The Histone Methyltransferase SETDB1 Controls T Helper Cell Lineage Integrity by Repressing Endogenous Retroviruses.

Upon activation, naive CD4+ T cells differentiate into distinct T cell subsets via processes reliant on epigenetically regulated, lineage-specific developmental programs. Here, we examined the function of the histone methyltransferase SETDB1 in T helper (Th) cell differentiation. Setdb1-/- naive CD4+ T cells exhibited exacerbated Th1 priming, and when exposed to a Th1-instructive signal, Setdb1-/- Th2 cells crossed lineage boundaries and acquired a Th1 phenotype. SETDB1 did not directly control Th1 gene promoter activity but relied instead on deposition of the repressive H3K9me3 mark at a restricted and cell-type-specific set of endogenous retroviruses (ERVs) located in the vicinity of genes involved in immune processes. Refined bioinformatic analyses suggest that these retrotransposons regulate Th1 gene cis-regulatory elements or act as Th1 gene enhancers. Thus, H3K9me3 deposition by SETDB1 ensures Th cell lineage integrity by repressing a repertoire of ERVs that have been exapted into cis-regulatory modules to shape and control the Th1 gene network.

Peripheral regulatory T lymphocytes recirculating to the thymus suppress the development of their precursors.

Most T lymphocytes, including regulatory T cells (Treg cells), differentiate in the thymus. The age-dependent involution of this organ leads to decreasing production of T cells. Here we found that the output of new Treg cells from the thymus decreased substantially more than that of conventional T cells. Peripheral mouse and human Treg cells recirculated back to the thymus, where they constituted a large proportion of the pool of Treg cells and displayed an activated and differentiated phenotype. In the thymus, the recirculating cells exerted their regulatory function by inhibiting interleukin 2 (IL-2)-dependent de novo differentiation of Treg cells. Thus, Treg cell development is controlled by a negative feedback loop in which mature progeny cells return to the thymus and restrain development of precursors of Treg cells.

Robust intrathymic development of regulatory T cells in young NOD mice is rapidly restrained by recirculating cells.

Regulatory T lymphocytes (Treg) play a vital role in the protection of the organism against autoimmune pathology. It is therefore paradoxical that comparatively large numbers of Treg were found in the thymus of type I diabetes-prone NOD mice. The Treg population in the thymus is composed of newly developing cells and cells that had recirculated from the periphery back to the thymus. We here demonstrate that exceptionally large numbers of Treg develop in the thymus of young, but not adult, NOD mice. Once emigrated from the thymus, an unusually large proportion of these Treg is activated in the periphery, which causes a particularly abundant accumulation of recirculating Treg in the thymus. These cells then rapidly inhibit de novo development of Treg. The proportions of developing Treg thus reach levels similar to or lower than those found in most other, type 1 diabetes-resistant, inbred mouse strains. Thus, in adult NOD mice the particularly large Treg-niche is actually composed of mostly recirculating cells and only few newly developing Treg.

A Presurgical Study of Curcumin Combined with Anthocyanin Supplements in Patients with Colorectal Adenomatous Polyps.

Adenomatous polyps are precancerous lesions associated with a higher risk of colorectal cancer (CRC). Curcumin and anthocyanins have shown promising CRC-preventive activity in preclinical and epidemiological studies. The objective of this window-of-opportunity, proof-of principle trial was to evaluate the effect of curcumin combined with anthocyanin supplements on tissue biomarkers of colorectal adenomatous polyps. Eligible patients received either anthocyanin and curcumin supplementation or related matching placebo for 4-6 weeks before polyp removal. Adenomatous polyps and adjacent tissue biopsies were collected at baseline and after supplementation for immunohistochemical assessment of ß-catenin, NF-kappa B (NF-κB), Ki-67, P53, and dysplasia. No differences were observed in baseline biomarker expression between normal and dysplastic tissues. The combination of anthocyanins and curcumin resulted in a significant borderline reduction of NF-κB immunohistochemistry (IHC) expression in adenoma tissue (geometric mean ratio (GMR): 0.72; 95% confidence interval (CI): 0.51-1.00; p-value: 0.05) and a trend to a reduction of Ki-67 (GMR: 0.73; 95% CI: 0.50-1.08; p-value: 0.11). No significant modulation of biomarkers in normal adjacent mucosa was observed. We concluded that the combined supplementation of anthocyanins and curcumin seems to lead to a potentially favorable modulation of tissue biomarkers of inflammation and proliferation in colon adenomas.

