Enhancement of CD4(+) T cell response and survival via coexpressed OX40/OX40L in Graves' disease.

OX40/OX40L pathway plays a very important role in the antigen priming T cells and effector T cells. In the present study, we aimed to examine the involvement of OX40/OX40L pathway in the activation of autoreactive T cells in patients with Grave's disease (GD). We found that OX40 and OX40L were constitutively coexpressed on peripheral CD4(+) T cells from GD patients using flow cytometry analysis. The levels of OX40 and OX40L coexpression on CD4(+) T cells were shown to be correlated with TRAbs. Cell proliferation assay showed that blocking OX40/OX40L signal inhibited T cell proliferation and survival, which suggested that OX40/OX40L could enhance CD4(+) T cell proliferation and maintain their long-term survival in GD by self-enhancing loop of T cell activation independent of APCs. Confocal microscopy and coimmunoprecipitation analysis further revealed that OX40 and OX40L formed a functional complex, which may facilitate signal transduction from OX40L to OX40 and contribute to the pathogenesis of GD.

The expression of programmed death-1 in circulating CD4+ and CD8+ T cells during hepatitis B virus infection progression and its correlation with clinical baseline characteristics.

BACKGROUND/AIMS: Programmed death-1 (PD-1) expression was investigated in CD4(+) and CD8(+) T cells from hepatitis B virus (HBV)-infected patients at the chronic hepatitis B (CHB) infection, liver cirrhosis (LC), and hepatocellular carcinoma (HCC) stages. METHODS: PD-1 expression in circulating CD4(+) and CD8(+) T cells was detected by flow cytometry. The correlations between PD-1 expression and HBV viral load, alanine aminotransaminase (ALT) levels and aspartate aminotransferase (AST) levels were analyzed using GraphPad Prism 5.0. RESULTS: PD-1 expression in CD4(+) and CD8(+) T cells was significantly increased in both the CHB group and advanced-stage group (LC plus HCC). In the CHB group, PD-1 expression in both CD4(+) and CD8(+) T cells was positively correlated with the HBV viral load, ALT, and AST levels. However, in the LC plus HCC group, significant correlations between PD-1 expression and the clinical parameters were nearly absent. CONCLUSIONS: PD-1 expression in peripheral CD4(+) and CD8(+) T cells is dynamic, changes with HBV infection progression, and is related to HBV viral load and liver function, especially in CHB. PD-1 expression could be utilized as a potential clinical indicator to determine the extent of virus replication and liver injury.

[Effect of soluble PD-L1 released by lung cancer cells in regulating the function of T lymphocytes].

OBJECTIVE: To explore the expression of soluble programmed death ligand-1 on lung cancer cells and to clarify its biological function through PD-1/PD-L1 pathway in regulating the function of T lymphocytes. METHODS: Labeled monoclonal antibody and flow cytometry were used to analyze the expression of PD-L1 and its receptor PD-l on lung cancer cells and human T lymphocytes, respectively. The level of sPD-L1 in the supernatant of lung cancer cells was determined with an ELISA kit. The inhibition of proliferation of T lymphocytes by mPD-L1 and sPD-L1 was studied using CCK-8 incorporation. RESULTS: Low or no expression [(16.08 ± 2.28)%] of PD-1 was found on resting T lymphocytes from human peripheral blood with flow cytometry, but up-regulated expression of PD-1 [(78.06 ± 7.21)%] was found on the surface of activated T lymphocytes. Soluble PD-L1 was found in supernatant of some lung cancer cell lines, such as H1299, HO8910, SPCA-1, H460, H446 cells, with PD-L1 expressing on their cell surface [(78.34 ± 10.25)%, (68.17 ± 11.56)%, (45.32 ± 7.98)%, (47.52 ± 9.62)% and (40.95 ± 8.56)%, respectively], but very low expression on A549 cells [(16.02 ± 6.28)%]. The level of mPD-L1 on H1299 cells was highest [(78.34 ± 10.25)%], compared with HO8910 cells (68.17 ± 11.56)%, SPCA-1 cells (45.32 ± 7.98)%, H446 cells (40.95 ± 8.56)%, and H460 cells (47.52 ± 9.62)%. At the same time, the sPD-L1 level on H1299 cells was low [(0.17 ± 0.01) ng/ml], compared with HO8910 cells (0.30 ± 0.03) ng/ml, SPCA-1cells (0.59 ± 0.03) ng/ml, H446 cells (0.34 ± 0.02) ng/ml, and H460 cells (0.57 ± 0.03) ng/ml, but not expressed on A549 cells. PD-L1 expressing H1299 cells inhibited the proliferation of T lymphocytes in the co-culture system. Supernatant of the cultured PD-L1(+) lung cancer cells also inhibited T cell proliferation. Anti-human PD-L1 blocking antibody could partly restore the proliferation capacity of T lymphocytes. CONCLUSIONS: Membrane-bound PD-L1 and soluble PD-L1 released from lung cancer cells can effectively inhibit the proliferation of T lymphocytes in mixed culture system and down-regulate cell-mediated immunity in vitro. This may lead to inactivation of tumor antigen-specific T cells and immune escape of lung cancer cells.

