Point-of-care testing and antibiotics prescribing in out-of-hours general practice: a register-based study in Denmark

BACKGROUND

Point-of-care testing may reduce diagnostic uncertainty in case of suspicion of bacterial infection, thereby contributing to prudent antibiotic prescribing. We aimed to study variations in the use of point-of-care tests (C-reactive protein test, rapid streptococcal antigen detection test, and urine dipstick) among general practitioners (GPs) and the potential association between point-of-care testing and antibiotic prescribing in out-of-hours general practice.

METHODS

We conducted a population-based observational register-based study, based on patient contacts with out-of-hours general practice in the Central Denmark Region in 2014-2017. The tendency of GPs to use point-of-care testing was calculated, and the association between the use of point-of-care testing and antibiotic prescribing was evaluated with the use of binomial regression.

RESULTS

Out-of-hours general practice conducted 794,220 clinic consultations from 2014 to 2017, of which 16.1% resulted in an antibiotic prescription. The GP variation in the use of point-of-care testing was largest for C-reactive protein tests, with an observed variation (p90/p10 ratio) of 3.0; this means that the GPs in the 90th percentile used C-reactive protein tests three times as often as the GPs in the 10th percentile. The observed variation was 2.1 for rapid streptococcal antigen detection tests and 1.9 for urine dipsticks. The GPs who tended to use more point-of-care tests prescribed significantly more antibiotics than the GPs who tended to use fewer point-of-care tests. The GPs in the upper quintile of the tendency to use C-reactive protein test prescribed 22% more antibiotics than the GPs in the lowest quintile (21% for rapid streptococcal antigen detection tests and 8% for urine dipsticks). Up through the quintiles, this effect exhibited a positive linear dose-response correlation.

CONCLUSION

The GPs varied in use of point-of-care testing. The GPs who tended to perform more point-of-care testing prescribed more antibiotics compared with the GPs who tended to perform fewer of these tests.

Interprofessional team-based collaboration between designated GPs and care home staff: a qualitative study in an urban Danish setting

BACKGROUND

Being a general practitioner for residents in many care homes may challenge communication with residents, relatives, and care home staff, and potentially lead to lower quality of care. Several countries have therefore introduced different solutions to reduce the number of general practitioners at each care home. In 2017, the designated general practitioner model was introduced at many Danish care homes. This study aimed to evaluate experiences from the interprofessional team-based collaboration between designated general practitioners and care home staff with regular contact with the designated general practitioners in an urban Danish setting.

METHODS

A qualitative design was applied using semi-structured interviews. Eight interviews (three group interviews and five individual interviews) were conducted with four designated general practitioners and seven care home staff members at four care homes in an urban setting of Central Denmark Region, Denmark. The interviews were transcribed verbatim, and data were analysed using content analysis with inspiration from the theory of relational coordination. The study followed the guidelines addressed in the COREQ (Consolidated Criteria for Reporting Qualitative Research) framework.

RESULTS

The initiation of the designated general practitioner model was experienced to contribute to more clear, precise, and timely communication between care homes and the general practitioner. An improved mutual acknowledgement of roles and competencies was experienced between designated general practitioners, care home nurses, and sometimes also social and health care assistants. The more frequent visits by the general practitioners at the care homes, as a result of the designated general practitioner model, resulted in more face-to-face communication between care home staff and designated general practitioners. Professional differences in the interpretation of the patient's needs were still present, which at times caused a frustrating compromise of own professional competencies. An important reason for the overall perception of improved collaboration was attributed to the more frequent dialogue in which the care homes staff and the designated general practitioners exchanged knowledge that could be applied in future patient encounters.

CONCLUSION

The designated general practitioner model implied an improved collaboration between general practitioners and care homes staff. Clear, precise, and timely communication between care homes and the general practitioners, as well as mutual trust and acknowledgement was experienced to be essential for the collaboration. An important reason for the overall perception of an improved collaboration was attributed to the more frequent dialogue (more frequent general practitioner visits at the care homes) in which the care homes staff and the designated general practitioners exchange knowledge which again could be applied in future patient encounters.

Involving patients in medicines optimisation in general practice: a development study of the “PREparing Patients for Active Involvement in medication Review” (PREPAIR) tool

Background

Many patients have multiple health conditions and take multiple medications (polypharmacy). Active patient involvement may improve treatment outcomes and ensure patient-centred care. Yet, patient involvement remains a challenge in clinical practice. We aimed to develop and pilot test a questionnaire-based preparation and dialogue tool, the PREparing Patients for Active Involvement in medication Review (PREPAIR) tool, to encourage the involvement of patients with polypharmacy in medicines optimisation in general practice.

Methods

We conducted a literature review followed by a co-production process to develop the tool: a workshop with six GPs and pilot testing, including observations and interviews, with 22 patients, three GPs and three practice staff. During this process, we made continuous adaptations to the prototype. We analysed the qualitative data thematically, focusing on the development process and mechanisms of impact.

Findings

The final PREPAIR tool included five items concerning the patient’s experience of 1) adverse drug reactions, 2) excess medication, 3) unnecessary medication, 4) medication satisfaction and 5) medication-related topics to discuss with the GP (open-ended question). The applied workflow during testing was as follows; the patient completed the PREPAIR tool at home, to encourage reflection on the medication, and brought it to the GP consultation. During the consultation, the GP and the patient reviewed the patient’s responses and discussed potential medication-related problems. For some patients, the increased reflection led to worries about the medications. Still, the pilot testing showed that, when using the PREPAIR tool, the patients arrived at the clinic well prepared and empowered to speak. From the PREPAIR-supported dialogue, the GPs obtained a better understanding of patients’ perspectives and provided a more patient-centred consultation. For the patients, the PREPAIR-supported dialogue ultimately promoted an increased sense of security, satisfaction and insight into their medication, despite initial worries for some patients.

Conclusions

We developed a brief tool to support active patient involvement in medication review in general practice. The PREPAIR-tool was well received by both patients and GPs and fitted well into the existing clinical practice. Our findings suggest that the PREPAIR-tool can support patient involvement during consultations and facilitate patient-centred care.

Hospitalisation and use of medication of Danish nursing home residents at the end of life

INTRODUCTION

The end-of-life period remains sparsely investigated in Danish nursing home residents. This study aimed to estimate medication use, drug reimbursement for terminal illness and hospital admissions and to compare these estimates between two groups of nursing home residents.

METHODS

This small-scale observational study was based on residents who died while residing in a nursing home in 2019. Medication use was estimated three months before the residents' death. Estimates for residents registered with a GP designated to the nursing home were compared with estimates for residents who maintained their usual GP.

