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Memory-phenotype (MP) CD4+ T cells are a substantial population of conventional T cells that exist in steady-state mice, and their immunologic functions in autoimmune disease have not yet been studied. In this work, we unveil a unique phenotype of MP CD4+ T cells by analyzing single-cell transcriptomics and T cell receptor (TCR) repertoires. We found that steady-state MP CD4+ T cells exist regardless of germ and food-antigen which are composed of heterogenous effector subpopulations. Distinct subpopulations of MP CD4+ T cells are specifically activated by IL-1 family cytokines and STAT activators, revealing that the cells have TCR-independent bystander effector functions like innate lymphoid cell. Especially, CCR6high MP CD4+ T cells are major responders to IL-1β and IL-23 without MOG35 − 55 antigen reactivity, which gives them pathogenic-Th17 characteristics and allows them to contribute to autoimmune encephalomyelitis. We identified Bhlhe40 in CCR6high MP CD4+ T cells drives the expression of GM-CSF through IL-1β and IL-23 signaling, contributing to CNS pathology in experimental autoimmune encephalomyelitis. Collectively, our findings reveal clearly distinct effector-like heterogeneity of MP CD4+ T cells in steady state and CCR6high MP CD4+ T cells exacerbate autoimmune neuroinflammation by Bhlhe40/GM-CSF axis in bystander manner synergistically with antigen-specific T cells.

Memory-phenotype (MP) CD4+T cells are a substantial population of conventional T cells that exist in steady-state mice, and their immunologic functions in autoimmune disease have not yet been studied. In this work, we unveil a unique phenotype of MP CD4+T cells by analyzing single-cell transcriptomics and T cell receptor (TCR) repertoires. We found that steady-state MP CD4+T cells exist regardless of germ and food-antigen which are composed of heterogenous effector subpopulations. Distinct subpopulations of MP CD4+T cells are specifically activated by IL-1 family cytokines and STAT activators, revealing that the cells have TCR-independent effector functions. Especially, CCR6highMP CD4+T cells are major responders to IL-1β and IL-23 without MOG35-55antigen reactivity, which gives them pathogenic-Th17 characteristics and allows them to contribute to autoimmune encephalomyelitis. We identified Bhlhe40 in CCR6highMP CD4+T cells drives the expression of GM-CSF, contributing to CNS pathology in experimental autoimmune encephalomyelitis. Collectively, our findings reveal heterogeneity of MP CD4+T cells that can contribute to autoimmune neuroinflammation in bystander manner synergistically with antigen-specific T cells.

Biosilica is a material extracted from the shell (cell wall) of Melosira nummuloides, a type of sea diatom, and is one of the widely distributed biominerals. Recently, some studies have revealed that biosilica has a characteristic bio-modulatory activity compared to synthetic silica. However, there has been little research on the effects and action mechanisms of biosilica in immune cells. In this study, we investigated the effect of biosilica water on mouse dendritic cells (DCs), the most potent antigen-presenting cells in immunity, and whether it may alter the function of DCs. Biosilica water decreased the metabolic activity of DCs at 20% concentration (v/v) and the production of IL-1 beta in a concentration-dependent manner. And also, more cells with fragmented nuclei were observed in the DCs treated with 20% biosilica water compared to other treatment groups. The mixed leukocyte response experiment showed the biosilica water-treated DCs significantly modulated the metabolic activity and proliferation of allogeneic spleen cells compared to control DCs. This result suggests that biosilica water may modulate the antigen-presenting capability of DCs. Taken together, this study shows the immunomodulatory activity of biosilica on DCs and may affect immune responses. Further research is needed to investigate the immunological activity of biosilica water.

Current organoid models are limited by their inability to mimic mature organ architecture and associated tissue microenvironments1,2. Here we create multilayer bladder ‘assembloids’ by reconstituting tissue stem cells with stromal components to represent an organized architecture with an epithelium surrounding stroma and an outer muscle layer. These assembloids exhibit characteristics of mature adult bladders in cell composition and gene expression at the single-cell transcriptome level, and recapitulate in vivo tissue dynamics of regenerative responses to injury. We also develop malignant counterpart tumour assembloids to recapitulate the in vivo pathophysiological features of urothelial carcinoma. Using the genetically manipulated tumour-assembloid platform, we identify tumoural FOXA1, induced by stromal bone morphogenetic protein (BMP), as a master pioneer factor that drives enhancer reprogramming for the determination of tumour phenotype, suggesting the importance of the FOXA1–BMP–hedgehog signalling feedback axis between tumour and stroma in the control of tumour plasticity. Multilayer 3D reconstitution of bladder stem cells with stromal cells enables recapitulation of the architecture and molecular functions of bladder tissue.