Different roles of PD-L1 and FasL in immunomodulation mediated by human placenta-derived mesenchymal stem cells.

Mesenchymal stem cells (MSCs) derived from either bone marrow (BMSCs) or placenta (PMSCs) have the capacity to suppress immune responses to mitogenic and allogeneic stimulations. Both cell contact and soluble factor dependent mechanisms have been proposed to explain this immunosuppression. This study explored the roles of some of cell surface molecules expressed on human PMSCs (hPMSCs) in hPMSC mediated immunomodulation. hPMSCs strongly suppressed mitogen and allogeneic peripheral mononuclear cells (PBMCs) induced T cell activation and proliferation. hPMSCs constituently expressed programmed death-ligand 1 (PD-L1) and Fas ligand (FasL) molecules. Neutralising antibodies to-PD-L1 and FasL significantly reduced the suppressive effect of hPMSCs on T cell proliferation. However, only anti-PD-L1 antibody partially restored early T cell activation suppressed by hPMSCs. Anti-FasL antibody but not anti-PD-L1 antibody reduced apoptosis of activated T cell indicating that FasL molecule plays a role in inducing apoptosis of activated T cells, although overall hPMSCs diminished T cell apoptosis. Different effects of PD-L1 and FasL molecules on T cell activation and activated T cell apoptosis suggest that these two molecules influence T cell response at different stages. hPMSCs significantly prevented activated T cells from going into S phase. Both antibodies to PD-L1 and FasL had significant effect on reversing the effect of hPMSCs on cell cycles. hPMSCs reduced INF-γ but increased IL-10 production by mitogen activated T cells. Both antibodies partially abolished the effect of hPMSCs on INF-γ and IL-10 production. These data demonstrated that PD-L1 and FasL molecules play significant roles in immunomodulation mediated by hPMSCs. This study provides a rational basis for modulation of negative costimulators on hPMSCs to increase their immunosuppressive properties in their therapeutic applications.

[Expression of PD-1/PD-L1 in peripheral blood mononuclear cells in lung cancer patients and its biological significance].