RESULTS

We included 67 residents (mean age: 88 years, 78% female). On average, residents with a designated GP (n = 21) received ten different medications, and residents who maintained their usual GP (n = 46) received seven. In all, 90% of residents were prescribed on average three "often inadequate" medications in their final three months of life. Furthermore, 39 (58%) residents received drug reimbursement for terminal illness; most were residents who maintained their usual GP (65% versus 43%). Among residents who had a designated GP, five (24%) died at the hospital compared with eight (17%) of the residents who maintained their usual GP.

CONCLUSIONS

The residents received many drugs, including "often inadequate" medication, in the three months leading up to their death. No significant differences were found between the two groups. A stronger focus should be placed on optimising end-of-life care for nursing home residents.

FUNDING

Honoraria received from the Danish Medical Association.

TRIAL REGISTRATION

not relevant.

Health care utilization related to the introduction of designated GPs at care homes in Denmark: a register-based study

OBJECTIVE

To investigate the correlation between having designated general practitioners (GPs) in residential care homes and the residents' number of contacts with primary care, number of hospital admissions and mortality.

DESIGN

A retrospective register-based longitudinal study.

SETTING

Forty-two care homes in Aarhus Municipality, Denmark.

SUBJECTS

A total of 2376 care home residents in the period from 1 September 2016 to 31 December 2018.

MAIN OUTCOME MEASURES

We used two models to calculate the incidence risk ratio (IRR) for primary care contacts, hospital admission or dying. Model 1 compared the residents' risk time before with their risk time after implementation of the designated GP model. Model 2 included only risk time after implementation and was based on calculations of successful (rate ≥60%) implementation.

RESULTS

Weighted by time at risk, the proportion of females across the two models ranged from 64% to 68%. The largest group was aged '85-94' years. In Model 1, the mere implementation of the model did not correlate with changes in primary care contacts, hospital admissions, or mortality. Contrarily, in Model 2, residents living in care homes with successful implementation had fewer email contacts (IRR = 0.81, 95%CI: 0.68;0.96), fewer telephone contacts (IRR = 0.78, 95%CI: 0.68;0.90) and fewer hospital admissions (IRR = 0.85, 95%CI: 0.73;0.99), but more home visits (IRR = 1.70, 95%CI: 1.29;2.25) than residents living in care homes with lower implementation rates.

CONCLUSION

The designated GP model seems promising, as a high implementation degree of the model correlated with a reduced the number of acute admissions, short-term admissions and readmissions. Future studies should focus on gaining deeper insight into the mechanisms of the designated GP model to further optimize the model.Key pointsA new care model was introduced in Denmark in 2017, designating dedicated GPs to residential care homes for the elderly.Successful implementation correlated with significantly fewer hospital admissions, specifically for acute admissions, but also with fewer short-term admissions and readmissions.The implementation of the model correlated significantly with fewer e-mail and telephone contacts and with more home visits.Future studies should gain more insight into the mechanisms of the designated GP model to further optimize the model.

Guidance for Implementing Video Consultations in Danish General Practice: Rapid Cycle Coproduction Study

Background

The COVID-19 pandemic has changed various spheres of health care. General practitioners (GPs) have widely replaced face-to-face consultations with telephone or video consultations (VCs) to reduce the risk of COVID-19 transmission. Using VCs for health service delivery is an entirely new way of practicing for many GPs. However, this transition process has largely been conducted with no formal guidelines, which may have caused implementation barriers. This study presents a rapid cycle coproduction approach for developing a guide to assist VC implementation in general practice.

Objective

The aim of this paper is to describe the developmental phases of the VC guide to assist general practices in implementing VCs and summarize the evaluation made by general practice users.

Methods

The development of a guide for VC in general practice was structured as a stepped process based on the coproduction and prototyping processes. We used an iterative framework based on rapid qualitative analyses and interdisciplinary collaborations. Thus, the guide was developed in small, repeated cycles of development, implementation, evaluation, and adaptation, with a continuous exchange between research and practice. The data collection process was structured in 3 main phases. First, we conducted a literature review, recorded observations, and held informal and semistructured interviews. Second, we facilitated coproduction with stakeholders through 4 workshops with GPs, a group interview with patient representatives, and individual revisions by GPs. Third, nationwide testing was conducted in 5 general practice clinics and was followed by an evaluation of the guide through interviews with GPs.

Results

A rapid cycle coproduction approach was used to explore the needs of general practice in connection with the implementation of VC and to develop useful, relevant, and easily understandable guiding materials. Our findings suggest that a guide for VCs should include advice and recommendations regarding the organization of VCs, the technical setup, the appropriate target groups, patients’ use of VCs, the performance of VCs, and the arrangements for booking a VC.

Conclusions

The combination of coproduction, prototyping, small iterations, and rapid data analysis is a suitable approach when contextually rich, hands-on guide materials are urgently needed. Moreover, this method could provide an efficient way of developing relevant guide materials for general practice to aid the implementation of new technology beyond the pandemic period.

Potentially inappropriate medications (PIMs): frequency and extent of GP-related variation in PIMs: a register-based cohort study

OBJECTIVES

Potentially inappropriate medications (PIMs) pose an increasing challenge in the ageing population. We aimed to assess the extent of PIMs and the prescriber-related variation in PIM prevalence.

DESIGN

Nationwide register-based cohort study.

SETTING

General practice.

PARTICIPANTS

The 4.2 million adults listed with general practitioner (GP) clinics in Denmark (n=1906) in 2016.

MAIN OUTCOME MEASURES

We estimated the patients' time with PIMs by using 29 register-operationalised STOPP criteria linking GP clinics and redeemed prescriptions. For each criterion and each GP clinic, we calculated ratios between the observed PIM time and that predicted by multivariate Poisson regressions on the patients. The observed variation was measured as the 90th/10th percentile ratios of these ratios. The extent of expectable random variation was assessed as the 90th/10th percentile ratios in randomly sampled GP populations (ie, the sampled variation). The GP-related excess variation was calculated as the ratio between the observed variation and sampled variation. The linear correlation between the observed/expected ratio for each of the criteria and the observed/expected ratio of total PIM time (for each clinic) was measured by Pearson's rho.

RESULTS

Overall, 294 542 individuals were exposed to 1 44 117 years of PIMs. The two most prevalent PIMs were long-term use (>3 months) of non-steroidal anti-inflammatory drugs (51 074 years of PIMs) or benzodiazepines (48 723 years of PIMs). These two criteria showed considerable excess variation of 2.33 and 3.05, respectively; for total PIMs, this figure was 1.65. For more than half of the criteria, we observed a positive correlation between the specific PIM and the sum of remaining PIMs.

