Automated and app-based activation of first responders for prehospital cardiac arrest: an analysis of 16.500 activations of the KATRETTER system in Berlin.

BACKGROUND: Bystander CPR is one of the main independent factors contributing to better survival after out-of-hospital cardiac arrest. Simultaneously, the rate of bystander CPR in Germany is below the European average. First responder applications (apps) contribute to reducing the time period without CPR (no-flow time) until professional help can arrive on-scene. METHODS: The KATRETTER app was introduced in Berlin as one of the first apps in Europe which do not require any medical qualifications to register as a first responder. The activation of volunteer first responders for suspected cardiac arrest cases through the Berlin Emergency Medical Services integrated control center was evaluated based on data collected between 16 Oct 2020 and 16 Oct 2022. Our descriptive analysis includes the number of registered first responders, number of activations, the number and percentages of accepted activations, as well as all reports where first responders arrived at the scene. RESULTS: As of 15 Oct 2022, a total of 10,102 first responders were registered in the state of Berlin. During this specified period, there were 16.505 activations of the system for suspected out-of-hospital cardiac arrest. In 38.4% of the accepted cases, first responders documented patient contact, and in 34.6% of cases with patient contact, CPR was performed. Only 2% of registered first responders did not have any medical qualifications. CONCLUSIONS: Smartphone-based first responder applications should not be understood as a means of alerting professional help, but rather like a digitally amplified "call for help" in the vicinity of an emergency location. A large number of first responders can be recruited within 24 months, without large-scale public relations work necessary. No qualifications were required to become a first responder, contributing to a low-threshold registration process with the effect of a more widespread distribution of the app and cost reduction during implementation.

Surgical Treatment of Osteochondral Lesions of the Tibial Plafond: A Systematic Review and Meta-Analysis.

BACKGROUND: The literature on osteochondral lesions of the tibial plafond (OLTPs) is sparse. The aim of this study was therefore to provide an overview of clinical and radiological outcomes following treatment of OLTPs. METHODS: We performed a systematic search of the MEDLINE, Embase, and Cochrane library databases. The review was performed in accordance with the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines and included all original articles on treatment outcomes for OLTPs. The methodological quality of the articles was assessed using the Methodological Index for Non-Randomized Studies (MINORS). Baseline patient and lesion characteristics were pooled and weighted according to the number of lesions per study. The primary outcome was any clinical or patient-reported outcome measure pooled by treatment method when separable data were available. Secondary outcomes were complications, reoperation rates, radiological outcomes, and sport outcomes. RESULTS: The search yielded 2,079 articles, of which 10 studies (1 prospective case series, 1 retrospective comparative study, and 8 retrospective case series) with a total of 175 patients were included. The overall methodological quality of the studies was low. All patients were treated surgically; 96% of the lesions were primary cases (i.e., first-time surgery) and 58% were solitary tibial lesions (i.e., no opposing talar lesion). Arthroscopic bone marrow stimulation was the most frequently used treatment strategy (51%), followed by cartilage transplantation (17%), chondrogenesis-inducing techniques (11%), osteochondral transplantation (3%), retrograde drilling (3%), and mixed (i.e., inseparable) treatments (15%). The clinical outcomes of the different surgical therapies were considered to be moderate to good. The pooled postoperative AOFAS (American Orthopaedic Foot & Ankle Society) score for bone marrow stimulation and osteochondral transplantation was 54.8 (95% confidence interval [CI], 49.5 to 85.0) (n = 14) and 85.3 (95% CI, 56 to 100) (n = 3), respectively. Overall, complications and reoperations were rarely reported. The pooled complication and reoperation rates could only be calculated for bone marrow stimulation and were 5% and 7%, respectively. CONCLUSIONS: Surgical interventions for OLTPs appear to yield moderate to good clinical outcomes. Bone marrow stimulation resulted in a moderate AOFAS score. Complications and reintervention rates were found to be low. The current evidence in the literature is limited because of the underreporting of clinical, radiological, and sport data and the heterogenous outcome scores reported. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Adequate union rates for the treatment of acute proximal fifth metatarsal fractures.