OBJECTIVE: To analyze the expression of co-stimulatory molecules PD-1/PD-L1 in peripheral blood mononuclear cells in lung cancer patients, and to explore its biological significance. METHODS: One hundred and thirty-three lung cancer patients, 25 lung infection patients and 23 healthy donors were enrolled in this study. 100 µl of whole blood from these subjects were collected. Multi-color immunofluorescence staining and flow cytometry were used to detect PD-1/PD-L1 expression. The results were statistically analyzed. RESULTS: The expression level of CD3⁺CD8⁺ T cells in the lung cancer patients was (38.83 ± 1.74)%, significantly lower than that in the control group [(43.25 ± 3.35)%, P < 0.05]. CD8⁺CD28⁺ T cell subset in the peripheral blood of lung cancer patients was (17.73 ± 1.21)% significantly lower than that of the healthy donors [(27.96 ± 2.72)%, P < 0.01]. The CD8⁺CD28⁻ T cell subset was (21.19 ± 1.92)% in the lung cancer patients, significantly higher than that of the healthy control group [(15.18 ± 2.93)%, P < 0.05]. The expression level of PD-1 on the surface of CD8⁺CD28⁺ T cells was (10.67 ± 1.12)% in the group of lung cancer patients, significantly higher than that of the control group [(5.32 ± 1.58)%, P < 0.01]. It was also found that the expression of PD-1 on CD8⁺CD28⁻ T cells was up-regulated in the group of lung cancer patients (7.46 ± 1.25)%, significantly higher than that of the healthy control group [(2.68+1.07)%, P < 0.01]. The expression level of PD-L1 on CD68⁺ cells in the lung cancer patients was (16.03 ± 2.06)%, significantly higher than that of the healthy control group [(9.32 ± 2.00)%, P < 0.05]. CONCLUSION: Up-regulation of PD-1/PD-L1 on peripheral blood cells in lung cancer patients negatively regulates the lymphocytes, inhibits the immune response for killing tumor cells, and promotes tumor development and immune escape.

[Expression of B7-H3 costimulatory molecule in peripheral blood of myasthenia gravis patients].

AIM: To reveal the clinical significance of B7-H3 costimulatory molecule in myasthenia gravis (MG) patients by analyzing membranous B7-H3 (mB7-H3) and soluble B7-H3 (sB7-H3) expressions. METHODS: We collected peripheral blood samples of 35 MG patients and 44 health controls (HC) and detected the expression of mB7-H3 on peripheral blood mononuclear cells (PBMCs) using flow cytometry. ELISA was performed to analyze the levels of sB7-H3 in plasma samples from MG patients and HC. RESULTS: There was no significant difference in the expressions of mB7-H3 on T lymphocytes, monocytes or B cells between MG patients and HC. However, the level of sB7-H3 from MG patients was (2.166±0.958) ng/mL, significantly lower than that from HC (3.379±0.768) ng/mL. The level of sB7-H3 in general MG (GMG) patients (1.664±0.699) ng/mL was lower than that in ocular MG (OMG) patients (2.396±0.985) ng/mL. In MG patients complicated with abnormal thymus, the level of sB7-H3 was (1.593±0.441) ng/mL, also lower than that in MG patients with normal thymus (2.364±1.014) ng/mL. In addition, a significant negative correlation was found between the levels of sB7-H3 and QMGS in MG patients (r=-0.4189, P=0.012), but sB7-H3 was not associated with mB7-H3 in MG patients. CONCLUSION: In MG patients, down-regulation of sB7-H3 is finely correlated to the severity of the disease. Its different expression levels in various types of MG patients indicate that this costimulatory molecule may be involved in the immunopathogenesis of MG.

[The level of soluble programmed death-1 in peripheral blood of patients with lung cancer and its clinical implications].

OBJECTIVE: To analyze the expression of soluble programmed death-1 ligand 1 (sPD-L1) in the serum of patients with lung cancer and to explore its biological and clinical implications. METHODS: Fifty-five male and twenty-six female lung cancer patients ages 34 to 87 years (mean age 65 ± 6) were selected from the Department of Respiratory Diseases in The Second Affiliated Hospital of Soochow University from June 2009 to March 2011. All lung cancer patients were newly-diagnosed, treatment-free and confirmed by histopathology or cytopathology. Eight-eight healthy volunteers matching in sex and age from the Healthcare Center of the hospital were also enrolled as controls. The sPD-L1 protein expression in serum was determined by Western blot and self-developed ELISA kit. Fluorescence-labeled monoclonal antibody and cytometry were used to examine changes in lymphocyte subsets in the peripheral blood of lung cancer patients and healthy controls. RESULTS: A higher level of sPD-L1 level in the lung cancer patients [1.6 (0.7 - 7.8) µg/L] was found compared to the control group [0.9 (0.4 - 3.7) µg/L] (P < 0.001). High expression of sPD-L1 in the lung cancer patients was closely correlated to lymph node metastasis and the extent of distant metastasis (χ(2) = 5.636, P < 0.05; χ(2) = 4.601, P < 0.05). The sPD-L1 level in lung cancer patients with objective response to treatment (complete response + partial response) was 2.7 (1.6 - 7.0) µg/L and 1.1 (0.8 - 1.7) µg/L before and after treatment, respectively (P < 0.01). The level of sPD-L1 with progression disease was 1.9 (1.3 - 8.5 µg/L) which was significantly increased compared to the baseline level 1.4 (0.8 - 2.2) µg/L (P < 0.01). Additionally, abnormal changes of T and B lymphocytes and their subsets were found, with a significant decrease of CD(8)(+) T lymphocytes (P < 0.05) and a rise in CD(4)/CD(8) ratio (P < 0.05). Further double-labeling study showed increased percentages of CD(4)(+)PD-1(+) T lymphocytes and CD(8)(+)PD-1(+) T lymphocytes (P < 0.05). CONCLUSIONS: The elevated expression of sPD-L1 in lung cancer patients was closely related to lung cancer staging, metastasis and clinical response. sPD-L1 may become a predictive marker and an important anti-tumor target in individualized treatment of lung cancer.

