition of preventable harm. Only English language publications were included. Definitions were coded for common concepts and themes. We included any study type, both original studies and reviews. Two reviewers screened the references for eligibility and 28% (127/460) were finally included. Data collected from studies included study type, description of the study population and setting, and data corresponding to the outcome of interest. Three reviewers extracted the data. The level of agreement between the reviewers was calculated.

Results

One hundred and twenty seven studies were eligible. The three most prevalent preventable harms in the included studies were: medication adverse events (33/127 studies, 26%), central line infections (7/127, 6%) and venous thromboembolism (5/127, 4%). Seven themes or definitions for preventable harm were encountered. The top three were: presence of an identifiable modifiable cause (58/132 definitions, 44%), reasonable adaptation to a process will prevent future recurrence (30/132, 23%), adherence to guidelines (22/132, 16%). Data on the validity or operational characteristic (e.g., accuracy, reproducibility) of definitions were limited.

Conclusions

There is limited empirical evidence of the validity and reliability of the available definitions of preventable harm, such that no single one is supported by high quality evidence. The most common definition is “presence of an identifiable, modifiable cause of harm”.

Demonstration of differences in virulence between two Theileria parva isolates

In areas with a low incidence of infection due to unimodal presence of ticks, Theileria parva has been observed to induce a disease with relatively low pathology. This is followed by a carrier state, rather than death and therefore provides a better chance of transmission of the parasite back to the tick vector since in unimodal conditions, the different tick stages occur at different times. One isolate from such an area in Zambia, T. parva Chitongo, was compared for virulence with T. parva Muguga, isolated from an area exhibiting a continuous presence of all vector stages in East Africa. To reduce any variation due to infection dose, an in vitro standardized dose was used to initiate infection of groups of three local zebu cattle with each isolate. Parameters of virulence measured were prepatent period, fever, survival (based on ECF index), parasitosis, piroplasm parasitaemia and hematological parameters. Our results suggest that T. parva Chitongo developed a slightly later onset (1-2 days) and lower levels of parasitosis in the lymph node, causing less and later mortality. Comparison of the in vitro rate of transformation confirmed that the time needed to transform an infected lymphocyte took 4 days longer for T. parva Chitongo than T. parva Muguga. Elucidating the mechanism responsible for the lower virulence of T. parva Chitongo could be useful for designing an attenuated vaccine.

Demonstration of two allelic forms of the bovine T cell antigen Bo5 (CD5) and studies of their inheritance

Two monoclonal antibodies (mAbs), CC17 and IL-A67, which are specific for the bovine equivalent of the CD5 antigen, Bo5, were each found to react with the cells of some animals but not others. The cattle tested were all positive for one or both of the mAbs, but the level of expression on cells expressing both determinants was slightly lower than that on cells expressing either of the determinants on their own. Both mAbs precipitated an antigen of 67 kD. However, sequential immunoprecipitation experiments with cells that reacted with both mAbs demonstrated that the determinants are present on two different sets of molecules. These findings suggested that the mAbs recognize two co-dominantly expressed allelic forms of Bo5. This was confirmed in family studies, with groups of full- and half-sibling offspring of sires and dams of defined phenotypes. These experiments also showed that the gene encoding the Bo5 antigen is not linked to the major histocompatibility complex (MHC). The frequencies of the two alleles, which have been designated Bo5.1 and Bo5.2, in the cattle populations tested were 100% and 0%, respectively, in Bos taurus, and 10% and 90%, respectively, in Bos indicus.

Evaluating the relative clinical efficiency of family medicine satellite clinics

A study was conducted to evaluate the impact of decentralization in family medicine clinic services by comparing utilization of services in 3 satellite clinics to utilization patterns of patients served at the hub clinic. It was expected that a hub clinic would be more efficient than satellite clinics because of tighter administrative control and economies of scale. Stable chronically ill patients were used as a homogeneous tracer condition in a secondary analysis of 12 months of archival data. Three types of service use were analyzed: laboratory visits, x-ray visits, and visits to specialists. Among 1,410 stable chronically ill family medicine patients, 303 (21.5%) had 10 more laboratory visits, 222 (15.7%) had 2 or more x-ray visits, and 617 (43.8 %) had 2 or more visits to a specialist. Patients at one of the satellite clinics had greater odds of receiving 2 or more x-rays but lower odds of receiving 10 or more laboratory visits, in comparison with the hub clinic. Patients at the other 2 satellite clinics did not differ from hub patients for any type of service use. Overall, stable chronically ill patients were treated with approximately equal clinical efficiency in our satellite clinics. Some differences in efficiency may occur in some clinics, but these appear to be idiosyncratic rather than due to clinic size or distance from central control.

