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PubMed2025

Multi-strain carriage and intrahost diversity of Staphylococcus aureus among Indigenous adults in the USA.

Staphylococcus aureus (SA) is an opportunistic pathogen and human commensal that is frequently present in the upper respiratory tract, gastrointestinal tract and skin. While SA can cause diseases ranging from minor skin infections to life-threatening bacteraemia, it can also be carried asymptomatically. Indigenous individuals in the Southwest USA experience high rates of invasive SA disease. As carriage is the most significant risk factor for disease, understanding the dynamics of SA carriage, and in particular co-carriage of multiple strains, is important to develop strategies to prevent transmission in vulnerable communities. Here, we investigated SA co-carriage and intrahost evolution by sampling several colonies from multiple anatomical sites and whole-genome sequencing (WGS) on 310 SA isolates collected from 60 Indigenous adults participating in a cross-sectional carriage study. We assessed the richness and diversity of SA isolates via differences in multilocus sequence type, core-genome SNPs and genome content. Using WGS data, we identified 95 distinct SA intra-subject lineages (ISLs) among 60 participants; co-carriage was detected in 42% (25/60). Notably, two participants each carried four distinct SA ISLs. Variation in antibiotic resistance determinants among carried strains was identified among 42% (25/60) of participants. Lastly, we found unequal distribution of clonal complex by body site, suggesting that certain lineages may be adapted to specific anatomical sites. Together, these findings suggest that co-carriage may occur more frequently than previously appreciated and further our understanding of SA intrahost diversity during carriage, which has implications for surveillance activities and epidemiological investigations.

Humans↗
PubMed2026

Loss of Function Dnmt3a Mutation Leads to Aberrant Neutrophil Migration.

Clonal hematopoiesis (CH), an age-related expansion of somatically mutated hematopoietic clones, is associated with increased risk of severe infections including coronavirus disease (COVID)-19, yet the underlying mechanisms remain unclear. Here, we investigated the impact of Dnmt3a deficiency in a murine model of influenza A virus (IAV) pneumonia. Dnmt3a-deficient mice exhibited increased pulmonary viral burden and reduced neutrophil accumulation in IAV-infected lungs despite comparable circulating neutrophil numbers. Functional analyses of neutrophils showed impaired chemotactic migration in vitro, whereas maturation, antimicrobial enzyme content, and metabolic capacity were unchanged. Transcriptomic profiling revealed downregulation of pathways involved in chemotaxis, cytokine signaling, and cellular activation, including reduced expression of Cxcr1. Supporting the translational relevance of these findings, proteomic analysis of plasma from individuals with germline DNMT3A mutations (Tatton-Brown-Rahman syndrome) revealed alterations in proteins associated with cell migration and cytoskeletal dynamics. Collectively, our findings demonstrate that Dnmt3a loss compromises innate immune defense by impairing neutrophil migration in a cell-intrinsic manner, leading to ineffective pathogen clearance. This work provides mechanistic insight into how CH-associated mutations contribute to age-associated susceptibility to infection and highlights altered leukocyte trafficking as a potential therapeutic target in aging populations with CH.

Animals↗
PubMed2004

A Bayesian approach to reconstructing genetic regulatory networks with hidden factors.

MOTIVATION: We have used state-space models (SSMs) to reverse engineer transcriptional networks from highly replicated gene expression profiling time series data obtained from a well-established model of T cell activation. SSMs are a class of dynamic Bayesian networks in which the observed measurements depend on some hidden state variables that evolve according to Markovian dynamics. These hidden variables can capture effects that cannot be directly measured in a gene expression profiling experiment, for example: genes that have not been included in the microarray, levels of regulatory proteins, the effects of mRNA and protein degradation, etc. RESULTS: We have approached the problem of inferring the model structure of these state-space models using both classical and Bayesian methods. In our previous work, a bootstrap procedure was used to derive classical confidence intervals for parameters representing 'gene-gene' interactions over time. In this article, variational approximations are used to perform the analogous model selection task in the Bayesian context. Certain interactions are present in both the classical and the Bayesian analyses of these regulatory networks. The resulting models place JunB and JunD at the centre of the mechanisms that control apoptosis and proliferation. These mechanisms are key for clonal expansion and for controlling the long term behavior (e.g. programmed cell death) of these cells. AVAILABILITY: Supplementary data is available at http://public.kgi.edu/wild/index.htm and Matlab source code for variational Bayesian learning of SSMs is available at http://www.cse.ebuffalo.edu/faculty/mbeal/software.html.

