Figure 6

PB1-F2 may influence apoptosis induction in immune organs but has no impact on the development of necrotizing inflammation in other tissues. Scoring of tissue lesions after HE staining yielded comparable results after ΔF2 and wt infection in most tissues including the brain, skin, nasal conchae, and lungs. Particularly high lesion scores were found in immune organs after ΔF2 infection (A). Detailed scoring of immune organs after HE staining showing particular high lesion scores in the thymus after ΔF2 infection (B). Scores for necrotizing inflammation given as 0 = no lesion, 1 = rare, affected cells/tissue < 5% or up to 3 foci per tissue; 2 = multifocal, 6–40% affected; 3 = coalescing, 41%–80% affected; 4 = diffuse, > 80% affected. Decreased lymphocyte cellularity, increased tingible body macrophages (TBM) numbers was scored 0 = not present, 1 = minimal, 2 = mild, 3 = moderate, 4 = severe. Asterisks indicate cumulative scores for the immune organs (thymus, spleen, bursa) and brain (necrotizing inflammation, glial nodules, perivascular infiltrates). Representative images for HE-based lesion scores after ΔF2 or wt infection in the thymus, spleen and bursa (C–K). Green bar = cortex of the thymus with inlay in (F) showing TBM; green arrow = periarteriolar lymphoid sheaths in the spleen; green asterisk = cortex of the bursa, yellow asterisk = medulla of the bursa. Hematoxylin and eosin staining, bar 100 µm.