[Effects of different Toll-like receptor agonists on the function of T helper cells in mice]

To investigate the secretion of IL-12p40 and IL-6 by splenocytes, dendritic cells stimulated by different Toll-like receptor (TLR) agonists or in the sera of mice immunized with different TLR agonists, and evaluate the effects of different TLR agonists on the function of T helper (Th) cells, especially the differentiation of Th1 cells.

Supernatants of splenocytes and dendritic cells stimulated with different TLR agonists for 24 hours or sera of mice immunized with different TLR agonists at different time points were used to determine the levels of IL-12p40 and IL-6 by ELISA. CD4⁺ T cells isolated from the spleens of ovalbumin-T cell receptor (OVA-TCR) transgenic BALB/c (DO11.10) mice were co-cultured with antigen presenting cells (APCs) from congenic BALB/c mice at 1:3 ratio of T:APCs. Cultures were stimulated with OVA peptide or OVA peptide plus different doses of TLR agonists and the supernatants collected at different time points were assayed by ELISA for detecting IFN-γ.

Pam3CSK4, R848 and CpG oligodeoxynucleotide (ODN) promoted the production of IL-12p40 and IL-6 by splenocytes and dendritic cells obviously, and induced the expression of IFN-γ in antigen specific CD4⁺ T cells in a time- and dose-dependent manner. Monophosphoryl lipid A from Salmonella minnesota R595 lipopolysaccharide (MPLA-SM) induced low levels of cytokines by splenocytes and couldn't promote the production of IFN-γ by antigen specific CD4⁺ T cells, but increased the expressions of IL-12p40 and IL-6 by DCs. All the sera of mice immunized with the four TLR agonists expressed high levels of IL-12p40 and IL-6.

Splenocytes, DCs stimulated or sera of mice immunized with different TLR agonists produced different levels of cytokines, which could further affect the differentiation of Th1 cells.