PURPOSE: To compare the bone healing, clinical, and return to daily activity outcomes after either surgical or conservative management of acute zone 1, 2, and 3 fifth metatarsal fractures. METHODS: A literature search was performed to identify studies published from the earliest record to January 2019 using EMBASE (Ovid), MEDLINE via PubMed, CINAHL, and Web of Science. All articles assessing clinical outcomes of acute proximal fifth metatarsal fractures were included. Bone healing and clinical outcomes were thereafter calculated using a simplified pooling method. RESULTS: Thirty-two articles comprising of a total of 1,239 fractures were included, of which one was a randomized controlled trial, seven were prospective studies, and 24 were retrospective studies. 627 zone 1 fractures demonstrated union rates of 93.2% following conservative treatment and 95.1% following surgical treatment. Conservatively managed zone 1 fractures were displaced 49.5% of the time, compared to a rate of 92.8% for the surgically treated cases. For Jones' (zone 2) fractures, bone healing outcomes of conservative versus surgical treatment showed union rates of 77.4% versus 96.3%, refracture rates of 2.4% versus 2.1%, and mean time to union of 11.0 weeks versus 9.4 weeks, respectively. Only ten proximal diaphyseal (zone 3) fractures were reported, with a mean return to work of 8.2 weeks. CONCLUSION: Acute zone 1 fractures are preferably treated conservatively as similar union rates were found after both conservative and surgical management. In contradistinction, acute zone 2 fractures demonstrate higher union rates and faster time to union when treated surgically. The outcomes of acute zone 3 fractures are rarely reported in the literature, so treatment recommendations remain unclear. Further research of proximal fifth metatarsal fractures is warranted to provide more definitive conclusions, but current findings can aid surgeons during the shared clinical decision making process. LEVEL OF EVIDENCE: IV.

Talar OsteoPeriostic grafting from the Iliac Crest (TOPIC) for large medial talar osteochondral defects : Operative technique.

OBJECTIVE: Provision of a natural scaffold, good quality cells, and growth factors in order to facilitate the replacement of the complete osteochondral unit with matching talar curvature for large medial primary and secondary osteochondral defects of the talus. INDICATIONS: Symptomatic primary and secondary medial osteochondral defects of the talus not responding to conservative treatment; anterior-posterior or medial-lateral diameter >10 mm on computed tomography (CT); closed distal tibial physis in young patients. CONTRAINDICATIONS: Tibiotalar osteoarthritis grade III; multiple osteochondral defects on the medial, central, and lateral talar dome; malignancy; active infectious ankle joint pathology. SURGICAL TECHNIQUE: A medial distal tibial osteotomy is performed, after which the osteochondral defect is excised in toto from the talar dome. The recipient site is microdrilled in order to disrupt subchondral bone vessels. Then, the autograft is harvested from the ipsilateral iliac crest with an oscillating saw, after which the graft is adjusted to an exact fitting shape to match the extracted osteochondral defect and the talar morphology as well as curvature. The graft is implanted with a press-fit technique after which the osteotomy is reduced with two 3.5 mm lag screws and the incision layers are closed. In cases of a large osteotomy, an additional third tubular buttress plate is added, or a third screw at the apex of the osteotomy. POSTOPERATIVE MANAGEMENT: Non-weight bearing cast for 6 weeks, followed by another 6 weeks with a walking boot. After 12 weeks, a CT scan is performed to assess consolidation of the osteotomy and the inserted autograft. The patient is referred to a physiotherapist. RESULTS: Ten cases underwent the TOPIC procedure, and at 1 year follow-up all clinical scores improved. Radiological outcomes showed consolidation of all osteotomies and all inserted grafts showed consolidation. Complications included one spina iliaca anterior avulsion and one hypaesthesia of the saphenous nerve; in two patients the fixation screws of the medial malleolar osteotomy were removed.

[Introduction of emergency paramedic investigators in the context of the COVID-19 pandemic in the Berlin emergency medical service]. / Einführung von NotSan-Erkundern im Rahmen der COVID-19-Pandemie in der Berliner Notfallrettung.

