T Follicular Helper Cell Heterogeneity.

T follicular helper (Tfh) cells specialize in helping B cells and are therefore critical contributors to the generation of humoral immunity. Tfh cells aid immunoglobulin class-switch recombination and support the germinal center response, thereby promoting immunoglobulin affinity maturation and the generation of humoral immune memory. Although their primary function is to promote B cell responses, Tfh cells also display phenotypic and functional diversity determined by the immunological and spatial contexts from which they emerge. We review recent advances in understanding the heterogeneity within Tfh cell subsets along with their differentiation and migratory trajectory, the phenotype they adopt, their ontological relationships with one another, and their function in their respective environments. Expected final online publication date for the Annual Review of Immunology, Volume 42 is April 2024. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Dual growth factor-modified microspheres nesting human-derived umbilical cord mesenchymal stem cells for bone regeneration.

BACKGROUND: Modular tissue engineering (MTE) is a novel "bottom-up" approach that aims to mimic complex tissue microstructural features. The constructed micromodules are assembled into engineered biological tissues with repetitive functional microunits and form cellular networks. This is emerging as a promising strategy for reconstruction of biological tissue. RESULTS: Herein, we constructed a micromodule for MTE and developed engineered osteon-like microunits by inoculating human-derived umbilical cord mesenchymal stem cells (HUMSCs) onto nHA/PLGA microspheres with surface modification of dual growth factors (BMP2/bFGF). By evaluating the results of proliferation and osteogenic differentiation ability of HUMSCs in vitro, the optimal ratio of the dual growth factor (BMP2/bFGF) combination was derived as 5:5. In vivo assessments showed the great importance of HUMSCs for osteogneic differentiation. Ultimately, direct promotion of early osteo-differentiation manifested as upregulation of Runx-2 gene expression. The vascularization capability was evaluated by tube formation assays, demonstrating the importance of HUMSCs in the microunits for angiogenesis. CONCLUSIONS: The modification of growth factors and HUMSCs showed ideal biocompatibility and osteogenesis combined with nHA/PLGA scaffolds. The micromodules constructed in the current study provide an efficient stem cell therapy strategy for bone defect repair.

Cutting Edge: IL-21 and Tissue-Specific Signals Instruct Tbet+CD11c+ B Cell Development following Viral Infection.

Tbet+CD11c+ B cells, also known as age-associated B cells (ABCs), are pivotal contributors to humoral immunity following infection and in autoimmunity, yet their in vivo generation is incompletely understood. We used a mouse model of systemic acute lymphocytic choriomeningitis virus infection to examine the developmental requirements of ABCs that emerged in the spleen and liver. IL-21 signaling through STAT3 was indispensable for ABC development. In contrast, IFN-γ signaling through STAT1 was required for B cell activation and proliferation. Mice that underwent splenectomy or were deficient in lymphotoxin α generated hepatic ABCs despite the lack of secondary lymphoid organ contributions, suggesting that the liver supported de novo generation of these cells separately from their development in lymphoid organs. Thus, IFN-γ and IL-21 signaling have distinct, stage-specific roles in ABC differentiation, while the tissue microenvironment provides additional cues necessary for their development.

Chemical Composition and In Vitro Antioxidant Activity and Anti-Acetylcholinesterase Activity of Essential Oils from Tadehagi triquetrum (L.) Ohashi.

The present study aimed to determine the chemical compositions of essential oils (EOs) from Tadehagi triquetrum (L.) Ohashi and evaluate their antioxidant and anti-cholinesterase activity under the comprehensive influence of chemical components. The essential oils were extracted from T. triquetrum (L.) Ohashi by hydrodistillation. A total of 58 organic compounds were identified by GC-FID and GC-MS analysis. The major components of T. triquetrum (L.) Ohashi EOs were identified as palmitic acid (22.46%), 1-Octen-3-ol (14.07%), Caryophyllene (7.20%), (Z)-18-Octadec-9-enolide (6.04%), and 3-Hexen-1-ol (4.55%). The antioxidant activity of the essential oils was determined by using ABTS assay, DPPH assay, and FRAP assay, with IC50 values of 2.12 ± 0.05 mg/mL, 4.73 ± 0.91 mg/mL against the ABTS, DPPH, and FRAP value 117.42 ± 8.10 mM/g. The result showed that it had moderate antioxidant activities in the experiment, which why it is likely that it will be used as an antioxidant. At the same time, the EOs also showed moderate anti-acetylcholinesterase activity. This study expands the chemical and biological knowledge of the EOs of T. triquetrum.