CONCLUSIONS

This study documents considerable variations in the prescribing practice of GPs for certain PIMs. These findings highlight a need for exploring the causal explanations for such variations, which could be markers of suboptimal GP-prescribing strategies.

Medication-related experiences of patients with polypharmacy: a systematic review of qualitative studies

BACKGROUND

We aimed to synthesise qualitative studies exploring medication-related experiences of polypharmacy among patients with multimorbidity.

METHODS

We systematically searched PubMed, Embase and Cumulative Index to Nursing and Allied Health Literature in February 2020 for primary, peer-reviewed qualitative studies about multimorbid patients' medication-related experiences with polypharmacy, defined as the use of four or more medications. Identified studies were appraised for methodological quality by applying the Critical Appraisal Skills Programme checklist for qualitative research, and data were extracted and synthesised by the meta-aggregation approach.

RESULTS

We included 13 qualitative studies, representing 499 patients with polypharmacy and a wide range of chronic conditions. Overall, most Critical Appraisal Skills Programme items were reported in the studies. We extracted 140 findings, synthesised these into 17 categories, and developed five interrelated syntheses: (1) patients with polypharmacy are a heterogeneous group in terms of needing and appraising medication information; (2) patients are aware of the importance of medication adherence, but it is difficult to achieve; (3) decision-making about medications is complex; (4) multiple relational factors affect communication between patients and physicians, and these factors can prevent patients from disclosing important information; and (5) polypharmacy affects patients' lives and self-perception, and challenges with polypharmacy are not limited to practical issues of medication-taking.

DISCUSSION

Polypharmacy poses many challenges to patients, which have a negative impact on quality of life and adherence. Thus, when dealing with polypharmacy patients, it is crucial that healthcare professionals actively solicit individual patients' perspectives on challenges related to polypharmacy. Based on the reported experiences, we recommend that healthcare professionals upscale communicative efforts and involve patients' social network on an individualised basis to facilitate shared decision-making and treatment adherence in multimorbidpatients with polypharmacy.

Patterns of Multimorbidity and Differences in Healthcare Utilization and Complexity Among Acutely Hospitalized Medical Patients (≥65 Years) - A Latent Class Approach

PURPOSE

The majority of acutely admitted older medical patients are multimorbid, receive multiple drugs, and experience a complex treatment regime. To be able to optimize treatment and care, we need more knowledge of the association between different patterns of multimorbidity and healthcare utilization and the complexity thereof. The purpose was therefore to investigate patterns of multimorbidity in a Danish national cohort of acutely hospitalized medical patients aged 65 and older and to determine the association between these multimorbid patterns with the healthcare utilization and complexity.

PATIENTS AND METHODS

Longitudinal cohort study of 129,900 (53% women) patients. Latent class analysis (LCA) was used to develop patterns of multimorbidity based on 22 chronic conditions ascertained from Danish national registers. A latent class regression was used to test for differences in healthcare utilization and healthcare complexity among the patterns measured in the year leading up to the index admission.

RESULTS

LCA identified eight distinct multimorbid patterns. Patients belonging to multimorbid patterns including the major chronic conditions; diabetes and chronic obstructive pulmonary disease was associated with higher odds of healthcare utilization and complexity than the reference pattern ("Minimal chronic conditions"). The pattern with the highest number of chronic conditions did not show the highest healthcare utilization nor complexity.

CONCLUSION

Our study showed that chronic conditions cluster together and that these patterns differ in healthcare utilization and complexity. Patterns of multimorbidity have the potential to be used in epidemiological studies of healthcare planning but should be confirmed in other population-based studies.

A Collaborative Medication Review Including Deprescribing for Older Patients in an Emergency Department: A Longitudinal Feasibility Study

Medication review for older patients with polypharmacy in the emergency department (ED) is crucial to prevent inappropriate prescribing. Our objective was to assess the feasibility of a collaborative medication review in older medical patients (≥65 years) using polypharmacy (≥5 long-term medications). A pharmacist performed the medication review using the tools: Screening Tool of Older Persons’ potentially inappropriate Prescriptions (STOPP) criteria, a drug–drug interaction database (SFINX), and Renbase^® (renal dosing database). A geriatrician received the medication review and decided which recommendations should be implemented. The outcomes were: differences in Medication Appropriateness Index (MAI) and Assessment of Underutilization Index (AOU) scores between admission and 30 days after discharge and the percentage of patients for which the intervention was completed before discharge. Sixty patients were included from the ED, the intervention was completed before discharge for 50 patients (83%), and 39 (61.5% male; median age 80 years) completed the follow-up 30 days after discharge. The median MAI score decreased from 14 (IQR 8-20) at admission to 8 (IQR 2-13) 30 days after discharge (p < 0.001). The number of patients with an AOU score ≥1 was reduced from 36% to 10% (p < 0.001). Thirty days after discharge, 83% of the changes were sustained and for 28 patients (72%), 1≥ medication had been deprescribed. In conclusion, a collaborative medication review and deprescribing intervention is feasible to perform in the ED.

Use of prescription drugs in the older adult population-a nationwide pharmacoepidemiological study

PURPOSE

Multi-morbidity and polypharmacy are common among older people. It is essential to provide a better understanding of the complexity of prescription drug use among older adults to optimise rational pharmacotherapy. Population-based utilisation data in this age group is limited. Using the Danish nationwide health registries, we aimed to characterise drug use among Danish individuals ≥ 60 years.

METHODS

This is a descriptive population-based study assessing drug prescription patterns in 2015 in the full Danish population aged ≥ 60 years. The use of specific therapeutic subgroups and chemical subgroups and its dependence on age were described using descriptive statistics. Profiles of drug combination patterns were evaluated using latent class analysis.

RESULTS

We included 1,424,775 residents (median age 70 years, 53% women). Of all the older adults, 89% filled at least one prescription during 2015. The median number of drug groups used was five per person. The most used single drug groups were paracetamol and analogues (34%), statins (33%) and platelet aggregation inhibitors (24%). Eighteen drug profiles with different drug combination patterns were identified. One drug profile with expected use of zero drugs and 11 drug profiles expected to receive more than five different therapeutic subgroup drugs were identified.

CONCLUSION

The use of drugs is extensive both at the population level and increasing with age at an individual level. Separating the population into different homogenous groups related to drug use resulted in 18 different drug profiles, of which 11 drug profiles received on average more than five different therapeutic subgroup drugs.