BACKGROUND: It has been shown throughout the COVID-19 pandemic that the condition of a number of patients deteriorates acutely when not monitored. This is set against an increased demand for emergency medical services and the resulting scarcity of resources, which makes it necessary to prioritise inpatient treatment or ensure that patients are provided with appropriate outpatient care. In this context, the Berlin Fire Department has introduced emergency paramedic investigators (NotSan-Erkunder) as an additional operating resource. METHODOLOGY: We assessed all operations from 28.03.2020 to 28.04.2020 during which Emergency Paramedic Investigators of the Berlin emergency services were deployed. A total of 341 operations were included from the 31 days. Alongside data from the dispatch system, all operational documentation was assessed. RESULTS: In 57% of cases, mNACA II patients (outpatient treatment) were identified, in 42% of cases, mNACA III patients (inpatient treatment) were identified, and in 1% of cases, mNACA IV (imminent danger to life) patients were identified. In 51% of cases, the emergency services transported the patient to a hospital, and in 49%, alternative care measures were employed. These included referral to a local physician in 28% of cases. In 11% of cases, patients were referred to on-call services of the Association of Statutory Health Insurance Physicians (KV in German). In 4% of cases, the Berlin Fire Department emergency dispatch center deployed a physician of the KV (KV-ARE investigator). DISCUSSION: The results show that additional operational resources serve an important function during a pandemic with regards to an initial assessment and pilot function. This can help relieve not only the emergency services but also the medical facilities responsible for providing further care. The standardised dispatch enquiry enables the linking with the appropriate codes from the low-priority operational spectrum and support by a Tele-emergency physician lends additional professional competency to the emergency paramedics.

[Indications, procedure and outcome of prehospital emergency resuscitative thoracotomy-a systematic literature search]. / Indikation, Prozedere und Outcome der präklinischen Notfallthorakotomie ­ eine systematische Literaturrecherche.

BACKGROUND: Prehospital resuscitative thoracotomy (PHRT) is a controversially discussed measure for the acute treatment of traumatic cardiac arrest (TCA) recommended by the current guidelines of the European Resuscitation Council (ERC). The aim of this work is the comprehensive presentation and summary of the available literature with the underlying hypothesis that the available publications show the feasibility and survival following PHRT in patients with TCA with a good neurological outcome. METHOD: A systematic literature search was performed in the databases PubMed, EMBASE, Google Scholar, Springer LINK and Cochrane. The study selection, data extraction and evaluation of bias potential were performed independently by two authors. The outcome of patients with TCA after PHRT was selected as the primary endpoint. RESULTS: A total of 4616 publications were found of which 21 publications with a total of 287 patients could be included in the analyses. For a detailed descriptive analysis, 15 publications with a total of 205 patients were suitable. The TCA of these patients was most commonly caused by pericardial tamponade, thoracic vascular injuries and severe extrathoracic multiple injuries. In 24% of the cases TCA occurred in the presence of the emergency physician. Clamshell thoracotomy (53%) was used preclinically more often than anterolateral thoracotomy (47%). Of the PHRT patients after TCA 12% (25/205) left the hospital alive, 9% (n = 19/205) with good neurological outcome and 1% (n = 3/205) with poor neurological outcome (according to the Glasgow outcome scale, GOS). CONCLUSION: The prognosis of TCA seems to be much better than has long been assumed. Decisive for the success of resuscitation efforts in TCA seems to be the immediate, partly invasive treatment of all reversible causes. The measures for TCA recommended by the ERC resuscitation guidelines, seem to be poorly implemented, especially in the preclinical setting. A controversy regarding the recommendations of the guidelines is the question of whether a PHRT can be successfully implemented and if the comprehensive introduction in Germany seems to be meaningful. Despite the recommendation of the guidelines, this systematic review and meta-analysis underlines the lack of high-quality evidence on PHRT, whereby a survival probability to hospital discharge of 12% was reported, of which 75% had a good neurological outcome. The risk of bias of the results in individual publications as well as in this review is high. Further systematic research in the field of preclinical trauma resuscitation is particularly necessary also for acceptance of the guidelines.

The effect of foot rotation on measuring ankle alignment using simulated radiographs: a safe zone for pre-operative planning.

