Abstract
Background. Recent studies in mice have suggested that T cell immunity may be protective against pneumococcal infection. Methods. CD4 T cell proliferative responses to the pneumococcal proteins pneumolysin (Ply), Ply toxoid (F433), and choline-binding protein A were investigated in peripheral blood mononuclear cells (PBMCs) and adenoidal mononuclear cells (MNCs) obtained from children undergoing adenoidectomy. Results. Ply and F433 induce significant proliferation of CD4 T cells in both PBMCs and adenoidal MNCs, and both memory and naive phenotypes of CD4 T cells proliferated after stimulation. In PBMCs, CD4 T cell proliferation induced by Ply and F433, which was associated with increased production of interferon (IFN)—γ and tumor necrosis factor (TNF)—α, was significantly lower in children who were culture positive for pneumococcus than in those who were culture negative for pneumococcus (P < .05). Between groups, no such difference was observed in adenoidal MNC CD4 T cell proliferation, which was associated with production of IFN-γ and interleukin (IL)—10. The CD4 T cell proliferation induced by Ply and F433 was inhibited by antibodies to Toll-like receptor 4. Conclusion. These data suggest that Ply induces CD4 T cell proliferative responses with production of IFN-γ and TNF-α in PBMCs or of IFN-γ and IL-10 in adenoidal MNCs, which may be important in modulating pneumococcal carriage in children.