[show abstract][hide abstract] ABSTRACT: Oligodeoxynucleotides (ODN) with unmethylated CpG dinucleotides mimic the immune stimulatory activity of bacterial DNA in vertebrates and are recognized by Toll-like receptor 9 (TLR9). It is also possible to detect immune activation with certain phosphorothioate sequences that lack CpG motifs. These ODN are less potent than CpG ODN and the mechanism by which they stimulate mammalian leucocytes is not understood. We here provide several lines of evidence demonstrating that the effects induced by non-CpG ODN are mediated by TLR9. First, non-CpG ODN could not stimulate cytokine secretion from the splenocytes of TLR9-deficient (TLR9(-/-)) mice. Second, immunization of TLR9(+/+) but not TLR9(-/-) mice with non-CpG ODN enhanced antigen-specific antibody responses, although these were T helper type 2 (Th2)-biased. Third, reactivity to non-CpG ODN could be reconstituted by transfection of human TLR9 into non-responsive cells. In addition, we define a new efficient immune stimulatory motif aside from the CpG dinucleotide that consists of a 5'-TC dinucleotide in a thymidine-rich background. Non-CpG ODN containing this motif induced activation of human B cells, but lacked stimulation of Th1-like cytokines and chemokines. Our study indicates that TLR9 can mediate either efficient Th1- or Th2-dominated effects depending on whether it is stimulated by CpG or certain non-CpG ODN.
[show abstract][hide abstract] ABSTRACT: Oligodeoxynucleotides (ODN) with unmethylated deoxycytidyl-deoxyguanosine (CpG) dinucleotides (CpG ODN) mimic the immunostimulatory activity of bacterial DNA and are recognized by the Toll-like receptor 9 (TLR9). CpG ODN of the B-Class stimulate strong B cell and NK cell activation and cytokine production. The highest degrees of NK stimulation as well as IFN-alpha secretion by plasmacytoid DC were found to occur only with A-Class ODN. A third class of CpG ODN combines the immune effects of A- and B-Class CpG ODN. C-Class ODN strongly stimulate B cell or NK cell activation and IFN-alpha production. In contrast to the A-Class, the C-Class is wholly phosphorothioate, has no poly-G stretches, but has palindromic sequences combined with stimulatory CpG motifs. All classes stimulate TLR9-dependent signaling, but with strikingly different dose-response relationships that are quite in contrast to those observed for IFN-alpha. Effects similar to those on human cells were observed on mouse splenocytes. In contrast, splenocytes from TLR9-deficient mice did not show any response to the three CpG ODN classes. In vivo studies demonstrate that C-Class ODN are very potent Th1 adjuvants. C-Class ODN may represent new therapeutic drugs that combine the effects of A- and B-Class ODN for broad applications in infectious disease or cancer therapy.
European Journal of Immunology 02/2004; 34(1):251-62. · 4.97 Impact Factor