We previously demonstrated that Bordetella bronchiseptica (B. bronchiseptica) antigen (Ag) enhances the Mycoplasma hyopneumoniae Ag-specific immune response. The focus of this study was whether acellular bacterin of B. bronchiseptica could be used as an adjuvant to increase antigen-presenting capability of dendritic cells (DCs) by increasing the level of activation. The metabolic activity of DCs was increased by B. bronchiseptica, similar to lipopolysaccharide (LPS). Flow cytometry analysis revealed that B. bronchiseptica increases the expression of major histocompatibility complex class-2, cluster of differentiation (CD)40, CD54, and CD86 which are closely related to DC-mediated immune responses. B. bronchiseptica enhanced the production of cytokines related to adaptive immune responses. Furthermore, the survival rate of B. bronchiseptica-injected groups was 100% at 15 and 20 mg/kg doses, whereas that of LPS-injected groups was only 20%, 0% at 15 and 20 mg/kg doses respectively, and so B. bronchiseptica is likely to be safer than LPS. Taken together, these results indicate that B. bronchiseptica can be used as an adjuvant to enhance the antigen-presenting capability of DCs. B. bronchiseptica is a candidate for producing vaccines, especially in case of DC-mediating efficacy and safety demands. This study provides researchers and clinicians with valuable information regarding the usage of B. bronchiseptica as a safe bacteria-derived immunostimulating agent for developing efficient vaccines.

Quercetin is a flavonoid and is abundant in the plant kingdom. Green nanoparticles (gold and silver) were synthesized by using quercetin as a reductant via a green route for their potential nanoarchitechtonic applications. There were no toxic chemicals involved during the synthesis. The gold and silver nanoparticles exhibited surface plasmon resonance at 527 nm and 401 nm, respectively. Both nanoparticle solutions retained excellent colloidal shelf stability for 7 days and in cell culture medium. The crystal structure of the nanoparticles was observed by X-ray diffraction analysis. Field emission transmission electron microscopy images revealed that spherical nanoparticles were synthesized, with an average size of 20.2±4.8 nm for gold nanoparticles and 32.4±14.0 nm for silver nanoparticles. Observation of clear lattice fringes in the microscopic images suggested that both types of nanoparticles possessed a face-centered cubic structure. Catalytic activity was evaluated with respect to 4-nitrophenol reduction and methyl orange degradation. When increasing the amount of gold or silver nanoparticles used as a catalyst, the rate constant of the catalytic reaction was also increased. Cytotoxicity assessment on cancer cells demonstrated that both types of nanoparticles can be appropriate candidates for delivery vehicles of biologically active molecules, such as anticancer agents.

You Jeong Lee, Yeon-Jeong Kim, Youmie Park College of Pharmacy and Inje Institute of Pharmaceutical Sciences and Research, Inje University, Gimhae, Gyeongnam, 50834, Republic of KoreaCorrespondence: Youmie Park, Tel +82-55-320-3884, Fax +82-55-320-3940, Email youmiep@inje.ac.krBackground: Advances in the field of nanotechnology have shed light on the applications of nanoparticles for cancer treatment.Methods: Folic acid and chitosan-functionalized gold nanorods (FACS-R) and triangular silver nanoplates (FACS-T) were synthesized and their properties were elucidated by UV-visible spectrophotometry, Fourier-transform infrared spectroscopy, field emission transmission electron microscopy and high-resolution X-ray diffraction.Results: The average size of the FACS-R was determined to be a transverse length of 13.1 ± 1.8 nm and a longitudinal length of 47.2 ± 8.9 nm with an aspect ratio of 3.6. The average size of FACS-T was measured to be 31.8 ± 7.7 nm. Colloidal solutions of FACS-R and FACS-T were stable on the shelf at ambient temperature for 14 days in the dark. Anticancer agents were encapsulated in FACS-R and FACS-T. FACS-T showed a higher encapsulation efficiency with docetaxel, paclitaxel and diallyl disulfide than FACS-R. The cell viability on human gastric adenocarcinoma cells (AGS), human epithelial cervix adenocarcinoma cells (HeLa) and human colorectal adenocarcinoma cells (HT-29) after treatment with anticancer agent-encapsulated FACS-R and FACS-T was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Interestingly, paclitaxel-encapsulated FACS-R and FACS-T showed the highest percentages of early and late apoptosis on HeLa cells. A cell cycle analysis demonstrated increased G2/M arrest on HeLa cells with docetaxel and paclitaxel-encapsulated FACS-R and FACS-T. The FACS-T induced more G2/M arrest on HeLa cells than the FACS-R. To assess applications in near-infrared photothermal therapy (PTT), the cell viability on HeLa cells with the anticancer agent-encapsulated FACS-R and FACS-T was assessed in the presence or absence of 808 nm laser irradiation. The results showed that 808 nm laser irradiation significantly decreased cell viability.Conclusion: Collectively, the triangular silver nanoplates were more effective than the gold nanorods for PTT. We believe that as-prepared nanoparticles have remarkable features and will become promising future nanomedicine.Keywords: folic acid, chitosan, triangular silver nanoplates, gold nanorods, anticancer activity, photothermal therapy, HeLa cells

