University of Michigan - Ann Arbor

- Checkpoint inhibitors block "proteins called checkpoints that are made by some types of immune system cells, such as T cells, and some cancer cells" (NIH).
- "These checkpoints help keep immune responses from being too strong and sometimes can keep T cells from killing cancer cells" (NIH). 
- As seen in the image below, examples of checkpoint proteins are PD-1 and PD-L1 and examples of checkpoint inhibitors are anti-PD-1 and anti-PD-L1.

Cancer Immunotherapy | Checkpoint Inhibitors

American Association for Cancer Research (AACR)

- PD-1 is a checkpoint protein on T cells (a type of immune cell).
- "When PD-1 binds to PD-L1, it basically tells the T cell to leave the other cell alone. Some cancer cells have large amounts of PD-L1, which helps them hide from an immune attack" (cancer.org).
- Checkpoint inhibitors that inhibit PD-1 and/or PD-L1 have great potential in battling certain cancers.
- Image from NIH - National Cancer Institute

Cancer Immunotherapy | Checkpoint Inhibitors against PD-1 and PD-L1

Most common side effects are ...
- Diarrhea
- Pneumonitis (inflammation in the lungs)
- Rashes and itchiness
- Problems with some hormone levels
- Kidney infections

The list above is copied verbatim from cancer.org.

Cancer Immunotherapy | Checkpoint Inhibitors | Side Effects

CTLA-4 is another checkpoint protein on T cells.

Cancer Immunotherapy | Checkpoint Inhibitors against CTLA-4

15% of all human cancers worldwide are caused by viruses. The viruses that cause cancer contain either single-stranded RNA or double-stranded DNA genomes.  RNA viruses include Human T lymphotropic Virus type 1 and Hepatitis C and DNA viruses are HPV, Human Herpesvirus-8, Epstein-Barr Virus, Hepatitis B Virus. All of these viruses are blood-borne pathogens and are transmitted via blood transfusions, sexual contact, and during parturition. Oncogenesis driven by viral proteins are easier to treat through targeted therapy and immunotherapy because the presence of viral gene products differentiates between normal cells and cancerous cells. Vaccination is recommended for prophylaxis and treatment of this kind of cancer in order to strengthen the immune system, stop viral replication, and inactivate the virus. Although virus-mediated tumorigenesis is slow, other factors can play an important role in cancer progression such as genetic factors, environmental factors, and immunosuppression. Below is the infectious viruses that lead  to carcinogenesis in exposed individuals:



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