Detection of complement activation on antigen microarrays generates functional antibody profiles and helps characterization of disease associated changes of the antibody repertoire

Krisztián Papp, Péter Végh, Kata Miklós, Julianna Németh, Klára Rásky, Ferenc Péterfy, Anna Erdei, József Prechl

Journal of Immunology 2008, 181:8162-8169

Humoral immune responses are traditionally characterized by determining the presence and quality of antibodies specific for certain antigens. Arraying of large numbers of antigens allows the parallel measurement of antibodies, generating patterns called antibody profiles. Functional characterization of these antibodies could help draw an even more informative map of an immune response. To generate functional antibody profiles we simultaneously tested not only IgM, IgG and IgA binding to but also complement activation by a panel of endogenous and exogenous antigens printed as microarrays, using normal and autoimmune human sera. We show that complement activation by a particular antigen in a given individual cannot be predicted by the measurement of antigen specific antibodies, in spite of a general correlation between the amount of antigen-bound antibody and the deposited C3 fragments. This is due to both differences in the isotypes that dominate in the recognition of an antigen and individual variations for a given isotype, resulting in altered complement activation potential. Thus, antigen specific C3 deposition can be used as an additional parameter in immune response monitoring. This is exemplified by comparing the coordinates of antigens, used for the diagnosis of systemic lupus erythematosus, of normal and autoimmune serum samples in a two-dimensional space derived from C3 deposition and antibody binding. Since cleavage fragments of C3 mediate important immunological processes we propose that measurement of their deposition on antigen microarrays, in addition to antibody profiling, can provide useful functional signature about the tested serum.