Impact of a novel pre-hospital stroke notification programme on acute stroke care key performance indicators in Hong Kong: a multicentre prospective cohort study with historical controls

INTRODUCTION

Early identification and initiation of reperfusion therapy is essential for suspected acute ischaemic stroke. A pre-hospital stroke notification (PSN) protocol using FASE (facial drooping, arm weakness, speech difficulties, and eye palsy) was implemented to improve key performance indicators (KPIs) in acute stroke care delivery. We assessed KPIs and clinical outcomes before and after PSN implementation in Hong Kong.

METHODS

This prospective cohort study with historical controls was conducted in the Accident and Emergency Departments of four public hospitals in Hong Kong. Patients were screened using the PSN protocol between August 2021 and February 2022. Suspected stroke patients between August 2020 and February 2021 were included as historical controls. Door-to-needle (DTN) and door-to-computed tomography (DTC) times before and after PSN implementation were compared. Clinical outcomes including National Institutes of Health Stroke Scale score at 24 hours and modified Rankin Scale score at 3 months after intravenous recombinant tissue-type plasminogen activator (IV-rtPA) were also assessed.

RESULTS

Among the 715 patients (266 PSN and 449 non-PSN) included, 50.8% of PSN patients and 37.7% of non-PSN patients had a DTC time within 25 minutes (P<0.001). For the 58 PSN and 134 non-PSN patients given IV-rtPA, median DTN times were 67 and 75.5 minutes, respectively (P=0.007). The percentage of patients with a DTN time within 60 minutes was higher in the PSN group than in the non-PSN group (37.9% vs 21.6%; P=0.019). No statistically significant differences in clinical outcomes were observed.

CONCLUSION

Although the PSN protocol shortened DTC and DTN times, clinical outcomes did not significantly differ.

Association between Intake of Edible Mushrooms and Algae and the Risk of Cognitive Impairment in Chinese Older Adults

Previous studies have investigated the association between diet and cognitive impairment, yet there is limited investigation into the link between edible mushrooms and algae intake and cognitive decline. This study aims to explore the association between edible mushrooms and algae intake and the risk of cognitive impairment in individuals aged 65 years and above in China. Cross-sectional data from the 2018 Chinese Longitudinal Healthy Longevity Survey (CLHLS) formed the basis of this study. Edible mushrooms and algae intake was evaluated using a simplified food frequency questionnaire (FFQ) and cognitive function was assessed using the Mini-Mental State Examination (MMSE). A binary logistic regression model was used to evaluate odds ratios (ORs) and 95% confidence intervals (CIs), with subgroup analysis conducted. Among 14,150 older adults, the average age was (85.33 ± 11.55), with a cognitive impairment prevalence of 22.7; multi-model adjustments showed a 25.3% lower probability of cognitive impairment for those occasionally consuming edible mushrooms and algae (OR: 0.747, 95% CI: 0.675~0.826). Furthermore, a 29% lower risk was observed in those with daily intake (OR: 0.710, 95% CI: 0.511~0.987). Subgroup analysis demonstrated significant risk reduction in women (OR: 0.589, 95% CI: 0.375~0.925, p = 0.022), individuals with disability in activities of daily living (OR: 0.568, 95% CI: 0.367~0.878, p = 0.011), and those with low social activity levels (OR: 0.671, 95% CI: 0.473~0.950, p = 0.025). This study concludes that edible mushrooms and algae intake significantly impacts the risk of cognitive impairment in older adults. These results provide insights and impetus for further research into this area. Additional cohort studies or intervention trials are necessary to confirm the potential benefits of edible mushrooms and algae in promoting cognitive health.

A mediation analysis of metabolic and inflammatory factors in the severe sleep apnea-coronary heart disease association

BACKGROUND

It is unclear whether metabolic and inflammatory factors mediate the association between severe sleep apnea and coronary heart disease (CHD) in observational studies based on the large-scale population. This study aims to assess the association between severe sleep apnea and CHD and to explore the extent to which this association is mediated by metabolic factors and C-reactive protein (CRP).

