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

The up-regulation of membrane-bound CEACAM receptors might be necessary to counteract the presence of soluble receptor forms that might act as decoys to prevent bacterial/viral infections or immune evasion. Even though bacteria possess redundant targeting mechanisms, and bacterial adhesins often work in a sequential manner, Hill et al. showed that perturbing CEACAM1-, CEACAM5-and CEACAM6-based adhesion by using a CEACAM-binding peptide prevents host cell binding by M. catarrhalis, H. influenzae, N. meningitidis and N. gonorrhoeae in a cell culture model [7] . The amounts of soluble CEACAMs, with high concentrations of soluble CEACAM6 in all and lower concentrations of soluble CEACAM5 in 78.5% of the bronchoalveolar lavage fluid samples is mirrored in the expression levels of their membrane-bound counterparts in lung tissues (Figures 1, 2, 3, 4 and [58] [59] [60] ). The fact that soluble CEACAM1 is all but absent in BALF (98% negative BALF samples) increases the importance of this receptor for colonization by pathogens despite its comparatively low expression levels in human lung.