The ion transporter Na+-K+-ATPase enables pathological B cell survival in the kidney microenvironment of lupus nephritis.

The kidney is a comparatively hostile microenvironment characterized by highsodium concentrations; however, lymphocytes infiltrate and survive therein in autoimmune diseases such as lupus. The effects of sodium-lymphocyte interactions on tissue injury in autoimmune diseases and the mechanisms used by infiltrating lymphocytes to survive the highsodium environment of the kidney are not known. Here, we show that kidney-infiltrating B cells in lupus adapt to elevated sodium concentrations and that expression of sodium potassium adenosine triphosphatase (Na+-K+-ATPase) correlates with the ability of infiltrating cells to survive. Pharmacological inhibition of Na+-K+-ATPase and genetic knockout of Na+-K+-ATPase γ subunit resulted in reduced B cell infiltration into kidneys and amelioration of proteinuria. B cells in human lupus nephritis biopsies also had high expression of Na+-K+-ATPase. Our study reveals that kidney-infiltrating B cells in lupus initiate a tissue adaption program in response to sodium stress and identifies Na+-K+-ATPase as an organ-specific therapeutic target.

Chemical Composition and In Vitro Antioxidant Activity of Sida rhombifolia L. Volatile Organic Compounds.

In the current study, the phytochemical constituents of volatile organic compounds (VOCs) obtained from Sida rhombifolia L. were identified by GC-FID and GC-MS analysis. A total of 73 volatile organic compounds were identified. The major components of S. rhombifolia VOCs were identified as palmitic acid (21.56%), phytol (7.02%), 6,10,14-trimethyl-2-pentadecanone (6.30%), oleic acid (5.48%), 2-pentyl-furan (5.23%), and linoleic acid (3.21%). The VOCs are rich in fatty acids (32.50%), olefine aldehyde (9.59%), ketone (9.41%), enol (9.02%), aldehyde (8.63%), and ketene (6.41%). The antioxidant capacity of S. rhombifolia VOCs was determined by 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH), 2,2-azinobis-(3-ethylbenzothiazolin-6-sulfonic acid) diammonium salt (ABTS), and ferric reducing/antioxidant power (FRAP) methods with butylated hydroxytoluene (BHT) and Trolox as standard. The VOCs showed dose-dependent antioxidant activity with IC50 (50% inhibitory concentration) values of 5.48 ± 0.024 and 1.47 ± 0.012 mg/mL for DPPH and ABTS assays, respectively. FRAP antioxidant capacity was 83.10 ± 1.66 mM/g. The results show that the VOCs distilled from S. rhombifolia have a moderate antioxidant property that can be utilized as a natural botanical supplement or an antioxidant.

Development of Tbet- and CD11c-expressing B cells in a viral infection requires T follicular helper cells outside of germinal centers.

Tbet+CD11c+ B cells arise during type 1 pathogen challenge, aging, and autoimmunity in mice and humans. Here, we examined the developmental requirements of this B cell subset. In acute infection, T follicular helper (Tfh) cells, but not Th1 cells, drove Tbet+CD11c+ B cell generation through proximal delivery of help. Tbet+CD11c+ B cells developed prior to germinal center (GC) formation, exhibiting phenotypic and transcriptional profiles distinct from GC B cells. Fate tracking revealed that most Tbet+CD11c+ B cells developed independently of GC entry and cell-intrinsic Bcl6 expression. Tbet+CD11c+ and GC B cells exhibited minimal repertoire overlap, indicating distinct developmental pathways. As the infection resolved, Tbet+CD11c+ B cells localized to the marginal zone where splenic retention depended on integrins LFA-1 and VLA-4, forming a competitive memory subset that contributed to antibody production and secondary GC seeding upon rechallenge. Therefore, Tbet+CD11c+ B cells comprise a GC-independent memory subset capable of rapid and robust recall responses.

High-affinity, neutralizing antibodies to SARS-CoV-2 can be made without T follicular helper cells.

