CD86 and infection: To investigate whether HP and LP strains differed in inducing M1-type macrophages (M1-MØ), we performed immunofluorescence labelling of M1-MØ in lung sections of mice towards CD86, a specific surface marker of M1-MØ[28], at the early stage (14 dpi) and late stage (death or up to 90 dpi) of infection and conducted a semiquantitative analysis.