[Preparation and characterization of three novel monoclonal antibodies against human PD-L1].

AIM: To prepare a functional mouse anti-human PD-L1 monoclonal antibody and to characterize its biological activities. METHODS: A stable human PD-L1 transfected cell line L929/PD-L1 was used as an antigen to immunize BALB/c mice. By means of the cell fusion technique, multiple cell subcloning, repeated screening with L929/ PD-L1 as target cells and the L929/mock cells used as the negative control, the hybridomas specifically secreting mouse anti-PD-L1 monoclonal antibodies were generated. Then its biological characterization was investigated by rapid murine Ig-subclass typing, Western blotting, indirect immune of luorescene assay, mutual competitive inhibition test. By means of MTT incorporation assay, detected the infection of mAb to T cell proliferation. Three mouse anti-human PD-L1 monoclonal antibodies were generated, named as 11G8, 2G5 and 5C3. RESULTS: The results of characterization study showed that the monoclonal antibodies could recognize the PD-L1 on the activated T cells. The mAbs could promote T cells proliferation. CONCLUSION: It is evident that the functional monoclonal antibodies for human PD-L1 have been generated, and it would provide the initial material for further study on the role of PD-1/PD-L1 signaling pathways.

[Construction of murine CXCR3 gene transfected cell line, identifiction and study of its biological function].

AIM: To construct recombinant murine CXCR3 gene retroviral vector and obtain L929-mCXCR3 gene transfected cell line for stably expressing murine CXCR3. We further study on L929-mCXCR3 migration effect resulted from interaction by CXCR3 and its ligand IP-10. METHODS: One female BALB/c mouse (7 weeks) was injected with 0.5 mg Con A intravenously (i.v.) via a tail vein. Twelve hours later the mouse was sacrificed and the spleen was removed.The spleen was pressed through a 150 microm stainless steel mesh. The isolated splenocytes were cultured in RPMI1640 supplemented with 50 U/mL human IL-2 for 3 days.Total RNA was extracted with TRIzol. Murine CXCR3 gene of full length was amplified by RT-PCR, then, it was inserted into retrovirus vector pEGZ-term. The recombinant vector together with its helper virus vector were co-transfected into package cell 293T with Lipofectamine(TM); 2000.The supernatant of 293T was collected for infecting L929 cells (repeated three times), and cell clones stably expressing murine CXCR3 molecule were screened by zeocin(500 mg/L). We used FCM and RT-PCR to verify expression of CXCR3 from protein level and gene level, respectively. Studied migration ability of L929-mCXCR3 interacted with its ligand IP-10 by transwell system. RESULTS: We have constructed recombinant murine CXCR3 gene retroviral vector and obtained L929-mCXCR3 gene transfected cell line which can stably expressing murine CXCR3 molecule. Positive expression rate of membrane is 97.0%, and it can directly migrate induced by IP-10, the chemotatic index is 4.356%. CONCLUSION: Construction of L929-mCXCR3 cell line has laid a good foundation on research of biologic characteristics of CXCR3 signal path , establishment of tumor metastasis model and preparation of anti-murineCXCR3 monoclonal antibody.