Age-Dependent Changes in Regulatory T Lymphocyte Development and Function: A Mini-Review.

The generation and function of immuno-suppressive regulatory T lymphocytes (Treg), which can differentiate in the thymus (tTreg) or in the periphery (pTreg), are regulated in an age-dependent manner. tTreg are produced at high levels in the first weeks of age, when they expand and colonize secondary lymphoid organs and peripheral tissues to protect the organism from autoimmune diseases and to promote tissue repair. Once this population of Treg is operational in the periphery, at puberty, thymic output of Treg declines, but self-reactive tTreg generated early on in life are maintained over time and play a major role in preserving homeostasis of the immune system. Extra-thymic pTreg differentiation declines later on in life. pTreg generated throughout life mainly protect the organism from chronic inflammation and the semi-allogeneic fetus from rejection. In this review, age-dependent modulation of the production and function of these two populations of Treg is described.

Antimicrobial resistance: A global emerging threat to public health systems.

Antimicrobial resistance (AMR) became in the last two decades a global threat to public health systems in the world. Since the antibiotic era, with the discovery of the first antibiotics that provided consistent health benefits to human medicine, the misuse and abuse of antimicrobials in veterinary and human medicine have accelerated the growing worldwide phenomenon of AMR. This article presents an extensive overview of the epidemiology of AMR, with a focus on the link between food producing-animals and humans and on the legal framework and policies currently implemented at the EU level and globally. The ways of responding to the AMR challenges foresee an array of measures that include: designing more effective preventive measures at farm level to reduce the use of antimicrobials; development of novel antimicrobials; strengthening of AMR surveillance system in animal and human populations; better knowledge of the ecology of resistant bacteria and resistant genes; increased awareness of stakeholders on the prudent use of antibiotics in animal productions and clinical arena; and the public health and environmental consequences of AMR. Based on the global nature of AMR and considering that bacterial resistance does not recognize barriers and can spread to people and the environment, the article ends with specific recommendations structured around a holistic approach and targeted to different stakeholders.

Mouse and human CD8(+) CD28(low) regulatory T lymphocytes differentiate in the thymus.

Regulatory T (Treg) lymphocytes play a central role in the control of immune responses and so maintain immune tolerance and homeostasis. In mice, expression of the CD8 co-receptor and low levels of the co-stimulatory molecule CD28 characterizes a Treg cell population that exerts potent suppressive function in vitro and efficiently controls experimental immunopathology in vivo. It has remained unclear if CD8(+) CD28(low) Treg cells develop in the thymus or represent a population of chronically activated conventional T cells differentiating into Treg cells in the periphery, as suggested by their CD28(low) phenotype. We demonstrate that functional CD8(+) CD28(low) Treg cells are present in the thymus and that these cells develop locally and are not recirculating from the periphery. Differentiation of CD8(+) CD28(low) Treg cells requires MHC class I expression on radioresistant but not on haematopoietic thymic stromal cells. In contrast to other Treg cells, CD8(+) CD28(low) Treg cells develop simultaneously with CD8(+) CD28(high) conventional T cells. We also identified a novel homologous naive CD8(+) CD28(low) T-cell population with immunosuppressive properties in human blood and thymus. Combined, our data demonstrate that CD8(+) CD28(low) cells can develop in the thymus of mice and suggest that the same is true in humans.

Long-term prevention of chronic allograft rejection by regulatory T-cell immunotherapy involves host Foxp3-expressing T cells.

Despite the use of immunosuppressive drugs, chronic allograft rejection remains a major hurdle in transplantation medicine. Induction of specific immunologic tolerance to antigens expressed by the graft would avoid its eventual functional loss and the severe side effects of paralyzing the immune system. We previously showed that donor-specific regulatory T-lymphocytes prevent rejection of fully allogeneic bone marrow (BM) grafts in mice. Thus generated hematopoietic chimeras then accepted skin and heart allografts of the same donor. We noticed that injected regulatory T-cells (Tregs) disappeared with time and investigated the mechanisms involved in the nevertheless long-term persistence of allograft tolerance. Using Tregs that can be depleted in vivo with diphtheria toxin, we show that injected cells are required for induction but not for maintenance of tolerance to BM allografts. We observed progressive deletion of donor-specific T-lymphocytes, accounting at least in part for maintenance of tolerance. Toxin-induced depletion of administered as well as host Tregs did not affect hematopoietic chimerism but it led to rapid loss of skin allografts. Therefore, our data show that newly generated host Tregs can prevent chronic allograft rejection. Long-lasting tolerance to allografts is thus achieved.