Development of the "chronic condition measurement guide": a new tool to measure chronic conditions in older people based on ICD-10 and ATC-codes

PURPOSE

The aim of the study was to develop a comprehensive open-source measurement guide of the most prevalent chronic conditions among persons aged 65+ based on registry data of both diagnoses and prescribed drugs [the chronic condition measurement guide (CCMG)]. Furthermore, to investigate proof of concept of the measurement guide, different years of history and in- and excluding data on prescribed drugs. Finally, to investigate the measurement guide with other measurement guides designed to identify chronic conditions in persons aged 65+.

METHODS

The measurement guide was based on the 200 most prevalent chronic ICD10 codes in the Danish population 65+ years in 2015; the 200 most prevalent chronic ICD10 codes and causes of death in a cohort of 209,337 people who died of non-traumatic causes (January 2011-January 2016). Prescribed drugs were included in the measurement guide based on a literature review and specialist opinions.

RESULTS

We identified 83 different chronic conditions based on 1241 unique ICD-10 codes. Multimorbidity prevalence ranged from 10% (1-year history, excluding prescribing information) to 69% (15-year history, including prescribing information). We identified 95% of the persons with multimorbidity using the 29 most prevalent chronic conditions. Inclusion of these 29 conditions affected the prevalence of multimorbidity and 1-year mortality when the CCMG was compared with other measurement guides.

CONCLUSION

The CCMG is easily implemented using registry data. When implementing the measurement guide 10 years of history and drug prescribing information should be used. Using the CCMG to study multimorbidity, we recommend using at least the 29 most prevalent chronic conditions.

Physicians' Non-Uniform Approach to Prescribing Drugs to Older Patients - A Qualitative Study

Multi-morbidity and polypharmacy are common in older patients and increase their susceptibility to adverse drug events and hospitalizations. Rational drug prescription is critical; however, little is known about physicians' perspectives on how to prescribe drugs for older patients. The aim of this study was to explore physicians' approach to prescribe drugs to older patients, including identifying the drugs that physicians perceive to be risk drugs for older patients and comparing them with established lists of potentially inappropriate medications. Short semi-structured interviews were conducted with 50 medical specialists in 23 different specialities throughout Denmark who had contact with older patients. Content analysis was performed to identify the relevant themes. Regardless of their medical or surgical background and how often they prescribed drugs for older patients in daily work, all physicians expressed a cautious approach when prescribing risk drugs. Despite their shared caution, physicians had different strategies for prescribing drugs to older patients. The following strategies were identified: (1) 'Start low, go slow', (2) 'Trial and error', (3) 'Dose reduction', and (4) 'Never prescribe'. The most frequently mentioned risk drugs considered to cause hospitalization were vitamin K antagonists, opioids and diuretics; these drugs are relatively highly consistent with established lists of PIMs. Physicians were relatively knowledgeable about risk drugs. Although the physicians agreed that a cautious approach was needed when prescribing drugs for older people, there was no consensus about how to best accomplish this in practice.

Recruitment of CD34+ cells during large-volume leukapheresis

Mobilized peripheral blood stem and progenitor cells (PBPCs) are increasingly used to restore hematopoiesis after myeloablative treatment. To obtain a sufficient number of CD34(+) cells, many studies have focused on the improvement of the collection technique during the leukapheresis procedure (LP), and so-called large-volume leukapheresis (LVL) procedures have been developed. Such procedures can be performed by extending the duration of the LP and/or by increasing the inlet flow rate. However, no previous studies have compared the efficiency of these procedures. In the present study, we compared the kinetics of PBPCs recruitment (including CD34(+) cell subsets), the PBPCs yield, and the collection efficiency as well as the overall feasibility of the procedures during a single LVL performed by standard (group I) (median 85 ml/min; range 50-97 ml/min) and high inlet flow rates (group II) (median 130 ml/min; range 110-150 ml/min). Seven patients with hematological malignancies were enrolled and allocated to each group. The patients' blood volumes (BV) were processed four times. The apheresis product (AP) was collected in four separate bags, which were changed every time one BV had been processed. The CD34(+) cell number and CD34(+) cell subsets were assessed in the four collection bags and in peripheral blood (PB) before every time one BV had been processed and after the leukapheresis. The CD34(+) cell yield exceeded the pre-apheresis CD34(+) cell number per ml BV in 6 out of 7 patients in group I and in 3 out of 7 patients in group II. In group II, the recruitment of CD34(+) cells from the bone marrow (BM) to PB starts in the second collection period--as early as 30-60 min after initiating the procedure. No exhaustion in the recruitment was observed in the two groups for at least 5 h during the leukapheresis, and all CD34(+) cell subsets were recruited at a steady rate. However, the collection efficiency in group II was only half of that in group I. In addition, we experienced many technical problems during the leukapheresis in group II. Thus, in 4 out of 7 patients in this group, it was not possible to perform the maximal inlet flow rate because of catheter problems. In conclusion, due to the technical problems associated with the high inlet flow rate procedure and the fact that the relative number of CD34(+) cells harvested and recruited during the leukapheresis was higher in group I than II and, also reflected an approximately two-fold higher collection efficiency, we recommend that LVL be performed by standard inlet flow rate.

Extracellular accumulation of bioactive substances during preparation and storage of various platelet concentrates

BACKGROUND

Side effects of platelet transfusion may be associated with infusion of bioactive substances. We therefore studied extracellular accumulation of histamine, plasminogen activator inhibitor (PAI)-1, vascular endothelial growth factor (VEGF), and interleukin (IL)-6 during preparation and storage of various platelet concentrates.

METHODS

Twenty buffy-coat-derived platelet pools (BCPC) were prepared and stored in platelet additive solutions (PAS). Twelve apheresis platelet (APC) units were prepared using the COBE Spectra LRS, and 14 were prepared using the Fenwal Amicus Separator. After preparation half of the content was drawn from each APC unit. The normal ranges of the substances were determined in plasma from all donors, and the extracellular concentrations of the substances were determined in supernatants collected on days 0, 1, 3, 5, and 7 of storage from all platelet preparations.

RESULTS

The platelet counts were not significantly different in BCPC units and APC units. The BCPC units had a significantly higher white cell count than the APC units (P < 0.0001), but the count was significantly higher in the Amicus APC units than in the COBE APC units (P < 0.0001). The extracellular histamine concentration was significantly (P < 0.001) increased in BCPC units after preparation and without further increase during storage, while there was no accumulation of histamine in APC units. After preparation the PAI-1 concentration was significantly (P < 0.02) higher in BCPC units than in APC units, but during storage PAI-1 increased significantly (P < 0.05) more in APC units than in BCPC units. Similarly, VEGF concentration was significantly (P < 0.05) higher in BCPC units than in APC units after preparation. During storage, however, VEGF increased more in BCPC units compared with COBE Spectra APC units (P < 0.05), but compared with Amicus Separator APC units only for the first 3 days of storage. At days 5 and 7 of storage the VEGF concentration was significantly higher in the Amicus APC units than in the COBE APC units (P < 0.05). IL-6 was not detectable in any of the concentrates after preparation or during storage.

