Cytokine RNA expression in an equine CD4+ subset differentiated by expression of a novel 46-kDa surface protein.

This study uncovered a unique cell surface molecule, identified as EqWC4, present on a subpopulation of equine T-lymphocytes. The research suggests that this molecule may play a role in the immunological response in horses, given its presence on lymphocytes and its capacity to modify the expression of cytokines like IL-2 and IFN-gamma.

Study Objective and Methodology

• The goal of the study was to investigate the role and expression of a unique cell surface molecule, designated as EqWC4, on certain subsets of equine lymphocytes. This molecule was found using two monoclonal antibodies (MAb), namely HB65A (IgG2a) and HB86A (IgGI).
• The expression of EqWC4 was evaluated across different breeds of horses, such as Arabian, Pony, and Thoroughbred, by focusing on the distribution of EqWC4 among leukocytes.
• The research used a technique called reverse transcriptase-polymerase chain reaction (RT-PCR) to examine the cytokine RNA profiles of the EqWC4+ lymphocytes. The researchers studied the expression of specific cytokines, such as interleukin-2 (IL-2) and interferon-gamma (IFN-gamma), under both stimulated and unstimulated conditions, to understand the immune-regulatory role of EqWC4.

Study Findings

• The study found that EqWC4 is present on a subset of CD4+ equine lymphocytes (6.3-10.2% of Arabian lymphocytes CD4+ WC4+) and a smaller population of CD8+ lymphocytes (0.5% to 1.2% of Arabian lymphocytes CD8+ WC4+).
• The molecule was proven to be absent from B-lymphocytes, granulocytes, and macrophages. Therefore, its presence seems to be exclusive to T-lymphocytes.
• The research also found that the activation by a specific substance called a mitogen does not increase the expression of EqWC4 on the equine lymphocytes, indicating that its expression and role may not be impacted by general immune system activation.
• There were significant differences observed in the expression of EqWC4 across various horse breeds. Specifically, fewer Pony lymphocytes bound to HB65A and HB86A when compared to Arabian and Thoroughbred breeds.
• The cytokine RNA profile of EqWC4+ lymphocytes appeared to be dominated by IL-2 and IFN-gamma for unstimulated cells. Following stimulation, IL-4 was also expressed at low levels, while the IL-2 levels decreased and the IFN-gamma levels increased. These variations suggest that EqWC4 has a significant role in the modulation of immune responses in horses.
• Lastly, due to similarities in molecular weight and formation of dimers, EqWC4 could be an equine orthologue of CD28, a costimulatory molecule required for T cell activation in humans. However, due to expression differences with CD28, EqWC4 likely represents a previously uncharacterized equine lymphocyte marker.

Conclusion

• This research sheds light on a new, previously uncharacterized lymphocyte marker in horses, EqWC4, and provides a deeper understanding of its role in the equine immune system. The findings could set the stage for further studies on enhancing horse health and treatment protocols for immune system-related disorders.