Final answer:
IgM is the most common antibody associated with Rheumatoid Arthritis, particularly in the form of rheumatoid factor (RF) which binds to the patient's own IgG, leading to immune complex formation and joint inflammation.
Step-by-step explanation:
The most common antibody associated with Rheumatoid Arthritis is IgM. Specifically, the antibody is known as rheumatoid factor (RF), which is an IgM antibody that binds to the patient's own IgG antibodies. This binding can lead to the formation of immune complexes which are significant in the development of Rheumatoid Arthritis.
During the immune response against these complexes, there is chronic release of inflammatory cytokines such as IL-1, IL-6, and TNF-α, which leads to the joint inflammation characteristic of the disease. Diagnosis of Rheumatoid Arthritis often includes testing for RF, which is the presence of IgM that agglutinates IgG-coated latex beads in a diagnostic assay.