CONCLUSION

Platelet concentrates prepared by the apheresis method may contain less white cell derived bioactive substances than platelet concentrates prepared by the buffy-coat method. However, a substantial storage time dependent platelet derived bioactive substance accumulation takes place in all platelet concentrates tested, presumably due to platelet disintegration.

Monoclonal antibodies with neuroblastoma specificity: a flow cytometric analysis of cross-reactivity with CD34+ hematopoietic stem cells

The aim of this study was to evaluate the specificity of a number of monoclonal antibodies (MAbs) used for immunological in vitro purging of stem cell grafts from neuroblastoma patients. The extent of cross-reactivity of 10 neuroblastoma-specific MAbs (NB-MAb) with CD34+ stem cells from 14 leukapheresis products was analyzed. The level of cross-reactivity was analyzed on a Coulter (Fullerton, CA) flow cytometer using biotinylated NB-MAbs. There was a marked difference in the reactivity of the ten NB-MAbs with CD34+ stem cells. The antibodies could be divided into three groups with increasing levels of cross reactivity. Four antibodies (126-4, 5.1 H11, UJ127.11, and 14.G2a) all reacted with median levels of less than 2% (range 0.0 to 5.4) of CD34+ stem cells (median of 14 patients). Another three antibodies reacted with a median of 3.1-4.1% of the stem cells (UJ13A, Ab390, and Ab459) but with a wide range (0.2 to 25.6). Finally, M340, HSAN 1.2, and antiThy-1 reacted with a median of 9-16% of the stem cells (range 0.6 to 51.5). We conclude that there is a significant variation in the proportion of CD34+ stem cells reacting with each of the ten neuroblastoma antibodies investigated in this study. Therefore, to avoid a significant loss of CD34+ cells from the stem cell product, we find it important to carefully consider which antibodies to use for immunomagnetic purging.

Linear reduction of clonal cells in stem cell enriched grafts in transplanted multiple myeloma

In 30 patients with multiple myeloma who were scheduled for peripheral blood stem-cell transplantation, a quantitative analysis of the stem cells following enrichment by anti-CD34 was carried out. To detect the cells of the specific myeloma clone, polymerase chain reaction (PCR) was performed using unique allele-specific oligo primers for the immunoglobulin heavy chain rearrangement. The clonogenic cells before and after stem-cell enrichment, were quantified by a limiting dilution assay and a highly sensitive semi-nested PCR combined with a real-time quantitative PCR. In order to accomplish a statistically adequate end-point analysis, a large number of PCR analyses (40 per sample) were performed. By this technique the lowest detection limit observed was one myeloma cell per 106 cells. Myeloma cells were detected in 29/30 samples from the CD34-enriched fraction. The CD34 selection procedure resulted in a median 28-fold enrichment of CD34+ haemopoietic precursor cells. The stem-cell selection reduced the median concentration of clonal cells per million total cells by half, with a highly significant linear relationship between the number of myeloma cells before and after stem cell enrichment. The median depletion of clonal cells by the overall procedure was 2.15 log units, corresponding to a reduction of the total quantity of clonal cells reinfused into the patients by at least 99.3%. We conclude that CD34+ cell enrichment led to a reliable tumour cell depletion of the order of 2 log, which may not be sufficient since the total number of tumour cells in the leukapheresis product was 7.2 log (median).

BEAM+autologous stem cell transplantation in malignant lymphoma: 100 consecutive transplants in a single centre. Efficacy, toxicity and engraftment in relation to stem-cell source and previous treatment

One hundred consecutive patients with malignant lymphoma treated with high-dose chemotherapy and autologous stem cell transplantation, followed at least 1 yr post-transplant, are reported, 68 with non-Hodgkin's lymphoma and 32 with Hodgkin's disease. At transplant, 23 patients were in first remission, 69 in later chemosensitive disease and 8 were chemotherapy resistant. Based on previous treatment and stem-cell source, the patients were subdivided into 3 cohorts: BMT1: bone-marrow harvest and transplant after > or =3 treatment regimens (38 patients); BMT2: bone marrow harvest and transplant after less than 3 treatment regimens (24 patients); PBSCT: peripheral-blood stem cell transplant (38 patients, 5 of these with CD34+ cell selected PBSC). The 4-yr survival and progression-free survival of all patients was 45 and 40%, respectively. Forty-one patients have died, 27 of lymphoma, evenly distributed in the cohorts. Fourteen treatment-related deaths occurred, 13 of these in the BMT1 cohort, significantly more than in the other cohorts (p=0.001). In univariate survival analysis cohort, age, disease status at transplant and number of previous treatment regimens were significant. In multivariate survival analysis cohort, age and sex were independently significant, women having a shorter survival. The patients transplanted with unselected PBSC had significantly shorter duration of pancytopenia and hospital stay than the otherwise comparable BMT2 patients, but their progression-free survival was identical. We confirm that high-dose therapy with autologous stem cell transplant from blood or bone marrow in not-too-heavily pretreated patients is a safe procedure but will cure only half the patients.

Treatment of relapse after allogeneic BMT with donor leukocyte infusions in 16 patients

Sixteen patients with relapse after allogeneic BMT were treated with donor leukocyte infusions (DLI) from the original donor. The diagnoses at relapse were: CML in chronic phase (CP) (two patients), CML in accelerated phase (AP) (four patients), AML (four patients), MDS (one patient), ALL (four patients) and relapse of Hodgkin's disease (one patient). The patients received a mean of 5.2 x 10(8) leukocytes/kg with a range of 1.4-12.3 x 10(8) leukocytes/kg. Six patients obtained complete remission (CR), one with CML in CP, three with CML in AP, one MDS and one ALL. Partial remission (PR) was seen in three patients, one patient with CML in AP, one with AML and one with Hodgkin's disease. Seven patients had no response (NR) to the infusions, including one patient with CML in CP transplanted with a syngeneic donor. Four patients developed marrow hypoplasia after DLI (three CR and one PR) and two patients (ALL with CR and MDS with CR) were hypoplastic at relapse and marrow hypoplasia continued after DLI. GVHD occurred without GVL, but GVL only occurred in one patient with absence of GVHD. Eleven patients died of leukemia, six patients are alive. Three patients with CML are in CR 12, 12 and 32 months after DLI and one patient with ALL is in CR 15 months after DLI.

