C1q deficiency and autoimmunity: the effects of genetic background on disease expression.
Gene-targeted C1q-deficient mice have been shown to develop a syndrome reminiscent of human systemic lupus erythematosus with antinuclear Abs and proliferative glomerulonephritis. Initial phenotypic analysis conducted in (129 x C57BL/6) hybrid mice showed that background genes were a significant factor for the full expression of the autoimmune disease. To assess the contribution of background genes in the expression of the autoimmune phenotype, the disrupted C1qa gene was backcrossed for seven generations onto C57BL/6 and MRL/Mp(+/+) strains. These were intercrossed with C57BL/6.lpr/lpr and MRL/Mp-lpr/lpr strains to generate C1q-deficient substrains. In C1q-deficient C57BL/6 mice, no evidence of an autoimmune phenotype was found, and C1q deficiency in both the C57BL/6.lpr/lpr and MRL/Mp-lpr/lpr strains did not modify the autoimmune phenotype observed in wild-type controls. However, in C1q-deficient MRL/Mp(+/+) animals an acceleration of both the onset and the severity of antinuclear Abs and glomerulonephritis was seen. Disease was particularly pronounced in females, which developed severe crescentic glomerulonephritis accompanied by heavy proteinuria. In addition, the C1q-deficient MRL/Mp(+/+) mice had an impairment in the phagocytic clearance of apoptotic cells in vivo. These data demonstrate that the expression of autoimmunity in C1q-deficient mice is strongly influenced by other background genes. The work also highlights the potential value of the C1q-deficient MRL/Mp(+/+) strain as a tool with which to dissect further the underlying mechanisms of the autoimmune syndrome associated with C1q deficiency.
Mitchell
Daniel A
DA
Rheumatology Section, Division of Medicine, Imperial College School of Medicine, Hammersmith Hospital, Du Cane Road, London, UK W12 0NN.
Pickering
Matthew C
MC
Warren
Joanna
J
Fossati-Jimack
Liliane
L
Cortes-Hernandez
Josefina
J
Cook
H Terence
HT
Botto
Marina
M
Walport
Mark J
MJ
D000818:Animals; D000974:Antibodies, Antinuclear / Q000096:biosynthesis; D015551:Autoimmunity; D015922:Complement C1q / Q000235:genetics*; D018450:Disease Progression; D005260:Female; D006801:Humans; D019169:Jurkat Cells; D007668:Kidney / Q000473:pathology; D008180:Lupus Erythematosus, Systemic / Q000235:genetics* / Q000276:immunology / Q000473:pathology; D017737:Macrophages, Peritoneal / Q000276:immunology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D019463:Mice, Inbred MRL lpr; D018345:Mice, Knockout; D010587:Phagocytosis; D010641:Phenotype; D015996:Survival Rate
D000974:Antibodies, Antinuclear; D015922:Complement C1q