[Generation and preliminary functional study of a CD133-2-harboring L929 cell line].

AIM: To generate an engineered L929 cell line harboring human CD133-2 and perform the functional study of the gene-modified cell line. METHODS: The human CD133-2 gene was obtained by PCR from a cDNA library of foetus liver. After digested with Hind III and BamH I, the PCR product was cloned into pIRES2-EGFP vector. The recombinant plasmid CD133-2/pIRES2-EGFP was transfected into L929 cell line using lipofectamine, followed by G418 selection. RT-PCR, Western blot and flow cytometry (FCM) were used to detect the expression of CD133-2. MTT was used to analyze the effect of the CD133-2/L929 cells on proliferation of T cells. FCM was performed to monitor T cell activation by detecting T cell surface markers of CD4CD25 and CD8CD25 after T cells were cocultured with the CD133-2/L929 cells in the presence of an anti-CD3 mAb. RESULTS: A stable cell line constitutively expressing the human CD133-2 was established successfully. In the presence of the anti-CD3 mAb, CD133-2/L929 cells caused inhibition of T cell proliferation and down-regulation of the activation markers of CD4CD25 and CD8CD25 on T cells. CONCLUSION: The engineered CD133-2/L929 cell line provides a gain-of-function cell model for further understanding the biological role of CD133-2.

[Inhibitory and lethal effects of human-mouse chimeric antibody against CD80 on the growth of B lymphoma cell lines Raji and Daudi].

AIM: To study the inhibitory and lethal effects of human-mouse chimeric antibody against CD80 (named ch-4E5) on the growth of B lymphoma cell lines Daudi and Raji. METHODS: Immunofluorescence and flow cytometry were used to analyze the detection of membrane CD80 in Raji and Daudi by ch-4E5. After the co-culture of ch-4E5 with Raji and Daudi, respectively, at the final concentration of 10 mg/L, the expression of Fas and FasL was observated to be at the 0 h, 4 h, 10 h, 16 h, 24 h and 48 h by direct immunofluorescence and flow cytometry, and the blocking effect on cell growth of ch-4E5 was determined at 72 h by MTT assay. MTT assay was also used to study the ADCC effect with PBMC as effector cells and Raji and Daudi as target cells. The efficiency target ratio was 20:1. RESULTS: The combination rate between ch-4E5 and Raji and Daudi was 98.6% and 96.4%, respectively. After the co-culture of ch-4E5 with Raji and Daudi cells for 4 hs, the expression of FasL in Raji began to up-regulate. It reached the peak at 16 h and its positive rate was 16.8%. Compared with human IgG1 control group, it was increased obviously (P<0.01). The expression of Fas increased at 10 h, and then reached the top at 24 h. The combination rate was 15.6%. There was significant deviation compared with human IgG1 control group (P<0.01). Moreover, the expression of FasL and Fas on Daudi was also altered. The trend was similar to these on Raji, and the highest expression was 15.9% and 13.7%, respectively. The inhibitory rate was 34.60% and 32.64% respectively when ch-4E5 with Raji and Daudi had been co-cultured for 72 h (P<0.01). Furthermore, ch-4E5 could mediate the ADCC effect and the maximum killing rate was 55.61% and 54.42%, respectively(P<0.01). CONCLUSION: The human-mouse chimeric antibody against CD80 can inhibit the proliferation of B lymphoma cell lines Daudi and Raji cells through Fab and Fc sections in vitro.

Fine-tuned expression of programmed death 1 ligands in mature dendritic cells stimulated by CD40 ligand is critical for the induction of an efficient tumor specific immune response.

