Uncoupling of T cell receptor zeta chain function during the induction of anergy by the superantigen, staphylococcal enterotoxin A

Antigen specific activation of cytotoxic CD8+ T cells by Staphylococcus aureus infected dendritic cells

Staphylococcus aureus (S. aureus) is a pathogen associated with a wide variety of diseases, from minor to life-threatening infections. Antibiotic-resistant strains have emerged, leading to increasing concern about the control of S. aureus infections. The development of vaccines may be one way to overcome these resistant strains. However, S. aureus ability to internalize into cells - and thus to form a reservoir escaping humoral immunity - is a challenge for vaccine development. A role of T cells in the elimination of persistent S. aureus has been established in mice but it remains to be established if CD8+ T cells could display a cytotoxic activity against S. aureus infected cells. We examined in vitro the ability of CD8+ T cells to recognize and kill dendritic cells infected with S. aureus. We first evidenced that both primary mouse dendritic cells and DC2.4 cell line can be infected with S. aureus. We then generated a strain of S. aureus expressing a model CD8 epitope and transgenic F5 CD8+ T cells recognizing this model epitope were used as reporter T cells. In response to S. aureus-infected dendritic cells, F5 CD8+ T cells produced IFN-γ in an antigen-specific manner and displayed an increased ability to kill infected cells. Altogether, these results demonstrate that cells infected by S. aureus display bacteria-derived epitopes at their surface that are recognized by CD8+ T cells. This paves the way for the development of CD8+ T cell-based therapies against S. aureus.

Immune-checkpoint inhibitors for combating T-cell dysfunction in cancer

Under normal conditions, the immune system responds effectively to both external and internal threats without damaging healthy tissues. Cells undergoing a neoplastic transformation are one such threat. An efficient activation of T cells is enabled by T-cell receptor (TCR) interactions with antigen-presenting class I and class II molecules of the major histocompatibility complex (MHC), co-stimulatory molecules, and cytokines. After threatening stimuli are removed from the body, the host's immune response ceases, which prevents tissue damage or chronic inflammation. The recognition of foreign antigens is highly selective, which requires multistep regulation to avoid reactions against the antigens of healthy cells. This multistep regulation includes central and peripheral tolerance toward the body's own antigens. Here, we discuss T-cell dysfunction, which leads to poor effector function against foreign antigens, including cancer. We describe selected cellular receptors implicated in T-cell dysfunction and discuss how immune-checkpoint inhibitors can help overcome T-cell dysfunction in cancer treatment.