SPECIFIC IMMUNE-RESPONSE TO THE 40-KDA OUTER-MEMBRANE PROTEIN OF PORPHYROMONAS-GINGIVALIS IN MICE

Whether B-cell activation to Porphyromonas gingivalis in periodontal d iseases 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. gingiva[is, was investigat ed. Patients' sera strongly reacted to this recombinant antigen. Purif ied splenic T and B cells from mice immunized with 40-kDa antigen or f rom normal mice were reconstituted in vitro and cultured in the presen ce or absence of the P. gingivalis 40-kDa protein antigen and antigen- presenting cells (APCs). In vitro antibody production to this particul ar antigen was analysed with respect to the requirement of helper T ce lls 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 a ntibody 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 an tibody response to the 40-kDa protein of P. gingivalis was generated i n an immunologically antigen-specific manner and was not simply the re sult of polyclonal B-cell activation. This in vitro system could be us ed in the detection of antigen-specific memory B or T cells in patient s with periodontal diseases.