Increased thymic development of regulatory T cells in NOD mice is functionally dissociated from type I diabetes susceptibility.

Regulatory T (Treg) lymphocytes play a central role in the control of autoimmune pathology. Any alteration in Treg-cell biology in mouse strains used for the study of these disorders therefore raises the question of its direct link with disease susceptibility. Paradoxically, in non-obese diabetic (NOD) mice increased numbers of Treg cells develop in the thymus. In this report we identify a locus of <7 Mbp that quantitatively controls Treg-cell development in the thymus of the NOD mouse. This 'Trd1' region is located centromeric to the H2 complex on chromosome 17 and does not include genes encoding classical MHC molecules. The genomic region identified here contains the Idd16 diabetes susceptibility locus and the use of congenic mouse strains allowed us to investigate the potential link between quantitatively altered thymic Treg cells and diabetes susceptibility. Hybrid mice present similar levels of thymic Treg cells as B6 animals but they developed diabetes with the same kinetics as NOD mice. Therefore, the increased Treg-cell development in NOD mice controlled by Trd1 is functionally dissociated from the susceptibility of NOD to diabetes.

The thymic niche does not limit development of the naturally diverse population of mouse regulatory T lymphocytes.

Thymus-derived CD4(+)Foxp3(+) regulatory T lymphocytes (Tregs) play a central role in the suppression of immune responses to self-antigens and thus avoid autoimmune disorders. It remains unclear if the specialized thymic niche controls the number of differentiating Tregs. We investigated development of murine Tregs from precursors expressing the naturally very large repertoire of TCRs. By analyzing their developmental kinetics, we observed that differentiating Tregs dwell in the thymus ∼1 d longer than their conventional T cell counterparts. By generating hematopoietic chimeras with very low proportions of trackable precursors, we could follow individual waves of developing T cells in the thymus. We observed strongly increased proportions of Tregs at the end of the waves, confirming that these cells are the last to leave the thymus. To assess whether the thymic niche limits Treg development, we generated hematopoietic chimeras in which very few T cell precursors could develop. The substantial increase in the proportion of Tregs we found in these mice suggested a limiting role of the thymic niche; however, this increase was accounted for entirely by the prolonged thymic dwell time of Tregs. We conclude that, when precursors express a naturally diverse TCR repertoire, the thymic niche does not limit differentiation of Tregs.

Autoimmune regulator (AIRE)-deficient CD8+CD28low regulatory T lymphocytes fail to control experimental colitis.

Mutations in the gene encoding the transcription factor autoimmune regulator (AIRE) are responsible for autoimmune polyendocrinopathy candidiasis ectodermal dystrophy syndrome. AIRE directs expression of tissue-restricted antigens in the thymic medulla and in lymph node stromal cells and thereby substantially contributes to induction of immunological tolerance to self-antigens. Data from experimental mouse models showed that AIRE deficiency leads to impaired deletion of autospecific T-cell precursors. However, a potential role for AIRE in the function of regulatory T-cell populations, which are known to play a central role in prevention of immunopathology, has remained elusive. Regulatory T cells of CD8(+)CD28(low) phenotype efficiently control immune responses in experimental autoimmune and colitis models in mice. Here we show that CD8(+)CD28(low) regulatory T lymphocytes from AIRE-deficient mice are transcriptionally and phenotypically normal and exert efficient suppression of in vitro immune responses, but completely fail to prevent experimental colitis in vivo. Our data therefore demonstrate that AIRE plays an important role in the in vivo function of a naturally occurring regulatory T-cell population.

Organic toxicants and emerging contaminants in hospital interiors before and during the SARS-CoV2 pandemic: alkanes and PAHs.

