Target T Cells and Could Be an Efficient Vaccine +Internalizes Antigen for Presentation to CD4 Adaptive Immunity: Toll-Like Receptor 2 Cutting Edge: Link Between Innate and

An ideal vaccine for induction of CD4 (cid:1) T cell responses should induce local inflammation, maturation of APC, and peptide loading of MHC class II molecules. Ligation of Toll-like receptor (TLR) 2 provides the first two of these three criteria. We have studied whether targeting of TLR2 results in loading of MHC class II molecules and enhance-ment of CD4 (cid:1) T cell responses. To dissociate MHC class II presentation from APC maturation, we have used an antagonistic, mouse anti-human TLR2 mAb (TL2.1) as ligand and measured proliferation of a mouse C (cid:2) -specific human CD4 (cid:1) T cell clone. TL2.1 mAb was 100-1000 times more efficiently presented by APC compared with isotype-matched control mAb. Moreover, TL2.1 mAb was internalized into endosomes and processed by the conventional MHC class II pathway. This novel function of TLR2 represents a link between innate and adaptive immunity and indicates that TLR2 could be a promising target for vaccines. The Journal of Immunology, 2003, 171: 32–36.