Bayes Theorem↗
PubMedDate not supplied

In vitro senescence of immune cells.

Immune cells are eminently suitable model systems in which to address the possible role of replicative senescence during in vivo aging. Since there are more than 10(8) unique antigen specificities present within the total T lymphocyte population of each individual, the immune response to any single antigen requires massive clonal expansion of the small proportion of T cells whose receptors recognize that antigen. The Hayflick Limit may, therefore, constitute a barrier to effective immune function, at least for those T cells that encounter their specific antigen more than once over the life course. Application of the fibroblast replicative senescence model to the so-called cytotoxic or CD8 T cell, the class of T cells that controls viral infection and cancer, has revealed certain features in common with other cell types as well as several characteristics that are unique to T cells. One senescence-associated change that is T cell-specific is the complete loss of expression of the activation signaling surface molecule, CD28, an alteration that enabled the documentation of high proportions of senescent T cells in vivo. The T cell model has also provided the unique opportunity to analyze telomere dynamics in a cell type that has the ability to upregulate telomerase yet nevertheless undergoes senescence. The intimate involvement of the immune system in the control of pathogens and cancer as well as in modulation of bone homeostasis suggests that more extensive analysis of the full range of characteristics of senescent T cells may help elucidate a broad spectrum of age-associated physiological changes.

Aging↗
PubMed2006

Mitf regulation of Dia1 controls melanoma proliferation and invasiveness.

It is widely held that cells with metastatic properties such as invasiveness and expression of matrix metalloproteinases arise through the stepwise accumulation of genetic lesions arising from genetic instability and "clonal evolution." By contrast, we show here that in melanomas invasiveness can be regulated epigenetically by the microphthalmia-associated transcription factor, Mitf, via regulation of the DIAPH1 gene encoding the diaphanous-related formin Dia1 that promotes actin polymerization and coordinates the actin cytoskeleton and microtubule networks at the cell periphery. Low Mitf levels lead to down-regulation of Dia1, reorganization of the actin cytoskeleton, and increased ROCK-dependent invasiveness, whereas increased Mitf expression leads to decreased invasiveness. Significantly the regulation of Dia1 by Mitf also controls p27(Kip1)-degradation such that reduced Mitf levels lead to a p27(Kip1)-dependent G1 arrest. Thus Mitf, via regulation of Dia1, can both inhibit invasiveness and promote proliferation. The results imply variations in the repertoire of environmental cues that determine Mitf activity will dictate the differentiation, proliferative, and invasive/migratory potential of melanoma cells through a dynamic epigenetic mechanism.

Actins↗
PubMed2005

Clonal association between Streptococcus pneumoniae serotype 23A, circulating within the United States, and an internationally dispersed clone of serotype 23F.

Streptococcus pneumoniae is an important pathogen in the United States and is associated with significant morbidity and mortality. Since the introduction of the seven-valent conjugate vaccine, a significant decline in pneumococcal disease has been reported. However, surveillance for pneumococcal disease remains essential, as the extent of cross protection against vaccine-related serotypes is still unclear. Further, any increase in non-vaccine-related serotypes also needs monitoring. We report on a new clonal association between a vaccine-related serotype, serotype 23A, obtained as part of the Active Bacterial Core surveillance, with an established internationally dispersed Pneumococcal Molecular Epidemiology Network (PMEN) clone, clone Colombia(23F)-26. Sixty-two isolates of serotype 23A collected from sterile sites during a 2-year period (2002 and 2003) were characterized. Twenty-one (34%) isolates were penicillin nonsusceptible, although none were fully resistant. Pulsed-field gel electrophoresis and multilocus sequence typing analysis showed that 24 (39%) of the serotype 23A isolates shared either genetic identity or high genetic relatedness with PMEN clone Colombia(23F)-26. Extensive variability was noted within the sequenced region of pbp2b in two penicillin-nonsusceptible isolates as well as in PMEN clone Colombia(23F)-26, suggesting that these isolates probably acquired penicillin resistance independently. The emergence of such new serotype and genotype associations highlights the dynamic nature of the pneumococcal population, necessitating continuous monitoring in the post-vaccine era.

Adolescent↗
PubMed2006

Fine-scale spatial genetic structure of the distylous Primula veris in fragmented habitats.