Fenbendazole (FBZ) is a benzimidazole anthelmintic widely used to treat parasitic infections. The anticancer effect of FBZ has been recently highlighted leading to its consideration as a potential anticancer agent. Although previous studies have demonstrated the effect of FBZ on cancer cells, there is a paucity of studies on the effect of FBZ on lymphoma cells and normal immune cells. Herein, we investigated the effects of FBZ on a mouse lymphoma cell line, EL-4 cells, and spleen cells, using vincristine as a positive control. The cellular metabolic activity of EL-4 cells was decreased by FBZ, but that of the spleen cells was not decreased. Moreover, FBZ reduced the mitochondrial membrane potential and induced reactive oxygen species production in EL-4 cells, but not in spleen cells. FBZ induced G2/M phase arrest and increased the sub G0/G1 phase ratio, indicating apoptosis. Furthermore, compared to the control cells, the reactivity of spleen cells pretreated with FBZ to lipopolysaccharide was maintained. In summary, FBZ is cytotoxic to EL-4 cells, but not to spleen cells. This study provides experimental evidence that FBZ exerts an anticancer effect, and less cytotoxic effects and functional damage to normal spleen cells.

Dietary antigens affect the adaptive immunity of the host by inducing regulatory T cells and IgE-producing B cells. However, their roles in innate immune compartments such as innate lymphoid cells (ILCs) and intestinal epithelial cells (IECs) are unclear. Here, using antigen-free (AF) mice, which are germ-free (GF) mice fed with amino-acid-based diet, we found dietary proteins suppress the development of GATA-3-expressing ILC2s independent of the adaptive immune cells. These cells produce more type 2 cytokines and upregulated proliferation and activation markers such as Ki-67, CD69, and CD25. With this, AF mice had increased expressions of tuft cell-specific transcripts such as Il25, Il33, Dclk1, Trpm5, and Pou2f3 in IECs. Accordingly, expanded ILC2s upregulated IL-17RB, a receptor of IL-25, and their proliferation was blocked by IL-25 neutralizing or IL-17RB blocking antibodies. These results suggest a new dialogue between dietary antigens, IECs, and ILCs in which dietary antigens suppress ILC2 activation and proliferation by restraining homeostatic IL-25 production, potentially limiting type 2 immunity by food antigens.

B-1 cell development mainly occurs via fetal and neonatal hematopoiesis and is suppressed in adult bone marrow hematopoiesis. However, little is known about the factors inhibiting B-1 cell development at the adult stage. We report that capicua (CIC) suppresses postnatal B-1a cell development and survival. CIC levels are high in B-1a cells and gradually increase in transitional B-1a (TrB-1a) cells with age. B-cell-specific Cic-null mice exhibit expansion of the B-1a cell population and a gradual increase in TrB-1a cell frequency with age but attenuated B-2 cell development. CIC deficiency enhances B cell receptor (BCR) signaling in transitional B cells and B-1a cell viability. Mechanistically, CIC-deficiency-mediated Per2 derepression upregulates Bhlhe41 levels by inhibiting CRY-mediated transcriptional repression for Bhlhe41, consequently promoting B-1a cell formation in Cic-null mice. Taken together, CIC is a key transcription factor that limits the B-1a cell population at the adult stage and balances B-1 versus B-2 cell formation.