Impact of open-access scheduling on realized access

Open-access or advanced-access scheduling, which opens the clinic calendar to patients without requiring them to schedule far in advance of the visit, is being introduced in primary care for the purpose of improving access. None of the evaluations reported to date have measured differences in actual visits that might be associated with different scheduling systems. The purpose of this study was to compare utilization of visits to primary care providers for patients served by an open-access clinic with utilization patterns of patients served at clinics not using open-access scheduling. We hypothesized that the odds that a continuing patient received more than one primary care visit would be greater in the clinic where open-access scheduling was in use than in comparison clinics. Our study provides mixed support for the hypotheses. After adjustment for case mix, stable chronic patients treated in open-access clinics may sometimes have greater odds of receiving two or more preventive care visits. However, these effects do not occur in all clinics, suggesting that other clinic characteristics may overcome the effects of open-access scheduling.

Gene expression profiling in a mouse model for African trypanosomiasis

This study aimed to provide the foundation for an integrative approach to the identification of the mechanisms underlying the response to infection with Trypanosoma congolense, and to identify pathways that have previously been overlooked. We undertook a large-scale gene expression analysis study comparing susceptible A/J and more tolerant C57BL/6 mice. In an initial time course experiment, we monitored the development of parasitaemia and anaemia in every individual. Based on the kinetics of disease progression, we extracted total RNA from liver at days 0, 4, 7, 10 and 17 post infection and performed a microarray analysis. We identified 64 genes that were differentially expressed in the two strains in non-infected animals, of which nine genes remained largely unaffected by the disease. Gene expression profiling at stages of low, peak, clearance and recurrence of parasitaemia suggest that susceptibility is associated with high expression of genes coding for chemokines (e.g. Ccl24, Ccl27 and Cxcl13), complement components (C1q and C3) and interferon receptor alpha (Ifnar1). Additionally, susceptible A/J mice expressed higher levels of some potassium channel genes. In contrast, messenger RNA levels of a few immune response, metabolism and protease genes (e.g. Prss7 and Mmp13) were higher in the tolerant C57BL/6 strain as compared to A/J.

Pathology of Tnf-deficient mice infected with Plasmodium chabaudi adami 408XZ

Tumor necrosis factor alpha (Tnf) plays a pleiotropic role in murine malaria. Some investigations have correlated Tnf with hypothermia, hyperlactatemia, hypoglycemia, and a suppression of the erythropoietic response, although others have not. In this study, we have evaluated parasitemia, survival rate and several pathological features in C57BL/6JTnf(-/-) and C57BL/6JTnf(+/+) mice after infection with Plasmodium chabaudi adami 408XZ. Compared to the C57BL/6JTnf(+/+) mice, C57BL/6JTnf(-/-) mice showed increased parasitemia and decreased survival rate, whereas blood glucose, blood lactate and body weight were not significantly different. However, C57BL/6JTnf(-/-) mice suffered significantly more from severe anemia and hypothermia than C57BL/6JTnf(+/+) mice. These results suggest that Tnf is an important mediator of parasite control, but not of anemia development. We hypothesize that the high mortality observed in the Tnf knock-out mice is due to increased anemia and pathology as a direct result of increased levels of parasitemia.

Bovine trypanotolerance: A natural ability to prevent severe anaemia and haemophagocytic syndrome?