Indoor pollution and deposition dust (DD), in particular, are acquiring concern, due to long exposure time and importance of intake by humans through contact and ingestion. Hospitals look a special category of sites, owing to peculiar contaminants affecting them and to presence of people prone to adverse effects induced by toxicants. Four in-field campaigns aimed at understanding the chemical composition of DD were performed in five Italian hospitals. Measurements were performed before (autumn 2019), during (spring 2021), and after (winter 2022) the peak of SARS-CoV2 and when restrictions caused by pandemic were revoked (winter 2023). Parallel measurements were made outdoors (2022), as well as in a university and a dwelling. Targeted contaminants were n-alkanes and polycyclic aromatic hydrocarbons (PAHs), while iso- and anteiso-alkanes were analyzed to assess the impact of tobacco smoking. Total n-alkanes ranged from 3.9 ± 2.3 to 20.5 ± 4.2 mg/g, with higher percentages of short chain homologs in 2019. PAHs ranged from 0.24 ± 0.22 to 0.83 ± 0.50 mg/g, with light congeners (≤ 228 a.m.u.) always exceeding the heavy ones (≥ 252 a.m.u.). According to carbon preference indexes, alkanes originated overall from anthropogenic sources. Microorganisms resulted to affect a hospital, and tobacco smoke accounted for ~ 4-20‰ of DD mass. As for PAH sources, the diagnostic concentration ratios suggested the concourse of biological matter burning and vehicle emission. Benzo[a]pyrene equivalent carcinogenic and mutagenic potencies of depositions at hospitals ranged ~ 9-39 µg/g and ~ 15-76 µg/g, respectively, which seems of concern for health. DD composition in hospitals was different from that outside the premises, as well as that found at university and at dwelling.

The type 1 diabetes susceptibility locus Idd5 favours robust neonatal development of highly autoreactive regulatory T cells in the NOD mouse.

Regulatory T lymphocytes expressing the transcription factor Foxp3 (Tregs) play an important role in the prevention of autoimmune diseases and other immunopathologies. Aberrations in Treg-mediated immunosuppression are therefore thought to be involved in the development of autoimmune pathologies, but few have been documented. Recent reports indicated a central role for Tregs developing during the neonatal period in the prevention of autoimmune pathology. We therefore investigated the development of Tregs in neonatal NOD mice, an important animal model for autoimmune type 1 diabetes. Surprisingly, we found that, as compared with seven other commonly studied inbred mouse strains, in neonatal NOD mice, exceptionally large proportions of developing Tregs express high levels of GITR and PD-1. The latter phenotype was previously associated with high Treg autoreactivity in C57BL/6 mice, which we here confirm for NOD animals. The proportions of newly developing GITRhighPD-1+ Tregs rapidly drop during the first week of age. A genome-wide genetic screen indicated the involvement of several diabetes susceptibility loci in this trait. Analysis of a congenic mouse strain confirmed that Idd5 contributes to the genetic control of GITRhighPD-1+ Treg development in neonates. Our data thus demonstrate an intriguing and paradoxical correlation between an idiosyncrasy in Treg development in NOD mice and their susceptibility to type 1 diabetes.

Molecular signatures of organic particulates as tracers of emission sources.

Chemical signature of airborne particulates and deposition dusts is subject of study since decades. Usually, three complementary composition markers are investigated, namely, (i) specific organic compounds; (ii) concentration ratios between congeners, and (iii) percent distributions of homologs. Due to its intrinsic limits (e.g., variability depending on decomposition and gas/particle equilibrium), the identification of pollution sources based on molecular signatures results overall restricted to qualitative purposes. Nevertheless, chemical fingerprints allow drawing preliminary information, suitable for successfully approaching multivariate analysis and valuing the relative importance of sources. Here, the state-of-the-art is presented about the molecular fingerprints of non-polar aliphatic, polyaromatic (PAHs, nitro-PAHs), and polar (fatty acids, organic halides, polysaccharides) compounds in emissions. Special concern was addressed to alkenes and alkanes with carbon numbers ranging from 12 to 23 and ≥ 24, which displayed distinct relative abundances in petrol-derived spills and exhausts, emissions from microorganisms, high vegetation, and sediments. Long-chain alkanes associated with tobacco smoke were characterized by a peculiar iso/anteiso/normal homolog fingerprint and by n-hentriacontane percentages higher than elsewhere. Several concentration ratios of PAHs were identified as diagnostic of the type of emission, and the sources of uncertainty were elucidated. Despite extensive investigations conducted so far, the origin of uncommon molecular fingerprints, e.g., alkane/alkene relationships in deposition dusts and airborne particles, remains quite unclear. Polar organics resulted scarcely investigated for pollution apportioning purposes, though they looked as indicative of the nature of sources. Finally, the role of humans and living organisms as actual emitters of chemicals seems to need concern in the future.

