The exact role of anti-ds (
double stranded) DNA antibodies in the pathogenesis of kidney injury in
lupus nephritis remains a focus of continuing investigation. One theory explaining the pathogenicity of
anti-dsDNA antibodies in
lupus nephritis is direct cross-reactivity with renal
antigens. Several years ago,
alpha-actinin was identified as a major cross-reactive target for pathogenic
anti-dsDNA antibodies in murine SLE. Indeed, binding of a nephritogenic murine
anti-dsDNA antibody was stronger to the
alpha-actinin derived from a lupus prone mouse mesangial cell line as compared to
alpha-actinin in a non-autoimmune mouse mesangial cell line. Furthermore, we recently showed that immunization of non-autoimmune mice with
alpha-actinin induces anti-
chromatin antibodies, glomerular
IgG deposition and
proteinuria. In humans, anti-
alpha-actinin autoantibodies (Ab) were associated with anti-dsDNA Ab in SLE. In those patients, anti-
alpha-actinin rather than anti-dsDNA Ab were significantly associated with
glomerulonephritis and disease activity. The anti-
alpha-actinin reactivity was associated with high avidity anti-dsDNA Ab. Moreover, the anti-
alpha-actinin response was related to the actin-binding site of
alpha-actinin. Taken together, these studies indicate that detection of anti-
alpha-actinin Ab, in association with anti-dsDNA Ab, may constitute a new marker in
lupus nephritis.