Crystallization and preliminary X-ray analysis of the Fab fragment of a human monoclonal IgM rheumatoid factor (2A2).

Abstract Crystals of the Fab fragment of a human monoclonal IgM rheumatoid factor have been obtained and are suitable for X-ray structure determination. This molecule, derived from the synovial B cells of a patient with rheumatoid arthritis, is an autoantibody with specificity for IgG Fc. The crystals have space group P 2 1 , cell dimensions a = 69·0 A, b = 76·6 A, c = 98·8 A and β = 90·6°, and diffract to a resolution of at least 2·8 A.