Abstract:
Legionella pneumophila, the causative agent of Legionnaires’ disease, is an intracellular pathogen that presents with a reduced MHC class I expression on infected host cells. This study shows, that despite the down regulation of MHC class I molecules, the cytotoxicity of autologous natural killer cells against Legionella-infected monocytes was not enhanced.
Monocytes from healthy individuals were infected with L. pneumophila and the toxicity of autologous natural killer cells (NK) was determined by performing a 51chromium release essay. K-562 cells, a NK-sensitive erythroblastoid leukemia cell line, served as positive control, uninfected autologous monocytes served as negative control.
Autologous monocytic cells infected with L. pneumophila using an MOI (multiplicity of infection) of 1:1 or 10:1 either showed only marginal or no lysis at all, whereas incubation of NK cells with K-562 cells resulted in a specific lysis between 40 and nearly 80% depending on the effector-to-target-ratio.