Immune checkpoint
Immune self-tolerance
Also searched as Immune self-tolerance.
These are the switches that teach immune cells to leave healthy tissue alone. Animals born without them develop spontaneous heart inflammation, which shows the brakes are not optional — the heart depends on them every day. Cancer immunotherapy works by releasing them deliberately.
In depth
The molecular safety catches that stop immune cells attacking the body’s own tissue.
What drives it
Immune support increases it.
T-cell activation induces PD-1 and CTLA-4 expression as a negative-feedback brake on the immune response. PMID 15776283
Antiviral signal increases it.
Interferon-gamma upregulates PD-L1 on target tissue, engaging the PD-1 inhibitory axis. PMID 35011581
What it drives
It reduces Immunotherapy heart inflammation.
A cause that did not exist twenty years ago, and it is the deadliest one. Cancer drugs that release the immune system's brakes can let it attack the heart. 'Inflammation of the heart muscle... resulting from ICI targeting cytotoxic T lymphocyte-associated antigen 4 (CTLA4), programmed cell death protein 1 (PD1) and PD1 ligand 1 (PDL1) is an infrequent but potentially fatal complication' (PubMed 38982146 · doi 10.1038/s41568-024-00715-5 — Immune-checkpoint inhibitor-mediated myocarditis: CTLA4, PD1 and LAG3 in the heart, Nat Rev Cancer 2024;24(8):540-553). The numbers ARE stark: 'the fatal rate is as high as 39.7%-50%, and our results indicate the fatal rate is 47.4%' (doi 10.3389/fimmu.2023.1275254 — Immune checkpoint inhibitor-associated myocarditis: a systematic analysis of case reports), and 'combination ICI regimens (anti-CTLA-4 plus anti-PD-1) carry an approximately five-fold higher risk' (doi 10.3389/fphar.2026.1845366 — Immune checkpoint inhibitor-related cardiotoxicity: a cellular pharmacology perspective). And it is growing: 'nearly 50% of all patients with cancer ARE eligible for treatment with ICIs'. doi 10.1038/s41568-024-00715-5
It reduces Immune balance.
A cause that did not exist twenty years ago, and it is the deadliest one. Cancer drugs that release the immune system's brakes can let it attack the heart. 'Inflammation of the heart muscle... resulting from ICI targeting cytotoxic T lymphocyte-associated antigen 4 (CTLA4), programmed cell death protein 1 (PD1) and PD1 ligand 1 (PDL1) is an infrequent but potentially fatal complication' (PubMed 38982146 · doi 10.1038/s41568-024-00715-5 — Immune-checkpoint inhibitor-mediated myocarditis: CTLA4, PD1 and LAG3 in the heart, Nat Rev Cancer 2024;24(8):540-553). The numbers ARE stark: 'the fatal rate is as high as 39.7%-50%, and our results indicate the fatal rate is 47.4%' (doi 10.3389/fimmu.2023.1275254 — Immune checkpoint inhibitor-associated myocarditis: a systematic analysis of case reports), and 'combination ICI regimens (anti-CTLA-4 plus anti-PD-1) carry an approximately five-fold higher risk' (doi 10.3389/fphar.2026.1845366 — Immune checkpoint inhibitor-related cardiotoxicity: a cellular pharmacology perspective). And it is growing: 'nearly 50% of all patients with cancer ARE eligible for treatment with ICIs'. doi 10.1038/s41568-024-00715-5
It reduces Cardiac autoantibodies.
And here is proof of the strongest kind for the autoantibody: transfer it alone, and the heart fails. 'autoantibodies against cardiac troponin i appeared in spontaneously developing autoimmune myocarditis in PD-1 deficient mice, who lack the T-cell receptor costimulatory molecule PD-1. The passive transfer of this antibody induced myocardial dysfunction. Later, this autoantibody was found in patients with myocarditis' (doi 10.1007/s00059-012-3692-z — Matsumori a. Lessons learned from experimental myocarditis, Herz 2012). ⇒ the antibody alone, with NO virus and NO immune cells, made the heart work worse — and the same antibody was then found in real patients. Troponin i is also the protein measured in a blood test when a heart is damaged. the marker and the target are the same molecule. doi 10.1007/s00059-012-3692-z
Blends that modulate it
Each blend page names this pathway and carries the study behind its claim.
See it on the map
Open the causal map to follow this pathway upstream and downstream, arrow by arrow, each with its study.