METHODS

In UK Biobank, 213 442 CHD-free (mean age: 55.00) adults were followed up for 15 years to detect incident CHD. Metabolic factors included hyperglycemia, hypertension, dyslipidemia, hypertriglyceridemia, and hyperuricemia. A higher CRP concentration level was defined as a cutoff point of >3.0 mg/l. Data were analyzed using Cox proportional hazards models and the generalized structural equation model.

RESULTS

During follow-up, 9278 participants developed incident CHD (4.3%). The multi-adjusted hazard ratio and 95% confidence interval of CHD related to severe sleep apnea were 1.76 (1.44-2.15). In the mediation analysis, the strongest indirect association was for dyslipidemia, accounting for 20.8% of the association between severe sleep apnea and CHD (β = 0.22, 95% confidence interval = 0.16-0.28), followed by hypertriglyceridemia (12.3%). The proportion of mediation increased to 29.1% when CRP was added to the metabolic mediators.

CONCLUSIONS

Severe sleep apnea was associated with an increased risk of CHD. Lipid factors might play an essential role in the severe sleep apnea-CHD relationship. CRP increased the magnitude of mediation effects of overall metabolic factors. What is already known on this topic It is unknown whether the association between severe sleep apnea and CHD among the large population-based cohort study. Evidence on the mediating effect of metabolic and inflammatory factors in the severe sleep apnea-CHD association remains unclear. What this study adds Lipid factors were the biggest mediation driver in the severe sleep apnea-CHD path. C-reactive protein increased the magnitude of mediation effects of overall metabolic factors. How this study might affect research, practice or policy Investigating mediation analyses not only enhances comprehension of the pathophysiological connection between severe sleep apnea and CHD but also offers valuable insights into preventing CHD.

Plant-Based Diet Indices and Their Association with Frailty in Older Adults: A CLHLS-Based Cohort Study

Within the realm of aging, the nexus between diet and health has garnered considerable attention. However, only select studies have amalgamated insights into the correlation between plant and animal food consumption and frailty. Our aim was to appraise the connections between the overall plant-based diet index (PDI), healthful plant-based diet index (hPDI), and unhealthful plant-based diet index (uPDI) and frailty in the elderly, utilizing data from the Chinese Longitudinal Healthy Longevity Survey (CLHLS). This cohort study drew upon CLHLS data spanning from 2008 to 2018. The PDI, hPDI, and uPDI were gauged using a simplified food frequency questionnaire (FFQ). A frailty index, encompassing 35 variables across major health domains, was formulated. Cox proportional hazard models were employed to scrutinize the associations between the three plant-based dietary indices and frailty in older adults, including an exploration of gender disparities in these associations. A cohort of 2883 study participants was encompassed, with 1987 (68.9%) observed to be either frail or in the pre-frail stage. The Cox model with penalized spline exhibited linear associations of PDI, hPDI, and uPDI with the frailty index. Following covariate adjustments, it was discerned that older adults situated in the highest quartiles of PDI (HR = 0.86, 95% CI: 0.77-0.95) and hPDI (HR = 0.83, 95% CI: 0.74-0.93) experienced a 14% and 17% diminished risk of frailty compared to those in the lowest quartiles of PDI and hPDI, respectively. Conversely, when contrasted with those in the lowest quartile of uPDI, older adults adhering to the highest tertile of uPDI exhibited a 21% elevated risk of frailty (HR = 1.21, 95% CI: 1.08-1.36), with both associations achieving statistical significance (p < 0.01). Moreover, additional subgroup analyses revealed that the protective effects of PDI and hPDI against frailty and the deleterious effects of uPDI were more conspicuous in men compared to women. To forestall or decelerate the progression of frailty in the elderly, tailored dietary interventions are imperative, particularly targeting male seniors.

