Study on the Mechanisms of FVE-mediated Murine T Cell Activation
Date Issued
2008
Date
2008
Author(s)
Tong, Man-Hua
Abstract
FVE, a fungal immunomodulatory protein purified from Flammulina velutipes, is capable to stimulate lymphocyte proliferation, to suppress systemic anaphylaxis responses, and to increase IL-2 and IFN-γ production. It is known that FVE may exhibit potent mitogenic effects on human peripheral blood lymphocytes and murine splenic T cells only in the presence of antigen presenting cells (APCs). However, cell proliferation stimulated by mitogens is greater than FVE, and the activity of FVE is much better than conventional antigens. These information exclude the possibility that FVE is a mitogen and suggest FVE might activate T cells throuth a pathway similar to what superantigen does. The objective of this study is to study the mechanisms of FVE-mediated murine T cell activation and to argue FVE a superantigen. To demonstrate that APCs are necessary in FVE-mediated T cell activation, result shows that FVE incubated paraformaldehyde-fixed murine splenocytes are able to induce cell proliferation of MACS-purified murine T cells, and this effect is not found in the T cell alone control cells This evidence suggests that FVE-mediated T cell activation performs only in a synergistic incubation of both APCs and FVE is directly presented by the receptor on APCs without processing procedure that common antigens need.n the other hand, most superantigens are a class of antigens presented by MHC molecules on APCs and they recognized the variable region of the β-chain (Vβ) of the T cell receptors (TCR). In this study, fluorescent-activated cell sorting (FACS) and real-time PCR methods are carried out to determine the expression of variable regions within TCR. Result shows that no T cell bearing specific Vβ extension and a remarked Vα enhancement, especially Vα 19 mRNA (above 6 folds of the enhancement), are observed, suggesting that FVE could bind to Vα 19 and further enhance its expression. urthermore, the cross-linking between FVE and MHC molecules is also investigated. And the result shows that both anti-MHC class I and class II neutralizing antibodies (anti-H-2Kd and anti-IA/IE, respectively) are capable to inhibit FVE-stimulated cell proliferation in a dose-dependent manner. The addition of both the antibodies also reduces IL-12 p35, IL-12 p40, and IL-18 gene expression stimulated by FVE. These results indicate that FVE can not only activate CD4+ T cell but also CD8+ T cell proliferation, and MHC class II and MHC class I on APCs are probably responsible for presenting FVE to further activate T cells. The pathway that FVE activates cytokine gene expansion within APCs might also through MHC class I and class II molecules. aken together, this study clearly demonstrates that FVE, which activates T cells through the binding of MHC molecules in APCs and Vα 19 TCR region in T cells, is a superantigen-like immunomodulatory protein. This finding clarifies the molecular mechanism of FVE-mediated T cell activation and supports the further utilization of FVE in immune-related pharmaceutical and medicinal applications.
Subjects
FVE
paraformaldehyde-fixed murine splenocytes
superantigen
Type
thesis
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