IN VITRO CO-STIMULATORY ACTIVITY OF HUMAN B7.2(IgV+C) PROTEIN PRODUCED BY ENGINEERED BACTERIA

Objective To express human B7. 2 extracellular domain with prokaryote expression system and to evaluate its biological activity in vitro. Methods PCR was used to amplify the extracellular region of human B7. 2 which contained both the IgV and IgC domains. The recombinant PGEX-4T-3/hB7. 2 (IgV+C) was obtained by cloning the PCR product into a prokaryote expression plasmid PGEX-4T-3 and was transformed into the host strain of DH5-a. Tke fusion protein consisted of GST and hB7. 2(IgV+C) was identified by SDS-PAGE and Western blotting. T cell activation was observed by exposing purified T lymphocytes to the fusion protein and [3H]-TdR incorporation with the presence of the first signal imitated hy anti-CD3 antibody. Results The fusion protein GST-hB7. 2 (IgV+ C) was produced and detected in inclusive body form from engineered bacterial cells. With the first signal existed,T lymphocytes proliferated when it was co-stimulated by the fusion protein. Conclusion These results indicated that the functional human B7. 2(IgV+C) fusion protein can be produced in bacterial cells and the fusion protein displays the co-stimulatory activity in T lymphocytes activation.

Regulating regulatory T cells to achieve transplant tolerance

BACKGROUND:Regulatory T cells(Tregs) play crucial roles in both induction and maintenance of tolerance. This active immune regulation may contribute not only to the control of immune responses to self-antigens and thereby prevent autoimmune diseases,but also the control of responses to non-self molecules in adaptive immunity. Numerous experimental and clinical studies indicate that manipulating the balance between regulatory and responder T cells is an effective strategy to control immune responsiveness after transplantation. DATA SOURCES:Literature search was conducted using PubMed on the related subjects. Part of the material was based on the most recent work in the authors’ laboratory. RESULTS:We propose some new strategies to achieve transplant tolerance in rodent animals via manipulating Treg function,including using histone deacetylase(HDAC) inhibitor to regulate Foxp3 transcription and enhance Treg suppression,induction of Treg-sparing apoptosis via Nur77,and identification of the co-inhibitory molecule herpes virus entry mediator(HVEM) as an effector molecule for Treg function. CONCLUSION:Regulation of Treg function will definitely provide us very promising tools to achieve clinical tolerance in the future.

FGF-receptor substrate 2 functions as a molecular sensor ntegrating external regulatory signals into the FGF pathway

Fibroblast growth factor （FGF） receptor substrate 2a （FRS2α） is the main mediator of signaling in the FGF pathway. Recent studies have shown that mitogen-activated protein kinase （MAPK） phosphorylates serine and threonine residues in FRS2, negatively affecting FGF-induced tyrosine phosphorylation （PY） of FRS2. Several kinds of stimuli can induce serine/threonine phosphorylation （PS/T） of FRS2, indicating that FRS2 may be useful for studying crosstalk between growth factor signaling pathways. Here, we report that FGF-induced PY of FRS2 can be attenuated by EGF co-stimulation in PC12cells; this inhibitory effect could be completely reversed by U0126, an inhibitor of MEK. We further identified the ERK1/2-binding motif in FRS2 and generated FRS2-3KL, a mutant lacking MAPK binding and PT upon FGF and/or EGF stimulation. Unlike wild-type （WT） FRS2, FGF-induced PY of FRS2-3KL could not be inhibited by EGF co-stimulation, and FRS2-3KL-expressing PC12 cells exhibited more differentiating potential than FRS2-WT-expressing cells in response to FGF treatment. These results suggest that PS/T of FRS2 mediated by the FRS2-MAPK negative regulatory loop may function as a molecular switch integrating negative regulatory signals from other pathways into FGFR-generated signal transduction.

B7-H4 as a protective shield for pancreatic islet beta cells

Auto- and alloreactive T cells are major culprits that damage β-cells in type 1 diabetes(T1D) and islet transplantation. Current immunosuppressive drugs can alleviate immune-mediated attacks on islets. T cell co-stimulation blockade has shown great promise in autoimmunity and transplantation as it solely targets activated T cells, and therefore avoids toxicity of current immunosuppressive drugs. An attractive approach is offered by the newly-identified negative T cell cosignaling molecule B7-H4 which is expressed in normal human islets, and its expression co-localizes with insulin. A concomitant decrease in B7-H4/insulin colocalization is observed in human type 1 diabetic islets. B7-H4 may play protective roles in the pancreatic islets, preserving their function and survival. In this review we outline the protective effect of B7-H4 in the contexts of T1 D, islet cell transplantation, and potentially type 2 diabetes. Current evidence offers encouraging data regarding the role of B7-H4 in reversal of autoimmune diabetes and donor-specific islet allograft tolerance. Additionally, unique expression of B7-H4 may serve as a potential biomarker for the development of T1 D. Futurestudies should continue to focus on the islet-specific effects of B7-H4 with emphasis on mechanistic pathways in order to promote B7-H4 as a potential therapy and cure for T1 D.

Essential concept of transplant immunology for clinical practice

Our understanding of transplant immunology has advanced from gross allograft rejection to cellular response and to current molecular level. More sensitive assays have been developed to characterize patient sensitization and to detect pre-existing donor-specific antibodies(DSA) in pre-transplant crossmatch. After a transplant, pre-existing or de novo DSA are increasingly monitored to guide clinical management. Therefore, it is important for clinicians to understand the basic concepts and key components of transplant immunology as well as be familiarized with the modern immunological techniques used in kidney transplantation.