CD40 MFI on the different monocyte subsets.

Visceral leishmaniasis (VL) is a neglected tropical disease caused by parasites from the Leishmania (L.) donovani complex. VL is characterised by uncontrolled parasite replication in spleen, liver and bone marrow, and by an impaired immune response and high systemic levels of inflammation. Monocytes have been poorly characterised in VL patients. The aim of this study was to evaluate the expression levels of markers involved in the regulation of T cell responses on different subsets of monocytes from the blood of VL patients and healthy non-endemic controls (HNEC). Monocytes can broadly be divided into three subsets: classical, intermediate and non-classical monocytes. Our results show that the percentages of all three subsets stayed similar at the time of VL diagnosis (ToD) and at the end of anti-leishmanial treatment (EoT). We first looked at co-stimulatory receptors: the expression levels of CD40 were significantly increased on classical and intermediate, but not non-classical monocytes, at ToD as compared to EoT and HNEC. CD80 expression levels were also increased on intermediate monocytes at ToD as compared to EoT and HNEC, and on classical monocytes only as compared to HNEC. The levels of CD86 were similar at EoT and ToD and in HNEC on classical and intermediate monocytes, but significantly higher at EoT on non-classical monocytes. We also looked at an inhibitory molecule, PD-L1. Our results show that the expression levels of PD-L1 were significantly higher on all three monocyte subsets at ToD as compared to HNEC, and to EoT on classical and intermediate monocytes. These results show that monocytes from the blood of VL patients upregulate both co-stimulatory and inhibitory receptors and that their expression levels are restored at EoT.

内脏利什曼病（Visceral leishmaniasis, VL）是一种由杜氏利什曼原虫复合体（Leishmania (L.) donovani complex）寄生虫引发的被忽视热带病。VL的病理特征为寄生虫在脾脏、肝脏与骨髓内发生不受控增殖，同时伴随免疫应答受损与全身炎症水平升高。目前针对VL患者体内单核细胞（monocytes）的特征解析仍较为匮乏。本研究旨在评估VL患者血液与健康非流行区对照（healthy non-endemic controls, HNEC）的不同单核细胞亚群上，参与T细胞应答调控的标志物表达水平。

单核细胞大致可分为三类：经典型、中间型与非经典型单核细胞。本研究结果显示，在VL确诊时（Time of Diagnosis, ToD）与抗利什曼原虫治疗结束时（End of Treatment, EoT），三类单核细胞的占比均无显著差异。

本研究首先分析了共刺激受体（co-stimulatory receptors）：相较于EoT组与HNEC组，VL确诊时经典型与中间型单核细胞上CD40的表达水平显著升高，而非经典型单核细胞则未出现该变化。相较于EoT组与HNEC组，VL确诊时中间型单核细胞上CD80的表达水平同样升高；仅相较于HNEC组时，经典型单核细胞上的CD80表达水平才显著升高。经典型与中间型单核细胞上CD86的表达水平在EoT、VL确诊时与HNEC组间均无显著差异，但非经典型单核细胞上CD86的表达水平在EoT时显著更高。

本研究同时分析了抑制性分子程序性死亡受体配体1（PD-L1）。结果显示，相较于HNEC组，VL确诊时三类单核细胞上PD-L1的表达水平均显著升高；相较于EoT组，经典型与中间型单核细胞上PD-L1的表达水平在VL确诊时同样显著更高。

综上，VL患者血液中的单核细胞会上调共刺激受体与抑制性受体的表达，且上述受体的表达水平可在抗利什曼原虫治疗结束后恢复至正常水平。