Kinetics of cytokine release and expression of lymphocyte cell-surface activation markers after in vitro stimulation of human peripheral blood mononuclear cells with Streptococcus pneumoniae.

The aim of this study was to describe the kinetics of the cytokine release and the expression of activation markers on lymphocytes after stimulation of peripheral blood mononuclear cells (PBMC) with whole killed Streptococcus pneumoniae. The cytokine release and the expression of CD25 and HLA-DR on T cells, and CD69 on T cells, B cells and NK cells, were measured at different times. Our results show that tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-10 and IL-12 reached maximal levels at 24 h, while IL-6, IL-8, TNF-beta and interferon (IFN)-gamma increased throughout the 1-week test period. The strains tested gave an increased expression of CD69 on all cell types, as well as an increase of CD25 and HLA-DR expression on T cells. The maximal CD69 expression was seen after 24 h on T cells and NK cells, while the B-cell expression of CD69 reached a plateau at the same time. All the cells still expressed CD69 on their surfaces after 1 week. In conclusion the results indicate that there was probably an early activation of monocytes leading to a polyclonal activation of lymphocytes.