The Humoral Immune Response in Autoimmunity

Polyreactive antibodies in multidonor-derived immunoglobulin G: theory and conclusions drawn from experiments

Multidonor-derived (md) preparations of IgG antibodies, agents of therapeutic potential, contain molecules interacting at clonal concentrations (concns) and with affinities recently estimated to cover a considerable range. Here we demonstrate that polyreactivity of the monomeric molecules represents the essential driving force of formation of the main reaction product, the IgG-dimers. This conclusion is obtained by applying the principles of the law of mass action to dimer formation by polyreactive monomeric reactants. In addition, general interrelationships involving the mean number of reactants per reactor, the experimental dimer portion (w/w) and the mean concentrations of monomers in a polyreactive and monoreactive antibody system are derived. These interrelationships, together with quantitative results obtained from simplified computational kinetic models of polyreactive antibodies, allow to estimate a remarkably high value for the mean number of reactants per reactor, exceeding 60 for the underlying IgG preparation obtained from pooled human plasma units of 5000 donors. Moreover, the potential origin and other consequences of polyreactivity are outlined.

Antibody-based vaccines for the treatment of melanoma

Malignant melanoma remains a difficult clinical problem. Chemotherapy is not effective and immunotherapy has long been contemplated as the preferred approach to this disease. Extensive passive and active immunotherapy trials have been conducted. Active vaccination with whole cells or defined antigens, administered with a panoply of techniques to increase immunogenicity, has yielded inconsistent results. The development of antibody-based vaccines has allowed vaccination without the need for tumor tissue material or purified antigens. The idiotype network theory originally proposed by Lindemann and by Jerne provided the basis for the development of anti-idiotype (anti-Id) antibody vaccines, which mimic the internal image of the epitope targeted for immunization. Preclinical and phase I clinical data are available for various malignancies. In melanoma, some of the anti-Id vaccines have targeted gangliosides. One of these vaccines, TriGem, has been successful in generating a robust and specific humoral immunity in melanoma patients. Phase II data suggest this anti-Id vaccine has clinical activity.

Human monoclonal natural autoantibodies against the T-cell receptor inhibit interleukin-2 production in murine T cells

Natural autoantibodies (NAAbs) specific for the T-cell receptor (TCR) are present in all human sera, but individuals with rheumatoid arthritis (RA) generally produce higher titres of immunoglobulin M (IgM) isotype autoantibodies (AAbs) against Vbeta TCR epitopes. To investigate possible correlations between the specificity of such AAbs and their role in immunomodulation, we generated seven B-cell hetero-hybridomas, secreting monoclonal IgM NAAbs, from the synovial tissue and peripheral blood of patients with RA. Here we report three anti-TCR monoclonal autoantibodies (mAAbs)--OR2, OR5 and Syn 2H-11--with the ability to bind subsets of murine T cells, including the ovalbumin-specific DO-11.10 clone. These antibodies did not induce apoptosis in vitro, but prevented interleukin-2 (IL-2) production by antigen-specific T cells. These findings suggest an immunomodulatory function for NAAbs to TCR V-region epitopes and serve as the foundation for testing human anti-TCR mAAbs in animal models with the eventual goal of using them as therapeutic agents in human disease.