Single-cell fate mapping reveals widespread clonal ignorance of low-affinity T cells exposed to systemic infection

T cell ignorance is a specific form of immunological tolerance. It describes the maintenance of naivety in antigen-specific T cells in vivo despite the presence of their target antigen. It is thought to mainly play a role during the steady state, when self-antigens are presented in absence of costimulatory signals and at low density or to T cells of low affinity. In how far antigen-specific T cells can also remain clonally ignorant to foreign antigens, presented in the inflammatory context of systemic infection, remains unclear. Using single-cell in vivo fate mapping and high throughput flow cytometric enrichment, we find that high-affinity antigen-specific CD8⁺ T cells are efficiently recruited upon systemic infection. In contrast, most low-affinity antigen-specific T cells ignore the priming antigen and persist in the naïve state while remaining fully responsive to subsequent immunization with a high-affinity ligand. These data establish the widespread clonal ignorance of low-affinity T cells as a major factor shaping the composition of antigen-specific CD8⁺ T cell responses to systemic infection.     

Kinds and locations of mutations arising spontaneously in the coding region of theHPRT gene of finite-life-span diploid human fibroblasts

Spontaneous thioguanine-resistant mutants were derived from populations of finite-life-span, diploid human fibroblasts by means of a fluctuation analysis. cDNA was prepared from mutantHPRT mRNA and amplified by the polymerase chain reaction, and the sequence of the product was analyzed. Exon deletions, which very likely arose from mutations in the intron splice site consensus sequences, were found in 10 of the 37 mutants examined (27% of the total). Among the 28 mutations in the coding sequence, base pair substitutions predominated (89%). With the exception of one base pair involved in a tandem mutation, all base pair substitutions resulted in alterations in the predicted amino acid sequence of the protein. In addition there were three frameshift mutations, consisting of the deletion of one or two base pairs. Although mutations occurred throughout the coding sequence, 50% (14/28) were found in the 5 portion of exon 3.     

Heterogeneity of toxicant response: sources of human variability.

While risk assessment models attempt to predict human risk to toxicant exposure, in many cases these models cannot account for the wide variety of human responses. This review addresses several primary sources of heterogeneity that may affect individual responses to drug or toxicant exposure. Consideration was given to genetic polymorphisms, age-related factors during development and senescence, gender differences associated with hormonal function, and preexisting diseases influenced by toxicant exposure. These selected examples demonstrate the need for additional steps in risk assessment that are needed to more accurately predict human responses to toxicants and drugs.     

Gorlin's syndrome: Diffuse appendicular skeletal involvement with scintigraphic correlation

Gorlin's syndrome (also known as basal cell nevus syndrome, Gorlin?Goltz syndrome, and nevoid basal cell carcinoma syndrome) is a rare, inherited disorder characterized by multiple basal‐cell epitheliomas, intracranial calcification, keratocysts of the mandible, and unusual and striking skeletal abnormalities. We present the interesting case of a 45‐year‐old woman who was informed that she had fibrous dysplasia of the extremity at another institution before extensive radiological work‐up showed a diffuse skeletal process. The skeletal abnormalities, in conjunction with the patient's history of multiple basal cell carcinomas, is consistent with the diagnosis of Gorlin's syndrome. We describe this unusual case of striking radiological and scintigraphic findings in a patient with Gorlin's syndrome.     

Gene amplification in esophageal adenocarcinomas and Barrett's with high-grade dysplasia.

PURPOSE: The purpose of this study was to determine the frequency and overall contribution of specific gene amplification events in the formation of Barrett's adenocarcinomas. The relationship of gene amplification to clinical-pathological variables and its potential usefulness as a marker for early cancer detection were also examined. EXPERIMENTAL DESIGN: We used quantitative PCR and Southern blot analysis to screen 87 cases of Barrett's adenocarcinoma for the presence or absence of 13 distinct gene amplification events. Gene amplification was then examined for correlation with other amplification events and clinical variables (survival, stage, nodal involvement, tumor invasion, smoking history, and gender). Additionally, 22 specimens of Barrett's with high-grade dysplasia (HGD) were examined for the presence of gene amplification. RESULTS: One or more amplification events were present in 50 of 87 (57%) adenocarcinomas. The ERBB2 gene was amplified in 19 of 87 (21.8%), CCNE1 in 11 of 87 (12.6%), GATA4 in 9 of 87 (10.3%), KRAS in 9 of 87 (10.3%), EGFR in 7 of 87 (8.0%), CCND1 in 6 of 87 (6.8%), HNF3alpha in 5 of 87 (5.7%), PIK3CA in 5 of 87 (5.7%), C-MYC in 4 of 87 (4.6%), DYRK2 in 2 of 87 (2.3%), and AIB1, AKT1, and IGF1R were amplified in 0 of 87 (0%) of the tumors. CCND1 amplification was found to correlate negatively with survival (P < 0.05). In addition, the ERBB2 amplicon positively correlated (P < 0.05) with GATA4 amplification. Increased copy number of the ERBB2 (1 of 22), GATA4 (1 of 22), KRAS (2 of 22), C-MYC (1 of 22), CCNE1 (2 of 22), and CCND1 (2 of 22) genes was also observed in one or more Barrett's adenocarcinomas with HGD. CONCLUSIONS: The high frequency of gene amplification in esophageal adenocarcinomas and HGD indicates the important role of these events in esophageal adenocarcinoma development. Additionally, these results underscore the possible usefulness of early detection approaches and chemotherapeutic strategies (ErbB2 and cyclin D1) targeted against amplified gene products.     