In Flanders (northern Belgium), the distylous self-incompatible perennial herb Primula veris is common, but mainly occurs in fragmented habitats. Distyly, which favours disassortative mating, is characterized in P. veris by two genetically determined floral morph types (pin or thrum). Using 18 polymorphic loci, we investigated fine-scale spatial genetic structure (SGS) and spatial distribution of the morphs within four populations from two regions that differ in degree of habitat fragmentation. We studied the contributions made by sexual reproduction and clonal propagation and compared the SGS patterns between pin and thrum morph types. Clonal growth was very restricted to a few individuals and to short distances. One population showed a non-random spatial distribution of the morphs. Pin and thrum individuals differed in SGS patterns at a small scale, suggesting intrapin biparental inbreeding, also related to high plant densities. This may be explained by partial self-compatibility of the pin morph combined with restricted seed dispersal and pollinator behaviour. There is an indication of more pronounced SGS when populations occur in highly fragmented habitats. From our findings, we may hypothesize disruption of the gene flow processes if these large populations evolve into patchworks of small remnants, but also a possible risk for long-term population survival if higher intrapin biparental inbreeding leads to inbreeding depression. Our study emphasizes the need for investigating the interactions between the heterostylous breeding system, population demographic and genetic structure for understanding population dynamics in fragmented habitats and for developing sustainable conservation strategies.

Breeding↗
PubMed2006

Multilocus sequence typing for global surveillance of meningococcal disease.

The global surveillance of bacterial pathogens is particularly important for bacteria with diverse and dynamic populations that cause periodic epidemics or pandemics. The isolate characterization methods employed for surveillance should: (1) generate unambiguous data; (2) be readily implemented in a variety of scenarios and be reproducible among laboratories; (3) be scalable and preferably available in a high throughput format; and (4) be cost effective. Multilocus sequence typing (MLST) was designed to meet these criteria and has been implemented effectively for a wide range of microorganisms. The 'Impact of meningococcal epidemiology and population biology on public health in Europe (EU-MenNet)' project had amongst its objectives: (1) to disseminate meningococcal MLST and sequence-based typing throughout Europe by establishing a centre for training and data generation, and (2) to produce a comprehensive Europe-wide picture of meningococcal disease epidemiology for the first time. Data produced from the project have shown the distribution of a relatively small number of STs, clonal complexes and PorA types that account for a large proportion of the disease-associated isolates in Europe. The project demonstrates how molecular typing can be combined with epidemiological data via the Internet for global disease surveillance.

Computational Biology↗
PubMed2004

Invasion dynamics of two alien Carpobrotus (Aizoaceae) taxa on a Mediterranean island: II. Reproductive strategies.

This study compares sexually and asexually produced fruit set, seed production, biomass, germination, and seedling size in Carpobrotus acinaciformis and C. edulis following controlled pollination experiments in order to evaluate the potential role of reproductive traits with respect to the invasive potential of these taxa. C. edulis is slightly agamospermic, completely self-fertile, slightly preferentially self-compatible, experiences no inbreeding depression, and has low hybrid vigour. In contrast, C. acinaciformis does not have reliable agamospermy, is only slightly self-fertile and self-compatible, experiences a slight inbreeding depression, and has a strong hybrid vigour. Both taxa have relatively low, although significantly different germination frequencies, and insignificantly different seedling sizes. Owing to the high performance in hybridisation as compared to all other controlled pollinations in C. acinaciformis, as well as a large amount of previously demonstrated introgression, we refer to the population studied on the island of Bagaud (France) as C. affine acinaciformis. We conclude that both C. edulis and C. affine acinaciformis should be considered as harmful invasive plants in the Mediterranean Basin, the former because of the flexibility of its mating system and high seed production, and the latter because of its strong clonality, high hybrid vigour, and potential for continued introgression from C. edulis genes. These differences require different control strategies, while the avoidance of sympatry is a distinct priority.

Aizoaceae↗
PubMed2005

Dwindling competition with constant demand: can homeostatic adjustments explain age-associated changes in peripheral B cell selection?

The close relationship between specificity-based selection and homeostatic processes in maintaining peripheral B cell pools has become increasingly evident. Thus, age-associated changes observed within these pools may reflect homeostatic responses to proximal primary lesions. Marked shifts in the size and dynamics of most B lymphocyte subsets and their progenitors occur with age: perturbations in B lineage precursors result in reduced production of immature B lymphocytes in the bone marrow and transitional pools in the periphery, but these effects appear to be offset by compensatory homeostatic processes at the marrow-periphery interface. We propose a model whereby these "distal" homeostatic adjustments relax the stringency of specificity based selection, affording a potential explanation for the increased frequency of autoreactive specificities with age.