Decreased number of CD73 (ecto-5'-nucleotidase) molecules on lymphocytes from patients with primary immunoglobulin deficiencies. Correlation between number of CD73 molecules and T-lymphocyte function in vitro

CD73 is a bifunctional glycosyl phosphatidylinositol anchored leucocyte differentiation antigen which has specific ecto-5'-nucleotidase (ecto-5'-NT) activity and is an accessory T-lymphocyte activation molecule. The aim of the present study was to investigate the CD73 expression on blood mononuclear cells (BMC) from a group of patients with primary immunoglobulin deficiency (IGD). This group of patients had both significantly decreased levels of ecto-5'-NT on BMC (P = 0.002) and decreased numbers of CD73 molecules per CD73+ lymphocyte (P = 0.01). Five of the 10 patients had a decreased percentage of CD73+ lymphocytes. Among B-lymphocytes the patients had normal percentages of CD73+ cells but four of the 10 patients had numbers of CD73 molecules per CD73+ B-lymphocyte below the normal range. Among CD4-lymphocytes three out of 10 patients had percentages of CD73+ below the normal range and four out of 10 patients had decreased percentages of CD73+ CD8-lymphocytes. Significant correlations were found between in vitro proliferative responses to mitogens and the number of CD73 molecules per CD73+ lymphocyte (rs = 0.60, P < 0.01) and per CD73+ CD8-lymphocyte (rs = 0.64, P < 0.02). In addition, a positive correlation was found between ability to proliferate and level of ecto-5'-NT on BMC (rs = 0.53, P < 0.05). Furthermore the ability of BMC to synthesize ecto-5'-NT was studied. During 2 days culture ecto-5'-NT activity increased markedly on BMC from both patients and healthy donors. The level of activity on BMC from all patients attained levels higher than on freshly isolated BMC from healthy donors. This shows that the decreased levels of ecto-5'-NT found on freshly isolated BMC from patients with IGD is due to defective regulation of the enzyme activity in vivo.

[Autologous stem cell transplantation. From bone marrow to selected blood stem cells: 100 consecutive procedures at a single center]

One hundred consecutive autologous stem cell transplants are reported: Non-Hodgkin's lymphoma 51 cases, Hodgkin's disease 27 cases, acute leukaemia 14 cases, multiple myeloma seven cases and chronic myeloid leukaemia one case. Most patients were in their second or later remission. The overall three-year survival for all patients was 60% and the three-year disease-free survival was 50% for lymphoma patients and 30% for acute leukaemia patients. The dominant source of stem cells was bone marrow during 1993, but from 1994 it has been peripheral blood, now totalling 33 cases. There were 12 toxic deaths, all among patients who were heavily treated before bone marrow harvest and transplantation. The patients transplanted with blood stem cells had significantly shorter duration of pancytopenia, and hospital stay, but their disease-free survival was not longer than that of a comparable group of bone marrow transplanted patients. Six patients were transplanted with purified CD34+ cells (selected by avidity column (Ceprate (R)), and had duration of thrombocytopenia and hospital stay similar to the patients transplanted with unmanipulated blood stem cells, but slightly longer duration of neutropenia. We conclude that high-dose therapy with autologous stem cell transplantation in not too heavily pretreated patients is a safe procedure irrespective of the source of stem cells.

No correlation between CD73 expression and ecto-5'-nucleotidase activity on blood mononuclear cells in vitro. Evidence of CD73 (ecto-5'-nucleotidase) on blood mononuclear cells with distinct antigenic properties

Monoclonal antibodies against ecto-5'-nucleotidase (ecto-5'-NT) have been clustered to CD73. The aim of the present study was to elucidate whether specific ecto-5'-NT activity on blood mononuclear cells (BMC) was correlated with CD73 expression measured by flow cytometry. During culture of CD73-negative lymphocytes the percentage of cells with ecto-5'-NT activity increased without there being a comparable increase in CD73 expression. After 2 days' culture, 9% (3-16, median and range given) demonstrated ecto-5'-NT activity, whereas CD73-positive cells comprised only 1.6% (0.0-3.0). These results show the existence of lymphocytes with ecto-5'-NT activity but without expression of CD73. The ecto-5'-NT activity increased significantly (p<0.02) during culture of unseparated BMC, whereas the number of anti-CD73 binding sites did not change. As a consequence. the number of anti-CD73 binding sites per U ecto-5'-NT activity decreased during culture. Exposure to interleukin-4 or prostaglandin E2 changed the enzymatic activity but not the number of anti-CD73 binding sites. Treatment of BMC with phosphatidylinositol-specific phospholipase-C released 57% (51%-75%) of the ecto-5'-NT activity into the supernatants, without a detectable decrease in CD73 expression. The fact that ecto-5'-NT was removed from the supernatant after precipitation with anti-CD73 showed that the released ecto-5'-NT activity was due to enzymatic activity of CD73 molecules. The results of this study indicate that CD73 exists on BMC in isoforms with distinct capacities to bind mouse monoclonal anti-CD73.

In vitro evaluation of a new filter for leucocyte depletion of platelet concentrate during component preparation

A newly developed filter for prestorage leucocyte depletion of platelet concentrates (PC) was studied. The filter is designed for leucocyte depletion during the preparation of the pool PC from platelet rich buffy coats. In all the leucocyte depleted PC (LD-PC) leucocyte depletion was satisfactory. 19 of 20 units of LD-PC had a leucocyte content below 3 x 10(5) per PC and 1 contained 8 x 10(5) leucocytes. The standard PC contained 2.53 x 10(8) (0.87 x 10(8)-15.3 x 10(8); n = 20) leucocytes per PC (median and range). The quality of the LD-PC was evaluated by measuring platelet activation, platelet morphology, and pre- and poststorage pH. There were no differences in any of the parameters studied.

