Downregulating immunogenicity of Schwann cells via inhibiting a potential target of class II transactivator (CIITA) gene

Immunological rejection induced by allogeneic Schwann cells remains a problem for construction of artificial nerves. Class II transactivator (CIITA) gene is a chief regulator of major histocompatibility complex class II (MHC II) molecules which contributes to the immunogenicity of Schwann cells. This study aimed to downregulate MHC II expression by suppressing CIITA expression, therefore reducing the immunogenicity of Schwann cells. Recombinant siRNA expression vectors targeting the CIITA gene were produced and subsequently transfected into rat RSC96 Schwann cells. Interferon (IFN)-gamma was used to augment immunological rejection of RSC96 cells. The mRNA levels of CIITA and MHC II were assessed by fluorescence quantitative PCR. The protein levels of MHC II were determined using flow cytometry assays. Finally, the immunogenicity of RSC96 cells was analyzed using mixed lymphocytes reactions. Results indicated the expression of MHC II molecules was at a low level in cultured RSC96 cells, while significantly elevated after treatment with IFN-gamma. Concurrent treatment with the constructed CIITA siRNAs efficiently downregulated the mRNA levels of CIITA and MHC II in RSC96 cells at 48 h post-transfection. MHC II protein levels were also significantly reduced after CIITA siRNAs transfection. Correspondingly, the immunogenicity of RSC96 cells was significantly downregulated post-transfection. These studies suggest suppressing CIITA gene was efficient in reducing MHC II expression and thus decreasing the immunogenicity of rat Schwann cells.