Association of Plant-Based Diet Indices and Abdominal Obesity with Mental Disorders among Older Chinese Adults

We aimed to explore the correlation between plant-based diet indices and abdominal obesity with depression and anxiety among older Chinese adults. This study used a cross-sectional design using data from the 2018 Chinese Longitudinal Healthy Longevity Survey (CLHLS). We used a simplified food frequency questionnaire to evaluate the overall plant-based diet index (PDI), the healthful plant-based diet index (hPDI), and the unhealthful plant-based diet index (uPDI) separately, based on the potential health effects of the foods. Waist circumference (WC) was used to define abdominal obesity. The 10-item Center for Epidemiologic Studies Depression Scale (CES-D-10) and the 7-item Generalized Anxiety Disorder Scale (GAD-7) were applied to estimate depression symptoms and anxiety symptoms, respectively. Multi-adjusted binary logistic regression models were conducted to explore the effects of the three plant-based diet indices, abdominal obesity status, and their interaction on depression and anxiety. We enrolled a total of 11,623 participants aged 83.21 ± 10.98 years, of which 3140 (27.0%) participants had depression and 1361 (11.7%) had anxiety. The trend in the prevalence of depression/anxiety across increasing quartiles of the plant-based diet indices was statistically significant after controlling for potential confounders (p-trend < 0.05). Abdominal obesity was related to a lower prevalence of depression (OR = 0.86, 95% CI: 0.77-0.95) and anxiety (OR = 0.79, 95% CI: 0.69-0.90) compared with non-abdominal obesity. The protective effects of the PDI and hPDI against depression (OR = 0.52, 95% CI: 0.41-0.64; OR = 0.59, 95% CI: 0.48-0.73, respectively) and anxiety (OR = 0.75, 95% CI: 0.57-1.00; OR = 0.52, 95% CI: 0.39-0.70, respectively) were more pronounced in non-abdominally obese participants. The harmful effects of the uPDI against depression (OR = 1.78, 95% CI: 1.42-2.23) and anxiety (OR = 1.56, 95% CI: 1.16-2.10) were more pronounced in non-abdominally obese participants. In addition, a significant interaction between the plant-based diet indices and abdominal obesity was observed in terms of causing the prevalence of depression and anxiety. Consuming more of a healthful plant-based diet and less of an animal-based diet is related to a lower prevalence of depression and anxiety. A healthful plant-based diet plays a vital role in non-abdominally obese individuals.

Delays in the Presentation of Stroke Patients to Hospital and Possible Ways of Improvement

Objective

Stroke patients often came late to hospital and arrived beyond the therapeutic time window for thrombolytic therapy. We studied the time from stroke onset to arrival at Accident and Emergency (A&E) department and examined what barred them from early medical attendance.

Methods

All acute stroke patients attending A&E between 15 March 1999 to 14 June 1999 were recruited. For those brought in by ambulance, their time intervals were divided into three: phase I was between stroke onset to call 999; phase II was between call 999 to A&E arrival; and phase III was between A&E arrival to being seen by doctor. For those who did not come by ambulance, they were divided into two groups: those who consulted other doctors and those who did not consult other doctors before coming to A&E. Their time lags from stroke onset to A&E consultation were compared.

Results

One hundred and fifteen stroke patients were consecutively recruited. Sixty-five ambulance users had median time for phase I as 151 minutes, for phase II as 32 minutes, for phase III as 17 minutes. The total median time lag was 190 minutes. Fifty were ambulance non-users. For those who did not consult other doctors before A&E attendance, the median time lag was 641 minutes. For those who consulted others doctors before A&E attendance, their median time lag was 3,672 minutes. As a group their median time lag was 950 minutes. For the 65 ambulance users, we further studied the time intervals between A&E arrival and being seen by doctors; and the median waiting time for doctors was 17 (range 0 to 60) minutes.

