LSC Abstract – Monocyte-derived macrophages upregulate surface MR1 in response to NTHi

Non-typeable Haemophilus influenzae (NTHi) is frequently found in the COPD airway and is strongly associated with recurrent exacerbations. Although increased numbers of CD8 + T cells are present in the COPD airway, the response of NTHi-specific CD8 + populations is not well understood. In particular, recently identified CD8 + mucosal-associated invariant T (MAIT) cells may respond to NTHi, but the mechanism of MAIT activation in the airway is unclear. It is known that MAIT activation is dependent on expression of the antigen presenting molecule, MR1. The aim of this study was to determine whether macrophages, which are a key line of defence in the airway, express MR1 in response to NTHi and can activate MAIT cells. Human monocyte-derived macrophages (MDM) were infected with NTHi for 2 h and cell surface expression of markers was analysed using flow cytometry after a further 22 h. NTHi infection lead to a 2-fold increase of surface MR1 indicating that MDM may present antigens to MAIT cells. This response appeared specific to NTHi as stimulation of MDM with TNFα and IL-6 did not significantly affect surface MR1 expression. NTHi-infected MDM also caused significant (P Investigating the role macrophages play in MAIT activation will ultimately lead to greater understanding of bacterial exacerbations of COPD.