T follicular helper (TFH) cells are the conventional drivers of protective, germinal center (GC)­based antiviral antibody responses. However, loss of TFH cells and GCs has been observed in patients with severe COVID-19. As T cell­B cell interactions and immunoglobulin class switching still occur in these patients, noncanonical pathways of antibody production may be operative during SARS-CoV-2 infection. We found that both TFH-dependent and -independent antibodies were induced against SARS-CoV-2 infection, SARS-CoV-2 vaccination, and influenza A virus infection. Although TFH-independent antibodies to SARS-CoV-2 had evidence of reduced somatic hypermutation, they were still high affinity, durable, and reactive against diverse spike-derived epitopes and were capable of neutralizing both homologous SARS-CoV-2 and the B.1.351 (beta) variant of concern. We found by epitope mapping and B cell receptor sequencing that TFH cells focused the B cell response, and therefore, in the absence of TFH cells, a more diverse clonal repertoire was maintained. These data support an alternative pathway for the induction of B cell responses during viral infection that enables effective, neutralizing antibody production to complement traditional GC-derived antibodies that might compensate for GCs damaged by viral inflammation.

Type I Interferon-Activated STAT4 Regulation of Follicular Helper T Cell-Dependent Cytokine and Immunoglobulin Production in Lupus.

OBJECTIVE: To assess the role of STAT4 activation in driving pathogenic follicular helper T (Tfh) cell secretion of the cytokines interleukin-21 (IL-21) and interferon-γ (IFNγ) in murine and human lupus. METHODS: The effect of STAT4-dependent Tfh cell signaling on cytokine production and autoreactive B cell maturation was assessed temporally during the course of lupus in a murine model, with further assessment of Tfh cell gene transcription performed using RNA-Seq technology. STAT4-dependent signaling and cytokine production were also determined in circulating Tfh-like cells in patients with systemic lupus erythematosus (SLE), as compared to cells from healthy control subjects, and correlations with disease activity were assessed in the Tfh-like cells from SLE patients. RESULTS: IL-21- and IFNγ-coproducing Tfh cells expanded prior to the detection of potentially pathogenic IgG2c autoantibodies in lupus-prone mice. Tfh cells transcriptionally evolved during the course of disease with acquisition of a STAT4-dependent gene signature. Maintenance of Tfh cell cytokine synthesis was dependent upon STAT4 signaling, driven by type I IFNs. Circulating Tfh-like cells from patients with SLE also secreted IL-21 and IFNγ, with STAT4 phosphorylation enhanced by IFNß, in association with the extent of clinical disease activity. CONCLUSION: We identified a role for type I IFN signaling in driving STAT4 activation and production of IL-21 and IFNγ by Tfh cells in murine and human lupus. Enhanced STAT4 activation in Tfh cells may underlie pathogenic B cell responses in both murine and human lupus. These data indicate that STAT4 guides pathogenic cytokine and immunoglobulin production in SLE, demonstrating a potential therapeutic target to modulate autoimmunity.

Peri-implant keratinized gingiva augmentation using xenogeneic collagen matrix and platelet-rich fibrin: A case report.

BACKGROUND: Keratinized gingival insufficiency is a disease attributed to long-term tooth loss, can severely jeopardizes the long-term health of implants. A simple and effective augmentation surgery method should be urgently developed. CASE SUMMARY: A healthy female patient, 45-year-old, requested implant restoration of the her left mandibular first molar and second molar. Before considering a stage II, as suggested from the probing depth measurements, the widths of the mesial, medial, and distal buccal keratinized gingiva of second molar (tooth #37) were measured and found to be 0.5 mm, 0.5 mm, and 0 mm, respectively. This suggested that the gingiva was insufficient to resist damage from bacterial and mechanical stimulation. Accordingly, modified apically repositioned flap (ARF) surgery combined with xenogeneic collagen matrix (XCM) and platelet-rich fibrin (PRF) was employed to increase the width of gingival tissue. After 1 mo of healing, the widths of mesial, medial, and distal buccal keratinized gingiva reached 4 mm, 4 mm, and 3 mm, respectively, and the thickness of the augmented mucosa was 4.5 mm. Subsequently, through the second-stage operation, the patient obtained an ideal soft tissue shape around the implant. CONCLUSION: For cases with keratinized gingiva widths around implants less than 2mm，the soft tissue width and thickness could be increased by modified ARF surgery combined with XCM and PRF. Moreover, this surgery significantly alleviated patients' pain and ameliorated oral functional comfort.

Magnetic Targeting of HU-MSCs in the Treatment of Glucocorticoid-Associated Osteonecrosis of the Femoral Head Through Akt/Bcl2/Bad/Caspase-3 Pathway.