Conclusions

Public education was of paramount importance. Some common stroke signs could be widely propagated for recognition. Phase I should be less than 80 minutes. The median time for phase II would likely remain to be 32 minutes. Further shortening could be achieved in phase III. As category III & IV patients were most likely potential candidates for thrombolysis, they should be seen within 15 minutes. This would leave only 53 minutes for clinical assessment, CT brain and preparation of thrombolytic agent. These measures could increase the chance of providing thrombolytic treatment within the therapeutic time window.

Association of long non-coding RNA H19 and microRNA-21 expression with the biological features and prognosis of non-small cell lung cancer

In recent years, long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) have been shown to play important roles in tumor biological function. The aim of this study was to investigate the diagnostic and prognostic value of lncRNA H19 and miR-21 expression in non-small-cell lung cancer (NSCLC). H19 and miR-21 expression was measured in tumor tissues and corresponding non-tumor lung tissues from 200 patients by quantitative reverse transcription polymerase chain reaction. Moreover, the in vitro and in vivo effects of H19 knock out in A549 cells were investigated. Expression of both H19 and miR-21 was significantly higher in lung tissues from patients with NSCLC than in normal lung tissues. Increased expression of H19 and miR-21 was positively correlated with advanced tumor-node-metastasis stage and tumor size. miR-21 expression was highest in stage I and II NSCLC, whereas H19 expression was highest in stage III and IV NSCLC. Knockout of H19 significantly inhibited NSCLC cell proliferation both in vitro and in vivo. The results show that H19 may mainly contributes to the progression of NSCLC, and its expression levels can reflect the invasive and metastatic status to some extent. miR-21 expression more likely plays an important role in early stage NSCLC. Moreover, H19 and miR-21 interact in the regulation of NSCLC, and with greater expression of both H19 and miR-21, overall survival decreased. The combination of H19 and miR-21 may have diagnostic value in NSCLC and represent a target for new NSCLC treatments.

Obesity inversely correlates with prostate-specific antigen levels in a population with normal screening results of prostate cancer in northwestern China

Serum prostate-specific antigen (PSA) is a diagnostic biomarker of prostate cancer and is possibly associated with obesity. This study aimed to explore the relationships between obesity indicators [body mass index (BMI) and waist circumference (WC)] with PSA in Chinese men. A cross-sectional study of men aged 30-85 years undergoing prostate cancer screening was conducted from August 2008 to July 2013 in Xi'an, China. Data were obtained from clinical reports, condition was recorded based on self-report including demographics, weight, height, and WC (>90 cm=obese). Fasting blood glucose (FBG) and prostate volume (PV) were assessed clinically. Patients were grouped by BMI (normal=22.9, overweight=23-27.4, obese≥27.5 kg/m²). PSA parameters of density (PSAD), PSA serum level, and PSA increasing rate per year (PSAR) were calculated per BMI and age groups (30-40, 41-59, 60-85 years). Obesity indicators (BMI and WC) and PSA parameter relationships were modeled by age-stratified linear regression. Of 35,632 Chinese men surveyed, 13,084 were analyzed, including 13.44% obese, 57.44% overweight, and 29.12% normal weight, according to BMI; 25.84% were centrally (abdominally) obese according to WC. BMI and WC were negatively associated with all PSA parameters, except PSAD and PSAR [P<0.05, BMI: β=-0.081 (95%CI=-0.055 to -0.036), WC: β=-0.101 (-0.021 to -0.015)], and independent of FBG and PV (P<0.05) in an age-adjusted model. In conclusion, obesity was associated with lower PSA in Chinese men. Therefore, an individual's BMI and WC should be considered when PSA is used to screen for prostate cancer.

Atrial fibrillation patients who sustained warfarin-associated intracerebral haemorrhage have poor neurological outcomes: results from a matched case series

INTRODUCTION

Coagulopathy-associated intracerebral haemorrhage has become increasingly common because of the rising demand in the ageing population for anticoagulation for atrial fibrillation. This study compared the clinical features and neurological outcomes of intracerebral haemorrhage in patients with atrial fibrillation who were prescribed warfarin with those who were not.

