| Bovine mastitis not only caused severe economic loss in dairy herds, but also brought serious and potential damage for humans healthy because antibiotics was widely used during therapy. In order to further know immunopathology and look for more ideal method to provide basic data.This study investigated the pathogens from five clinical mastitis farms in Baoding area;the mice experimental mastitis model induced by Staphylococcus aureus was established, local and body symptoms,immunopathology were observed;the effect of GL on the pathological mechanism and immune function was discussed when mice experimental mastitis.The pathogens of forty three milk samples from clinical dairy mastitis were isolated and indentified by biochemical method. It showed that there were ninety-one strains,ten species,most of them were Staphylococcus aureus (21.98%),Streptococcus (19.78%)and Escherichia coli (19.78%) .The pregnant BALB/C female mice were randomly divided into nomal control group,sterile physiological saline solution (PSS) group and 1.0×10~2CFU/50μL,4.0×10~2CFU/50μL,7.0×10~2CFU/50μL, 1.0×10~3CFU/ 50μL,1.0×10~4CFU/50μL of Staphylococcus aureus groups.Either PSS or Staphylococcus aureus 50μL was inoculated into the fourth abdominal mammary gland via the teatduct 8～10d after parturition, inflammation reaction was observed on 24 hours later. Histopathologic examination of mammary gland revealed that polymorphonuclear neutrophils(PMN) and exfoliated epithelial cells in 7.0×10~2CFU/50μL Staphylococcus aureus group were found in alveoli Cases , vacuole and secretion of alveoli Cases were decreased, the interval width increased, inflammation of the mammary gland was significant. The interstitial width, the concentrations of TNF-α,IFN-γin mammary gland increased significantly (P＜0.01) compared with those of nomal control group, Staphylococcus aureus was reproduced in mammary gland and CFU was rapidly increased.The spontaneous diseased process of acute mastitis was factually reflected by body symptoms and pathological changes. Based on above results, the experimental mastitis model by 7.0×10~2CFU/50μL Staphylococcus aureus via teat duct in mice were established successfully. The pregnant BALB/C female mice were randomly divided into nomal control group,positive control group and experimental groups, and inoculated into the fourth abdominal mammary gland via the teatduct with 50μL 7.0×10~2CFU Staphylococcus aureus 8～10d after parturition. Then the mice administrated orally on-12,0,12,36 hours after intraperitoneal injection with different dosage of Glycyrrhizin (2.2mg/mL,4.4 mg/mL,8.8 mg/mL)or sterile physiological saline solution 0.2mL.The mice were sacrificed by cervical dislocation 6,18,42,66 hours later.The mammary lysate was collected. The contents of TNF-αand IFN-γwere assayed through ELISA. The mammary glands were fixed for histopathologic evaluations, the interval width. The number and distribution change of Mast Cell in mammary gland were observed by improved toluidine dye method.Good psychosis, balanced temperature and CFU of Glycyrrhizin groups decreased remarkably compared with those of positive control group (P＜0.01) .Histopathological findings showed that tissue scathe,pathological changes,interstitial width were mitigated. In comparison with those of PSS and PC groups, there were no significant difference among different dosages of GL groups (P＞0.05 ). The data indicated that GL could inhibit degranulating. ELISA results showed that TNF-αand IFN-γconcentration were significantly reduced by GL and depended on dosages, but were higher than that of normal control group.GL modulated the range of TNF-αand IFN-γin a normal level, not only concerned with immunoreaction but also controled severe inflammation. Conclusion: The incidence of Staphylococcus aureus, Streptococcus uberis and Escherichia coli isolated from five clinical mastitis farms in Baoding area were high. The body symptoms and pathological mechanism of the mice experimental mastitis induced by Staphylococcus aureus were same as pathology in normal bovine mastitis, the model could be used for immunopathologic and drug selection. The GL had protective and immunoregulatable effect on the mice experimental mastitis.
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