Correlation between complement breakdown products and immune complexes in plasma from patients with glomerulonephritis

An approach to the dynamic evaluation of complement has been recently provided by the detection of the complement breakdown products, C3d and Ba, which are increased when the complement system is activated (Perrin L. H. et al.: J. Clin. Invest., 56, 165, 1975). The authors present a study on 45 patients (70 serum samples) affected by idiopathic or related to systemic diseases glomerulonephritis. They evaluate the complement breakdown products C3d and Ba, and make a comparison with the levels of complement factors usually checked (C3, C4, properdin factor B, C1q), and those of the serum immune complexes detected by the ELISA solid phase C1q test. The measurement of complement breakdown products gives more precise information than the evaluation of the original factors C3 (C antigen) and properdin factor B, and point out pathological data otherwise not detectable such as a complement activation with a concomitant increased synthetic rate, or a decreased factors synthesis without consumption. Pathological data for complement breakdown products were mainly observed in mesangiocapillary glomerulonephritis, cryoglobulinemic glomerulophritis and lupus nephritis. Among these patients, only those affected by lupus nephritis, particulary in active disease stages, showed a significant increase of circulating immune complexes with the test employed. In various glomerulonephritides the evaluation of complement breakdown products at the same time as circulating immune complexes is well correlated with the clinical data; thus it is the authors' belief that the simultaneous evaluation of complement breakdown products and serum immune complexes may give precise information about the immunological involvement in human glomerulonephritis.