During maturation, murine myeloid dendritic cells (DCs) upregulated the expressions of CD11c, CD25, CD40, CD80, CD86, MHC II and programmed death 1 ligands 1 and 2 (PD-L1 and PD-L2). Differential expression patterns of PD-L1 and PD-L2 were found when DCs were triggered by CD40 ligand and TNF-alpha. PD-L1 expression was repressed and PD-L2 expression remained unchanged in mature CD40-ligated DCs, whereas TNF-alpha stimulated DCs kept high expression of PD-L1 and significantly enhanced PD-L2 expression on DCs. Proliferations of T lymphocytes stimulated by immature DCs were enhanced by blockade of the PD-1 and PD-1 ligand interaction. But inhibitive effects were found in T lymphocytes stimulated by CD40-ligated DCs. With the fine-tuned expressions of PD-L1 and PD-L2, CD40-ligated DCs could sustain a longer activation period and elicit a more efficient T lymphocyte activation.

[Preparation and characterization of two novel functional monoclonal antibodies against human OX40L].

AIM: To prepare novel anti-OX40L functional monoclonal antibodies and characterize their distinct biological functions. METHODS: Routine immunization of BALB/c mice by a tansfected cell line L929/OX40L expressing high level of OX40L as antigens. Then fuse the immunized spleen with Sp2/0, a kind of myloma, and screen the positive clones by FCS with L929/OX40L as a positive control.After acquisition of the hybidomas secreting anti-OX40L mAb, investigation of their biological activities by Western blot, rapid isotyping analysis, karyotype analysis, competitive inhibition test, indirect immunofluorescence and MTT incorporation assay were followed. RESULTS: Obtain two stable hybridomas, 4D6 and 5C2, which could continuously secret specific anti-OX40L monoclonal antibodies. The following biological activity studies showed that these monoclonal antibodies could both recognize the natural OX40L expressed on the mature DC, especially the OX40L on the several leukemia cell lines, such as Jurkat, SHI-1, U937 etc. Furthermore, they could also suppress the proliferation of SHI-1 in vitro. CONCLUSION: Two hybridomas secreting anti-OX40L monoclonal antibodies continuously and steadily have been established. These monoclonal antibodies could specifically recognize human OX40L and effect the proliferation of leukemia cell line SHI-1 through OX40/OX40L costimulatory signals.

[Expression of human-mouse chimeric antibody against CD40 in CHO cell line and characterization of its function].

AIM: To investigate the stable expression of a chimeric antibody against CD40 moleculeèch-5C11éin CHO and its biological activity. METHODS: Human-mouse chimeric antibody against CD40 recombinant plasmid and mock plasmid were transfected into CHO cell line through lipofectamine mediation. Human kappa chain and Fc fragment of ch-5C11 were characterized by FACS and Western blot. The concentration of ch-5C11 in cell supernatants was detected by Lowry assay and the inhibitory effect of ch-5C11 on the proliferation of Daudi cells was detected by MTT assay. RESULTS: RT-PCR showed that target CHO cells integrated chimeric heavy chain and chimeric light chain gene. FACS and Western blot showed that ch-5C11 in cell supernatants maintained the binding activity and specificity to human CD40 molecule, and contained human kappa chain and Fc fragment. Cell supernatants were purified using protein G affinity chromatography. The concentration of human-mouse chimeric antibody against CD40 in cell supernatants was 0.535 mg/L. When co-cultured with B lymphoma cell line Daudi, ch-5C11 induced proliferation arrest of Daudi cells. CONCLUSION: The human-mouse chimeric antibody against CD40 can be expressed in CHO stably and effectively, which inhibits proliferation of Daudi.

[Construction and expression of human-mouse chimeric antibody against human CD40].

AIM: To construct and express a chimeric antibody against human CD40 molecule by genetic engineering antibody transformation. METHODS: Total RNA was extracted from the murine hybridoma cell 5C11 which secreted anti-CD40 monoclonal antibody (mAb). The genes encoding V(H) and V(L) of mAb 5C11 were amplified by RT-PCR. According to sequence analysis, the primer was designed to amplify signal peptide sequences relative to V(H) and V(L) genes. The V(H) and V(L) genes of mAb 5C11 and relative signal peptide sequences were spliced with C(H) and C(kappa) genes of human IgG1 to construct expression plasmid pIRES/h5C11 of human-mouse chimeric antibody gene and the plasmid was transfected into 293T cells under Lipofectamine mediation for transient expression. Expressed product was analyzed by flow cytometry. RESULTS: The result of NCBI gene data bank blast revealed that cloned gene sequence accorded with mice' V(H) and V(L) genes and feature of signal peptide sequence. The constructed plasmid pIRES/h5C11 was correct. The restriction endonuclease digestion analysis and PCR showed that the recombinant genes were subsequently cloned into vector pIRES. FACS analysis showed that human-mouse chimeric antibody against human CD40 maintained the binding activity and specificity to human CD40 molecule. CONCLUSION: The gene encoding variable region of human-mouse chimeric antibody against CD40 is cloned successfully and the human-mouse chimeric antibody against CD40 is expressed transiently in 293T cells.

