Evidence of a functional CD1d lipid antigen presentation pathway in murine alveolar epithelial cells (APP3P.108)

Abstract

Abstract Lipid antigen presentation by CD1 molecule is an evolutionary conserved pathway that elicits rapid yet efficient cytotoxic response against fast mutating pathogens. CD1d molecule, the only isoform of CD1 family in mouse, has been shown to recognise important component of the Mycobacterium tuberculosis (Mtb) cell wall like phosphatidylinositol mannosides. We have recently shown that alveolar epithelial cells (AECs) present Mycobacterium bovis - BCG (an avirulent model for Mtb infection) antigens to sensitized Th cells in vitro, however, it remains unexplored whether AECs can also participate in the presentation of lipid antigens through CD1d pathway; that is, so far, know to operate only in professional antigen presenting cells like dendritic cells (DCs) and B cells. We started by establishing the expression of CD1d on LA4 (mouse airway epithelial) cell line and murine AECs by flow cytometry and immuno-histochemistry. qPCR showed significant up-regulation of mRNA expression of some of the crucial molecules involved in CD1d pathway in AECs upon BCG infection. The protein CD1d expression was also found to be boosted upon BCG infection. Finally, a functional CD1d antigen presentation by AECs (in vitro) was shown by using α-GalactosylCeramide (α-GalCer) antigen as model. Our findings suggest that AECs are capable of lipid antigen presentation through the CD1d pathway and this ability of AECs may contribute to the immune defences against pathogens like Mtb.