Priming of CD4+ T cells with porin of Shigella dysenteriae activates the cells toward type 1 polarization

Macrophages treated with porin of Shigella dysenteriae were potent stimulators of naive T-h cells since the porin-pulsed macrophages strongly proliferated the T cells and up-regulated the activation molecules CD69 and CD25 on CD4(+) T cells in allogeneic mixed leukocyte reaction. Immunization of C57BL/6 mice with porin selectively induced the intracellular expression and release of IFN-gamma and had no effect on IL-4 expression. In parallel to the predominant release of the T(h)1 cytokine IFN-gamma, up-regulation of CCR5 on the immune CD4(+) T cells and messenger ribonucleic acid (mRNA) expression of the T cell chemokines macrophage inflammatory protein-1 alpha and regulated on activation normal T cell expressed and secreted showed T(h)1 bias. The porin-primed CD4(+) T cells expressed the mRNA for T-box expressed in T cells, a T(h)1-specific transcription factor confirming the adjuvant-induced transition of T cells to polarized effector T(h)1 cells. The immune CD4(+) T cells proliferated and released IL-2 and IFN-gamma profoundly in response to re-challenge with porin-pulsed macrophages but not to BSA-pulsed macrophages in vitro, which demonstrated the presence of porin-specific CD4(+) T cells of T(h)1 phenotype. The study highlights that porin has the capacity of an adjuvant to unfold and maintain the T cell function and thereby to activate adaptive immunity.