Significance of low molecular weight C1q in systemic lupus erythematosus.
The significance of high serum concentrations of low molecular weight C1q (LMW-C1q) in patients with systemic lupus erythematosus (SLE) was studied. Concentrations of LMW-C1q were increased in SLE, but not in rheumatoid arthritis or acute poststreptococcal glomerulonephritis. Concentrations of LMW-C1q in SLE serum samples correlated with titres of anti-dsDNA and were inversely related to concentrations of normal C1q and C3. Serial studies in six patients, who had rising anti-dsDNA titres and who developed a major exacerbation requiring admission to hospital, showed that LMW-C1q increased in parallel with anti-dsDNA, reaching peak values of more than 2000% of normal just before or at the time of clinical relapse and decreasing during convalescence. Most marked increases in LMW-C1q were noted in the three patients in whom C1q concentrations remained normal, whereas increases were less in the three patients who had strongly depressed concentrations of normal C1q. A study of C1q biosynthesis by macrophages cultured from patients with SLE and high serum concentrations of LMW-C1q did not show impaired secretion of normal C1q in favour of LMW-C1q, but indicated that serum concentrations of LMW-C1q may reflect the synthetic rate of C1q in vivo. The results show that increased serum concentrations of LMW-C1q may be helpful in diagnosing SLE and suggest that serial determination of LMW-C1q in serum may have predictive value in monitoring patients with SLE.
Hoekzema
R
R
Central Laboratory of the Netherlands Red Cross Blood Transfusion Service, University of Amsterdam.
Swaak
A J
AJ
Brouwer
M C
MC
van Rooijen
A
A
Nieuwenhuys
E J
EJ
Hack
C E
CE
D000974:Antibodies, Antinuclear / Q000032:analysis; D001172:Arthritis, Rheumatoid / Q000276:immunology; D002478:Cells, Cultured; D015922:Complement C1q / Q000032:analysis*; D003176:Complement C3 / Q000032:analysis; D003181:Complement C4 / Q000032:analysis; D005921:Glomerulonephritis / Q000276:immunology; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000276:immunology*; D008970:Molecular Weight; D009000:Monocytes / Q000276:immunology; D011237:Predictive Value of Tests
D000974:Antibodies, Antinuclear; D003176:Complement C3; D003181:Complement C4; D015922:Complement C1q