AIM: To assess whether variation in foot rotation, in relation to camera position, affects the reliability of measurement of hindfoot alignment on radiographs and to define a "safe zone" where measurement of the alignment axis and thus preoperative planning is not affected by foot rotation. MATERIALS AND METHODS: Healthy volunteers were recruited of whom double-sided lower-leg weight-bearing computed tomography (CT) was acquired. Weight-bearing was simulated by means of providing axial compression force equal to the weight of the healthy volunteers. The scans were uploaded into custom-made three-dimensional analysis software to create digitally reconstructed radiographs. For each CT examination, a coordinate system was determined, which defines the neutral position of the leg. Rotation about the z-axis of this coordinate system simulates endo- and exorotation of the foot. Subsequently, radiographs were reconstructed for the leg between 30° of endorotation and 45° of exorotation, and the relation between the observed alignment axis and foot rotation was determined. RESULTS: A total of 20 healthy volunteers were included, 10 males (mean age 37.7±11.1) and 10 females (mean age 34±10.3). Per 5° of leg rotation, the alignment axis translated with a mean of 6.86% (SD ±13.1). No significant difference in position of the alignment axis was seen between 10° of endorotation and 10° of exorotation compared to the neutral ankle position. CONCLUSION: The "safe zone" for imaging the hindfoot alignment axis, is between 10° endo- and 10° exorotation of the foot.

[Validation of the Osteomyelitis Diagnosis Score on the Basis of a Retrospective Analysis of 100 Patients with Non-Union of the Tibia]. / Validierung des Osteomyelitis-Diagnose-Scores anhand einer retrospektiven Analyse von 100 Patienten mit Tibiapseudarthrose.

Background: The accurate diagnosis of "osteomyelitis" is difficult and is often delayed. However, early and radical therapy of osteomyelitis is essential. The osteomyelitis diagnosis score (ODS) was developed to predict the probability of osteomyelitis. The aim of our study was to validate the ODS and to investigate its practicability in daily routine. Material and Methods: The ODS is based on five diagnostic procedures: 1. clinical history/risk factors, 2. clinical examination/laboratory results, 3. diagnostic imaging, 4. microbiology and 5. histopathology. Each diagnostic procedure includes numerous individual findings, which are rated with 1-6 points, depending on their relevance. If the sum of the five diagnostic criteria is ≥ 17 points, the diagnosis "osteomyelitis" can be viewed as safe, between 8-17 points as probable and between 2-7 points as possible. This retrospective study included 100 patients with non-union of the tibia (2002-2010). The patients were classified into two groups: septic non-union of the tibia (experimental intervention; gold standard: positive detection of bacteria and/or positive histology) and aseptic non-union of the tibia (control intervention; no detection of bacteria and/or histology). Epidemiological data, the score's total number of points and the number of points of the score's five diagnostic procedures were analysed. Results: 71 patients exhibited aseptic non-union of the tibia, 29 patients septic non-union. Patients with septic non-union obtained a mean of 20.8 points, and 24 at least 18 points; the diagnosis "osteomyelitis" is then presumed to be certain. Patients with aseptic non-union obtained a mean of 11.3 points, and only 3/71 patients received > 17 points. Both groups obtained the majority of points in the diagnostic procedure "clinical history". The difference between the two groups is highly significant (p < 0.001). The score's sensitivity is 82.8 %, with a specificity of 95.8 %. Conclusion: The ODS was proved to be a valid score. Patients with septic non-union were identified, even if bacteria were not detected. However, the use of the ODS is demanding, as there are 104 individual findings. Many of these individual findings were negative in all patients. It would be desirable to optimise ODS, by reducing the number of queried parameters, without reduction sensitivity.

Arthroscopic treatment for ulnar-sided TFCC-tears.

OBJECTIVE: Ruptures of ulnar-sided triangular fibrocartilaginous complex (TFCC) often occur in cases of trauma. Golden standard for diagnosis is the arthroscopy of the wrist. TFCC lesions are classified according to their location if traumatic in origin or if degenerative according to their severity. MATERIALS AND METHODS: Recent literature has focused on the ruptures of ulnar-sided triangular fibrocartilaginous complex. This article describes conservative, operative and arthroscopic surgical techniques to reconstruct the triangular fibrocartilaginous complex and restore distal radioulnar joint stability. RESULTS: The main therapeutic goal should be the stabilization of the DRUJ by reattachment of the torn ligaments in ulnar-sided ruptures to the deep fibers in the fovea. This reinsertion can be performed by transosseous suture, a suture anchor or open. CONCLUSION: Central TFCC tears are typically located close to the sigmoid notch of the radius and are either traumatic or degenerative in origin. While central TFCC lesions are usually treated by arthroscopic debridement using small joint punches or a bipolar high frequency system, the ulnar TFCC avulsions can also be refixed arthroscopically in different techniques.