Aging↗
PubMed1998

Normal keratinocytes suppress early stages of neoplastic progression in stratified epithelium.

The importance of interactions between potentially neoplastic cells and their normal neighbors on malignant progression of precancerous lesions is not well understood. In this study, we have established novel human tissue models that simulate intraepithelial neoplasia in stratified epithelia to investigate the fate and phenotype of neoplastic keratinocyte clones in normal cell context during clonal expansion and early malignant progression. This was accomplished by mixing genetically marked keratinocytes with malignant potential (II-4) with normal keratinocytes at ratios of 1:1, 4:1, 12:1, and 64:1 (normal:II-4) to visualize nests of marked, dysplastic cells in organotypic cultures and in cultures transplanted to nude mice. Four weeks after transplantation of 4:1 mixtures, grafts were normal and demonstrated no beta-galactosidase (beta-gal)-positive cells, suggesting that cells with malignant potential were eliminated from the tissue at this mixing ratio. However, grafted 1:1 mixtures demonstrated persistence of expanded foci of dysplastic cells (4 weeks) and invasion (8 weeks). This demonstrated that the capacity of a keratinocyte clone with neoplastic potential to persist and invade is directly related to the threshold number of such keratinocytes present in the tissue. To explain the failure of II-4 to persist in vivo, the intraepithelial dynamics between the two populations were studied before grafting. Double-stain immunofluorescence for bromodeoxyuridine/beta-gal and filaggrin/beta-gal of mixtures grown in organotypic cultures for 7 days demonstrated that when increasing numbers of normal cells were added (12:1), II-4 ceased to proliferate and expressed filaggrin. This suggests a novel mechanism of tumor suppression wherein contact with normal cells induces cell cycle withdrawal and terminal differentiation of potentially malignant cells. These findings support the view that normal tissue architecture acts as a dominant suppressor of early neoplastic progression in stratified epithelium.

Animals↗
PubMed2004

Data mining of Mycobacterium tuberculosis complex genotyping results using mycobacterial interspersed repetitive units validates the clonal structure of spoligotyping-defined families.

Recently, a combination of spoligotyping and bioinformatics was proposed as a potential tool for defining major circulating clades of tuberculosis bacilli. In the present study, we attempted to validate the above mentioned classification using a new high-throughput marker, named mycobacterial interspersed repetitive units (MIRUs). Using 12 MIRU loci and spoligotyping, we performed data mining of results on clinical isolates of the Mycobacterium tuberculosis complex representative of global mycobacterial allelic diversity. Knowledge rules permitting automatic labeling of major M. tuberculosis families were defined. Using this strategy, MIRU 24 appeared to be most appropriate for classifying our dataset. The Bovis family was shown to be perfectly classified by a maximum of 3 MIRUs, followed by Africanum and East African Indian (EAI) families by 4 MIRUs, the Beijing family by 6 MIRUs, Haarlem and X families by 8 MIRUs, the T family by 9, and the Latin-American and Mediterranean (LAM) family by 10 MIRUs. Considering the hierarchy of family divergence, our results corroborate a recent suggestion that EAI is the ancestral family followed by Africanum and Bovis. On the other hand, T, X, LAM and Haarlem families appear to be of more recent evolution. These results indicate that data mining of MIRUs is a valuable new tool for analyzing the evolutionary dynamics of the M. tuberculosis complex, and for monitoring an infectious disease such as tuberculosis.

Bacterial Typing Techniques↗
PubMed1998

Telomere length dynamics in telomerase-positive immortal human cell populations.

It has been proposed that the progressive shortening of telomeres in somatic cells eventually results in senescence. Previous experiments have demonstrated that many immortal cell lines have acquired telomerase activity leading to stabilization of telomere length. Telomere dynamics and telomerase activity were examined in the telomerase-positive immortal cell lines HeLa and 293 and subclones derived from them. A mass culture of HeLa cells had a stable mean telomere length over 60 population doublings (PD) in vitro. Subclones of this culture, however, had a range of mean telomere lengths indicating that telomeric heterogeneity exists within a population with a stable mean telomere length. Some of the subclones lacked detectable telomerase activity soon after isolation but regained it by PD 18, suggesting that at least some of the variation in telomere length can be attributed to variations in telomerase activity levels. 293 subclones also varied in telomere length and telomerase activity. Some telomerase-positive 293 subclones contained long telomeres that gradually shortened, demonstrating that factors other than telomerase also act to modulate telomere length. Fluctuations in telomere length in telomerase-positive immortalized cells may contribute to chromosomal instability and clonal evolution.

