Psoriasis and Your Immune System

What causes psoriasis?

The answer is more than skin-deep.

Psoriasis is not just a skin disease—it’s a disease of your immune system that attacks your skin. By understanding psoriasis on this level, we can learn more about why it appears and how to better treat it.

How the immune system functions—and malfunctions

Your immune system protects you by attacking threatening bacteria, viruses, and other foreign invaders. It is critical to your health, comfort, and survival. But sometimes—for reasons we don’t fully understand—the immune system does not work properly. Instead of attacking foreign invaders, it can start attacking your own body.

How your immune system causes psoriasis

No one knows what triggers your immune system to cause psoriasis. It is believed that you must have a genetic tendency to be susceptible to the condition. But once your immune system is triggered, it sends a false alarm to your skin cells, telling them that they’ve been damaged. The skin cells react by attempting to repair this “damage.” They begin reproducing at an accelerated rate (the process that takes roughly 26 days in normal skin now occurs in about 5), rising to the skin surface, dying, and building up there. The skin surface thickens. As blood vessels expand and more blood flows to the skin, it becomes red. The result is the flaky, red patches you know as plaques.

The role T cells and cytokines play

This process is driven by a type of white blood cell called T cells, the attack force of the immune system. T cells start off as inactive, unable to recognize foreign invaders (or antigens) and with no instinct to attack them. However, once T cells are exposed to an antigen, they bind together with the antigen, and become active. They will now recognize the signal given off by the antigen, and target it for destruction whenever the signal is picked up.

In psoriasis, activated T cells move to your skin. This triggers the release of proteins called cytokines that serve as chemical messengers in your immune system. These cytokines send out the false alarm to your skin cells, activating their accelerated reproduction cycle. Cytokines also make the process snowball. They trigger inflammation. They cause the activation of even more T cells, and call T cells in other parts of your body to come to the skin. They even set off the release of more cytokines by the skin cells themselves.

The destructive role of TNF

One of the cytokines released by the T cells is called tumor necrosis factor (TNF). TNF plays a role in almost all psoriasis symptoms: inflammation, redness, pain, and itching in the plaques. It can make blood vessels multiply, and white cells move from the blood vessels into the skin. This may explain why you bleed so easily when you scratch psoriatic plaques.

The future of psoriasis medicines

Because psoriasis is a condition of the immune system, researchers have turned their efforts toward medicines that target the immune system directly. Learn more about a recently approved psoriasis medication.

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