Trypanotolerance is the capacity of certain West-African, taurine breeds of cattle to remain productive and gain weight after trypanosome infection. Laboratory studies, comparing Trypanosoma congolense infections in trypanotolerant N'Dama cattle (Bos taurus) and in more susceptible Boran cattle (Bos indicus), confirmed the field observations. Experiments using haemopoietic chimeric twins, composed of a tolerant and a susceptible co-twin, and T cell depletion studies suggested that trypanotolerance is composed of two independent traits. The first is a better capacity to control parasitaemia and is not mediated by haemopoietic cells, T lymphocytes or antibodies. The second is a better capacity to limit anaemia development and is mediated by haemopoietic cells, but not by T lymphocytes or antibodies. Weight gain was linked to the latter mechanism, implying that anaemia control is more important for survival and productivity than parasite control. Anemia is a marker for a more complex pathology which resembles human haemophagocytic syndrome: hepatosplenomegaly, pancytopenia and a large number of hyperactivated phagocytosing macrophages in bone marrow, liver and other tissues. Thus, mortality and morbidity in trypanosome-infected cattle are primarily due to self-inflicted damage by disproportionate immune and/or innate responses. These features of bovine trypanotolerance differ greatly from those in murine models. In mice, resistance is a matter of trypanosome control dependent on acquired immunity. However, a model of anaemia development can be established using C57BL/6J mice. As in cattle, the induction of anaemia was independent of T cells but its development differed with different trypanosome strains. Identification of the molecular pathways that lead to anaemia and haemophagocytosis should allow us to design new strategies to control disease.

Prevention of wound contamination using DuraPrep solution plus Ioban 2 drapes

The use of the preoperative skin preparation DuraPrep is thought to enhance the adhesion qualities of an incise drape. If there is less drape lift it was hypothesized that there may be a reduction in wound contamination. We did a single-center, randomized trial to determine if a preoperative skin preparation containing DuraPrep solution plus Ioban 2 drapes reduced wound contamination in total joint replacement surgery compared with a povidone iodine scrub and paint plus Ioban 2 drapes. Secondary research questions focused on comparisons of differences in drape lift and cost between the two groups. Of the 176 evaluable patients, the proportion of patients with a contaminated wound was similar in the two groups (DuraPrep 28.0% versus povidone iodine 36.4%). The mean drape lift in the DuraPrep group was less than the povidone iodine group (1.5 cm versus 9.9 cm respectively). The mean cost of prepping was lower for the DuraPrep group compared with the povidone iodine group (dollars 93.36 and dollars 248.91, respectively). A preoperative skin preparation regimen containing DuraPrep solution plus Ioban 2 drapes is equivalent to a povidone iodine scrub and paint and Ioban 2 for the prevention of wound contamination during total joint replacement surgery. Improved drape lift and cost may influence the choice between the two methods.

TNF-alpha mediates the development of anaemia in a murine Trypanosoma brucei rhodesiense infection, but not the anaemia associated with a murine Trypanosoma congolense infection

Development of anaemia in inflammatory diseases is cytokine-mediated. Specifically, the levels of tumour necrosis factor-alpha (TNF-alpha), produced by activated macrophages, are correlated with severity of disease and anaemia in infections and chronic disease. In African trypanosomiasis, anaemia develops very early in infection around the time when parasites become detectable in the blood. Since the anaemia persists after the first waves of parasitaemia when low numbers of trypanosomes are circulating in the blood, it is generally assumed that anaemia is not directly induced by a parasite factor, but might be cytokine-mediated, as in other cases of anaemia accompanying inflammation. To clarify the role of TNF-alpha in the development of anaemia, blood parameters of wild type (TNF-alpha+/+), TNF-alpha-null (TNF-alpha-/-) and TNF-alpha-hemizygous (TNF-alpha-/+) trypanotolerant mice were compared during infections with the cattle parasite Trypanosoma congolense. No differences in PCV, erythrocyte numbers or haemoglobin were observed between TNF-alpha-deficient and wild type mice, suggesting that the decrease in erythrocytes was not mediated by TNF-alpha. Erythropoetin (EPO) levels increased during infection and no significant differences in EPO levels were observed between the three mouse strains. In contrast, during an infection with the human pathogen Trypanosoma brucei rhodesiense, the number of red blood cells in TNF-alpha-deficient mice remained significantly higher than in the wild type mice. These data suggest that more than one mechanism promotes the development of anaemia associated with trypanosomiasis.

