Biomedical subjects

Hongyu Luo

Publications and source records attributed to Hongyu Luo.

14 recordsLinked to original sources

PubMed2025

Stereo-cell: Spatial enhanced-resolution single-cell sequencing with high-density DNA nanoball-patterned arrays.

Single-cell sequencing technologies have advanced our understanding of cellular heterogeneity and biological complexity. However, existing methods face limitations in throughput, capture uniformity, cell size flexibility, and technical extensibility. We present Stereo-cell, a spatial enhanced-resolution single-cell sequencing platform based on high-density DNA nanoball (DNB)-patterned arrays, which enables scalable and unbiased cell capture at a wide input range and supports high-fidelity transcriptome profiling. Stereo-cell further allows integration with imaging-based modalities and multiomics strategies, including immunofluorescence and epitope profiling. This platform is also compatible with profiling extracellular vesicles, microstructures, and large cells, whereas its spatial resolution facilitates in situ analysis of cell-cell interactions, cellular microenvironments, and subcellular transcript localization. Together, Stereo-cell provides a flexible framework for expanding single-cell research applications.

Animals↗

PubMed2006

Transgenic drak2 overexpression in mice leads to increased T cell apoptosis and compromised memory T cell development.

Drak2 is a death-associated protein family serine-threonine kinase. Its expression and roles in the immune system were investigated in this study. According to in situ hybridization, Drak2 expression was ubiquitous at the mid-gestation stage in embryos, followed by more focal expression in various organs in the perinatal period and adulthood, notably in the thymus, spleen, lymph nodes, cerebellum, suprachiasmatic nuclei, pituitary, olfactory lobes, adrenal medulla, stomach, skin, and testes. Drak2 transgenic (Tg) mice were generated using the human beta-actin promoter. These Tg mice showed normal T cell versus B cell and CD4 versus CD8 populations in the spleen, but their spleen weight cellularity was lower in comparison with wild type mice. After TCR activation, the proliferation response in Drak2 Tg T cells was normal, although their interleukin (IL)-2 and IL-4 but not interferon-gamma production was augmented. Activated Drak2 Tg T cells demonstrated significantly enhanced apoptosis in the presence of exogenous IL-2. At the molecular level, Drak2 Tg T cells manifested a lower increase of anti-apoptotic factors during activation; such a change probably rendered the cells vulnerable to subsequent IL-2 insults. The compromised apoptosis in Drak2 Tg T cells was associated with reduced numbers of T cells with the memory cell phenotype (CD62L(lo)) and repressed secondary T cell responses in delayed type hypersensitivity. Our study demonstrates that Drak2 expresses in the T cell compartment but is not T cell-specific; it plays critical roles in T cell apoptosis and memory T cell development.

Animals↗

PubMed2006

Ephrin-B1 is critical in T-cell development.

Eph kinases are the largest family of receptor tyrosine kinases, and their ligands, ephrins (EFNs), are also cell surface molecules. In this study, we investigated the role of EFNB1 and the Ephs it interacts with (collectively called EFNB1 receptors) in mouse T-cell development. In the thymus, CD8 single positive (SP) and CD4CD8 double positive (DP) cells expressed high levels of EFNB1 and EFNB1 receptors, whereas CD4 SP cells had moderate expression of both. Soluble EFNB1-Fc in fetal thymus organ culture caused significant subpopulation ratio skew, with increased CD4 SP and CD8 SP and decreased DP percentage, while the cellularity of the thymus remained constant. Moreover, in EFNB1-treated fetal thymus organ culture, CD117(+), CD25(+), DP, CD4 SP, and CD8 SP cells all had significantly enhanced proliferation history, according to bromodeoxyuridine uptake. In vitro culture of isolated thymocytes revealed that EFNB1-Fc on solid-phase protected thymocytes from anti-CD3-induced apoptosis, with concomitant augmentation of several antiapoptotic factors, particularly in CD4 SP and CD8 SP cells; on the other hand, soluble EFNB1-Fc promoted anti-CD3-induced apoptosis, as was the case in vivo. This study reveals that EFNB1 and EFNB1 receptors are critical in thymocyte development.

Animals↗

PubMed2005

Recent advances on T-cell regulation by receptor tyrosine kinases.

