An autoantibody is an antibody formed in response to an agent produced by the organism itself.

Christian Boitard has written:

'B cells and autoantibody production in autoimmune diseases'

The LE factor or lupus cell is an autoantibody found in 75% of people with systemic lupus erythematosus.

Autoimmune and rheumatic diseases can be difficult to diagnose. People with the same disease can have very different symptoms. A helpful strategy in the diagnosis of these diseases is to find and identify an autoantibody in the person's blood

There are a number of reasons pain in joints is witnessed. The most probable being arthritis, of which there are two types: osteoarthritis and rheumatoid arthritis. The former is due to damage and wear of the synovial membrane in joints, this is a degenerative issue due to age and causes erosion of the cartilage and bone. The latter is a genetically predisposed condition whereby a person's immune system creates an autoantibody which plays a role in the destruction of the synovial membrane, cartilage and bones of joints - a type of autoimmunity.