Western blot analysis with affinity-purified rabbit antisera. Each of the first seven lanes contains the immunizing peptide in the amount shown (in nanograms). The second band seems to be due to an alternative cleavage site in the fusion protein at amino acid 262. Lanes A–E contain synovial fluid from patients with various types of arthritis; it was immunoaffinity-purified to decrease the protein load before Western blotting. Lane A, psoriatic arthritis; lane B, reactive arthritis; lane C, gout; lane D, ankylosing spondylitis; lane E, rheumatoid arthritis. The samples in lanes A–D contained mactinin. Controls with rabbit IgG were negative for all samples.