PURPOSE OF REVIEW: This review summarizes recent knowledge on the role of receptor tyrosine kinases, particularly erythropoietin-producing hepatocyte kinases (Ephs), in T-cell function and development. RECENT FINDINGS: Erythropoietin-producing hepatocyte kinase function and signaling in the immune system have been recently investigated. Cross-linking some Ephs results in T-cell costimulation and reduces the response threshold of T-cell receptor activation. In vivo, T-cell-mediated responses are compromised in EphB6-/- mice. Some Ephs are shown to control T-cell migration and adhesion, as well as the integrity of lymphoid organ structure. SUMMARY: Ephs are the largest family of receptor tyrosine kinases. Some Ephs are expressed in the lymphoid organs. Ephrins, ligands of Ephs, are also cell surface molecules. Cross-linking of certain Ephs facilitates T-cell activation and proliferation. Under physiologic conditions, such cross-linking by ephrins likely occurs in lymphoid organs, where ephrins on T cells interact with ephrins on the surface of neighboring fraternal T cells or antigen-presenting cells; this may explain why T-cell responses are more effectively initiated in the lymphoid organs. Certain Ephs are also critical for lymphocyte adhesion and migration and for proper lymphoid organ structure. Ephs and ephrins are highly redundant and their interactions promiscuous, suggesting pivotal roles of these molecules in biology. Conversely, such redundancy represents a major challenge to further dissection of the function of individual Ephs. Multiple tissue-specific gene null mutations on Ephs or ephrins will likely reveal more interesting immune-related phenotypes.

Animals↗

PubMed2004

EphrinB1 is essential in T-cell-T-cell co-operation during T-cell activation.

Eph kinases are the largest family of receptor tyrosine kinases, and their ligands are ephrins (EFNs), which are also cell surface molecules. We have very limited knowledge about the expression and function of these kinases and their ligands in the immune system. In this study we investigated the effect of EFNB1 on mouse T-cells. EFNB1 and the Eph kinases it interacts with (collectively called EFNB1 receptors (EFNB1R)) were expressed on T-cells, B cells, and monocytes/macrophages. Some T-cells were double positive for EFNB1 and EFBB1R. Solid phase EFNB1 in the presence of suboptimal TCR ligation augmented T-cell responses in terms interferon-gamma secretion, proliferation, and cytotoxic T lymphocyte activity but not interleukin-2 production. After T-cell receptor (TCR) ligation, EFNB1R congregated to TCR caps, and then both of them translocated to raft caps. This provides a morphological basis for EFNB1R to enhance TCR signaling. Further downstream of the signaling pathway, EFNB1R stimulation led to increased LAT (linker for activation of T-cells) phosphorylation and p44/42 and p38 MAPK activation. Similar to CD28 costimulation, EFNB1R costimulation was insensitive to cyclosporin A inhibition. On the other hand, unlike the former, EFNB1R costimulation failed to activate Akt, which is essential in triggering interleukin-2 production. Our study suggests that EFNB1 is pivotal in T-cell-T-cell costimulation and in reducing T-cell response threshold to antigen stimulation.

Animals↗

PubMed2004

Dipeptide boronic acid, a novel proteasome inhibitor, prevents islet-allograft rejection.

BACKGROUND: We have demonstrated previously in vitro that proteasome inhibitors suppress the proliferation, and induce the apoptosis, of activated T cells. This implies that they could be used as a novel category of immunosuppressants to block allograft rejection. Therefore, in this study, dipeptide boronic acid (DPBA) was tested for its effect on mouse islet transplantation. METHODS: First, DPBA was investigated in vitro for its effect on mouse mixed lymphocyte reaction (MLR) and cytotoxic T-lymphocyte (CTL) activity. DPBA was then used in vivo to treat mouse islet-allograft rejection. RESULTS: Both MLR and CTL were dose dependently suppressed by the proteasome inhibitor. A 17-day DPBA regimen resulted in islet-allograft survival in 50% of the recipients for a duration of up to 60 days, whereas the control group without immunosuppressants rejected the islet graft in 7 days. DPBA showed moderate side effects according to blood biochemistry; the function of endogenous islets after treatment appeared normal on glucose challenge. CONCLUSIONS: The proteasome inhibitor could inhibit islet-allograft rejection in mice without serious side effects at therapeutic dose levels. This has opened a new dimension in the development of better immunosuppression regimens for islet transplantation.

Animals↗

PubMed2004

EphB6-null mutation results in compromised T cell function.

So far, there is very limited knowledge about the role of Eph kinases, the largest family of receptor tyrosine kinases, in the immune system. Here, using EphB6(-/-) mice, we demonstrated that in vitro and in vivo T cell responses such as lymphokine secretion, proliferation, and the development of delayed-type skin hypersensitivity and experimental autoimmune encephalitis in EphB6(-/-) mice were compromised. On the other hand, humoral immune responses, such as serum levels of different Ig isotypes and IgG response to tetanus toxoid, were normal in these mice. Mechanistically, we showed that EphB6 migrated to the aggregated TCRs and rafts after TCR activation. Further downstream, in the absence of EphB6, ZAP-70 activation, LAT phosphorylation, the association of PLCgamma1 with SLP-76, and p44/42 MAPK activation were diminished. Thus, we have shown that EphB6 is pivotal in T cell function.

