Demonstration of circulating immune complexes in Sjögren's syndrome
Lawley, T.J.; Moutsopoulos, H.M.; Katz, S.I.; Theofilopoulos, A.N.; Chused, T.M.; Frank, M.M.
Journal of Immunology 123(3): 1382-1387
1979
ISSN/ISBN: 0022-1767 PMID: 469255 Document Number: 152922
Sera of patients with Sjogren's syndrome were examined for circulating immune complexes with the 125I-C1q , P < 0.0005) although there was no association between C1q-binding activity and amount of IgG RF. To investigate positive association of C1q-binding activity and IgM rheumatoid factor, sera were treated with 2-mercaptoethanol to dissociate 19S IgM RF or solid phase protein A to absorb IgG and were then analyzed for C1q-binding activity and IgM RF. Pretreatment of the sera with 2-mercaptoethanol resulted in complete elimination of IgM RF activity, but only slight to moderate reductions in C1q-binding activity. Partially purified IgM RF when added to normal human serum did not result in increased C1q-binding activity. All C1q-binding activity could be removed from Sjogren's syndrome sera by absorption with solid phase protein A, which also caused slight to moderate decreases in the IgM RF titer. A high percentage of patients with Sjogren's syndrome have circulating immune complexes, most of which are distinct from 19S IgM and IgG RF.