Identification and characterization of equine blood plasmacytoid dendritic cells.

This research focused on identifying and characterizing a certain type of cell called dendritic cells (DCs) in horse’s blood, particularly plasmacytoid DCs (pDC). These are known to behave differently in horses than in other species, and the research highlights these differences in an attempt to understand the role of these cells in the horse’s immune system.

Objective of the Study

• The main goal of this research was to determine and analyze specific cell groups in equine peripheral blood, specifically focusing on plasmacytoid dendritic cells (pDC).
• The motivation for this study comes from the fact that dendritic cells exist in three different subsets, but none of these had been identified in horses prior to this research.

Methods and Findings

• A technique called surface marker analysis was used to differentiate between the DC subsets, based on the way they express specific proteins, CADM-1 and MHC class II.
• The plasmacytoid DC in horses was found to express certain markers in a unique pattern: Flt3(+) CD4(low) CD13(-) CD14(-) CD172a(-) CADM-1(-) MHCII(low).
• This means that compared to other mammals, horses’ pDC have lower CD4 expression, indicated by CD4(low).

Further Confirmation of Findings

• In addition, when these pDC were sorted using fluorescence-activated cell sorting, they were found to be the only type of cell capable of producing a large amount of IFN-α (a type of protein) in response to TLR9-agonist stimulation. This is a unique characteristic of pDC.
• To confirm the identity of these pDC cells, their high level of expression of PLAC8, RUNX2, and TCF4 genes were demonstrated. These genes show pDC-restricted expression in other mammals, meaning that they are typically only expressed by pDCs.

Significance of the Study

• This marks the first step in understanding the role that these cells play in horses’ immune response, as well as potentially uncovering why they behave differently in these animals.
• This information could potentially benefit veterinary science and contribute to the development of more advanced treatments for diseases in horses that relate to their immune system.