Animals↗

PubMed2003

Mouse ephrinB3 augments T-cell signaling and responses to T-cell receptor ligation.

Ephrins (EFN) are cell-surface ligands of Ephs, the largest family of cell-surface receptor tyrosine kinases. The function of EFNs in the immune system has not been well studied, although some EFNs and Ephs are expressed at high levels on certain leukocytes. We report here that EFNB3 and its receptors (collectively called EFNB3Rs, as EFNB3 binds to multiple EphBs) were expressed in peripheral T cells and monocytes/macrophages, with T cells being the dominant EFNB3+ and EFNB3R+ cell type. Solid-phase EFNB3-Fc in the presence of suboptimal anti-CD3 crosslinking enhanced T-cell responses in terms of proliferation, activation marker expression, interferon-gamma but not interleukin-2 production, and cytotoxic T-cell activity. EFNB3R costimulation in the presence of phorbol 12-myristate 13- acetate was insensitive to cyclosporin A, similar to CD28 costimulation, suggesting they might share a part of the signaling pathway. After crosslinking, T-cell receptor and EFNB3R congregated into aggregated rafts, and this provided a morphological basis for signaling pathways of T-cell receptor and EFNB3R to interact. Solid-phase EFNB3-Fc augmented p38 and p44/42 MAPK activation further downstream of the signaling pathway. These data suggest that EFNB3 is important in T-cell/T-cell and T-cell/antigen-presenting cell collaboration to enhance T-cell activation and function.

Animals↗

PubMed2003

Ephrin B2 induces T cell costimulation.

Eph kinases form the largest family of receptor tyrosine kinases, and their ligands are ephrins (EFNs), which are cell surface proteins. Some Eph kinases and EFNs are expressed on T cells, B cells, and dendritic cells, but their functions in the immune system are largely unknown. In this study, we investigated the effect of EFNB2 on murine T cells. EFNB2 mRNA was expressed in the cortex of the thymus and white pulp of the spleen. At the protein level, it was expressed on T cells and monocytes/macrophages, but not on B cells. EFNB2Rs were expressed mainly on T cells. Solid-phase EFNB2 along with suboptimal anti-CD3 strongly stimulated T cell proliferation, with concomitant augmentation of IFN-gamma but not IL-2 or IL-4 secretion. The activity of cytotoxic T cells was also significantly enhanced in the presence of solid-phase EFNB2. These results indicate that EFNB2R cross-linking results in costimulation of T cells. EFNB2Rs were normally scattered on the T cell surface; after TCR cross-linking, they rapidly congregated to capped TCR complexes and then to patched rafts. This provides a morphological base for EFNB2Rs to participate in T cell costimulation. We also demonstrated that EFNB2R signaling led to augmented p38 and p44/42 mitogen-activated protein kinase activation. Our study shows that EFNB2 plays important roles in immune regulation.

Adjuvants, Immunologic↗

PubMed2003

DcR3/TR6 effectively prevents islet primary nonfunction after transplantation.

Islet primary nonfunction (PNF) is defined as the loss of islet function after transplantation for reasons other than graft rejection. It is a major obstacle to successful and efficient islet transplantation. DcR3/TR6 is a soluble death decoy receptor belonging to the tumor necrosis factor (TNF) receptor family, and it can block apoptosis mediated by several TNF receptor family members such as Fas and LT beta R. In this study, we used TR6 to protect islets from PNF after transplantation. Untreated isogeneic or allogeneic islet transplantation had PNF incidence of 25 and 26.5%, respectively. Administration of TR6 totally prevented PNF in allogeneic islet transplantation. In vitro experiments showed an increased apoptosis among islets that were treated with FasL and gamma-interferon (IFN-gamma) in combination. TR6 significantly reduced such apoptosis. Functional study showed that insulin release was compromised after FasL and IFN-gamma treatment, and the compromise could be prevented with TR6-Fc. This indicates that TR6 indeed protected beta-cells from damage caused by FasL and IFN-gamma. Further in vivo experiments showed that syngeneic islet transplantation between lpr/lpr and gld/gld mice was significantly more efficacious than that conducted between wild-type mice. These results suggest that Fas-mediated apoptosis plays an important role in PNF, and use of TR6 may be a novel strategy to prevent PNF in clinical islet transplantation.

Animals↗

PubMed2002

A TNF family member LIGHT transduces costimulatory signals into human T cells.

