Figure 1.

Experimental design. Hsd:ICR (CD1) 8-week-old female outbred mice were mated with 10-week-old male mice. The female mice were isolated for 1 week to give birth to their offspring. To ease the intraductal accessibility of the lactating mothers, the 10-day-old pups were weaned 2 h before the first inoculation. Depending on the preconditioning experiment: lipopolysaccharide (LPS)/lipoteichoic acid (LTA)/PBS or ex vivo LPS-/LTA-/PBS-treated macrophages were injected 24 h prior to the induction of Staphylococcus aureus mastitis in mice. To deplete local alveolar macrophages, preconditioning experiments could be preceded by clodronate liposome treatment. All intraductal injections (100 µl) were performed in the fourth gland pair of each of the mice. At relevant time points, post-inoculation mice were sedated and subsequently euthanized through cervical dislocation. Mammary glands were harvested to determine local bacterial loads, cytokine levels, or histopathology.