Taurine attenuates Streptococcus uberis-induced mastitis in rats by increasing T regulatory cells.

Taurine (Tau) is reported to have a key role in the regulation of the innate immune response and thus reduce tissue damage induced by bacterial infection. In this study, the effects of Tau on a rat model of mastitis induced by Streptococcus uberis (S. uberis) and the changes of T regulatory cells (Tregs) were assessed. Starting on gestation day 14 and continuing until parturition, 100 mg/kg of taurine (group TS) or an equal volume of physiological saline (group CS) was administered daily, per os. Seventy-two hours after parturition, rats were infused with approximately 100 cfu of S. uberis into each of two mammary glands. The results showed that the resultant inflammation, evidenced by swelling, secretory epithelial cell degeneration, increased adipose tissue and neutrophil (PMN) infiltration were evident in mammary tissue following injection with S. uberis. Pre-treatment with Tau attenuated these morphologic changes, the expression of interleukin (IL)-2, interferon (INF)-γ mRNA, myeloperoxidase (MPO) activity and N-acetyl-β-D-glucosaminidase (NAGase) in mammary tissue. The percentages of Foxp3+CD25+CD4+/lymphocytes (Tregs) were dramatically increased after the S. uberis challenge. Significant differences (P<0.05) were observed at 24, and 72 h post S. uberis-injection (PI) in CS. Pre-treatment further increased the percentage of Tregs and a significant difference between CS and TS (P<0.05) was apparent at 24 h PI. Our data indicate that in rats, Tau can be used to regulate the immune response following infection by S. uberis and consequently prevent mammary tissue damage by increasing Tregs.