[Construction of human breast carcinoma cell line transfected with OX40L and its costimulatory effect on T cells].

BACKGROUND & OBJECTIVE: Costimulator OX40 (CD134) belongs to TNFR family, and its ligand OX40L (CD134L) belongs to TNF family. OX40-OX40L signal plays an important role in immune regulation, which can increase the production of cytokines and enhance the survival of antigen-specific T cells. This research was to transfect OX40L into human breast cancer cell line MDA-MB-435 to construct OX40L-MDA-MB-435 cells, and to investigate the costimulatory effect of OX40-OX40L signal on biological activity of T cells in vitro. METHODS: cDNA fragment encoding OX40L was obtained from human mature dendritic cells by reverse transcription-polymerase chain reaction (RT-PCR), and inserted into eukaryotic expression vector pcDNA3.1. The recombinant plasmid pcDNA3.1-OX40L was transfected into MDA-MB-435 cells, and verified by indirect immunophenotyping and RT-PCR. The effect of OX40L-MDA-MB-435 cells to the biological activity of T cells was investigated by MTT, enzyme-linked immunosorbent assay (ELISA), and direct immunophenotyping. RESULTS: OX40L-MDA-MB-435 cells were successfully constructed. These cells efficiently promoted the proliferation of T cells, enhanced the secretion of interleukin-2 (IL-2) (973.4 ng/ml at the 7th day) and interferon-gamma (IFN-gamma) (3,689.167 pg/ml at the 3rd day), and down-regulated the expression of Fas on T cells [(68.3+/-5.6)%, P<0.05]. CONCLUSION: OX40L-MDA-MB-435 cells could activate T cells in vitro, promote T cell proliferation and cytokine secretion, and suppress T cell activation-induced cell death.

Cloning, structural organization and chromosomal mapping of rat costimulatory molecule 4-1BBL.

4-1BBL (TNFSF9) is a member of the tumor necrosis factor (TNF) ligand superfamily, which is expressed on some activated antigen presenting cells and B cells. We isolated a rat cDNA clone encoding the rat homologue of the human 4-1BBL (GenBank accession No. AY259541). The deduced rat 4-1BBL protein, consisting of 308 amino acids with a molecular weight of 33,469 Da, was a typical type II transmembrane glycoprotein, the same as human and murine 4-1BBL. "SDAA" in the cytoplasmic domain of rat 4-1BBL was deduced to act as the phosphorylation site for casein kinase I ("SXXS" motif), which is present in the cytoplasmic domains of human and murine 4-1BBL, and all other TNF ligand family members known to utilize reverse signaling. The two introns of 4-1BBL were also cloned (GenBank accession No. AY332409). Rat 4-1BBL is much more homologous with murine 4-1BBL than with human 4-1BBL, in both nucleotide and amino acid sequences. Rat 4-1BBL was expressed in all tested tissues: brain, lung, colon, liver, thymus, testicle, kidney, adrenal, stomach, spleen and heart. The chromosomal location of rat 4-1BBL was first identified by bioinformatics, then by fluorescence in situ hybridization at 9q11 (GenBank accession UniGene No. Rn.46783). Rat, murine and human 4-1BBL genes are evolved from a common gene. The identification and characterization of the rat counterpart of human 4-1BBL will facilitate studies of the biological function of this molecule.

Apoptosis of multiple myeloma cells induced by agonist monoclonal antibody against human CD28.

