Anti-DNA antibodies--structure and function

Expression of monoclonal anti-DNA antibodies in vitro can be used to study the relationships between molecular structure, binding properties and pathogenicity. Bacterial and yeast systems can be used to produce antibody fragments such as Fab. The yields are potentially sufficient to allow structural studies such as crystallization, but purification of the anti-DNA Fab from the bacterial periplasm may be challenging. Mammalian cell expression systems produce lower yields, but the products are whole antibodies, which can be used in assays of pathogenicity. This article describes some recent experiments in which bacterial and mammalian systems were used to study human monoclonal anti-DNA antibodies. Light chain sequence motifs were found to be important both in binding to antigens and in determining pathogenicity of the antibodies in severe combined immunodeficiency mice. The distribution of B cell subpopulations is disturbed in patients with systemic lupus erythematosus (SLE). These patients, like those with infectious mononucleosis, have an overall B cell lymphopenia but an increased frequency of plasmablasts/early plasma cells in their blood. Some of these early plasma cells belong to clones that have rearranged the V(H) gene V4-34. There is a selective rise in immunoglobulins encoded by this gene in both infectious mononucleosis and SLE.