> See also: > - [[Autoimmunity]] # Rheumatoid Arthritis **Rheumatoid arthritis** is an autoimmune disease where the immune system attacks the synovium that lines joints (specifically hands & feet) - *~1.5 million* people in U.S. are affected - Symptoms are often *symmetrically* displayed - *Morning stiffness* is a common symptom, where most joint pains occur in the morning - Conditions typically improve over the day - *Women are 2-3x* more likely to be afflicted (as with most ADs) The rheumatoid factor is an antibody that is highly associated (not causing) with RA, being found in *~80% of patients*. - Is an Anti-IgG antibody (typically IgM but can be IgG/IgA) that binds to its Fc region ## Screening Techniques **Latex Agglutination** is a serological screening technique that can *suggest* the presence of rheumatoid factors (RFs) - Either the antigen or antibody can be the soluble component based on the usage needs Rose-Waaler test is the 1st test for rheumatoid factors - Uses *sheep red blood cells* coated in *anti-sheep antibodies* made in rabbits **Known** - Antigen (IgG) - Insoluble **Unknown** - Antibody (rheumatoid factor) - IgM (Anti-IgG) Generally, a titer of $\ge 80$ *suggests* rheumatoid arthritis *Nephelometry* can be used While IgG & IgA can also be rheumatoid factors, they - Can not be detected using latex agglutination as they do not form pentameric structures that can cause clumping