Why can glucocorticoids suppress immune system activity?

Glucocorticoids, which are steroid hormones produced by the adrenal gland, suppress immune system activity through several complex mechanisms.12

At the cellular level, these compounds inhibit the production and action of inflammatory cytokines. They also indirectly inhibit phospholipase A2, an enzyme essential for synthesizing prostaglandins and leukotrienes, which are key mediators of inflammation. Furthermore, glucocorticoids reduce the synthesis of specific proteins that drive the inflammatory response.21

When administered in high doses, these agents can impair immune function by reducing cell-mediated immune reactions and decreasing the production and effectiveness of antibodies. While these immunosuppressive properties are clinically valuable for treating autoimmune diseases and preventing transplant rejection, they also increase susceptibility to infections, as the body’s ability to mount a defense is significantly diminished.2