Which autoimmune disease is characterized by the immune system attacking the body and causing inflammation?

Rheumatoid arthritis is characterized by the immune system mistakenly attacking the body's own tissues, leading to inflammation and damage primarily in the joints. It is a systemic autoimmune disease, which means it can affect different parts of the body beyond just the joints. The inflammatory process can cause pain, swelling, and stiffness, often leading to decreased mobility and joint deformities over time.

In contrast, osteoporosis is a condition that affects bone density and strength but is not classified as an autoimmune disease. Osteoarthritis, on the other hand, is primarily a degenerative joint disease caused by wear and tear rather than an autoimmune process. Alzheimer's disease involves neurodegeneration and is also not classified as an autoimmune disorder. Thus, rheumatoid arthritis stands out as the appropriate answer due to its distinct characteristics of immune response and inflammation.