[S3 guideline on treatment of polytrauma/severe injuries. Initial surgical phase: significance--possibilities--difficulties?]. / S3-Leitlinie Polytrauma/Schwerverletzten-Behandlung. Erste Operationsphase: Bedeutung--Möglichkeiten--Schwierigkeiten?

There is no universal, generally established strategy for polytrauma management in Germany until now. The new S3 guideline on polytrauma patient care is the first high-level evidence-based compendium consented to by all major medical societies in Germany. This report emphasises all new guideline recommendations concerning the early operative care of multiply injured patients. With regard to the available evidence in the literature this report shows that the assessment of key recommendations is often difficult due to a lack of data. For guideline explanations with the highest grade of recommendation however it can be assumed that there is no alternative and that these will be implemented nationwide. This study also shows that the absolute and relative number of recommendations and the corresponding grade of recommendation do not correlate with the frequency and severity of injuries in an average polytrauma patient. It will now become a major challenge in German trauma care to incorporate all S3 guideline recommendations into the local treatment algorithms. Regional trauma networks could play a key role in this crucial task.

[Discoid menisci in children: ultrasonographic features]. / Le ménisque discoïde chez l'enfant: aspects échographiques.

OBJECTIVE: Discoid meniscus is a rare congenital pathology affecting mainly the lateral meniscus. Radiological diagnosis, initially based on arthrographic findings, is now established on well defined MRI criteria. In this study, ultrasonography (US) was the modality proposed for diagnosing discoid meniscus and compared to the normal sonographic meniscal pattern. Subjects and methods. 8 children aged from 6 to 11 years, with a symptomatology highly suggestive of meniscal pathology, were investigated by US of both knees, followed by MRI in 3 and arthroscopy in all cases. RESULTS: In all 8 cases, a meniscus was diagnosed as discoid when it no longer had its normal triangular shape, was abnormally elongated and thick and demonstrated a heterogeneous central pattern. Associated lesions (fracture, cystic degeneration) were well demonstrated on US. The lateral meniscus was involved in all 8 cases, the pathology was bilateral in 5 cases and MRI/US correlation was good in 3 cases. Arthroscopy confirmed US findings in all cases. CONCLUSION: US, a more widely available imaging modality, is a reliable technique for the diagnosis of discoid meniscus in children.

Chromosomal aberrations in couples undergoing intracytoplasmic sperm injection: influence on implantation and ongoing pregnancy rates.

OBJECTIVE: To determine the incidence of chromosomal aberrations in couples undergoing intracytoplasmic sperm injection (ICSI) and their influence on subsequent implantation and ongoing pregnancy rates. DESIGN: Prospective study. SETTING: Fertility center. PATIENT(S): Candidates for ICSI. INTERVENTION(S): Chromosomes were trypsin-banded in 2,280 patients. In all cases, 10 metaphases were karyotyped. Sex chromosome analysis was performed in 10 additional metaphases. When apparent chromosomal aberrations were detected, 100 metaphases were analyzed. MAIN OUTCOME MEASURE(S): Implantation and ongoing pregnancy rates in couples with a chromosomal disorder. RESULTS: A chromosomal abnormality was demonstrated in 7.2% of all couples. Among the male partners, 4.48% had aberrations. Autosomal aberrations were present in 2.96%, and numerical or structural sex chromosome abnormalities were found in 1.52%. Among the female partners, numerical or structural abnormalities were documented in 9.79%. Only 2.32% of the female partners had autosomal structural abnormalities. Numerical or structural anomalies involving sex chromosomes were found in 7.47%. Implantation rates of 9.4% and 16.3% per embryo were observed in female partners with sex chromosome mosaicism and autosomal aberrations, respectively. In male partners, the respective rates were 3.8% and 23.1%. CONCLUSION(S): The incidence of chromosomal disorders in couples seeking ICSI treatment is considerable, especially minor mosaicism (<10%) of sex chromosomes in the female partners. Preliminary data indicate a low implantation rate in couples with minor mosaicism of sex chromosomes.

