Figure 5.

Propionibacterium acnes-induced granulomatous pulmonary inflammation is reduced markedly in Toll-like receptor (TLR)-2^–/– mice compared to that observed in wild-type C57BL/6 animals. Both groups of animals received intraperitoneal (i.p.) sensitization followed by intratracheal (i.t.) challenge with P. acnes. The images show representative histology of two wild-type animals at low (a,b) and high magnification (c,d). As illustrated, wild-type animals displayed a marked influx of lymphocytes and macrophages that were primarily adjacent to bronchovascular-lymphatic bundles (PVL) and large veins (V). Varying degrees of intra-alveolar and interstitial (ALV) inflammation were also observed. Magnified views show loosely formed granulomas typical of those observed in mice (indicated by arrows). In contrast, P. acnes induced relatively little inflammation in TLR-2^–/– mice, as illustrated in (e) and (f) and the corresponding higher-power images (g) and (h). In these animals, peribronchovascular and lymphatic inflammation was minimal and intra-alveolar/interstitial regions were largely normal, as illustrated.