This chapter summarizes the results of investigations on the reactivity of CD 14 with structures other than lipopolysacharide (LPS). Nonclonal, poly specific receptors with multiple distinct ligand-binding sites or sites binding a range of distinct ligands have been defined as “pattern recognition receptors”. The latter group of toxins constitute cell wall components of bacteria. LPS, also termed endotoxin, of the outer leaflet of gram-negative bacteria and peptidoglycan (PG) represent such cell wall-associated compounds, which are of great biomedical importance in the mediation of pathophysiological reactions of an infected host. LPS and PG are the only bacterial cell wall compounds that express inflammatory properties. Lipoarabinomannan, lipoteichoic acid, lipopeptides, sphingolipids, and various bacterial cell wall preparations also induce the production of cytokines in monocytes/macrophages and, therefore, may contribute to an inflammatory reaction in an infected host. Lipoarabinomannan is a major antigen of the mycobacterial cell wall.