Specific immune response to the 40-kDa outer-membrane protein of Porphyromonas gingivalis in mice

Whether B-cell activation to Porphyromonas gingivalis in periodontal diseases is the consequence of a specific immune response or is due to non-specific polyclonal activation is still not clear. Here the immune response of mice to a purified 40-kDa recombinant protein antigen, a major outer-membrane protein specific to P. gingivalis, was investigated. Patients' sera strongly reacted to this recombinant antigen. Purified splenic T and B cells from mice immunized with 40-kDa antigen or from normal mice were reconstituted in vitro and cultured in the presence or absence of the P. gingivalis 40-kDa protein antigen and antigen-presenting cells (APCs). In vitro antibody production to this particular antigen was analysed with respect to the requirement of helper T cells and APCs by enzyme-linked immunosorbent assay. The results clearly showed that an effective secondary response required the presence of B cells, T cells and APCs. In the absence of CD4+ helper T cells, an antibody response to the 40-kDa protein was not observed. In addition, the requirement of H-2 restricted, Ia-positive APCs was evident for an adequate response to the 40-kDa protein of P. gingivalis. Thus the antibody response to the 40-kDa protein of P. gingivalis was generated in an immunologically antigen-specific manner and was not simply the result of polyclonal B-cell activation. This in vitro system could be used in the detection of antigen-specific memory B or T cells in patients with periodontal diseases.