Effects of immunomodulators on ecto-5'-nucleotidase activity on blood mononuclear cells in vitro

In this study the effects of immunomodulators on the ecto-5'-nucleotidase (ecto-5'-NT) activity on blood mononuclear cells (BMC) were examined in vitro. Interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) decreased the level of ecto-5'-NT activity on BMC whereas prostaglandin E2 (PGE2) increased the ecto-5'-NT level. All three immunomodulators influenced the ecto-5'-NT activity of isolated monocytes whereas only IL-4 and PGE2 had an effect on the enzyme level on isolated lymphocytes. The effect was dependent upon protein synthesis. The effect was dose dependent: IL-4 was effective at concentrations down to 0.5 U/ml, IFN-gamma down to 40 U/ml and PGE2 at nanomolar concentrations. These data indicate that immunomodulators may also take part in the regulation of ecto-5'-NT activity on BMC in vivo. BMC from 7 patients with different immunodeficiency syndromes showed decreased ecto-5'-NT activity on freshly isolated cells. However, following culture ecto-5'-NT activity was increased above the level found on freshly isolated BMC from healthy persons. On BMC from 3 patients with hypogammaglobulinaemia, the effect of IL-4 on the level of ecto-5'-NT activity was identical to that found on BMC from healthy donors, whereas PGE2 increased ecto-5'-NT activity on BMC from only 1 of the 3 patients investigated. The decreased ecto-5'-NT activity of BMC from patients with immunodeficiency may thus be due to a defective regulation of ecto-5'-NT activity in vivo.

Natural killer cells lack ecto-5'-nucleotidase

Ecto-5'-nucleotidase (ecto-5'-NUC, EC 3.1.3.5., CD73) is a plasma membrane enzyme, which catalyzes the hydrolytic dephosphorylation of purine nucleotides to the corresponding nucleosides so that they can pass through the plasma membrane. The distribution of ecto-5'-NUC is heterogeneous, but all blood mononuclear cell (BMC) subpopulations investigated until now have had ecto-5'-NUC activity. Purified natural killer (NK) cells were prepared by fluorescence-activated cell sorting of CD16-positive cells (purity 94%). In purified NK cells the ecto-5'-NUC activity was less than 1 U/10(6) as estimated by a radioisotope method. Using a cytochemical assay, the proportion of cells with activity was less than 1%. The most likely explanation is that NK cells have no ecto-5'-NUC activity and that the very small ecto-5'-NUC activity observed in this study was caused by contaminating non-NK cells. NK cells thus constitute the only BMC subset known without ecto-5'-NUC activity.

Complement receptor type 1 (CR1, CD35) expression on peripheral T lymphocytes: both CD4- and CD8-positive cells express CR1

T lymphocytes from 42 healthy blood donors were examined for expression of CR1 on the cell surface using a fluorescence-activated cell sorter. The fraction of CR1-positive T lymphocytes varied in the range from 1 to 8% (median 2.4%). The CR1-positive T lymphocytes constituted a homogeneous group of cells regarding both size and granulation; they seemed to be larger and more granulated than the average T lymphocytes. The CR1-expressing T lymphocytes were found both in the CD4- and in the CD8-positive subpopulations of T lymphocytes, and although the CD4-positive cells expressed CR1 with a slightly higher percentage than did the CD8-positive cells, this difference was not significant. The number of CR1-positive T lymphocytes did not correlate with the level of CR1 on erythrocytes. The presence of CR1 on a small T lymphocyte population suggests that CR1 on T lymphocytes might play a role in the immune regulation.

Elastolytic activity of human blood monocytes characterized by a new monoclonal antibody against human leucocyte elastase. Relationship to rheumatoid arthritis

The leucocyte elastase of human blood monocytes was investigated by applying a new monoclonal antibody which did not block the enzyme activity against elastin. In a fixed population of mononuclear cells (MNC) and using fluorescence activated cell sorting (FACS), the human leucocyte elastase (HLE) antibody identified a subgroup of CD14+ cells which contained all the elastase activity and which could be blocked by a specific chloromethylketone elastase inhibitor. By anti-CD14 labelling the HLE positive cells were identified as monocytes and amounted to 88% of this cell type (median: range 72-96%). In a parallel study of patients with active rheumatoid arthritis (RA) and control donors the elastolytic capacity of PMA-stimulated live MNC was higher for RA patients than for controls (p less than 0.02). For control donors the number of HLE+ cells correlated well to the elastolysis in the same MNC sample (Spearman's rho:0.83, p less than 0.05); in the samples from RA patients no correlation was found between the normal number of HLE+ cells and the increased elastolysis (rho: 0.54, p greater than 0.20).

Indomethacin in vitro and in vivo abolishes post-exercise suppression of natural killer cell activity in peripheral blood

The present study was designed to explain the mechanism of the post-exercise down-regulation of human natural killer (NK) cell activity recently described by us. Fifteen young, healthy volunteers underwent 60 min of bicycle exercise at 75% of maximal oxygen uptake (VO2max). Six of the volunteers were exercised twice with an interval of at least one month. At the second exercise test they received oral indomethacin. Blood samples were collected before and during the last minutes of exercise as well as 2 h and 24 h after work. The NK cell activity (lysis fixed number of mononuclear cells) increased during bicycle exercise, dropped to a minimum 2 h later and returned to pre-exercise levels within 24 h. During bicycle exercise the percentage of NK cells (CD16+ cells) of mononuclear cells increased significantly but returned to normal within 2 h after exercise. Two hours after exercise, however, increased monocyte cell count and neutrophils were found. The in vitro release of prostaglandin E2 from mononuclear cells was increased. Furthermore, the neutrophil chemiluminescence response was also increased in the 2 h post-exercise period; this response is associated with prostaglandin E2 production by neutrophils. Indomethacin, whether administered in vivo or in vitro, fully restored the suppressed post-exercise NK cell activity. Finally, the NK cell activity of monocyte depleted mononuclear cells did not decrease below basal levels after exercise. These findings strongly indicate that prostaglandins released from monocytes and neutrophils are involved in the post-exercise down-regulation of NK cells.

Lack of immunomodulating effect of disulfiram on HIV positive patients

Disulfiram (Antabuse (R)) is metabolized to two molecules of diethyldithiocarbamate, which has been reported to be an immunomodulating agent. In a double blind trial, 15 HIV antibody positive homosexual men were given daily doses of 100 mg or 400 mg of disulfiram or placebo, for 4 weeks. All had a CD4-count below 500 X 10(6)/l and/or a pokeweed mitogen response in a lymphocyte proliferation assay less than 50% of normal controls. None suffered from opportunistic infections. No significant effect of disulfiram on immunological, haematological, biochemical or clinical variables was observed in this short-term trial.

