On Day 4 of the bacterial challenge, mastitis animals in the positive control group exhibited significantly elevated levels of interleukin (IL)‐4, IL‐1β, and IL‐6 (p < 0.05 in all cases; Figure 1C) and significantly decreased levels of interferon (IFN)‐γ, IL‐2, and IL‐10 (p < 0.05) compared to the blank control group. Here, IL2 is linked to mastitis.