Generation of specific antibody-secreting cells in salivary glands of BALB/c mice following parenteral or oral immunization with Porphyromonas gingivalis fimbriae.

The humoral immune response and induction of antigen-specific antibody-secreting cells in mucosal lymphoid tissues were examined in mice immunized subcutaneously or orally with fimbrial protein purified from Porphyromonas gingivalis strain 381. A group of BALB/c mice was immunized subcutaneously with P. gingivalis fimbriae and semisynthetic adjuvant GM-53 in Freund's incomplete adjuvant on days 0 and 28. Another group of mice was immunized perorally with liposome containing fimbriae and GM-53 on days 0, 1, 27 and 28. In the mice immunized subcutaneously, salivary anti-fimbrial IgM antibodies were detected transiently on day 5, followed by the appearance of specific IgG and IgA antibodies on day 14. Higher concentrations of salivary IgG and IgA anti-fimbrial antibodies were found after the second immunization. Fimbria-specific IgM and IgG spot-forming cells (SFC) were detected in cervical lymph nodes of the immunized mice by the ELISPOT method. Fimbria-specific IgA SFC but not IgM and IgG appeared in the parotid and submandibular glands of subcutaneously immunized mice. On the other hand, mice immunized by gastric intubation generated almost exclusively salivary anti-fimbrial IgA antibodies. In agreement with this finding, increased numbers of antigen-specific IgA but not IgM and IgG SFC were seen in parotid and submandibular glands, but not in cervical lymph nodes of orally immunized mice. It can be concluded that systemic or oral immunization with fimbrial antigen induces distinct immune responses in specific lymphoid tissues or in the salivary glands in respect of their temporal sequences and the numbers of plasma cells secreting antigen-specific and non-specific immunoglobulins.