Interleukin 2 receptor expression by human blood lymphocytes after vaccination with pneumococcal polysaccharides

Proliferative responses of unseparated peripheral blood mononuclear cells (PBMC) and blood T cells to recombinant interleukin 2 (rIL-2) were significantly increased 7-21 days after the vaccination with pneumococcal polysaccharides (PPS). In contrast, non-T cells expressed increased responsiveness to rIL-2 only on post-vaccination day 7. Analysis of the proliferative response to rIL-2 among lymphocyte subsets (CD4+Leu8+, CD4+Leu8-, CD8+Leu8+, CD8+Leu8-, CD20+) in cultures of unseparated PBMC revealed that the CD8+Leu8- T cells expressed increased responsiveness 7-14 days after vaccination, whereas neither CD4+ (Leu8+ and Leu8-) nor CD8+Leu8+ T cells showed significantly increased responsiveness after vaccination. The CD20+ B cells, like non-T cells, expressed increased responsiveness to rIL-27 days after the vaccination only. Expression of the 55 kD low-affinity interleukin 2 receptor (IL-2R, CD 25) on freshly isolated PBMC, as judged by direct fluorescence staining with a MoAb anti-55 kD chain, was low (less than 3%) and an increased expression of this receptor was not detected following vaccination. In contrast, binding of 125I-labelled IL-2 to freshly isolated PBMC increased following vaccination (day 7). Scatchard plot analysis revealed a modest increase in the expression of high-affinity IL-2R (Kd = 1-2 pM), whereas the increase in expression of the 75-kD, intermediate-affinity IL-2R (Kd = 300 pM) was more pronounced (from 195 to 295 (means) receptors per PBMC). It is concluded that, following vaccination with PPS increased IL-2R expression is induced on blood lymphocytes. These investigations suggest a role for T cells in the human immune response against PPS.

Natural killer cell activity in peripheral blood of highly trained and untrained persons

Natural killer (NK) cell activity and concentration of CD16+ cells (NK cells) and CD20+ cells (monocytes) in peripheral blood were measured in highly trained racing cyclists and in age- and sex-matched untrained controls. Median NK cell activity was 38.1% (range 20.0%-57.1%) in trained vs 30.3% (range 19.7%-43.1%) in untrained (P = 0.008). Median %CD16+ cells was 17% (range 7%-33%) in trained vs 11% (3%-29%) in untrained (P = 0.007). Indomethacin in vitro enhanced the NK cell activity in both groups. There was, however, no significant difference between the NK cell activity in trained and untrained after exposure to indomethacin in vitro. Indomethacin-enhanced NK cell activity was 45.9% (range 24.4%-67.5%) in trained and 40.0% (range 23.9%-68.5%) in untrained (P = 0.138). Mean %CD14+ cells was 8.3% (range 2%-15%) in trained vs 3.8% (2%-8%) in untrained (P less than 0.0001). The increased NK cell function thus demonstrated in highly trained persons might result in better resistance against infectious disease.

Effect of physical exercise on blood mononuclear cell subpopulations and in vitro proliferative responses

The present study was designed to examine the effect of physical exercise on subsets and proliferative responses of blood mononuclear cells. Sixteen young, healthy volunteers underwent 60 min of bicycle exercise at 75% of maximal oxygen uptake (VO2max). After an interval of at least 1 week, six of the subjects underwent a 60-min back muscle training period at up to 30% of VO2max. Blood samples were collected before and during the last minutes of exercise, as well as 2 and 24 h later. Blood mononuclear cell (BMNC) subpopulations were determined and the proliferative responses after incubation with phytohaemagglutinin (PHA) or purified derivative of tuberculin (PPD), were quantified by [3H]thymidine incorporation. During bicycle exercise the relative blood concentration of T cells (CD3+ cells) declined, mainly due to a fall in T helper cells (CD4+ cells). The natural killer (NK) cell subset (CD16+ cells) increased during work, but reverted after; the monocytes (CD14+ cells) increased 2 h after work, whereas the B-cell subset (CD20+ cells) did not change. BMNC subsets were not significantly changed by back muscle exercise. The PHA-induced proliferative response decreased during bicycle exercise, whereas the PPD-induced response did not change. No significant changes occurred during back muscle exercise. Investigation of subgroups after incubation with [3H]thymidine showed that the proliferative response per CD4+ cell did not change in relation to exercise, but the contribution of the CD4+ subgroup to proliferation declined during bicycle exercise due to the decreased proportion of CD4+ cells. The suppression of the PHA response during bicycle exercise can be explained in part by a relative fall in CD4+ cells. The pool sizes of BMNC subfraction may be elicited by increased catecholamine and cortisol levels.

Inhibition of human lymphocyte proliferation and cleavage of interleukin-2 by Pseudomonas aeruginosa proteases

This study was undertaken to determine the effect of Pseudomonas aeruginosa alkaline protease (AP) and elastase (ELA) on human lymphocyte function. AP at 50 micrograms/ml and ELA at 12 micrograms/ml caused a 50% inhibition of phytohemagglutinin-induced proliferation. There was no difference in the effect of proteases on CD4- and CD8-positive cells. To determine the effect of proteases on interleukin-2 (IL-2)-induced cell proliferation, the proteases and IL-2 were added to the IL-2-dependent CTLL-2 cell line. AP and ELA inhibited the proliferation of these cells. When IL-2 was added in excess, the inhibition was partly reversed. ELA at 10 micrograms/ml cleaved IL-2, as judged by size chromatography of a reaction mixture containing 125I-labeled IL-2 and the proteases. The ELA-digested IL-2 exhibited a reduced binding capacity to IL-2 receptors on the lymphocytes. Furthermore, treatment of phytohemagglutinin-stimulated lymphocytes with AP and ELA resulted in inhibition of binding of intact IL-2 to IL-2 receptors on the stimulated lymphocytes. These results indicated that P. aeruginosa-derived enzymes are able to interfere with human lymphocyte function in vitro and that this effect might be due to cleavage of IL-2.

Interleukin 1-induced down-regulation of antibody binding to CD4 molecules on human lymphocytes

Interleukin 1 (IL-1) is involved in the early activation of T lymphocytes. The CD4 antigen, described as a phenotypic marker of helper T cells, is also important in early T-cell activation by its ability to bind to MHC class II molecules on antigen-presenting cells, and to transmit positive (and negative) signals to the cells. We observed that purified human monocyte IL-1 as well as recombinant IL-1 alpha and IL-1 beta selectively decreased the binding of monoclonal antibodies to CD4 on the surface of otherwise unstimulated blood T cells, in contrast to prestimulated and continuously grown CD4+ cells. Under optimal growth conditions, the initial reduction in antibody binding to CD4 was followed by an apparent re-expression of the CD4 antigen even in the presence of high concentrations of IL-1. This re-expression did not occur if the cells were cultured at 4 degrees C, or after treatment with actinomycin D or cytochalasin B, indicating that protein synthesis and intact microfilament function were essential for re-expression of CD4 binding. The mechanism by which CD4 molecules are physically and/or functionally modulated by IL-1 is unclear.