Carcinoembryonic antigen (CEA)-related cell adhesion molecules are co-expressed in the human lung and their expression can be modulated in bronchial epithelial cells by non-typable Haemophilus influenzae, Moraxella catarrhalis, TLR3, and type I and II interferons

Klaile, Esther; Klassert, Tilman E; Scheffrahn, Inka; Müller, Mario M; Heinrich, Annina; Heyl, Kerstin A; Dienemann, Hendrik; Grünewald, Christiane; Bals, Robert; Singer, Bernhard B; Slevogt, Hortense

Importantly, the present study shows that in addition to the primarily viral induced type I interferons, TLR3 agonist poly I:C also increased CEACAM1 expression ( Figure 3B ). TLR3 plays a key role in anti-viral immune responses and recognizes synthetic dsRNA like poly I:C and virus derived dsRNA contained in cells infected by positive-stranded RNA viruses and DNA viruses [74, 75] . It was shown recently that poly I:C enhances the susceptibility to secondary pulmonary infections by gram-positive bacteria in a mouse model [76] . The positive-stranded RNA virus rhinovirus enhances CEACAM5 expression in human nasal epithelial cells and two negative-stranded RNA viruses, respiratory syncytial virus (RSV) and human parainfluenza virus 3 (HPIV-3), enhance CEACAM1 expression in A549 and NHBE cells [67, 77] . Since the latter viruses have to be recognized via TLR7 or TLR8, this is the first indication that the pathogen receptor CEACAM1 might also be up-regulated by positive-stranded RNA viruses via TLR3.