Abstract：
This study aims to evaluate the responses of peripheral blood monocyte-derived macrophages (PBMDMs) from Theileria orientalis carrier cattle following exposure to Pasteruella multocida B:2 (PM B:2) and latex beads. Twenty-six male crossbred Kedah-Kelantan (KK) cattle were sampled for this study and quantitative PCR (qPCR) was employed in the detection of T. orientalis MPSP gene. Bactericidal assay using a 10:1 multiplicity of infection was performed to measure the phagocytosis and intracellular killing of PM B:2 by PBMDMs. The cell cultures were inoculated with 107 cfu/mL of PM B:2 and incubated in a humidified incubator. The absence of clinical signs, previous history of T. orientalis infection and an MPSP gene copy number below 15,000 GC/μL suggest that the cattle were asymptomatic chronic carriers. A non-significant phagocytic and mean cell death rates were observed in the PBMDMs of T. orientalis positive cattle relative to clinically healthy cattle (CHC) (p > 0.05). The PBMDMs of T. orientalis positive cattle had the lowest mean rate of intracellular killing relative to the CHC at the 30th minute post-infection only (p < 0.05). Exposure to latex beads caused an increase in the appearance of multinucleated macrophages following incubation of PBMDMs from T. orientalis positive cattle. Furthermore, the phagocytic index of PBMDMs of T. orientalis positive cattle were low or poor compared to that of CHC (p = 0.000). Therefore, our findings suggest that PBMDMs from cattle with chronic T. orientalis infection can efficiently phagocytise and kill PM: B2 but exhibited poor phagocytosis ability for foreign bodies despite appearance of multinucleated macrophages.
摘要：
这项研究旨在评估暴露于多杀性菌属B：2（PMB：2）和乳胶珠后，来自东方Theileria携带者牛的外周血单核细胞衍生巨噬细胞（PBMDM）的反应。本研究对26只雄性杂交吉打吉兰丹（KK）牛进行了采样，并采用定量PCR（qPCR）检测了东方毛虫MPSP基因。使用10：1感染复数进行杀菌试验，以测量PBMDM对PMB：2的吞噬作用和细胞内杀伤作用。细胞培养物用107cfu/mLPMB：2接种，并在加湿培养箱中孵育。没有临床症状，先前的东方毛虫感染史和MPSP基因拷贝数低于15,000GC/μL表明牛是无症状的慢性携带者。相对于临床健康牛(CHC),在东方毛虫阳性牛的PBMDM中观察到不显著的吞噬率和平均细胞死亡率(p>0.05)。仅在感染后第30分钟,相对于CHC,东方毛虫阳性牛的PBMDM具有最低的平均细胞内杀伤率(p<0.05)。暴露于乳胶珠导致多核巨噬细胞的外观增加。此外，与CHC相比，东方毛虫阳性牛的PBMDM的吞噬指数较低或较差（p=0.000）。因此,我们的发现表明，来自慢性T.Orientalis感染的牛的PBMDM可以有效地吞噬和杀死PM：B2，但尽管出现了多核巨噬细胞，但对异物的吞噬能力却很差。