Comparison of pathology in susceptible A/J and resistant C57BL/6J mice after infection with different sub-strains of Plasmodium chabaudi

Susceptible A/J and more resistant C57BL/6J mice were infected with Plasmodium chabaudi chabaudi 54X, P.c. chabaudi AS and Plasmodium chabaudi adami 408XZ. As expected, most C57BL/6J mice survived the infections with the different isolates. But in contrast to previous observations, not all A/J mice succumbed to infection: just over 50% of A/J mice survived infections with P.c. chabaudi 54X, while 80% survived P.c. chabaudi AS. The more virulent parasite, P.c. adami 408XZ, was able to kill all A/J mice and 20% of C57BL/6J mice after an intravenous infection with 10(5) pRBC. A detailed study of four parameters of pathology (body weight, body temperature, blood glucose and RBC counts) in both mouse strains after a P.c. adami 408XZ infection showed similar patterns to those previously reported after infection with P.c. chabaudi AS. These data suggest that environmental factors as well as parasite polymorphisms might influence the severity of malaria between susceptible and resistant mice.

Identification of mechanisms of natural resistance to African trypanosomiasis in cattle

Natural resistance to African trypanosomiasis in certain Bos taurus cattle in West Africa, called trypanotolerance, may hold solutions for control of this economically crippling disease. Comparison of immune responses between trypanotolerant and trypanosusceptible cattle have shown some differences in antibody response, complement level and cytokine expression, but it is not known whether these differences are the cause of resistance. Two experiments were carried out to assess the contribution of the immune and haemopoietic systems to trypanotolerance. The production of haemopoietic chimaeras from trypanotolerant and susceptible twin calves and comparison of their responses after infection with singleton calves, allowed an assessment of the role of the haemopoietic system in trypanotolerance. An in vivo depletion of CD4 cells in the two breeds allowed an appraisal of the role of T and B lymphocytes in trypanotolerance. The results of the two experiments suggest that natural resistance comprises at least two mechanisms, an innate mechanism that controls parasite growth, and another, involving the haemopoietic system, that is able to limit anaemia. This supports the hypothesis that innate mechanisms in trypanotolerant cattle are more efficient in controlling disease, making them less reliant on antibody responses.

Identity of activation molecule 3 on superantigen-stimulated bovine cells is CD26

Most CD8(+) T cells in cultures of bovine mononuclear cells stimulated with staphylococcal enterotoxin C1 develop an unusual phenotype characterized by expression of activation molecule 3 (ACT3). This superantigen-dependent phenotype may be relevant to immunopathogenesis mediated by certain microbial toxins. The size and N-terminal sequence of immunoprecipitated ACT3 indicate that ACT3 is the bovine orthologue of CD26.

An accessory role for the diacylglycerol moiety of variable surface glycoprotein of African trypanosomes in the stimulation of bovine monocytes

The membrane-associated form of the variable surface glycoprotein (mfVSG) from African trypanosomes is a potent macrophage activator capable of inducing production of tumor necrosis factor alpha (TNFalpha) in both bovine and murine models. Using a bovine model, we have re-investigated the hypothesis that the diacylglycerol moiety of the glycosylphosphatodylinositol (GPI) anchor is involved in macrophage activation and might be the actual parasite toxin. The anchor of the variable surface glycoprotein (VSG) was labeled with (3)H-myristic acid and VSG purified in its membrane-associated form. The dimyristylglycerol moiety of the anchor was released by phospholipase C cleavage. Integrity of the anchor and efficiency of cleavage was verified by autoradiography and methanol:hexane extraction. For analysis of biological function, bovine monocytes were used which had been incubated with bovine interferon gamma (primed) or with culture medium (unprimed). The VSG purified in its membrane-associated form was found to stimulate both primed and unprimed cells to secrete TNFalpha. The same preparation from which the dimyristylglycerol moiety had been cleaved was no longer able to stimulate unprimed cells but could still stimulate primed cells. Our data indicate that the presence of the dimyristylglycerol is not an absolute requirement for induction of TNFalpha production but can substitute for the interferon gamma priming. Therefore, we favor the hypothesis that stimulation of macrophages to secrete TNFalpha by the mfVSG is mediated by an as yet unknown trigger moiety and is facilitated by the dimyristylglycerol anchor.

