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.