How do corticosteroids affect the immune system?

Corticosteroids are known for their ability to suppress the immune system, which is why the correct answer highlights this key effect. These steroid hormones, which are produced by the adrenal cortex or synthetically manufactured, play a significant role in modulating various immune responses within the body. When corticosteroids are administered, they inhibit the function of white blood cells, including lymphocytes and macrophages, which are critical components of the immune response.

The suppression occurs through several mechanisms: corticosteroids reduce the proliferation of lymphocytes, limit the production of cytokines and other inflammatory mediators, and decrease the activity of inflammatory cells. This can be particularly beneficial in situations where the immune system is overactive, such as in autoimmune diseases or in conditions leading to excessive inflammation. However, this immunosuppressive effect also makes patients more susceptible to infections, as their immune system is less capable of responding to pathogens.

While other choices imply possible effects of corticosteroids, they do not accurately reflect their primary action on the immune system's functionality.