Trypanosome non-specific IgM antibodies detected in serum of Trypanosoma congolense-infected cattle are polyreactive

Serum Ig from Trypanosoma congolense-infected cattle were affinity-purified using immobilised trypanosome or non-trypanosome antigens (beta-galactosidase, cytochrome C and ferritin). The bound and unbound IgG and IgM fractions were collected and tested in ELISA for reactivity to each antigen. The results indicated that the presence of reactivity to non-parasite antigens in serum of infected cattle is due to polyreactive IgM antibodies. However, the IgG fraction only bound to trypanosome antigens and was only present in post-infection sera, indicating that it was induced by the infecting trypanosomes. Since the polyreactive IgM antibodies were also present in pre-infection sera, it is probable that they were natural antibodies that were not induced but only amplified by the trypanosome infection.

B-1-like cells exist in sheep. Characterization of their phenotype and behaviour

Two populations of B lymphocytes, B-1 (CD5+ and/or CD11b+) and B-2 (CD5- and CD11b-) cells have been described. In mice, which is the species of reference for B-1 and B-2 cell studies, these two subsets present different developmental schemes, phenotypes, antibody repertoires, localization and behaviours. Interestingly, in sheep, B cells rearrange their immunoglobulin (Ig) loci around the neonatal period, similarly to murine B-1 cells. However, the phenotype of the sheep B cells has not been characterized with regards to their developmental pathway. In this report, we show that two sheep B-cell subsets can be distinguished on the basis of CD11b expression. Relative to CD11b- B cells, the CD11b+ B cells frequently co-express CD5, CD11c, higher levels of surface IgM (sIgM), show larger cell size and higher cell-cycling activity, and thus present a B-1-like phenotype. However, unlike murine B-1 cells, sheep B-1 like cells mainly localize in blood, display a higher propensity to spontaneous apoptosis relative to B-2-like cells, and proliferate after sIgM stimulation. Our data show that despite neonatal immunoglobulin loci rearrangements, sheep B cells do not all express a B-1-like phenotype. However, B-1-and B-2-like cells co-exist and present phenotypic and behavioural specificities. Nevertheless, sheep B-1-and B-2-like cells differ from the murine B-1 and B-2 cells in their cell behaviour. These subsets can thus not be considered as true homologues among species.

Effective in vivo depletion of T cell subpopulations and loss of memory cells in cattle using mouse monoclonal antibodies

Conditions were established to obtain depletion of T lymphocyte subsets in lymphoid tissues of calves by injection of mouse monoclonal antibodies to T cell antigens. Adverse reactions were avoided by injecting small quantities of antibody, until target cells had disappeared from blood. Two different mechanisms appeared to be responsible for elimination of the target cells. Rapid depletion of T cells was associated with complement-binding antibody isotypes (IgG2a, IgM), suggesting a complement-mediated mechanism. Clearance of T cells after several days was observed with a non complement-binding isotype (IgG1), suggesting phagocytosis or induction of apoptosis as possible mechanisms. Clearance of the cells in peripheral blood and spleen was obtained with 10-20 mg of anti-CD4 or anti-CD8, but almost ten times as much was needed to obtain depletion of the cells in lymph nodes and Peyer's patches. Depletion lasted for 12 days for CD4 T cells and 3 weeks for CD8 T cells. Successful and lasting depletion (at least 2 weeks) was also obtained with other T cell reagents, such as anti-CD2 and anti-WC1 (gamma/delta T cells). Although B lymphocytes could be removed by a complement-binding antibody, complete depletion of these cells only lasted for a few hours, probably because B cells regenerate faster than T cells. T cell function was severely inhibited when CD4+ T cells were depleted. Stimulation of T cells with foot and mouth disease viral antigen (FMDV) in vaccinated calves was non-existent after depletion. Even 2 months after restoration of normal CD4 T cell levels in blood, activity to FMDV was low. This suggested that the depleted T cells were replaced by naive cells.

Proteolytic cleavage of surface proteins enhances susceptibility of lymphocytes to invasion by Theileria parva sporozoites

A flow cytometric method using anti-parasite antibodies was developed to measure binding of Theileria parva sporozoites to the target bovine lymphocyte membrane. Parasite-host cell interactions could be inhibited by monoclonal antibodies to bovine MHC class I and partially by one of two antibodies to BoCD45R. Proteolysis of the lymphocyte surface removed CD45R but not MHC class I determinants, and enhanced sporozoite binding. These observations support the hypothesis that CD45R and CD45R antibodies may nonspecifically prevent close approximation between sporozoites and lymphocytes. Interestingly, under normal conditions, sporozoites of T. parva did not attach to lymphocytes from goats, but did so when the cells were treated with the protease, suggesting that receptor(s) for T. parva sporozoites might be present on caprine cells but are not easily accessible. These and other results indicate that proteases may be involved in binding and entry of T. parva sporozoites. Electron microscopy revealed that the process of binding and entry of sporozoites into protease-treated goat lymphocytes was very similar to that of the bovine cells. However, schizonts did not develop and lymphocyte proliferation was not induced, indicating that cell entry by sporozoites and cellular transformation are separate processes.

