Studies in the structure and regulation of expression of anti-dsDNA antibodies

Abstract

Systemic lupus erythematosus (SLE) is an autoimmune disorder in which an individual makes an antibody response against self antigens. The clinical course of the disease is marked by fluctuations in disease activity. Anti-double stranded (ds) DNA antibodies have been of interest to those who study SLE since the titers of anti-DNA antibodies tend to parallel patients' clinical course. Additionally, there is evidence implicating anti-DNA antibodies in lupus glomerulonephritis.;The structure of anti-DNA antibodies and their regulation is poorly understood. Molecular studies, through sequence analyses, B cell genealogies, and X-ray crystallography, have just begun to define the basis for dsDNA binding. Speculations on those features which may enhance the affinity of an antibody to DNA have come to the forefront. The analysis of anti-DNA antibodies has also led investigators to speculate as to the origin of these antibodies. B cell genealogies have been used to determine whether anti-DNA antibodies are the result of an antigen driven response or polyclonal B cell activation.;One of the goals of my thesis research is to define the structural basis for DNA binding of anti-DNA antibodies and to better define those criteria which are used to characterize a response as antigen driven. A molecular genetic approach is used to mutate a mouse anti-DNA antibody. The mutant proteins are analyzed for antigen affinity to dsDNA. The data suggest very few amino acid changes are required to disrupt or enhance binding to dsDNA. In addition, the data also suggest that FW mutations may have dramatic effects on antigen binding.;A second goal of my thesis research utilizes transgenic mouse technology to study the regulation of a light chain gene, which in combination with the appropriate heavy chain gene, encodes an anti-dsDNA antibody in a nonautoimmune strain of mouse. The data suggest that these mice do not form pathogenic antibodies. They secrete normal amounts of antibody in their serum. However, they may be suppressing the utilization of the potentially pathogenic heavy chain partner.