College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.
J Dairy Sci. 2011 Dec;94(12):5903-12. doi: 10.3168/jds.2011-4167.
The objective of the current study was to investigate the toll-like receptors (TLR), including the soluble forms sTLR2 and sTLR4, involved in innate immune responses of dairy cows to experimentally induced Escherichia coli mastitis. Six clinically healthy Holstein dairy cows received an intramammary inoculation of E. coli O111:K58 between 63 and 83 d postpartum. Concentrations of sTLR2 and sTLR4, the proinflammatory cytokines IL-6 and tumor necrosis factor-α (TNF-α), and acute phase proteins serum amyloid A (SAA) and haptoglobin (Hp) in blood were measured by ELISA. Furthermore, 10mL of milk was collected from challenged quarters immediately before inoculation and at 6, 12, 24, 48, and 72 h after inoculation, and mRNA expression of selected genes, including TLR2, TLR4, IL-1β, IL-6, TNF-α, and IL-8, was quantified by real-time PCR. Escherichia coli intramammary infection elicited a decrease in the circulating levels of leukocytes. Rectal temperature was elevated at 6h postinoculation (PI). Similarly, the serum concentrations of TNF-α, IL-6, and SAA increased at 6h PI. However, serum concentrations of sTLR2, sTLR4, and Hp did not differ after challenge. The mRNA expression of TLR2, IL-1β, and IL-8 in milk somatic cells increased at 12h PI, whereas a decreased IL-6 mRNA expression was detected from 6 to 48 h PI. In conclusion, we found that TLR2 mRNA expression increased in milk somatic cells collected from infected quarters of cows challenged with E. coli, whereas the concentrations of sTLR2 and sTLR4 remained unchanged after challenge. Thus, sTLR2 and sTLR4 may protect the host by sequestrating pathogen-associated molecular patterns during E. coli mastitis.
本研究旨在探讨 Toll 样受体(TLR),包括可溶性形式的 sTLR2 和 sTLR4,在奶牛对大肠杆菌乳腺炎的固有免疫反应中的作用。6 头临床健康的荷斯坦奶牛在产后 63-83 天接受大肠杆菌 O111:K58 乳内接种。通过 ELISA 测定血液中 sTLR2 和 sTLR4、促炎细胞因子 IL-6 和肿瘤坏死因子-α(TNF-α)以及急性相蛋白血清淀粉样蛋白 A(SAA)和触珠蛋白(Hp)的浓度。此外,在接种前和接种后 6、12、24、48 和 72 小时,从受挑战的乳区采集 10mL 牛奶,并通过实时 PCR 定量测定选定基因(包括 TLR2、TLR4、IL-1β、IL-6、TNF-α和 IL-8)的 mRNA 表达。大肠杆菌乳内感染导致循环白细胞数量减少。接种后 6 小时直肠温度升高(PI)。同样,接种后 6 小时血清 TNF-α、IL-6 和 SAA 浓度升高。然而,挑战后 sTLR2、sTLR4 和 Hp 的血清浓度没有差异。接种后 12 小时,乳体细胞中 TLR2、IL-1β 和 IL-8 的 mRNA 表达增加,而 6 至 48 小时 PI 时检测到 IL-6 mRNA 表达降低。总之,我们发现,在受到大肠杆菌挑战的奶牛感染乳区的乳体细胞中,TLR2 mRNA 表达增加,而 sTLR2 和 sTLR4 浓度在挑战后保持不变。因此,sTLR2 和 sTLR4 可能通过在大肠杆菌乳腺炎期间隔离病原体相关分子模式来保护宿主。