A serum antibody in patients with rheumatoid arthritis stimulates cathepsin B activity in peritoneal mouse macrophages.
Mouse peritoneal macrophages were stimulated by sera from patients with active rheumatoid arthritis (RA) to increased intracellular cathepsin B activity. By gel filtration of three RA sera, the stimulatory activity was found in the IgG and to a lesser extent in the IgM containing fraction. The DEAE-cellulose purified IgG preparations of five additional RA patients stimulated intracellular cathepsin B activity significantly above IgG from healthy controls. IgG and IgM antibodies to macrophages were detected in sera from RA patients but not from controls by indirect immunofluorescence (IIF) technique. Pepsin F (ab')2 fragments of IgG from the RA patients also gave clearcut membrane fluorescent staining of the macrophages which demonstrated the antibody nature of the binding. A good correlation between the cathepsin B assay and the IIF was found when serial dilutions of serum were compared.
D000818:Animals; D000906:Antibodies / Q000276:immunology*; D001172:Arthritis, Rheumatoid / Q000276:immunology*; D002401:Cathepsin B; D002403:Cathepsins / Q000096:biosynthesis*; D002850:Chromatography, Gel; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000032:analysis; D007074:Immunoglobulin G / Q000096:biosynthesis; D007075:Immunoglobulin M / Q000096:biosynthesis; D008264:Macrophages / Q000201:enzymology*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains
D000906:Antibodies; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D002403:Cathepsins; D002401:Cathepsin B