Role of T cell subset on the immunosuppression induced by Actinobacillus actinomycetemcomitans.

Purified splenic T cells from C3H/HeN mice primed with sonic extract (SE) from Actinobacillus actinomycetemcomitans were adoptively transferred to syngeneic mice with sheep red blood cell (SRBC). The transfer of splenic T cells from mice, primed with SE for 8 days, resulted in the dose-dependent inhibition of IgM anti-SRBC plaque forming cells (PFC) compared with normal and BSA-primed splenic T cells. Furthermore, the transfer of cells from mice primed with 200 micrograms of SE for 8 days to syngeneic mice caused the highest inhibition. Immunosuppression did not depend on the B cell population in spleen from donor mice primed with SE. Splenic T cells from SE-treated mice could suppress the T cell-dependent proliferative responses of co-cultured normal spleen cells in vitro. Analysis of T cell subsets of spleen cells from mice treated with immunosuppressive factor (ISF) showed that the suppressor cell is susceptible to treatment with anti-CD8 and complement (C). SE-sensitized suppressor T cells also suppressed the secondary IgG anti-SRBC-PFC response after immunization with SRBC in vivo depending on sensitized periods induced by ISF. Treatment of T cells from mice which primed with ISF for 8 days, with goat anti-mouse CD8 antibody and C abrogated their suppressive effects, and secondary IgG response occurred. These results indicate that the adoptive transfer of SE-induced T cells, which increased suppressor function, caused the perfect blocking of the immunoresponse, allowing promotion of secondary infection.