Figure 3. In vivo proinflammatory activity of health- and acne-associated P.

acnesstrains. Mice were injected with 1 × 10⁷ P. acnes, and sebum (20 μl) was applied topically daily. After 3 days the skin was excised and homogenized, and cytokines levels were determined by ELISA. Data are shown as mean ± SEM (n = 5 mice per group). Data analysis compared cytokines induced by P. acnes RT4/5 (all 5 strains) versus RT2/6 (all 4 strains) using nonparametric Mann-Whitney U test. P < 0.001, comparing red and green strains.