CD28 is expressed abnormally on human multiple myeloma (MM) cells but the significance had not been identified until now. In this paper, we are suggesting that abnormal expression of CD28 might be a marker of tumour progression. We therefore took the approach of generating a hybridoma cell line capable of secreting agonist monoclonal antibody directed against human CD28 (agonist anti-CD28 mAb) and then determined the expression of CD28 molecules on the MM cell lines U266 and XG1. The biological effects of agonist anti-CD28 mAb on cell growth and proliferation of U266 and XG1 cell lines were then analysed. Our results showed that the expression of CD28 on U266 and XG1 was significantly higher than that of PBTC or Jurkat cells. We found that by adding the agonist anti-CD28 mAb to cultures of U266 and XG1 cells their rate of growth and proliferation was obviously inhibited. Further morphological and molecular analyses found that U266 and XG1 incubated with agonist anti-CD28 mAb showed signs of nuclear condensation, chromatin marginal changes, cells membrane breaking, and cytoplasmic shrinkage. Vacuoles and apoptotic bodies were also observed using a transmission electron microscope and the development of typical DNA laddering patterns were found by the use of electrophoresis assays, suggesting that U266 and XG1 cells were undergoing apoptosis induced by agonist anti-CD28 mAb in vitro.

Sensitization of multiple myeloma and B lymphoma lines to dexamethasone and gamma-radiation-induced apoptosis by CD40 activation.

We examined the effects of CD40 activation with dexamethasone (Dex) or 60Co-gamma-irradiation on the growth of malignant B cells in vitro, using the human multiple myeloma (MM) cell line, XG2, and the B lymphoma Daudi cell line as models. Both lines are resistant to Dex and irradiation; 10(-7)M Dex or 10 Gy of gamma-irradiation induced only minimal growth arrest and apoptosis of the cells. Treatment of the cells with the agonistic anti-CD40 monoclonal antibody 5C11 partially inhibited the proliferation of the Daudi cells; XG2 underwent apoptosis. XG2 is an Interleukin-6 (IL-6)-dependent myeloma cell line and CD40 activation blocked XG2 in the G1 phase of the cell cycle, in a manner similar to the effect of IL-6 deprivation. Daudi was blocked in the G2/M phase after treatment with the agonistic CD40 mAb 5C11. Furthermore, the activation of CD40 on Daudi and XG2 enhanced their sensitivity to dexamethasone-and gamma-irradiation -induced growth arrest and apoptosis. CD40 activation stimulated both anti-apoptotic Bcl-XL and pro-apoptotic Bax mRNA synthesis in the Daudi cell line; CD40 activation increased the Bax mRNA level but had no effect on the Bcl-XL mRNA level in the XG2 cell line. Apoptosis in both cell lines was associated with an increasing ratio of Bax-to-Bcl-XL both in mRNA and in protein levels. It is concluded that use of the anti-CD40 mAb 5C11 either by itself or in combination with chemotherapy and/or radiotherapy may have significant therapeutic potential.

Refolding and characterization of recombinant human GST-PD-1 fusion protein expressed in Escherichia coli.

Programmed death-1 (PD-1) is a costimulatory molecule of CD28 family expressed on activated T, B and myeloid cells. The engagement of PD-1 with its two ligands, PD-L1 and PD-L2, inhibits proliferation of T cell and production of a series of its cytokines. The blockade of PD-1 pathway is involved in antiviral and antitumoral immunity. In this study, human PD-1 cDNA encoding extracellular domain was amplified and cloned into expression plasmid pGEX-5x-3. The fusion protein GST-PD-1 was effectively expressed in E. coli BL21 (DE3) as inclusion bodies and a denaturation and refolding procedure was performed to obtain bioactive soluble GST-PD-1. Fusion protein of above 95% purity was acquired by a convenient two-step purification using GST affinity and size exclusion columns. Furthermore, a PD-L1-dependent in vitro bioassay method was set up to characterize GST-PD-1 bioactivity. The results suggested that GST-PD-1 could competently block the interaction between PD-L1 and PD-1 and increase the production of IL-2 and IFN-gamma of phytohemagglutinin-activated T cells.