METHODS

This was a retrospective matched case series of patients with intracerebral haemorrhage from three tertiary hospitals in Hong Kong from 1 January 2006 to 31 December 2011. Patients who developed intracerebral haemorrhage and who were prescribed warfarin for atrial fibrillation (ICH-W group) were compared with those with intracerebral haemorrhage and not prescribed warfarin (ICH-C group); they were matched for age and gender in 1:1 ratio. Clinical features and neurological outcomes were compared, and the impact of coagulopathy on haematoma size was also studied.

RESULTS

We identified 114 patients in the ICH-W group with a mean age of 75 years. Both ICH-W and ICH-C groups had a median intracerebral haemorrhage score of 2. There was a non-statistically significant trend of higher intracerebral haemorrhage volume in the ICH-W group (12.9 mL vs 10.5 mL). The median modified Rankin Scale and the proportion with good recovery (modified Rankin Scale score ≤3) at 6 months were comparable. Nonetheless, ICH-W patients had higher hospital mortality (51.8% vs 36.0%; P=0.02) and 6-month mortality (60.5% vs 43.0%; P=0.01) than ICH-C patients. Overall, 60% of ICH-W patients had their admission international normalised ratio within the therapeutic range during intracerebral haemorrhage, and 14% had a subtherapeutic admission international normalised ratio. International normalised ratio at admission was not associated with intracerebral haemorrhage volume or neurological outcome.

CONCLUSION

Warfarin-associated intracerebral haemorrhage in patients with atrial fibrillation carried a higher stroke mortality than the non-warfarinised patients.

Pathways involved in the spread of buccal carcinoma on contrast-enhanced multislice CT

OBJECTIVES

To explore how buccal carcinoma spread, using contrast-enhanced multislice CT (CEMSCT).

METHODS

We retrospectively analysed the extent of lesions in 56 patients with primary buccal squamous cell carcinoma (SCCA). Abnormal manifestations on CEMSCT at oral subsites and involved adjacent structures were documented and evaluated, which were compared with the results of surgery and histopathology.

RESULTS

Infiltration and spread to oral subsites and/or adjacent structures was confirmed in 33 patients (58.9%). The opening of the Stensen duct was the most commonly invaded oral subsite (72.7%); other sites included the gingivobuccal sulcus (60.6%), pterygomandibular raphe (54.5%), gingiva (24.2%), retromolar trigone (24.2%), orbicularis oris (18.2%) and the floor of mouth (15.2%). Of the involved adjacent structures, the buccal space was the most common site of spread (69.7%), followed by the masticatory muscles and spaces (57.6%), bone (54.5%), skin and subcutaneous fat (39.4%), pharynx (30.3%), investing fascia (15.2%) and the base of the skull (6.1%). CEMSCT manifestations of the involvement in buccal SCCAs had correlations with pathological findings (p < 0.05). The sensitivities, specificities and accuracies of two radiologists' evaluation on buccal carcinoma involvement were 50.00%, 23.21% and 73.21%; and 51.79%, 32.14% and 83.93%, respectively.

CONCLUSIONS

Buccal SCCAs could superficially and deeply spread to multiple oral subsites and/or adjacent structures. CEMSCT could delineate their spread pathways and extents.

A registry of tuberculous meningitis in Hong Kong

BACKGROUND

A prospective observational study of the presentation, diagnosis, treatment and outcome of tuberculous meningitis (TBM).

METHODS

Demographic characteristics, clinical information, treatment and progress of TBM patients were followed. Their outcomes were ascertained every 6 months for 3 years after diagnosis. Prognostic factors associated with death or full recovery were examined using multivariate Cox's and logistic regression models, respectively.

