- Paper Report
- Open Access
T-antigen and anti-DNA antibody production
- Chaim Putterman
© Current Science Ltd 1999
- Published: 30 November 1999
- Anti-DNA antibodies
- systemic lupus erythematosus
- T antigen
IgG anti-double-stranded (ds) DNA antibodies are a distinctive serologic hallmark of systemic lupus erythematosus (SLE). The anti-dsDNA antibodies present in human SLE and in murine models of the disease have the characteristics of antibodies arising as an antigen driven response. Lupus-associated anti-DNA antibodies are class-switched to IgG, and somatic mutations are present in both heavy and light chains. Several studies have demonstrated an important role for T cells, particularly T cells specific for self-nucleosomal antigens, in providing help for the anti-DNA antibody response in lupus.
While immunization with mammalian DNA does not induce anti-dsDNA antibodies in non-autoimmune mice, it has been demonstrated in various experimental models that immunization with complexes of DNA and DNA-binding proteins can break tolerance to nuclear antigens. It has been postulated that peptides derived from the associated DNA binding proteins may be the antigen recognized by T cells providing help for anti-DNA antibody production.
In two previous studies, (paper%201) (paper%202) Rekvig et al have shown that expression of polyomavirus T antigen, a DNA binding protein important in viral replication, can induce the production of anti-dsDNA antibodies. Furthermore, they demonstrated that reactivation of polyomavirus in lupus patients is associated with anti-DNA antibody production. This led to the hypothesis that T antigen-specific T cells may provide help for anti-DNA antibody producing B cells. To investigate whether T antigen specific T cells are present in vivo, and if T antigen (T-Ag) complexed with nucleosomes is stimulatory for such T cells.
After demonstrating that T-Ag can bind nucleosomes, Rekvig et alshow that T-Ag (and to a lesser degree SV-T2) stimulated PBMCs as demonstrated by proliferation assays. Proliferation was inhibited by anti-CD4 monoclonal antibodies. T-Ag specific T cell lines were generated from both normal and SLE patients. These T cell lines responded to T-Ag, as well as to T-Ag complexed to nucleosomes. Finally, in coculture experiments, T-Ag specific T cells provided help for anti-T-Ag and anti-DNA antibody production from B cells of both normal and lupus patients.
Peripheral blood mononuclear cells (PBMCs) were obtained from four patients with SLE, and from ten normal controls. SV40 T-Ag was purified from recombinant baculovirus. Nucleosomes were prepared from cells with constitutive expression (SV-T2) or without expression (A31) of SV40 large T-Ag. T cell proliferation assays, generation of T cell lines, FACS analysis, and T and B cell co-culture were performed using standard methodologies.