5-Fluorouracil, doxorubicin, and vincristine are chemotherapy agents used to treat various cancers, such as breast cancer and lymphoma for decades, and their effects on cancer have been proven. On the other hand, these anti-cancer drugs cause fatal side effects, including immunosuppression. This study investigated whether sonicated Bordetella bronchiseptica bacterin can attenuate the immunosuppression of spleen cells induced by these chemotherapy agents and which subsets of spleen cells were affected. B. bronchiseptica increased the metabolic activity of spleen cells treated with 3 anti-cancer drugs. Cell death analysis using Annexin V/propidium iodide showed that B. bronchiseptica markedly decreased the death of spleen cells. The subsets of spleen cells were analyzed by flow cytometry using a surface marker-specific antibody. B. bronchiseptica increased nitric oxide production in the spleen cells treated with anti-cancer drugs (p < 0.0001). Despite the pharmacological effects of anti-cancer drugs, many patients suffer from the fatal side effects of immunosuppression. This study provides valuable information on how to overcome chemotherapy-induced immunosuppression.

Immunotherapy via interleukin-2 (IL-2) mediated activation of anti-tumor immune response is a promising approach for cancer treatment. The multi-potent cytokine, IL-2 has a central role in immune cell activation and homeostasis. Since IL-2 preferentially activates immunosuppressive T regulatory cells by IL-2Rα dependent manner, blocking IL-2:IL-2Rα interaction is a key to amplify the IL-2 activity in effector T cells toward anti-tumor response. Anti-IL-2 monoclonal antibodies are good candidates to control the IL-2:IL-2Rα interaction. In a previous study, we developed a new IL-2Rα mimetic antibody, TCB2, and showed that the human IL-2(hIL-2):TCB2 complex can stimulate T effector cells specifically and elicit potent anti-cancer immunotherapeutic effect, especially when administered in combination with immune checkpoint inhibitors. To understand the molecular mechanism, we determined the crystal structure of TCB2-Fab in a complex with hIL-2 at 2.5 Å resolution. Our structural analysis reveals that TCB2 binds to the central area of the hIL-2Rα binding region on hIL-2, and binding angle and epitope are different from previously known hIL-2Rα mimicking antibody NARA1 which recognizes the top part of hIL-2. TCB2 binding to hIL-2 also induces an allosteric effect that increases the affinity for the hetero-dimeric hIL-2 receptor, IL-2R(β + γ), on effector T cells.

Particulate matter (PM) induces neutrophilic inflammation and deteriorates the prognosis of diseases such as cardiovascular diseases, cancers, and infections, including COVID-19. Here, we addressed the role of γδ T cells and intestinal microbiome in PM-induced acute neutrophilia. γδ T cells are a heterogeneous population composed of Tγδ1, Tγδ2, Tγδ17, and naïve γδ T cells (TγδN) and commensal bacteria promote local expansion of Tγδ17 cells, particularly in the lung and gut without affecting their Vγ repertoire. Tγδ17 cells are more tissue resident than Tγδ1 cells, while TγδN cells are circulating cells. IL-1R expression in Tγδ17 cells is highest in the lung and they outnumber all the other type 17 cells such as Th17, ILC3, NKT17, and MAIT17 cells. Upon PM exposure, IL-1β-secreting neutrophils and IL-17-producing Tγδ17 cells attract each other around the airways. Accordingly, PM-induced neutrophilia was significantly relieved in γδ T- or IL-17-deficient and germ-free mice. Collectively, these findings show that the commensal microbiome promotes PM-induced neutrophilia in the lung via Tγδ17 cells.

Onion (Allium cepa) extract was used for the green synthesis of gold and silver nanoparticles. Each colloidal solution exhibited surface plasmon resonance, with a peak at 532 nm for gold nanopartic...