PURPOSE: Osteonecrosis of the femoral head (ONFH) is a chronic and irreversible disease that eventually develops into a joint collapse and results in joint dysfunction. Early intervention and treatment are essential for preserving the joints and avoiding hip replacement. In this study, a system of human umbilical mesenchymal stem cells-supermagnetic iron oxide nanoparticles (NPs) @polydopamine (SCIOPs) was constructed. The magnetic targeting system gathers in the lesion area, inhibits the apoptosis of bone cells, enhances osteogenic effect, and effectively treats ONFH under external magnetic field. MATERIALS AND METHODS: The supermagnetic iron oxide NPs @polydopamine (SPION@PDA NPs) were characterized by transmission electron microscopy and zeta potential, respectively. The effects of SPION@PDA NPs on the viability, proliferation, and differentiation of stem cells were detected by the CCK8 method, flow cytometry, and staining, respectively. The serum inflammatory indicators were detected by Luminex method. The bone mass of the femoral head was analyzed by micro computed tomography. The expression of apoptosis and osteoblast-related cytokines was detected by Western blotting. The osteogenesis of the femoral head was detected by histological and immunohistochemical sections. RESULTS: The SCIOPs decreased the pro-inflammatory factors, and the micro CT showed that the bone repair of the femoral head was enhanced after treatment. The hematoxylin and eosin sections also showed an increase in the osteogenesis in the femoral head. Western blotting results showed and increased expression of anti-apoptotic proteins Akt and Bcl-2, decreased expression of apoptotic proteins caspase-3 and Bad, and increased expression of osteogenic proteins Runx-2 and Osterix in the femoral head. CONCLUSION: Under the effect of magnetic field and homing ability of stem cells, SCIOPs inhibited the apoptosis of osteoblasts, improved the proliferation ability of osteoblasts, and promoted bone repair in the femoral head through the Akt/Bcl-2/Bad/caspase-3 signaling pathway, thereby optimizing the tissue repair ability.

Effects of Nanoparticle Size and Radiation Energy on Copper-Cysteamine Nanoparticles for X-ray Induced Photodynamic Therapy.

The Copper-cysteamine (Cu-Cy) nanoparticle is a novel sensitizer with a potential to increase the effectiveness of radiation therapy for cancer treatment. In this work, the effect of nanoparticle size and the energy of X-rays on the effectiveness of radiation therapy are investigated. The effect of the particle size on their performance is very complicated. The nanoparticles with an average size of 300 nm have the most intense photoluminescence, the nanoparticles with the average size of 100 nm have the most reactive oxygen species production upon X-ray irradiation, while the nanoparticles with the average size of 40 nm have the best outcome in the tumor suppression in mice upon X-ray irradiation. For energy, 90 kVp radiation resulted in smaller tumor sizes than 250 kVp or 350 kVp radiation energies. Overall, knowledge of the effect of nanoparticle size and radiation energy on radiation therapy outcomes could be useful for future applications of Cu-Cy nanoparticles.

Identification of a T follicular helper cell subset that drives anaphylactic IgE.

Cross-linking of high-affinity immunoglobulin E (IgE) results in the life-threatening allergic reaction anaphylaxis. Yet the cellular mechanisms that induce B cells to produce IgE in response to allergens remain poorly understood. T follicular helper (TFH) cells direct the affinity and isotype of antibodies produced by B cells. Although TFH cell-derived interleukin-4 (IL-4) is necessary for IgE production, it is not sufficient. We report a rare population of IL-13-producing TFH cells present in mice and humans with IgE to allergens, but not when allergen-specific IgE was absent or only low-affinity. These "TFH13" cells have an unusual cytokine profile (IL-13hiIL-4hiIL-5hiIL-21lo) and coexpress the transcription factors BCL6 and GATA3. TFH13 cells are required for production of high- but not low-affinity IgE and subsequent allergen-induced anaphylaxis. Blocking TFH13 cells may represent an alternative therapeutic target to ameliorate anaphylaxis.

T follicular helper cell heterogeneity: Time, space, and function.

