1. Pattern Recognition Receptors
Siamon Gordon 
Cell 
Volume 111, Issue 7, Pages (December 2002)
DOI: /S (02)

2. Figure 1 Antigen Presenting Cells in the Immune Response
Antigen presenting cells (APC) integrate signals from endogenous and exogenous ligands with cellular interactions to generate diverse responses. The thesis of this review is that many pattern recognition receptors are able to interact with both endogenous (host derived) and exogenous ligands.
Cell  , DOI: ( /S (02) )