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[Study on the expression of TLR4 on splenocytes and its relation with CD4(+) CD25(+) regulatory T cells in peripheral blood in severely burnt rats].

AIM
To investigate the expression of Toll like receptor 4(TLR4) on splenocytes and TNF-alpha mRNA, the dynamic changes of CD4(+) CD25(+) regulatory T cell(Treg) and endotoxin(ET) in peripheral blood of burnt rats during the early phase, and to explore the mechanism against inflammatory reaction in intestine-derived infection after burn.


METHODS
64 SD male rats were randomly separated into control group and burn model groups. Rats of burn model group were burnt with vapor under 3 mPa pressure and 108 degrees Celsius temperature for 8 seconds to achieve deep partial-thickness burn, and a 30% total body surface area (TBSA) burn model was made. Rats were sacrificed before and 2, 5, 8, 12, 24, 48 and 72 h after burn, and the TLR4 and TNF-alpha mRNA expression in splenocytes were measured at various intervals by RT-PCR. The expression of TLR4 protein was measured by Western blot, and the percentage of Treg cells in CD4(+) T cells was detected by flow cytometry (FCM), and the LPS concentration of plasma was detected by limulus lysate test.


RESULTS
The expression of TLR4 mRNA, TNF-alpha mRNA, TLR4 protein and the levels of Treg, ET were significantly increased at some times points after burn. The expression of TLR4 mRNA and protein reached the peak at 8 h, whereas the TNF-alpha mRNA at 12 h, and Treg and ET at 8 h. The peak values of them were 3.66+/-0.51, 2.27+/-0.19, 1.65+/-0.23, 63.19+/-12.65% and 11.68+/-1.71 Eu/mL respectively, which were of significant difference when compared with the control group (P<0.01). The expression of TLR4 mRNA showed a positive correlation with that of Treg, ET and TNF-alpha mRNA (r=0.898, 0.811, 0.462, P<0.01).


CONCLUSION
Treg might play a major role in the process of immune regulation in rats after burn, the mechanism of which may be correlated with the increase of LPS-TLR4 signal transduced by intestine-derived infection.