CD5+ B lymphocytes are the main source of antibodies reactive with non-parasite antigens in Trypanosoma congolense-infected cattle

Mice infected with African trypanosomes produce exceptionally large amounts of serum IgM, a major part of which binds to non-trypanosome antigens such as trinitrophenol and single-strand DNA. In this paper, we describe that in cattle infected with Trypanosoma congolense and T. vivax, similar antibodies are found, although they bind mainly to protein antigens, such as beta-galactosidase, ovalbumin and ferritin. The parasite non-specific IgM antibodies appear around the same time as the parasite-specific antibodies, but their origin and function are not clear. We tested the hypothesis that CD5+ B cells (or B-1 cells), which increase during trypanosome infections in cattle, are responsible for production of antibodies to non-trypanosome antigens. Splenic CD5+ and CD5- B cells from infected cattle were sorted and tested in a single cell blot assay. The numbers of immunoglobulin-secreting cells were similar in both B-cell populations. However, antibodies with reactivity for non-trypanosome antigens were significantly more prevalent in the CD5+ B-cell fraction and were exclusively IgM. The preference for production of these antibodies by CD5+ B cells and the expansion of this subpopulation during infections in cattle, strongly suggest that CD5+ B cells are the main source of trypanosome non-specific antibodies. We propose that these antibodies are natural, polyreactive antibodies that are predominantly secreted by CD5+ B cells. Since B-1 cells are up-regulated in many states of immune insufficiency, the immunosuppression associated with trypanosome infections may be responsible for the increase of this subset and the concomitant increase in trypanosome non-specific antibodies.

Surface Ig on B lymphocytes from cattle and sheep

IgD, first demonstrated in humans, has been unequivocally shown to exist in primates and rodents. In addition to IgM a second unique membrane isotype, generally considered to be IgD, has been demonstrated in a number of other species, including dogs and chickens. Because of its assumed widespread presence, it is widely accepted that IgD is phylogenetically conserved and therefore functionally important in B cell maturation. In the present paper, we could not demonstrate IgD on bovine B cells derived from peripheral blood, lymph nodes, spleen and fetal spleen by precipitation with anti-light chain antibodies. This lack of detectable IgD was confirmed in peripheral blood B cells of sheep, and raises questions on the requirement for IgD in cell differentiation and Ig secretion. At present it is not clear whether cattle (and sheep) are an exception in this context. Reports of the presence of IgD in different species are largely based on the assumption that non-IgM surface Ig is most likely IgD. Our data question this extrapolation and stress the need for further isotype characterization of the surface Ig in different species. Lack of surface IgD has been observed in human and mouse B-1 cells, most of which express the surface marker CD5. The possibility that all bovine B cells belong to the B-1 lineage is discussed.

Analysis of monoclonal antibodies specific for the gamma delta TcR

gamma delta T cells in ruminants can be subdivided in two or more subpopulations on the basis of the expression of surface antigen WC1, which can exist in different isoforms. In this study, 18 monoclonal antibodies (mAbs) submitted to the Third International Workshop that were predicted to react with gamma delta TcR molecules were analysed and expression of their antigens was investigated on the different gamma delta T cell subpopulations. A set of control mAbs positive for TcR1 (86D), BoCD3 (MM1A), WC1 (B7A1, BAQ4A, CACTB32A, and BAQ89A) was included for comparative studies. Previous investigations demonstrated eight of the mAbs immunoprecipitated peptides with apparent M(r)s of 37 and/or 47 kDa, indicating they recognized determinants on the T cell receptor, TcR1. Two color flow cytometric analyses in the present study demonstrated the mAbs formed three groups; group 1, a set of mAbs that recognize TcR1 determinants expressed on all gamma delta T cells and groups 2 and 3, sets of mAbs that recognize TcR1 determinants on some gamma delta T cells: TcR1-N6 and TcR1-N7 respectively. mAbs from the latter groups define families of TcR1 molecules that express either one or both of the determinants. These antigenically distinct forms of TcR1 are expressed in equal proportion on the two gamma delta T cell populations that express one of the mutually exclusive isoforms of WC1, WC1-N3 and WC1-N4. The data indicate usage of the mAb-defined families of the gamma delta TcR is primarily restricted to the WC1+ subpopulation of gamma delta T cells. However, a small subpopulation of CD2+, WC1- gamma delta T cells expresses a form of TcR1 positive for the determinant TcR1-N6.