Cell Transformation, Neoplastic↗
PubMed2003

The mitochondrial genome in embryo technologies.

The mammalian mitochondrial genome encodes for 37 genes which are involved in a broad range of cellular functions. The mitochondrial DNA (mtDNA) molecule is commonly assumed to be inherited through oocyte cytoplasm in a clonal manner, and apparently species-specific mechanisms have evolved to eliminate the contribution of sperm mitochondria after natural fertilization. However, recent evidence for paternal mtDNA inheritance in embryos and offspring questions the general validity of this model, particularly in the context of assisted reproduction and embryo biotechnology. In addition to normal mt DNA haplotype variation, oocytes and spermatozoa show remarkable differences in mtDNA content and may be affected by inherited or acquired mtDNA aberrations. All these parameters have been correlated with gamete quality and reproductive success rates. Nuclear transfer (NT) technology provides experimental models for studying interactions between nuclear and mitochondrial genomes. Recent studies demonstrated (i) a significant effect of mtDNA haplotype or other maternal cytoplasmic factors on the efficiency of NT; (ii) phenotypic differences between transmitochondrial clones pointing to functionally relevant nuclear-cytoplasmic interactions; and (iii) neutral or non-neutral selection of mtDNA haplotypes in heteroplasmic conditions. Mitochondria form a dynamic reticulum, enabling complementation of mitochondrial components and possibly mixing of different mtDNA populations in heteroplasmic individuals. Future directions of research on mtDNA in the context of reproductive biotechnology range from the elimination of adverse effects of artificial heteroplasmy, e.g. created by ooplasm transfer, to engineering of optimized constellations of nuclear and cytoplasmic genes for the production of superior livestock.

Animals↗
PubMed2002

Temporal and spatial dynamics of insecticide resistance in Myzus persicae (Hemiptera: Aphididae).

Advances in understanding insecticide resistance in the peach-potato aphid, Myzus persicae (Sulzer), at the genotypic, biochemical and molecular levels have led to rapid and precise methods for the detection of several resistance mechanisms (elevated carboxylesterase, modified acetylcholinesterase or MACE, and knockdown resistance or kdr) in individual insects, and for monitoring their frequencies over space and time. This paper summarises the results of two long-term surveys of resistance dynamics in M persicae in England, based on samples collected directly from field and glasshouse crops or from four 12.2-m suction traps. The study showed marked fluctuations in resistance frequencies that probably reflect the counteracting forces of selection imposed by insecticides for aphids possessing more copies of esterase resistance genes, and selection against these forms when insecticide use is relaxed. There is growing evidence that several different resistance mechanisms in M persicae have associated fitness costs. In the case of esterase and MACE, these costs are apparently strong enough to effect a decline in resistance frequency over winter, and a more prolonged decline over successive cropping seasons when aphid numbers are insufficient to trigger intensive chemical applications. Changes in the overall frequency of resistance genotypes may also be influenced by the predominance of year-round parthenogenesis in M persicae in the UK, leading to non-random associations between mechanisms and selection operating on clonal lineages rather than individual genotypes.

Acetylcholinesterase↗
PubMed2000

Molecular surveillance of European quinolone-resistant clinical isolates of Pseudomonas aeruginosa and Acinetobacter spp. using automated ribotyping.