Indexes of tobacco smoke contribution to environmental particulates based on molecular fingerprints of alkanes.

Tobacco smoke (TS) is the source of a number of toxicants affecting the atmosphere and poses a threat to smokers and the whole community. Chemical, physical, and toxicological features of smoking products (vapors as well as mainstream, side stream, and third-hand smoke) have been investigated extensively. Special attention is paid to organic compounds (individually or in combination giving rise to peculiar molecular fingerprints), potentially able to act as "chemical signature" of TS. In this regard, the percent distribution of long-chainnormal, iso, and anteiso alkanes was ascertained as typical of TS. Nevertheless, until now no indexes have been identified as suitable for assessing the global TS contribution to environmental pollution, e.g., the TS percentage in carbonaceous aerosol and in deposited dusts, the only exception consisting in the use of nicotelline as tracer. This paper describes the results of an extensive study aimed at chemically characterizing the nonpolar lipid fraction associated to suspended particulates (PMs) and deposition dusts (DDs) collected at indoor and outdoor locations. Based on the iso, anteiso, and normal C29-C34 alkane profile in the samples as well in tobacco smoke- and no-TS-related emissions (literature data), various parameters describing the distribution of compounds were investigated. Finally, a cumulative variable was identified as the tobacco smoke impact index (TS%) suitable for estimating the TS percentage occurring in the particulate matter. The TS% rates were plotted vs. the exceedance of normal C31 alkane with respect to the average of C29 and C33 homologs, which results higher in TS than in most other emissions, revealing a link in the case of suspended particulates but not of deposited dusts. According to back analysis carried out on all particulate matter sets, it was found that traces of TS affect even remote areas, while inside the smokers' homes the contributions of TS to PM could account for up to ~61% and ~10%, respectively, in PM and DD. This confirms the need of valuing the health risk posed by TS to humans, by means of tools easy to apply in extensive investigations.

IL-2 and IL-15 drive intrathymic development of distinct periphery-seeding CD4+Foxp3+ regulatory T lymphocytes.

Development of Foxp3-expressing regulatory T-lymphocytes (Treg) in the thymus is controlled by signals delivered in T-cell precursors via the TCR, co-stimulatory receptors, and cytokine receptors. In absence of IL-2, IL-15 or their receptors, fewer Treg apparently develop in the thymus. However, it was recently shown that a substantial part of thymic Treg are cells that had recirculated from the periphery back to the thymus, troubling interpretation of these results. We therefore reassessed the involvement of IL-2 and IL-15 in the development of Treg, taking into account Treg-recirculation. At the age of three weeks, when in wt and IL-15-deficient (but not in IL-2-deficient) mice substantial amounts of recirculating Treg are present in the thymus, we found similarly reduced proportions of newly developed Treg in absence of IL-2 or IL-15, and in absence of both cytokines even less Treg developed. In neonates, when practically no recirculating Treg were found in the thymus, the absence of IL-2 led to substantially more reduced Treg-development than deficiency in IL-15. IL-2 but not IL-15 modulated the CD25, GITR, OX40, and CD73-phenotypes of the thymus-egress-competent and periphery-seeding Treg-population. Interestingly, IL-2 and IL-15 also modulated the TCR-repertoire expressed by developing Treg. Upon transfer into Treg-less Foxp3sf mice, newly developed Treg from IL-2- (and to a much lesser extent IL-15-) deficient mice suppressed immunopathology less efficiently than wt Treg. Taken together, our results firmly establish important non-redundant quantitative and qualitative roles for IL-2 and, to a lesser extent, IL-15 in intrathymic Treg-development.

Exposure levels and health risk of PAHs associated with fine and ultrafine aerosols in an urban site in northern Algeria.

Size distribution of toxicants in airborne particulates remains insufficiently investigated in Algeria. A 1-year campaign was performed at Bab Ezzouar, Algiers (Algeria), aimed at characterizing particulates for their physical and chemical features. For this purpose, scanning electronic microscopy (SEM), Raman spectroscopy (RaS), and GC-MS methodologies were applied. The samples were collected on daily basis by means of a high-volume sampling (HVS) system equipped with cascade impactor separating three size fractions, i.e., particles with aerodynamic diameters d < 1.0 µm (PM1), 1.0 µm

The Repertoire of Newly Developing Regulatory T Cells in the Type 1 Diabetes-Prone NOD Mouse Is Very Diverse.