Multifaceted functions displayed by both pro- and anti-inflammatory properties of chitosan hinder its effective development as an immunomodulatory agent. Herein, the contributions of the bending stiffness of chitosan with regard to its immune regulatory properties toward inflammation are investigated. The anti-inflammatory properties of chitosan molecular weight (MW) with a shorter (≈1 kDa) or longer (≈15 kDa) than the persistent length (L

Anisotropic snowman-like silver nanoparticles (AgNPs) were synthesized using the extract of Caesalpinia sappan heartwood as a reducing agent in the presence of cetyltrimethylammonium bromide. Two surface plasmon resonance bands of the orange solution were observed at 446 nm and 539 nm in UV-visible spectra. High-resolution X-ray diffraction analysis confirmed the face-centered cubic structure of the AgNPs. High-resolution transmission electron microscopy images clearly revealed snowman-like AgNPs with an average size of 34.36 ± 11.44 nm. The C-O functional group was most likely involved in the synthesis of the AgNPs, which was demonstrated by Fourier transform infrared spectra. Most interestingly, the snowman-like AgNPs exhibited higher antibacterial activity than the spherical AgNPs and the extract alone. Among the tested strains, the snowman-like AgNPs showed the highest activity against Staphylococcus aureus, with minimum inhibitory concentrations of 4.69 μg/mL for the extract and 0.443 μg/mL for the silver. The antibacterial activity of the snowman-like AgNPs increased 24-fold against S. aureus. These results strongly suggested that the snowman-like AgNPs synthesized from C. sappan extract have potential for treating infected disease caused by S. aureus when the antibacterial activity was combined from plant extract and AgNPs. To our knowledge, the present report is the first in which the snowman-like AgNPs synthesized using a plant extract as a reducing agent showed excellent In Vitro antibacterial activity.

TCRαβ+CD4-CD8α+CD8β- intestinal intraepithelial lymphocytes (CD8αα IELs) are an abundant population of thymus-derived T cells that protect the gut barrier surface. We sought to better define the thymic IEL precursor (IELp) through analysis of its maturation, localization and emigration. We defined two precursor populations among TCRβ+CD4-CD8- thymocytes by dependence on the kinase TAK1 and rigorous lineage-exclusion criteria. Those IELp populations included a nascent PD-1+ population and a T-bet+ population that accumulated with age. Both gave rise to intestinal CD8αα IELs after adoptive transfer. The PD-1+ IELp population included more strongly self-reactive clones and was largely restricted by classical major histocompatibility complex (MHC) molecules. Those cells localized to the cortex and efficiently emigrated in a manner dependent on the receptor S1PR1. The T-bet+ IELp population localized to the medulla, included cells restricted by non-classical MHC molecules and expressed the receptor NK1.1, the integrin CD103 and the chemokine receptor CXCR3. The two IELp populations further differed in their use of the T cell antigen receptor (TCR) α-chain variable region (Vα) and β-chain variable region (Vβ). These data provide a foundation for understanding the biology of CD8αα IELs.

IL-2 is a pleiotropic cytokine that plays an essential role in the survival, expansion, and function of CD8 T cells, regulatory T cells (Tregs), and natural killer (NK) cells. Previous studies showed that binding IL-2 with an anti-IL-2 monoclonal antibody (mAb) with a particular specificity could block its interaction with IL-2Rα, which is mainly expressed on Tregs. This selectivity can enhance the anti-tumor effects of IL-2 by activating CD8 T and NK cells, while disfavoring Treg stimulation. Based on this, we newly developed a series of anti-human IL-2 (hIL-2) mAbs (TCB1-3) that selectively stimulate CD8 T and NK cells without overtly activating Tregs. Among them, the hIL-2/TCB2 complex (hIL-2/TCB2c) exerted the best efficacy by inducing a prodigious expansion of host memory phenotype (MP) CD8 T (60-fold) and NK cells (18-fold) with less efficient Treg proliferation (5-fold). As a result, there was an average eightfold increase in the ratio of MP CD8 to Tregs. Accordingly, hIL-2/TCB2c strongly inhibited the growth of B16F10, MC38, and CT26 tumors. More remarkably, hIL-2/TCB2c showed synergy with checkpoint inhibitors such as anti-CTLA-4 or PD1 antibodies, and resulted in almost complete regression of implanted tumors and resistance to secondary tumor challenge. For direct clinical use, we generated a humanized form of TCB2 that had equal immunostimulatory and anti-tumor efficacy as a murine one. Collectively, these results show that TCB2 can provide a potent immunotherapeutic modality either alone or together with checkpoint inhibitors in cancer patients.