Disruption of rat forebrain development by glucocorticoids: critical perinatal periods for effects on neural cell acquisition and on cell signaling cascades mediating noradrenergic and cholinergic neurotransmitter/neurotrophic responses.

Glucocorticoids are the consensus treatment for the prevention of respiratory distress in preterm infants, but there is evidence for increased incidence of neurodevelopmental disorders as a result of their administration. We administered dexamethasone (Dex) to developing rats at doses below or within the range of those used clinically, evaluating the effects on forebrain development with exposure in three different stages: gestational days 17-19, postnatal days 1-3, or postnatal days 7-9. At 24 h after the last dose, we evaluated biomarkers of neural cell acquisition and growth, synaptic development, neurotransmitter receptor expression, and synaptic signaling mediated by adenylyl cyclase (AC). Dex impaired the acquisition of neural cells, with a peak effect when given in the immediate postnatal period. In association with this defect, Dex also elicited biphasic effects on cholinergic presynaptic development, promoting synaptic maturation at a dose (0.05 mg/kg) well below those used therapeutically, whereas the effect was diminished or lost when doses were increased to 0.2 or 0.8 mg/kg. Dex given postnatally also disrupted the expression of adrenergic receptors known to participate in neurotrophic modeling of the developing brain and evoked massive induction of AC activity. As a consequence, disparate receptor inputs all produced cyclic AMP overproduction, a likely contributor to disrupted patterns of cell replication, differentiation, and apoptosis. Superimposed on the heterologous AC induction, Dex impaired specific receptor-mediated cholinergic and adrenergic signals. These results indicate that, during a critical developmental period, Dex administration leads to widespread interference with forebrain development, likely contributing to eventual, adverse neurobehavioral outcomes.     

Tuberculosis notifications in Australia, 2003.

The National Notifiable Disease Surveillance System (NNDSS) received 982 tuberculosis (TB) notifications in 2003, of which 947 were new cases, 33 were relapses and two were cases with unknown history. The incidence of TB in Australia has remained at a stable rate since 1985 and was 4.9 cases per 100,000 population in 2003. The high-incidence groups remain people born overseas and Indigenous Australians at 19.9 and 8.7 cases per 100,000 population, respectively. By contrast the incidence in non-Indigenous Australians was 0.9 per 100,000. Comparison of the 2003 TB notification data against the performance indicators set by National Tuberculosis Advisory Committee highlights that enhanced TB control measures should be considered among these high-risk groups.     

AAV-mediated delivery of the caspase inhibitor XIAP protects against cisplatin ototoxicity.

HYPOTHESIS: Delivery of the gene encoding X-linked inhibitor of apoptosis (XIAP) using an adeno-associated viral (AAV) vector can protect against cisplatin-mediated ototoxicity. BACKGROUND: Cisplatin is a widely used chemotherapeutic agent with significant ototoxic side effects. One possible mechanism of toxicity is apoptotic death of many cochlear cell types. Acute treatment with inhibitors of caspases- enzymes critical for apoptosis- has been shown to prevent hearing loss in vivo, but is too short-acting for therapeutic use. Gene therapy provides a specific and chronic means of delivering potential therapeutic gents. Introducing an anti-apoptotic gene into the cochlea could provide long-term prophylaxis against the ototoxic effects of cisplatin. METHOD: Two groups of rats were treated with unilateral injection into the round window of AAV harboring a gene encoding either XIAP or green fluorescent protein (GFP). After at least two months of gene expression, auditory-brainstem-response (ABR) threshold shifts and outer-hair-cell (OHC) number were measured in these two groups of animals after 72-hour treatment with cisplatin. RESULTS: Consistent with previous reports, uninjected and AAV.GFP-injected ears displayed profound ABR threshold elevations and OHC loss after cisplatin treatment. Ears that had been injected with AAV encoding XIAP, however, were significantly protected from these effects: cisplatin-induced ABR-threshold shift and hair-cell loss were attenuated by as much as 78% and 45%, respectively, when compared with contralateral (untreated) ears. CONCLUSION: XIAP delivery to the cochlea can protect against the audiometric changes and hair-cell loss associated with cisplatin ototoxicity. The efficacy, specificity, and duration of the protective effects make this a potentially attractive therapeutic paradigm.