Autoimmune diseases happen when the immune system, which usually protects us from germs, starts attacking the body's own tissues by mistake. There are several important reasons behind this:

1. Genetic Risk: Some people might have genes that make them more likely to get these diseases. For example, certain genes called HLA genes can increase this risk. About 20-30% of people with autoimmune diseases have family members who also have them.

2. Environmental Triggers: Things around us can also play a role. Infections, chemicals, and too much sun exposure can set off or make autoimmune responses worse. For instance, some viral infections are linked to diseases like multiple sclerosis and rheumatoid arthritis.

3. Immune System Issues: Our immune system has special cells called T and B lymphocytes that should attack only harmful things like viruses. However, sometimes they start making autoantibodies, which mistakenly target the body’s own cells. This leads to a situation where the immune system can't tell the difference between invaders and its own healthy cells.

4. Gut Health Effects: New studies show that the bacteria in our gut might affect our immune system. This could help explain why some people develop autoimmune diseases.

Some Key Facts:

• About 5-8% of people have autoimmune diseases.
• These diseases are more common in women than in men, with some diseases affecting women 2 to 10 times more.
• There are over 80 different autoimmune diseases, including rheumatoid arthritis, lupus, and type 1 diabetes.

Understanding how autoimmune diseases work is really important. It helps scientists create better treatments and ways to prevent them.