Sesquiterpenoids from the flower bud extract of Tussilago farfara were effectively utilized as a reducing agent for eco-friendly synthesis of silver and gold nanoparticles. The silver and gold nanoparticles had a characteristic surface plasmon resonance at 416 nm and 538 nm, respectively. Microscopic images revealed that both nanoparticles were spherical, and their size was measured to be 13.57 ± 3.26 nm for the silver nanoparticles and 18.20 ± 4.11 nm for the gold nanoparticles. The crystal structure was determined to be face-centered cubic by X-ray diffraction. Colloidal stability of the nanoparticle solution was retained in a full medium, which was used in the cell culture experiment. The antibacterial activity result demonstrated that the silver nanoparticles showed better activity (two- to four-fold enhancement) than the extract alone on both Gram-positive and Gram-negative bacteria. Interestingly, the highest antibacterial activity was obtained against vancomycin-resistant Enterococci Van-A type Enterococcus faecium. Cytotoxicity on cancer cell lines confirmed that gold nanoparticles were more cytotoxic than silver nanoparticles. The highest cytotoxicity was observed on human pancreas ductal adenocarcinoma cells. Therefore, both nanoparticles synthesized with the sesquiterpenoids from T. farfara flower bud extract can be applicable as drug delivery vehicles of anticancer or antibacterial agents for future nanomedicine applications.

Using alternating current electric fields, nanoribbons are fabricated from an aqueous suspension of gold nanoparticles (AuNPs) on mica substrate without resorting to further chemical functionalization of AuNPs. The potential and kinetic energies of AuNPs subjected to attractive forces from a mica substrate provide sufficient energy to pass the diffusion barrier of the gold atoms, which eventually leads to cold welding. A dielectrophoresis force exerted on polarizable particles in a non-uniform electric field contributes to the directed growth of the cold welding that occurs by adjusting the lattice structures of AuNPs. Depending on the concentration of the AuNP suspension, the frequency of the electric field, and the geometry of electrodes, various morphologies of nanoribbons are fabricated. It turns out that the welded region is nearly perfect to provide the same crystal orientation and strength as the rest of the nanostructures, which can be extensively utilized in the fabrication of various nanostructures.

Invariant NKT cells differentiate into three predominant effector lineages in the steady state. To understand these lineages, we sorted undifferentiated invariant NK T progenitor cells and each effector population and analyzed their transcriptional profiles by RNAseq. Bioinformatic comparisons were made to effector subsets among other lymphocytes, specifically Th cells, innate lymphoid cells (ILC), and γδ T cells. Myc-associated signature genes were enriched in NKT progenitors, like in other hematopoietic progenitors. Only NKT1 cells, but not NKT2 and NKT17 cells, had transcriptome similarity to NK cells and were also similar to other IFN-γ–producing lineages such as Th1, ILC1, and intraepithelial γδ T cells. NKT2 and NKT17 cells were similar to their analogous subsets of γδ T cells and ILCs, but surprisingly, not to Th2 and Th17 cells. We identified a set of genes common to each effector lineage regardless of Ag receptor specificity, suggesting the use of conserved regulatory cores for effector function.

A Portulaca oleracea (or purslane) extract was used as a green reductant for synthesizing both gold nanoparticles and silver/optical chloride nanoparticles without the use of any other external reductants, surfactants, stabilizing agents, or halide ions. Both nanoparticles demonstrated their surface plasmon resonance at 543 nm for the gold nanoparticles and 423 nm for the silver/silver chloride nanoparticles. The X-ray diffraction pattern exhibited a face-centered cubic nanoparticle structure. Mainly spherical-shaped nanoparticles were observed in field emission transmission electron microscopy images with an average size of 11.34 ± 4.23 nm for the gold nanoparticles and 15.01 ± 4.49 nm for the silver/silver chloride nanoparticles. Graphene oxide-grafted gold nanoparticles and silver/silver chloride nanoparticles using the P. oleracea extract were synthesized by either in situ or ex situ methods. X-ray photoelectron spectra confirmed that gold and silver/silver chloride nanoparticles were successfully grafted onto the graphene oxide sheet. The catalytic activity of these graphene oxide nanocomposites was assessed with the 4-nitrophenol reduction reaction. Among the tested nanocomposites, graphene oxide-grafted silver/silver chloride nanoparticles synthesized by the ex situ method exhibited an excellent capacity as a nanoscale catalyst with reasonable recyclability. The straightforward method offers new insight into grafting metallic nanoparticles onto graphene sheets via an entirely green strategy using plant extracts.