Western blots of synovial fluid samples from rheumatoid arthritis and osteoarthritis patients and organ donors. Representative western blots of synovial fluid samples from asymptomatic donors (D) and osteoarthritis (OA) and rheumatoid arthritis (RA) patients. (a) Nonreduced conditions with anti-pro-osteogenic protein 1 (OP-1) antibody (R2854). (b) Nonreduced conditions with anti-mature OP-1 antibody (MAB354). (c) Reduced gel with anti-mature OP-1 antibody (MAB354). Samples were diluted 1:100. The numbers on gels represent the size of the protein bands of interest. The same amount of protein was loaded onto each lane.