The potential role of Toll-like receptor-4 in high mobility group box-1 protein-mediated immune function of regulatory T cells in mice

Abstract

Objective To investigate the effect of high mobility group box-1 protein(HMGB1) on immune function of regulatory T cells(Tregs) in two gene-type mice and its potential receptor mechanism in vivo.Methods 10 μg or 20 μg HMGB1 was administered i.P.in C3H/HeN(TLR4 wild type,TLR4~(+/+))and C3H/HeJ (TLR4 mutant type,TLR4~(-/-))mice.Mice were sacrificed at the 48th h after HMGB1 challenge,and splenic CD4~+CD25~+ Tregs were harvested by magnetic beads aseptically following another 12 h culture.Cytotoxic T lymphocyte-associated antigen 4(CTLA-4)expressed on CD4~+ CD25~+ Tregs was detected by means of flow cytometry,and the production of interleukin(IL)-10 in supematants was examined by ELISA.Results The expression levels of CTLA-4 in two gene-type mice were similar (P>0.05).Compared to the controls,the expression of CTLA-4 on CD4~+ CD25~+ Tregs was markedly down-regulated in C3H/HeN mice with a maximal response at a dose of 20μg HMGB1(78.70±1 1.42 vs 60.76±7.64,P<0.01),and IL-10 release was also significantly decreased[(96.89±6.25)vs(47.11±4.25)ng/L,P<0.01].However,after treatment with various doses of HMGB1 in C3H/HeJ mice.the expression of CTLA-4 on CD4~+ CD25~+ Tregs and IL-10 release were markedly enhanced compared to the controls(P<0.01).Conclusion HMGB1 challenge can markedly influence the inununological activity of CD4~+ CD25~+ Tregs in mice,and TLR4 appears to be critically involved in down-regulation of HMGB1-mediated CTLA-4 expression and IL-10 production of CD4~+ CD25~+ Tregs in vivo. Key words: Regulatory T cells; High mobility group box-1 protein; Toll-like receptor; Interleukin-10