Fig. 3.

A PD-L1 vaccine and checkpoint inhibitors are complimentary. a PD-L1-expressing regulatory immune cells (red) degrade intracellular PD-L1 into peptides (yellow) that are subsequently processed into peptides and presented on the cell surface by HLA molecules, where they are recognized by PD-L1-specific T cells (green). Hence, PD-L1-specific T cells can promote local immune suppression by the secretion of effector cytokines or by killing regulatory immune cells directly (red arrow), thereby influencing general immune reactions. Similarly, they can eliminate PD-L1-expressing malignant cells, b PD-1-positive, PD-L1-specific T cells are themselves hampered by the suppressive effects of PD-L1 expression on their targets and c PD-L1-specific T cells may thus be further boosted by PD-L1 blockade, since PD-L1 mAbs target the same cells as vaccine-induced T cells; this therapeutic strategy will therefore make cells more vulnerable targets. Thus, a PD-L1-based vaccine should be viewed as complementing rather than competing with checkpoint inhibitors