Single colour flow cytometry analysis of changes in several immunologically relevant cell surface molecules of bone marrow-derived dendritic cells after 48 h of incubation with different PRRSV strains at a multiplicity of infection of 0.01 (as determined by titration in porcine alveolar macrophages). Grey histograms show cells stained with an irrelevant isotype-matched antibody and a secondary FITC or phycoerithrin conjugated antibody. Blue histograms show uninfected cells and red line histograms correspond to PRRSV-infected cells. Averages and variation coefficients are included. Grey values show the uninfected cell parameters and black values correspond to PRRSV-infected cells. A) SLA-I, SLA-II, CD80/86, CD14; B) SwC3, SwC9, CD163, CD16.