To study the expression of the chaperone family of J proteins in the synovial tissue of patients with rheumatoid arthritis (RA) or osteoarthritis.
Rabbit antibodies specific for a synthetic peptide (pHSJ1: EAYEVLSDKHKREIYD), representing the most conserved part of all J domains thus far identified--among them the Drosophila tumor suppressor Tid56--were used in immunohistochemical analyses of frozen sections of synovial tissue and immunoblotting of protein extracts of adherent synovial cells. IgG specific for Tid56 was also used.
Both antisera predominantly and intensely stained synovial lining cells from RA patients; other cells did not stain or stained only faintly. In immunoblots, anti-pHSJ1 specifically detected several bands with molecular weights of >74 kd (type I), 57-64 kd (type II), 41-48 kd (type III), and < or =36 kd (type IV). The strongest band detected in RA adherent synovial cells was the type II band, whereas in a B cell line, a type I band was prominent.
Several potentially new members of the J family are described. The type II band represents the human homolog of the Drosophila Tid56 protein and is strongly expressed in RA synovial tissue.