Innate Immune System:Toll-like receptor activation of APC CD28 B7 LPS Signal 2 IL-1,6,12 Toll Like Receptor “Signal3” (pattern Recognition R) Signal 1 TCR-MHC T Cell Anitgen Presenting Cell (APC) BDCInnate Immune System: Toll-like receptor activation of APC T Cell CD28 B7 TCR-MHC LPS Toll Like Receptor (pattern Recognition R) IL-1,6,12 “Signal 3” Signal 2 Signal 1 Anitgen Presenting Cell (APC) BDC