Convergent synthesis of neoglycopeptides by coupling of 2-bromoethyl glycosides to cysteine and homocysteine residues in T cell stimulating peptides.

The 2-bromoethyl beta-glycosides of the disaccharide galabiose [Gal(alpha1-4)Gal] and the trisaccharides globotriose [Gal(alpha1-4)Gal(beta1-4)Glc] and 3'-sialyllactose [Neu5Ac(alpha2-3)Gal(beta1-4)Glc] have been prepared by improved routes. The 2-bromoethyl glycosides were then used in cesium carbonate promoted alkylations of the sulfhydryl groups of cysteine and homocysteine residues in T cell stimulating peptides. This convergent and general approach was used to prepare 16 neoglycopeptides which were obtained in 52-95% yields after purification by HPLC. 1H NMR spectroscopy revealed that beta-elimination and epimerization of neoglycopeptide stereocentres did not occur during the synthesis.

External glycopeptide binding to MHC class-I in relation to expression of TAP transporters, beta 2-microglobulin and to pH.

MHC class-I binding glycopeptides are easily visualized on the cell surface by carbohydrate specific monoclonal antibodies. By comparing the staining intensity between anti-carbohydrate and anti-MHC class-I specific monoclonal antibodies, an estimation of the fraction of peptide accessible 'empty' sites on the cell surface of MHC class-I molecules can be made. This system was used to analyze glycopeptide binding to MHC class-I molecules in relation to transporter associated with antigen processing (TAP) peptide transporters and beta 2-M expression, using gene targeted mice, and in relation to pH. Approximately 15, 40, and 95% 'empty' Db molecules were found on activated T cells from normal, beta 2-M-/- and TAP -/- mice, respectively. The ASN9-6h-Gal2 glycopeptide also bound to transfected 'empty' Db molecules on T1-Db, T2-Db and T3-Db cells with a preference for T2-Db cells, lacking TAP peptide transporters. The stability of glycopeptide binding to H-2Db is also highest on T2-Db cells. pH was found to influence binding either positively or negatively, using four different glycopeptides, binding either to Db or Kb. We conclude that external glycopeptide binding may reflect important functional properties in the MHC class-I system and that pH in different processing compartments might influence the expressed peptide repertoire.

Surface characterization of fluorinated polymers (PTFE, PVDF, PFA) for use in ultratrace analysis.

Surface characterization of new unused PTFE, PFA and PVDF labware has been carried out by light microscopy, scanning electron microscopy, profilometry and atomic force microscopy. It has been found that in spite of higher micro-roughness, PFA exhibits the lowest nano-roughness and hence seems best suited as vessel material for relatively mild pressureless chemical operations for sample preparation of ultrapure substances, as container material for storage of ultrapure liquids, and for transport of such liquids, e.g., from the producer in the chemical to the end user in the microelectronics industry. This suitability refers only to the surface quality of the investigated materials. PTFE-surfaces, due to the sintering process of production, exhibit the most unfavourable surface quality of the investigated fluorinated polymers.

Immunization with glycosylated Kb-binding peptides generates carbohydrate-specific, unrestricted cytotoxic T cells.

Cytotoxic T cells (CTL) recognize target proteins as short peptides presented by major histocompatibility complex (MHC) class I restriction elements. However, there is also evidence for peptide-independent T cell receptor (TCR) recognition of target proteins and non-protein structures. How such T cell responses are generated is presently unclear. We generated carbohydrate (CHO)-specific, MHC-unrestricted CTL responses by coupling di- and trisaccharides to Kb- or Db-binding peptides for direct immunization in mice. Four peptides and three CHO have been analyzed with the CHO either in terminal or central position on the carrier peptide. With two of these glycopeptides, with galabiose (Gal alpha 1-4Gal; Gal2) bound to a homocysteine (via an ethylene spacer arm) in position 4 or 6 in a vesicular stomatitis virus nucleoprotein-derived peptide (RGYVYQGL binding to Kb), CTL were generated which preferentially killed target cells treated with glycopeptide compared to those treated with the core peptide. Polyclonal CTL were also found to kill target cells expressing the same Gal2 epitope in a glycolipid. By fractionation of CTL, preliminary data indicate that glycopeptide-specific Kb-restricted CTL and unrestricted CHO-specific CTL belong to different T cell populations with regard to TCR expression. The results demonstrate that hapten-specific unrestricted CTL responses can be generated with MHC class I-binding carrier peptides. Different models that might explain the generation of such responses are discussed.