Biochemical analysis of preliminary clusters in the non-lineage panel

After the preliminary clustering of the whole workshop panel using flowcytometry data, we selected those clusters that were composed of mAbs that bound a broad range of cells. To obtain evidence that mAbs in each of these preliminary clusters detected the same antigen, they were tested for their capacity to compete with each other for binding to a target cell and the molecular weights of their antigens were estimated after immunoprecipitation. Most preliminary clusters in the non-lineage panel contained control mAbs that had been characterised in one of the previous workshops, and this study therefore increased the number of mAbs available to each of these non-lineage antigens. One new interesting cluster, BoWC14, was described which defined an antigen on myeloid cells and a subpopulation of CD4, CD8 and WC1 T lymphocytes (BT3/8.12 and IL-A155). An additional cluster, which did not fit into any other panel, contained mAbs specific for an antigen restricted to the erythroid lineage and received the nomenclature BoWC15 (ANA8, IL-A135, IL-A137, IL-A138 and IL-A160).

Ruminant cluster CD71

Two monoclonal antibodies (mAbs) belong to this cluster: IL-A77 and IL-A165. They clustered closely in PC16c. The first mAb, an IgM, was raised against bovine activated B cells, the second was an IgG1 raised against bovine bone marrow cells.

Analysis of monoclonal antibodies reactive with molecules upregulated or expressed only on activated lymphocytes

Monoclonal antibodies potentially specific for antigens expressed or upregulated on activated leukocytes were selected for further analysis from the panel submitted to the third international workshop on ruminant leukocyte antigens. The kinetics of expression of these activation antigens on resting peripheral mononuclear cells (PBMC) and PBMC stimulated with concanavalin A or staphylococcal superantigen SECI for 4, 24 or 96 h were compared, as well as their appearance on various subsets of cells. For some of them, a molecular mass could be determined after immunoprecipitation from radio-labeled, lectin-stimulated cells. Based on the results from the clustering, kinetic studies and biochemical data, evidence was gathered for assigning two additional mAbs to cluster BoCD25 (IL-2 receptor) and two mAbs to cluster BoCD71 (transferrin receptor). Four mAbs recognized an early activation antigen predominantly expressed on gamma delta T cells in short-term cultures. A number of other activation antigens were further characterized.

Characterisation of bovine transferrin receptor on normal activated and Theileria parva-transformed lymphocytes by a new monoclonal antibody

A murine IgM monoclonal antibody (mAb), IL-A77, has been generated that recognises the bovine transferrin receptor (TfR) and will be a useful tool to measure the activation state of bovine lymphocytes and macrophages. The antigen is detected on immature erythroid cells and proliferating lymphocytes. It is undetectable on resting lymphocytes, but appears within 24 h after stimulation with concanavalin A (ConA) or pokeweed mitogen (PWM). Immune precipitations of lysates of both labeled activated lymphocytes and bone marrow erythroid cells showed that, similar to human TfR, the bovine receptor is a disulfide-bonded dimer of two identical chains of M(r) 97,000. A similar 97,000 M(r) protein was eluted from a column containing immobilised bovine transferrin (Tf) using conditions known to elute the human TfR, and this protein was recognised by mAb IL-A77, proving that it detected bovine TfR. Although the mAb inhibited binding of transferrin to its receptor, it did not block proliferation of Theileria parva-transformed or ConA-stimulated lymphocytes. When cells were metabolically labeled with 35S-methionine, a second 90,000-M(r) TfR band was detected in Theileria parva-transformed cells, but not in stimulated lymphocytes. This form of the TfR was not expressed on the cell surface. It may be an.