T follicular helper (Tfh) cells play a crucial role in orchestrating the humoral arm of adaptive immune responses. Mature Tfh cells localize to follicles in secondary lymphoid organs (SLOs) where they provide help to B cells in germinal centers (GCs) to facilitate immunoglobulin affinity maturation, class-switch recombination, and generation of long-lived plasma cells and memory B cells. Beyond the canonical GC Tfh cells, it has been increasingly appreciated that the Tfh phenotype is highly diverse and dynamic. As naive CD4+ T cells progressively differentiate into Tfh cells, they migrate through a variety of microanatomical locations to obtain signals from other cell types, which in turn alters their phenotypic and functional profiles. We herein review the heterogeneity of Tfh cells marked by the dynamic phenotypic changes accompanying their developmental program. Focusing on the various locations where Tfh and Tfh-like cells are found, we highlight their diverse states of differentiation. Recognition of Tfh cell heterogeneity has important implications for understanding the nature of T helper cell identity specification, especially the plasticity of the Tfh cells and their ontogeny as related to conventional T helper subsets.

Association Between Matrix Metalloproteinase-1, 2, 3 Polymorphisms and Oral Cancer Risk: A Meta-Analysis.

PURPOSE: Numerous studies have estimated the association between matrix metalloproteinases (MMPs) polymorphisms and the risk of oral cancer; the results, however, are inconsistent and conflicting. Therefore, we conducted a meta-analysis to evaluate the association of MMP-1, 2, and 3 polymorphisms with oral cancer risk. METHODS: A computerized literature search was conducted of electronic databases and search engines. Odds ratios (OR) and 95% confidence intervals (CI) were calculated for each gene, and the heterogeneity among studies was estimated using the Q-test and I2 values. Overall and subgroup analyses were undertaken. Statistical analyses were conducted using Review Manager v5.3 and Stata v12.0 software. RESULTS: Eighteen studies were included in this meta-analysis. For MMP-1(-1607) 1G/2G, a significant association was observed using the recessive genetic model (OR = 1.47; 95% CI = 1.14-1.91; I2 = 64%, pheterogeneity = 0.003). In the subgroup studies, a significant association was observed in the Asian subgroup (OR = 1.68; 95% CI = 1.42-1.99; I2 = 17%, pheterogeneity = 0.30 for the recessive model; and OR = 1.59; 95% CI = 1.19-2.13; I2 = 80%, pheterogeneity < 0.00001 for the allelic contrast model) and in the European subgroup (OR = 0.65; 95% CI = 0.44-0.98; I2 = 21%, pheterogeneity = 0.26 for the allelic contrast model). No significant associations were observed with either MMP-2(-1306) C/T or MMP-3(-1171) 5A/6A. CONCLUSIONS: The MMP-1(-1607) 1G/2G polymorphism is associated with oral cancer risk, and the 2G allele played different roles in Asian and European populations.

Cadmium transfer from contaminated soils to the human body through rice consumption in southern Jiangsu Province, China.

Consumption of crops grown in cadmium-contaminated soils is an important Cd exposure route to humans. The present study utilizes statistical analysis and in vitro digestion experiments to uncover the transfer processes of Cd from soils to the human body through rice consumption. Here, a model was created to predict the levels of bioaccessible Cd in rice grains using phytoavailable Cd quantities in the soil. During the in vitro digestion, a relatively constant ratio between the total and bioaccessible Cd in rice was observed. About 14.89% of Cd in soils was found to be transferred into rice grains and up to 3.19% could be transferred from rice grains to the human body. This model was able to sufficiently predict rice grain cadmium concentrations based on CaCl2 extracted zinc and cadmium concentrations in soils (R2 = 0.862). The bioaccessible Cd concentration in rice grains was also able to be predicted using CaCl2 extracted cadmium from soil (R2 = 0.892). The models established in this study demonstrated that CaCl2 is a suitable indicator of total rice Cd concentrations and bioaccessible rice grain Cd concentrations. The chain model approach proposed in this study can be used for the fast and accurate evaluation of human Cd exposure through rice consumption based on the soil conditions in contaminated regions.

A Rapid Detection Method of Brucella with Quantum Dots and Magnetic Beads Conjugated with Different Polyclonal Antibodies.

Brucella spp. are facultative intracellular bacteria that cause zoonotic disease of brucellosis worldwide. Traditional methods for detection of Brucella spp. take 48-72 h that does not meet the need of rapid detection. Herein, a new rapid detection method of Brucella was developed based on polyclonal antibody-conjugating quantum dots and antibody-modified magnetic beads. First, polyclonal antibodies IgG and IgY were prepared and then the antibody conjugated with quantum dots (QDs) and immunomagnetic beads (IMB), respectively, which were activated by N-(3-dimethylaminopropyl)-N'-ethylcar-bodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) to form probes. We used the IMB probe to separate the Brucella and labeled by the QD probe, and then detected the fluorescence intensity with a fluorescence spectrometer. The detection method takes 105 min with a limit of detection of 103 CFU/mL and ranges from 10 to 105 CFU/mL (R 2 = 0.9983), and it can be well used in real samples.