Regulatory T lymphocytes expressing the forkhead/winged helix transcription factor Foxp3 (Treg) play a vital role in the protection of the organism from autoimmune disease and other immunopathologies. The antigen specificity of Treg plays an important role in their in vivo activity. We therefore assessed the diversity of the T-cell receptors (TCRs) for antigen expressed by Treg newly developed in the thymus of autoimmune type 1 diabetes-prone NOD mice and compared it to the control mouse strain C57BL/6. Our results demonstrate that use of the TCRα and TCRß variable (V) and joining (J) segments, length of the complementarity determining region (CDR) 3, and the diversity of the TCRα and TCRß chains are comparable between NOD and C57BL/6 mice. Genetic defects affecting the diversity of the TCR expressed by newly developed Treg therefore do not appear to be involved in the etiology of type 1 diabetes in the NOD mouse.

Predicting mortality in non-variceal upper gastrointestinal bleeders: validation of the Italian PNED Score and Prospective Comparison with the Rockall Score.

OBJECTIVES: We sought (i) to validate a new prediction rule of mortality (Progetto Nazionale Emorragia Digestiva (PNED) score) on an independent population with non-variceal upper gastrointestinal bleeding (UGIB) and (ii) to compare the accuracy of the Italian PNED score vs. the Rockall score in predicting the risk of death. METHODS: We conducted prospective validation of analysis of consecutive patients with UGIB at 21 hospitals from 2007 to 2008. Outcome measure was 30-day mortality. All the variables used to calculate the Rockall score as well as those identified in the Italian predictive model were considered. Calibration of the model was tested using the chi2 goodness-of-fit and performance characteristics with receiver operating characteristic (ROC) analysis. The area under the ROC curve (AUC) was used to quantify the diagnostic accuracy of the two predictive models. RESULTS: Over a 16-month period, data on 1,360 patients were entered in a national database and analyzed. Peptic ulcer bleeding was recorded in 60.7% of cases. One or more comorbidities were present in 66% of patients. Endoscopic treatment was delivered in all high-risk patients followed by high-dose intravenous proton pump inhibitor in 95% of them. Sixty-six patients died (mortality 4.85%; 3.54-5.75). The PNED score showed a high discriminant capability and was significantly superior to the Rockall score in predicting the risk of death (AUC 0.81 (0.72-0.90) vs. 0.66 (0.60-0.72), P<0.000). Positive likelihood ratio for mortality in patients with a PNED risk score >8 was 16.05. CONCLUSIONS: The Italian 10-point score for the prediction of death was successfully validated in this independent population of patients with non-variceal gastrointestinal bleeding. The PNED score is accurate and superior to the Rockall score. Further external validation at the international level is needed.

Organic molecular markers in marine aerosols over the Western Mediterranean Sea.

A scientific campaign was undertaken along the Western sector of the Mediterranean Sea in the summer 2015 (26th Jun to 13th Jul), with the goal of gathering information about organic contaminants affecting marine aerosol over the Italian seas and with a special focus on changes in composition due to sources. 24 PM10 atmospheric samples in total were chemically characterized, including polycyclic aromatic hydrocarbons (PAHs), aliphatic hydrocarbons (n-alkanes) and phthalate esters. Contemporarily, regulated gaseous toxicants (i.e. ozone, nitrogen oxides and sulfur dioxide) and meteorological parameters were recorded. Samplings were carried out inshore in front of harbors (N = 7) and along the cruise, both during the vessel shipping (N = 11, transects) and at its stops offshore (N = 6). Total PAH concentrations ranged from 0.03 to 1.94 ng/m3 and raised close to harbors and coastal sites, confirming that continental sources were responsible for the strong increase of pollution levels there compared to offshore. The percent composition and diagnostic ratio rates of PAHs were different for harbors, while transects were in agreement with offshore stops, possibly due to the different impact of pollution sources. n-Alkanes (C21C38) and the corresponding carbon preference index rates (CPI) were assessed; their values ranged 8.7-90 ng/m3 and 1.1-2.9 respectively, which suggested that fossil fuel combustion was the dominant source, though biogenic emission could contribute. Alkyl phthalates revealed wide variability in concentrations among aerosol samples. Moreover, long-range atmospheric transport and particle ageing effect induced by photo-oxidants were important factors controlling the composition of organic aerosols in the Mediterranean Sea air.