RESULTS

Between 1993 and 2000, 166 TBM patients were recruited. Their mean age was 42.9, 153 were Chinese and 81 were males; 92% received HRZS (H = isoniazid; R = rifampicin; Z = pyrazinamide; S = streptomycin), HRZE (E = ethambutol) or HRZES. Steroids were given to 105 patients, with no significant effect on outcome. After 3 years of follow-up, 110 patients had completely recovered, 20 survived with disability and 26 died. Death was significantly associated with older age, lower cerebrospinal fluid (CSF) lymphocyte and poorer consciousness levels at the time of presentation, while full recovery was associated with younger age, being female and absence of complications.

CONCLUSIONS

Relatively good outcomes of TBM cases were documented in this Hong Kong study with a case-fatality ratio of 15.7% (26/166) up to 3 years. Early recognition, diagnosis and administration of effective treatment regimens were probably the most important factors in reducing mortality and morbidity.

Spinocerebellar ataxia type 6

We report a 39-year-old woman with spinocerebellar ataxia type 6. She presented with ataxia and a 3-year history of progressive ataxia and recurrent falls. There was no relevant family history. Genetic tests revealed an expanded allele of 24 CAG repeats at the spinocerebellar ataxia type 6 locus. This appears to be the first case reported in Hong Kong. As genetic testing becomes more widely available and clinical awareness increases, more such patients are expected to be diagnosed.

Clinical features of hereditary spinocerebellar ataxia diagnosed by molecular genetic analysis

OBJECTIVE

To assess the frequency and clinical features of different types of hereditary spinocerebellar ataxia in Hong Kong.

DESIGN

Cross-sectional study using a questionnaire and clinical examination, with the majority of the information retrospectively collected.

SETTING

Three regional hospitals, Hong Kong.

PARTICIPANTS

All patients with spinocerebellar ataxia that was confirmed by molecular genetic tests between January 2001 and October 2003.

MAIN OUTCOME MEASURES

History, latest physical examination results, clinical investigation results, and genetic profiles.

RESULTS

A total of 16 Chinese patients had received diagnoses of spinocerebellar ataxia. These patients had spinocerebellar ataxia type 1 (n=3), spinocerebellar ataxia type 3 (Machado-Joseph disease; n=12), and dentatorubro-pallidoluysian atrophy (n=1). The most common manifestation was ataxia (15/16), followed by pyramidal signs (12/16). Other features such as bulbar dysfunction, ophthalmoplegia, neuropathy, and cognitive impairment were present but variable.

CONCLUSIONS

The clinical manifestations of different types of spinocerebellar ataxia overlap, and genetic study is necessary to confirm the diagnosis. The frequency of spinocerebellar ataxia type 3 is greater than that of other types among these Chinese patients. The age of onset of this type may correlate inversely with the number of CAG repeats.

Kennedy's disease

Kennedy's disease is an X-linked, neurodegenerative disorder, characterised by lower motor neuron syndrome. This report gives the clinical details of six male patients with Kennedy's disease diagnosed at Princess Margaret Hospital. Three were initially diagnosed with other neurological diseases, with the diagnosis of Kennedy's disease made after genetic testing. This hereditary disease should be considered in male patients with muscle weakness, particularly those with a presentation suggesting atypical motor neuron disease.

Purified donor T cells alone activate transplantation immunity to the male antigen but induce tolerance in combination with Mac-1+ donor cells

BACKGROUND

In most experimental systems examined, "professional" antigen-presenting cells (APCs), such as dendritic cells, have been found to activate T cells, whereas "nonprofessional" antigen-bearing cells (nonAPC) may induce tolerance. Some recent studies have suggested that nonAPCs may under certain conditions prime a T-cell immune response. We have attempted to separate the roles of transplanted T cells and monocytic/dendritic cells in activating or tolerizing antigen-specific T cells in vivo, by examining the consequences of parenteral exposure to male antigen in anti-male TCR transgenic female mice.

