CD8+ T cells can recognize infected or cancerous cells and eliminate them by exocytosing cytolytic molecules or presenting death ligands on their surface, both of which can initiate apoptosis in target cells. Granzyme B (GzmB) and Fas Ligand (FasL) are two of the effector proteins that CD8+ T cells can use to kill infected or cancerous cells. GzmB is a soluble protein that shares a vesicle with other cytolytic enzymes that enter the target cell upon degranulation, and FasL is a transmembrane

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... and that can engage with the Fas death receptor on target cells. Past research has shown that these two cytolytic proteins can be stored and trafficked within the cell differently, and can be presented to the target cell in response to different T cell receptor signal strength in the context of target cell recognition. Furthermore, there is debate as to whether FasL is required for, contributes to, or is dispensable for clearance of tumors. Most of these studies have not characterized whether FasL protein is actually present in the cells responding to the tumors, or whether extrinsic factors can influence FasL protein expression in CD8+ T cells. As CD8+ T cells have the potential to be exploited therapeutically for patients with cancer, it is important to better understand expression patterns of effector mechanisms in activated CD8+ T cells and how these can be manipulated.