Structural, immunological and functional comparisons of factor H, rheumatoid arthritis protein (RHP), and its apparent normal counterpart (N-RHP).
The isolation and characterization of two human serum proteins, RHP and N-RHP, are described. N-RHP appears to be the normal counterpart of RHP which is found at elevated levels in sera of patients with rheumatoid arthritis [Rosano et al. (1988b) Inflammation 12, 351 - 360]. Although both proteins crossreact with anti-Factor H and have identical N-terminal amino acid sequences, they differ from Factor H in pI, solubility at low ionic strength, and in glycosylation. RHP differs from Factor H and N-RHP in antigenicity in the rabbit, in effect on the C1q-anti-C1q precipitin reaction, and in ability to disaggregate C1, the first component of the complement system. Removal of RHP, N-RHP and Factor H from binding to C1q is a prerequesite for separation of RHP and N-RHP from Factor H by anion exchange chromatography and isoelectric focusing. The finding of uniquely demonstrable RHP activity (enhancement of C1q-anti-C1q precipitin activity) in unfractionated sera from patients with rheumatoid arthritis, but not in normal sera, suggests that RHP is not an artefact of Factor H produced during isolation.
Hurwitz
C
C
Research Service, Stratton VA Medical Center, Albany, NY 12208, USA.
Rosano
C L
CL
Hechemy
K E
KE
Weber
P
P
Parhami
N
N
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001798:Blood Proteins / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D003166:Complement Activating Enzymes / Q000276:immunology / Q000378:metabolism; D017242:Complement Factor H / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D003165:Complement System Proteins / Q000276:immunology* / Q000378:metabolism; D000939:Epitopes / Q000276:immunology; D006801:Humans; D011817:Rabbits
D000596:Amino Acids; D001798:Blood Proteins; C493495:CFH protein, human; D000939:Epitopes; C045510:RHP protein, human; D017242:Complement Factor H; D003165:Complement System Proteins; D003166:Complement Activating Enzymes