Mean immune cell infiltration scores for lumen and intralobular stroma areas. Mammary tissues were collected from 18 saline and 18 Staph. aureus infused quarters and 8 representative lobules were scored for each experimental quarter. Error bars represent the standard error of the respective mean immune cell infiltration scores. Asterisks denote differences between saline and Staph. aureus quarter treatments within intralobular stoma and luminal areas. **P ≤ 0.01, ***P ≤ 0.001.