METHODS

Qualitative and quantitative changes in the large population of male-reactive transgenic T cells to various male donor cell populations in transgenic female mice were followed after injections of highly purified male lymphoid cells. Changes in male-reactive T cells with time and the long-term outcome of male skin grafts were measured.

RESULTS

When a nonAPC population consisting of highly purified male T cells alone was injected intravenously into H-Y antigen-specific TCR transgenic female mice, the number of host transgenic T cells was sustainably increased, and male graft rejection was accelerated. Injection of a combination of purified T cells and purified Mac-l+ cells induced massive and permanent deletion of the host male-reactive T-cell population and permanent graft tolerance. Mac-l+ cells alone gave no appreciable change in responsive T cells or graft rejection times.

CONCLUSIONS

The data indicate that highly purified T cells engrafted alone induce rapid sensitization toward the male antigen. They also show that both male donor T cells and a population of male monocytic/ dendritic cells are required to induce peripheral tolerance toward this antigen and that this tolerance is related to permanent peripheral deletion of male-reactive T cells.

All or none peripheral tolerance induction in H-Y antigen-specific TCR transgenic mice

In in vivo tolerance induction, the dose of tolerogen injected is generally linearly correlated to the length of tolerance induced. Small, medium and large doses are related to no, partial and long-term tolerance, respectively. However, even with injection of substantially large doses of tolerogen, the length of tolerance induced varies over a wide range. Most of the recipients can still reject donor grafts. In this study, it is shown that the linear dose-response can be altered into an all or nothing response in a H-Y antigen-specific TCR transgenic (Tg) mouse model. In thymectomized female Tg mice, injection of 3, 30 and 100 x 10(6) male spleen cells was correlated to no, partial and massive deletion of Tg (alpha T beta T) CD8 cells, respectively. When the thymectomized Tg mice were injected with 9 x 10(6) T cell-enriched (T+) male cells, one half of the recipients showed no deletion of alpha T beta T cells, and in the other half massive deletion occurred. In complete correlation with deletion, all male skin grafts were rejected in the undeleted group as PBS-injected controls, whereas with massive deletion they were indefinitely tolerized. Thus, partial deletion and partial tolerance can be avoided. Injection of 18 x 10(6) male T+ cells induced long-term tolerance in all the recipients. The all or none T cell deletion and long-term tolerance induction has not only significant implications in understanding the mechanism of peripheral tolerance induction, but also in tolerance induction in transplantation, gene therapy and the prevention and treatment of autoimmune diseases.

Prethymic expression of a transgenic TCR beta chain on a precursor of T-cells

Mice carrying a rearranged TCR Vbeta 8.2 transgene express the Vbeta protein on the vast majority of peripheral T-cells. The bone marrow and peripheral blood, as well as other lymphoid organs of both untreated animals and animals depleted of T-cells by neonatal thymectomy and/or injection from birth of monoclonal anti-TCR antibodies, contain a small population of cells that express low levels of the Vbeta transgene product, but no T-cell or other detectable lineage-specific phenotypic markers. When such TG-bearing BM cells are purified and injected directly into the non-TG thymus, they show the phenotypic maturation sequences of intrathymic T-cell development and, subsequently, mature TG-bearing peripheral T-cells. However, this population failed to support long-term recovery from lethal irradiation. Both Vbeta 8.2 TG and CD3delta mRNA transcripts are strongly expressed in the cell population, but no CD3gamma, CD3epsilon, CD3zeta, CD4, CD8beta, pre-Talpha, or RAG-1 transcript was detected. The transgene-encoded TCR component is not bound to the cell membrane exclusively by a phosphatidylinositol linkage. The data show that the fully rearranged TCR transgene and transcripts for at least one of the associated CD3 components, CD3delta, can be expressed on a subpopulation of BM and PBL cells that has not passed through the thymus. The phenotypic characteristics of this cell population resemble those described for the earliest thymocyte described by others. The TG protein molecule in this model may provide a specific developmental marker for a prothymocyte lineage subset that lacks pluripotential properties.