Page 1168 - Veterinary Immunology, 10th Edition

VetBooks.ir

FIG. 35.6 The principles of immune checkpoint therapy. A. CTLA-
4 is an inhibitory receptor expressed on T cells. Its ligand is B7
expressed on cancer cells blocking of CTLA-4 by antibodies permit
cytotoxic T cells to exercise their full activity against tumor cells. B.
Alternatively (or additionally), PD1 blocks tumor cell apoptosis by
binding to its ligand PD-L1. Blockage of this interaction allows
cytotoxicity and apoptosis to proceed.

Unfortunately, not all cancers respond to checkpoint inhibitors.
Some T cells may be irreversibly exhausted or so exhausted that
their function may only be restored temporarily, and the disease
relapses after an early response. Checkpoint inhibitors can also be
used in combination with other chemotherapeutic agents such as

tyrosine kinase inhibitors or therapeutic vaccines to enhance their

1168