Purpose: Cell surface proteins known as Siglecs exhibit a specific affinity for sialic acid. Primarily located on the surface of immune cells, Siglecs belong to the subset of lectins called I-type lectins. Siglecs have important roles in maternal-fetal immune tolerance. We aimed to analyze the expression of Siglecs on Human Villous Trophoblasts (HVT) cells.
 Materials and methods: Total RNA was extracted from the HVT cell line, cDNA was synthesized, and real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) was performed the determine the changes in Siglec -3, -5, -6, -7, -8, -9, -10, -11, and -16 mRNA levels. In addition, Siglec levels were assessed by using immunohistochemical staining. Immunoreactivity against Siglec-6 and Siglec-9 was evaluated separately according to the intensity of brown color. 
 Results: Expression levels of Siglec genes by qRT-PCR and melting curve analyses were performed using RNA extracted from the HVT cell line. Siglec -3, -5, -6, -7, -9, -10, -11, and -16 genes were found to be expressed in the HVT cell line. Differently, Siglec-8 results were undetected after cycle 40, which was considered a negative result. The immunocytochemical examination of the HVT cell line revealed that Siglec-6 expression was moderate in the cytoplasm (Score:2). Siglec-9 expression was prominent in the cytoplasm (Score:3). 
 Conclusion: The results showed that Siglec-6 and Siglec-9 were expressed more than other Siglec proteins in the human trophoblast cells. Immunocytochemistry results also support these findings. Our study is the first to show Siglec-9 expression in human trophoblast cells.
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