Autoantibodies to the collagenous region of C1q occur in three strains of lupus-prone mice

Abstract

We have developed an ELISA to measure murine autoantibodies to the collagenous region (CLR) of C1q, using the whole human C1q molecule as the solid-phase ligand, in the presence of 1 m NaCl. The assay was validated by testing positive sera from 20 mice using purified mouse C1q, and from 10 mice using purified human C1q-CLR, as the solid-phase ligands. There were highly significant correlations between results obtained with human C1q (whole molecule) and: (i) mouse C1q (r_Sp = 0.73, P < 0.001), and (ii) human C1q-CLR alone (r_Sp = 0.86, P = 0.001). Antibodies to C1q were measured in 53 MRL/lpr, 17 BXSB and 25 NZB/W lupus-prone mice. Median (range) anti-C1q (CLR) antibody levels in MRL/lpr, BXSB, and NZB/W autoimmune mice aged 3 months were 22 (16–66), 21 (17–39) and 19 (15–27) EU, respectively. The median anti-C1q antibody level in MRL/lpr mice aged 5 months was 76 (35–142) EU, significantly higher than that at 3 months (U = 558, P < 0.0005). Median anti-C1q antibody level in NZB/W mice at 8 months was 37 (13–74) EU and in BXSB mice at 11 months was 62 (31–231) EU, significantly higher than corresponding values at 3 months (U = 326, and U = 4, P < 0.001, respectively). This is the first demonstration of anti-C1q (CLR) antibodies in NZB/W and BXSB mice. The pathologic significance and the potential utility of these antibodies for monitoring disease in lupus-prone mice are under evaluation.

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