Major histocompatibility complex class I binding glycopeptides for the estimation of 'empty' class I molecules.

Different forms of major histocompatibility complex (MHC) class I heavy chains are known to be expressed on the cell surface, including molecules which are functionally 'empty'. Direct peptide binding to cells is obvious during sensitization of target cells in vitro for cytotoxic T lymphocyte killing and 'empty' MHC-I molecules are comparatively abundant on TAP-1/2 peptide transporter mutant cells. In the present work we have estimated the fraction of 'empty' MHC class I molecules using glycosylated peptides and cellular staining with carbohydrate specific monoclonal antibodies. Synthetic Db and Kb binding peptides were coupled at different positions with different di- or trisaccharides, using different spacing between the carbohydrate and the peptide backbone. Binding of sugar specific mAbs was compared in ELISA and cellular assays. An optimal Db binding glycopeptide was used for comparative staining with anti-Db and anti-carbohydrate monoclonal antibodies to estimate fractions of 'empty' molecules on different T lymphoid cells. On activated normal T cells, a large fraction of Db molecules were found to be 'empty'. The functional role of such 'empty' MHC class I molecules on T cells is presently unclear. However, on antigen presenting cells they might participate in the antigen presentation process.

Id gene expression during development and molecular cloning of the human Id-1 gene.

Id genes encode helix-loop-helix proteins that inhibit transcription by forming inactive heterodimers with basic helix-loop-helix (bHLH) proteins. bHLH proteins normally form either homodimers or heterodimers with other bHLH proteins and bind to a DNA sequence element activating transcription. Id-containing heterodimers are inactive because Id proteins lack the basic amino acid region necessary to form a DNA-binding domain. We have examined the relative levels of Id-1 and Id-2 mRNA during normal development and in malignant tissues. In the course of these experiments we cloned and sequenced the human Id-1 cDNA. Two related cDNA molecules encoding human Id-1 mRNAs were identified. Id-1a is a cDNA of 958 nucleotides and can encode a protein of 135 amino acids. Id-1b cDNA is 1145 nucleotides, can encode a protein of 149 amino acids, and appears to be a splice variant of Id-1a. The amino acid sequence of human Id-1 is greater than 90% homologous to that of mouse Id-1. The patterns of Id-1 and Id-2 expression during mouse development vary widely, and we detected Id-1 expression in human fetal and adult tissues from lung, liver, and brain. High Id-1 mRNA expression was found in many human tumor cell lines, including those isolated from nervous system tumors. We mapped Id-2 to human chromosome 2p25.

Glycosylphosphatidylinositol-linked Db does not induce an influenza-specific cytotoxic T lymphocyte response or recycle membrane-bound peptides.

Major histocompatibility complex (MHC) class I molecules, as well as MHC class I-bound peptides, are known to recycle between the cell surface and an undefined, endosomal-like compartment. Little is known about the functional significance of this process. We have explored this using two different forms of the H-2Db molecule expressed in transgenic mice, either transmembranous (Db-tm) or with a glycophosphatidylinositol (GPI)-lipid anchor (Db-GPI). The recycling capacity of peptides bound to Db-tm and Db-GPI was investigated using glycosylated Db-binding glycopeptides, which were detected by flow cytometry. Only the tm form of Db was found to readily internalize and recycle glycopeptides to the cell surface. When transgenic mice were immunized with influenza A virus (PR8) strain and tested for cytotoxic T lymphocyte (CTL) responses against an immunedominant nucleoprotein epitope (366-374, ASNENMETM), only Db-tm mice were found to generate specific CTL responses. The results support the idea that membrane recycling of MHC class I-bound peptides on antigen-presenting cells may be important for the generation of certain CTL responses.