The role of anti-variable surface glycoprotein antibody responses in bovine trypanotolerance

It has been reported that some breeds of cattle such as the N'Dama mount a more effective antibody response to the variable surface glycoprotein coat of trypanosomes and that this may contribute to their ability to control the infection. Thus we have investigated antibody responses to surface exposed epitopes of the variable surface glycoprotein in Trypanosoma congolense-infected N'Dama (trypanotolerant) and Boran (susceptible) cattle. Similar titres and isotypes were found in both N'Damas and Borans indicating that trypanotolerance is not associated with superior antibody-mediated destruction of trypanosomes. However, significant differences in antibody responses to cryptic VSG epitopes and non-trypanosome antigens were identified. Trypanosusceptible Boran cattle had low IgG1 responses to cryptic epitopes but high IgM responses to non-trypanosome antigens such as beta-galactosidase. In contrast the N'Dama cattle had significantly higher IgG1 responses to cryptic VSG epitopes and negligible responses to beta-galactosidase. These results indicate differences in the induction of anti-trypanosome immune responses between trypanotolerant and susceptible cattle infected with T. congolense.

Characterization of monoclonal antibodies to the alpha IIb beta 3 integrin on bovine platelets

A set of monoclonal antibodies (MoAbs) to leucocyte antigens is an essential tool to identify different cell types and functional membrane molecules involved in immune responses. Since no MoAbs existed to bovine integrins, except against the beta 2 subfamily, we generated MoAbs to beta 3 integrin after the immunization of mice with bovine platelets. Two MoAbs, IL-A164 (IgG2a) and IL-A166 (IgG1), were selected that reacted specifically with bovine platelets and detected the same membrane molecule. The antigen was a heterodimer of two polypeptide chains of 122 kDa and 95 kDa as resolved by SDS-PAGE under reducing conditions. Although the Mr of the smaller subunit is identical to that of beta 2 integrin, preabsorption with an antibody to beta 2 (or CD18) did not remove the bovine antigen. Comparing the molecular masses of the two subunits in reduced and non-reduced forms showed a pattern that was similar to that of human GPIIb/IIIa (also called alpha IIb beta 3 or CD41a). Reduction of the bovine molecule increased the apparent Mr of the light chain from 76 kDa to 95 kDa, while the heavy subunit changed from 136 kDa to 122 kDa. As with human GPIIb, the decrease in Mr of the alpha-subunit is probably a result of a small disulphide-linked polypeptide, although no additional evidence for this was detected for the bovine integrin. Sequencing of the N-terminal amino acids of both bovine polypeptides showed identity of the bovine integrin with human GPIIb/IIIa.

Infected lower extremity extra-anatomic bypass grafts: management of a serious complication in high-risk patients

To determine optimal management and outcome of infected extra-anatomic bypass grafts (EABG), we reviewed 28 patients (19 men and 9 women; mean age 70 years) treated over a 13-year period. Mean follow-up was 42 months. There were 16 axillofemoral (AF), 10 femorofemoral (FF), and two axillopopliteal (AP) grafts. Risk factors included previous prosthetic graft infection in 13 patients, enterocutaneous fistula in two, and mycotic aortic aneurysm in one. Initial management involved complete graft excision in 12 patients, partial graft excision in 10, and nonresectional therapy in six. Failure of nonresectional therapy and partial excision in three patients each required further operative intervention with graft excision. Reconstruction in patients eventually requiring graft excision (n = 25) entailed placement of a new prosthetic AF or AP graft in eight, an autogenous FF graft in five, combined prosthetic AF and autogenous FF bypass in two, autogenous iliofemoral bypass in one, obturator bypass in one, or no reconstruction in eight. Four autogenous FF reconstructions thrombosed immediately postoperatively, and three prosthetic reconstructions became infected. The mortality rate was 18% (FF = 20%, AF = 19%, AP = 0%). The amputation rate was 25% (AP = 100%, AF = 25%, FF = 10%) and was higher without arterial reconstruction (56% vs. 12%, p = 0.02). Two patients required hemipelvectomies and one had bilateral hip disarticulation. We conclude that EABG infections can be successfully treated but carry significant morbidity and mortality. Optimal management includes EABG resection and prompt revascularization, bearing in mind the risk of early thrombosis in autogenous grafts and reinfection in prosthetic grafts.