Indocyanine Green-Loaded Gold Nanoflowers@Two Layers of Silica Nanocomposites for Photothermal and Photodynamic Therapy of Oral Carcinoma.

Both photothermal therapy (PTT) and photodynamic therapy (PDT) are phototherapeutic approaches, which have been widely investigated for cancer therapy mediated by near infrared (NIR) light irradiation. Here, we successfully constructed a single-light triggered indocyanine green (ICG)-loaded gold nanocomposites which were composed of gold nanoflower core/two layers silica shell (AuNFs@SiO2@mSiO2-ICG) for enhanced PDT/PTT synergistic effect to oral carcinoma. The AuNFs@SiO2@mSiO2-ICG nanocomposites had no obviously cytotoxicity and could effectively arrest Cal27 cells in the G1 phase. Moreover, the conjugation of ICG caused significantly higher reactive oxygen species (ROS) productivity and apoptotic Cal27 cells compared to free ICG or free AuNFs@SiO2@mSiO2. In this study, compared with PTT or PDT alone, synchronous PTT and PDT produced by AuNFs@SiO2@mSiO2-ICG under NIR light irradiation induced enhanced Cal27 cells lethality in vitro and tumor growth inhibition in vivo, which might be a promising strategy for cancer treatment.

[Study on the Turning Effect of the Energy Gap of π Electron on Atomic Vibration in Conjugated Linear Polymer].

The Visible absorption and Raman spectra of ß-carotene were measured in dimethyl sulfoxide in temperature ranging from 81 to 25 ℃ and in carbon disulfide in pressure range from 0.04 to 0.60 GPa, respectively. The results indicated that the visible absorption and Raman spectra are both red-shifted, Raman scattering cross section increase with the temperature decreasing. And with the pressure increasing, the visible absorption spectra are red-shifted, but the frequency shift towards higher frequencies in the Raman spectra, the Raman scattering cross section decrease unexpectedly. The latter can't be explained by the model of "effective conjugation length" and "coherent weakly damped electron-lattice vibrations". In this paper, we combined electron-vibration coupling rule with theoretical calculations and found that the electron-phonon coupling constant had a certain changing trend with the temperature and pressure variation, which Indicate that the interaction between π-electron and CC bond vibration was essential for this experiment result. Thus, the turning effect of energy gap of the π on CC vibration mode is responsible for such phenomenon.

[Characteristic comparative study of particulate matters in Beijing before and during the Olympics].

Two city ecosystem research stations were selected for continuous monitoring of atmospheric fine particulate matter (PM2.5) concentration from June to September 2008, when the Beijing Olympic Games was held. The relationship between meteorological factors, artificial control management measures and PM2.5 dynamic characteristics were analyzed. The results showed that the daily average concentration of PM2.5 at RCEES Station, which is near the 5th North Ring, was 0.067 mg x m(-3) during the study period, and the particle concentration during the Olympic Games was 0.060 mg x m(-3), which was decreased by about 26% compared with the content before the Olympic Games (0.081 mg x m(-3)). As for JX Station located in the 2th South Ring, its daily average concentration of PM2.5 was 0.078 mg x m(-3). Similar to RCEES Station, PM2.5 average content during the Olympic Games (0.069 mg x m(-3)) was 27% lower compared with the content before the Olympic Games (0.095 mg x m(-3)). Two peaks could be found when daily distribution of PM2.5 was displayed, one appeared between 08:00 and 10:00 (the average content for RCEES and JX were 0.068 and 0.089 mg x m(-3), respectively), and the other appeared at 20:00-22:00, which could be attributed to traffic emission and road dust pollution, especially the emission from the growing number of cars in rush hours. Meteorological condition during the whole period was typical in summer in Beijing with both high temperature and humidity. Correlation analysis revealed that the concentrations of PM2.5 had a positive correlation with the air temperature (P < 0.01), while it had no significant relationship with wind speed, relative humidity or precipitation (P > 0.05). Our monitoring results suggested that the artificial air pollution control strategies were effective measures for air pollution control during 2008 Beijing Olympic Game.