Q. We heard in class today that steroids are used for autoimmune diseases, and I’ve heard this before but never understood why. What is it about steroids that make them effective as immunosuppressants?

A. There are lots of mechanisms by which steroids dampen the immune response. Here are a few of them:

1. Suppression of T cells. Steroids interfere with production of cytokines (like interleukins), which are critical in the proliferation and interaction of T cells.

2. Suppression of B cells. Steroids interfere with the binding of interleukins to B cells, which means that the B cells have a hard time proliferating and making antibodies.

3. Suppression of neutrophils. Steroids inhibit just about everything that neutrophils do: adhesion, chemotaxis, phagocytosis, and the release of toxic substances.

4. Suppression of macrophages. Steroids down-regulate the expression of Fc receptors on macrophages – so macrophages are less able to phagocytose opsonized things.

5. Diminished production of prostaglandins and leukotrienes. Steroids inhibit cyclooxygenase and phospholipase A2, which decreases the production of pro-inflammatory arachadonic acid metabolites.

Steroids are used in a ton of different immune and inflammatory disorders, like asthma, vasculitis, arthritis, gout, multiple sclerosis, sarcoidosis, alopecia areata…the list goes on and on.