Prostaglandin-related immune suppression in cattle

Prostaglandins (PGs) are lipid mediators derived from arachidonic acid by several enzymes including cyclooxygenase (COX)-1 and COX-2. We have previously shown that PGE₂ regulates immune responses, such as Th1 cytokine production and T-cell proliferation, in cattle. However, it is still unclear whether other PGs are involved in the regulation of immune responses in cattle. Here, immunosuppressive profiles of PGs (PGA₁, PGB₂, PGD₂, PGE₂, PGF_1α and PGF_2α) were firstly examined using bovine peripheral blood mononuclear cells (PBMCs). In addition to PGE₂, PGA₁ significantly inhibited Th1 cytokine production from PBMCs in cattle. Further analyses focusing on PGA₁ revealed that treatment with PGA₁ in the presence of concanavalin A (con A) downregulated CD69, an activation marker, and IFN-γ expression in both CD4⁺ and CD8⁺ T cells. Sorted CD3⁺ T cells stimulated with con A were cultivated with PGA₁, and IFN-γ and TNF-α concentrations decreased upon PGA₁ treatment. Taken together, these results suggest that the treatment with PGA₁in vitro inhibits T-cell activation, especially Th1 cytokine production, in cattle.