DcR3/TR6 is a secreted protein belonging to the TNFR family. It binds to Fas ligand, LIGHT, and TL1A, all of which are TNF family members. LIGHT is expressed on activated T cells. Its known receptors are TR2 and LTbetaR on the cell surface, and TR6 in solution. In the present study, we report soluble TR6-Fc or solid-phase TR6-Fc costimulated proliferation, lymphokine production, and cytotoxicity of human T cells in the presence of TCR ligation. These costimulating effects were blocked by soluble LIGHT but not by soluble Fas-Fc. TR6-Fc could also effectively costimulate gld/gld mouse T cells. We further demonstrated that TR6 bound to both Th1 and Th2 cells, according to flow cytometry, and that the association was inhibited by soluble LIGHT. Cross-linking Th1 and Th2 cells with solid-phase TR6-Fc along with a suboptimal concentration of anti-CD3 enhanced proliferation of both Th1 and Th2 cells, and augmented Th1 but not Th2 lymphokine production. These data suggest that TR6 delivers costimulation through its ligand(s) on the T cell surface, and at least the major part of such costimulation is via LIGHT.

Adjuvants, Immunologic↗

PubMed2002

Mouse T cells receive costimulatory signals from LIGHT, a TNF family member.

LIGHT is a tumor necrosis factor (TNF) family member and is expressed on activated T cells. Its known receptors are TR2 and LTbetaR on the cell surface, and TR6/DcR3 in solution. TR6/DcR3 is a secreted protein belonging to the TNF receptor family. It binds to Fas ligand (FasL), LIGHT, and TL1A, all of which are TNF family members. In the present study, we report that solid-phase TR6-Fc costimulated proliferation, lymphokine production, and cytotoxicity of mouse T cells upon T-cell receptor (TCR) ligation. A monoclonal antibody against LIGHT similarly costimulated mouse T cells in their proliferation response to TCR ligation. These data suggest LIGHT, although a ligand, can receive costimulation when expressed on the T-cell surface. Mechanistically, when T cells were activated by TCR and CD28 co-cross-linking, TCR and rafts rapidly formed caps where they colocalized. LIGHT rapidly congregated and colocalized with the aggregated rafts. This provided a molecular base for the signaling machinery of LIGHT to interact with that of TCR. Indeed, LIGHT cross-linking enhanced p44/42 mitogen-activated protein kinase activation after TCR ligation. This study reveals a new function and signaling event of LIGHT.

Animals↗

PubMed2002

[A novel stop codon mutation in S gene: the molecular basis of a patient with cryptogenic cirrhosis].

OBJECTIVE: To explore the pathogen and molecular basis of cryptogenic cirrhosis in a patient. METHODS: Serum was collected from a patient, male, aged 56, with cryptogenic cirrhosis. HBV serologic markers were qualitatively tested, and HBsAg, HBeAg, and anti-HBc were quantitatively determined again. HBV DNA in serum was qualitatively tested using PCR, and quantified using fluorescence quantitative PCR. S gene was amplified, cloned, and sequenced. RESULTS: HbsAg and anti-Hbe were negative, and anti-HBs, HBeAg, anti-HBc, and HBV DNA were all positive. HBsAg (S/N) was 0.77 (cutoff of S/N: >/= 2.00), HbeAg (S/N) was 56.43 (cutoff of S/N: >/= 2.10), anti-HBc (S/C(O)) was 0.03 (cutoff of S/C(O): </= 1.00); HBV DNA was 1.54 x 10(9) copies/ml. An uncommon point mutation at nucleotide 336 (C to A) in S gene was found, resulting in the change of the 61st codon into a novel stop codon and failure of synthesis of HbsAg. CONCLUSION: HBV proves the pathogen of this case. This special mutation well explains the patient's unusual serologic pattern. Moreover, this finding possesses important clinical and theoretical significance.

Base Sequence↗

PubMed2002

EphB6 crosslinking results in costimulation of T cells.

Erythropoietin-producing hepatocyte (Eph) kinases represent the largest receptor tyrosine kinase family. Some of them are expressed in the T cell compartment, but their function in T cells is unknown. In peripheral blood, EphB6 was predominantly expressed on T cells, and was upregulated after culture. EphB6 crosslinking by anti-EphB6 mAb or ephrinB2 in the presence of suboptimal T cell receptor (TCR) stimulation led to drastic T cell proliferation, suggesting that EphB6 can co-stimulate T cells. The proliferation was accompanied by enhanced production of several lymphokines, such as IFN-gamma, IL-6, IL-10, TGF-beta, TNF-alpha, and GM-CSF, but not IL-2 and IL-4. Sorted EphB6(+) T cells had significantly stronger response to anti-CD3 and anti-CD28 stimulation than EphB6(-) T cells had. Taken together, these data suggest an important role of EphB6 in normal T cell activation. Within two minutes of anti-CD3 and anti-CD28 stimulation, EphB6 aggregated and colocalized with TCR, and this provides a morphological basis for EphB6 to enhance TCR signaling. The capping was followed by p38 MAPK activation, showing that EphB6 is capable of signaling, in spite of its lack of intrinsic kinase activity. This study demonstrates that interaction between EphB6 and its ligands facilitates T cell responses to antigen.

Animals↗