Effect of TGF-β1 gene-modified dendritic cells on expressions of CD28/CTLA-4:B7 in peripheral blood mononuclear cells in rats with experimental autoimmune myasthenia gravis

Abstract

Objective To explore the effect of dendritic cells (DC) modified with transforming growth factor β1 (TGF-β1) gene on the expressions of CD28/CTLA-4:B7 costimulatory molecules in peripheral blood mononuclear cells (PBMC) in the Lewis rats with experimental autoimmune myasthenia gravis (EAMG). Methods Thirty inbreeding line, healthy, female Lewis rats were divided randomly into 6 groups: normal group, EAMG group, DC treatment group, pcDNA3-TGF-β1-DCtreatment group, pcDNA3-DC control group and normal saline group. The rats were immunized with the AChR protein extracted from electric organ of Narcine timilei and CFA in the groups except normal group. 2×106 pcDNA3-TGF-β1-DCs/rat were injected subcutaneously into the backs of the rats which had been immunized 5 d earlier with AChR+CFA. The rats in DC treatment group, pcDNA3-DC control group and normal saline group were injected in parallel with untreated DC, pcDNA3-DC and normal saline, respectively. Seven weeks after the first immunization, the expressions of CD28 mRNA and CTLA-4 mRNA were detected by reverse transcription-polymerase chain reaction (RT-PCR), and the levels of B7-1 and B7-2 on the surface of PBMC were examined using flow cytometry. Results (1)The low expression of CD28 mRNA and rare expression of CTLA-4 mRNA were found in the normal rats, and both expressions increased markedly in EAMG rats (P＜0.001). Compared to those in EAMG group, the expression of CD28 mRNA decreased and CTLA-4 mRNA was upregulated after the treatment with pcDNA3-TGF-β1-DC (P＜0.05). There was no significant difference in the expressions of CD28 mRNA and CTLA-4 mRNA among the EAMG group, DC treatment group, pcDNA3-DC control group and normal saline group (P＞0.05). (2) The expressions of CD28, CTLA-4, B7-1 and B7-2 on the surface of PBMC were rare in normal rats, which increased significantly in EAMG rats (P＜0.001). The levels of CD28, B7-1 and B7-2 in pcDNA3-TGF-β1-DC group were lower than those in EAMG group (P＜0.01), but the level of CTLA-4 was higher than that in EAMG group (P＜0.05). They showed no statistically difference among the EAMG group, DC treatment group, pcDNA3-DC control group and normal saline group (P＞0.05). Conclusions The expressions of CD28/CTLA-4:B7 costimulatory molecules are abnormal in the rats with EAMG. The regulation of CD28/CTLA-4:B7 costimulatory pathways may play a critical role in the mechanism of the treatment with DC transfected with pcDNA3-TGF-β1 in the incipient EAMG rats. Key words: Myasthenia gravis; Dendritic cell; Transforming growth factor-β1; CD28/CTLA-4:B7