Nosocomial isolates of Pseudomonas aeruginosa and Acinetobacter spp. exhibit high rates of resistance to antibiotics and are often multidrug resistant. In a previous study (D. Milatovic, A. Fluit, S. Brisse, J. Verhoef, and F. J. Schmitz, Antimicrob. Agents Chemother. 44:1102-1107, 2000), isolates of these species that were resistant to sitafloxacin, a new advanced-generation fluoroquinolone with a high potency and a broad spectrum of antimicrobial activity, were found in high proportion in 23 European hospitals. Here, we investigate the clonal diversity of the 155 P. aeruginosa and 145 Acinetobacter spp. sitafloxacin-resistant isolates from that study by automated ribotyping. Numerous ribogroups (sets of isolates with indistinguishable ribotypes) were found among isolates of P. aeruginosa (n = 34) and Acinetobacter spp. (n = 16), but the majority of the isolates belonged to a limited number of major ribogroups. Sitafloxacin-resistant isolates (MICs > 2 mg/liter, used as a provisional breakpoint) showed increased concomitant resistance to piperacillin, piperacillin-tazobactam, ceftriaxone, ceftazidime, amikacin, gentamicin, and imipenem. The major ribogroups were repeatedly found in isolates from several European hospitals; these isolates showed higher levels of resistance to gentamicin and imipenem, and some of them appeared to correspond to previously described multidrug-resistant international clones of P. aeruginosa (serotype O:12) and Acinetobacter baumannii (clones I and II). Automated ribotyping, when used in combination with more discriminatory typing methods, may be a convenient library typing system for monitoring future epidemiological dynamics of geographically widespread multidrug-resistant bacterial clones.

4-Quinolones↗
PubMed1999

Unusual MRI finding of multiple adenomas in the pituitary gland: a case report and review of the literature.

The simultaneous occurrence of multiple adenomas in the pituitary gland is a rare event. We report the coexistence of three non functioning pituitary microadenomas in a 37-year-old woman, referred to us for oligomenorrhea and headache. Biochemical evaluation revealed prolactin (131 U/liters), follicle-stimulating hormone (4.1 U/liters), luteinizing hormone (3.9 U/liters), 17beta-estradiol (74 pg/mL), free (2.0 pg/mL) and total testosterone (0.5 ng/mL), dehydroepiandrosterone-sulfate (3.5 microg/mL), 17OH-progesterone (0.8 ng/mL), cortisol (13.1 microg/dL), free triiodothyronine (4.8 pmol/L), free thyroxine (18.5 pmol/liters), thyrotropin (1.6 mU/L), and growth hormone (0.2 ng/mL) levels in the normal range, as for as the response to dynamic endocrine tests. MRI showed an enlarged sella turcica, occupied by three distinct hypointense areas that measured less than 5 mm in diameter in the left, medium and right side of the pituitary, respectively. This finding was confirmed 6 months later by a second MRI that revealed also a light increase in microadenomas dimensions. The patient, therefore, underwent neurosurgery by transfenoidal approach. Histologic examination showed no morphologic differences between the specimens obtained from the different microadenomas. Immunohistochemistry evaluation revealed a positive staining for the common alpha-subunit of glycoproteic hormones and negative for the other pituitary hormones tested, while electron microscopy showed cells with a poor secretory apparatus and a variable grade of cell differentiation. In conclusion, we report the fifth case described with multiple pituitary adenomas diagnosed in vivo and the first with three coexisting tumors revealed by MRI before neurosurgery. The occurrence of multiple pituitary tumors emphasizes the role of pituitary and extrahypophiseal factors in the clonal expansion of genetically altered cells.

Adenoma↗
PubMed1998

Dynamics of intra-hepatic lymphocytes in chronic hepatitis C: enrichment for Valpha24+ T cells and rapid elimination of effector cells by apoptosis.

Chronic viral hepatitis is characterized by a dramatic lymphocyte infiltrate in the liver. Although it is one of the most common chronic inflammatory diseases in humans, little information is available on the functional state of these intra-hepatic lymphocytes (IHL). To address this issue, we have optimized cytofluorimetric techniques to assess directly ex vivo the functions, dynamics and repertoires of IHL isolated from biopsies of patients with chronic hepatitis C. We estimate that 1% of the total body lymphocytes infiltrate the inflamed liver and find that, at variance with peripheral blood lymphocytes (PBL) isolated from the same patients, most IHL display an activated phenotype and produce Th1 type lymphokines when stimulated in vitro. Virtually all IHL are found in the G0/G1 state of the cell cycle, while a sizeable percentage of them is undergoing programmed cell death in vivo, as detected by the TUNEL assay performed on freshly isolated cells. In contrast again to PBL from the same patients, IHL show a preferential compartmentalization of NK and TCRgamma/delta+ cells, and a remarkable (up to 20-fold) enrichment for Valpha24+ T cells. Together our data suggest that in a liver injured by chronic hepatitis C, most IHL are pro-inflammatory activated cells which are highly enriched for effectors of innate resistance. These IHL do not undergo clonal expansion in the liver but rather display effector function and die in situ at a high rate, suggesting that maintenance of the IHL pool is dependent on continuous migration from extra-hepatic sites.

Antigens, CD1↗