Anti-DNA autoantibodies from a lupus-prone mouse: Ligand binding properties, structure and pathogenicity.

Although anti-DNA autoantibodies (anti-DNA) are a hallmark of human SLE and murine models of this disorder, the relationships between the ligand binding properties, structure, and pathogenicity of anti-DNA remain poorly understood. To address this problem, the affinity, specificity and mode of DNA recognition of eight anti-DNA derived from a lupus-prone MRL-lpr mouse were studied. The variable region gene usage and structure of these anti-DNA was subsequently determined to examine the factors responsible for their development as well as provide the basis for the construction of three-dimensional models of anti-DNA$\cdot$DNA complexes guided by the results from ligand binding studies. To compare the features of anti-DNA that may influence their pathogenicity in vivo, the ability of three representative anti-DNA in induce glomerulonephritis upon adoptive transfer to non-autoimmune mice was investigated. The results of ligand binding studies show that anti-DNA fall into groups based on their affinity and specificity for single-and double-stranded DNA (ssDNA and dsDNA, respectively), as well as their mode of DNA recognition. Variable region gene analysis of the anti-DNA studied suggest that anti-ssDNA reactivity is based on a limited repertoire of conserved three-dimensional motifs encoded by several variable region genes that possess few, if any, somatic mutations. Three-dimensional models constructed for three representative anti-DNA from the variable region sequences suggest that the shape of the binding site and the shape and stereoelectronic complementarity of specific subsites on the antibody surface to the structure of a thymidine base may partly explain the specificity of these antibodies for thymidine-containing sequences. Adoptive transfer experiments demonstrate that a putatively germline-encoded, anti-ssDNA induces a severe glomerulonephritis that resembles human diffuse proliferative glomerulonephritis, whereas another anti-ssDNA and an anti-dsDNA do not. The similarity of the variable region genes of the pathogenic antibody to those of anti-DNA obtained from normal mice immunized with DNA suggests that pathogenic anti-DNA can be encoded in the normal immune repertoire and that defects in tolerance may be responsible for their survival and proliferation.PhDChemistryUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/104870/1/9610248.pdfDescription of 9610248.pdf : Restricted to UM users only