Before surgery, bitches with pyometra had higher serum concentrations of IL-6 and IL-10 (149.4 (120.2–179.5) pg/ml and 53.9 (34.1–73.3) pg/ml, respectively) than the controls [1.8 (1.8–2.0) pg/ml and 21.2 (19.5–28.2) pg/ml] (P < 0.001 for both IL-6 and IL10) (Fig. 1). Here, IL6 is linked to pyometritis.