Killer T Cells Get Fat and Lazy

Were it not for our immune system surveillance, we would all succumb to cancer at a young age.  Our immune system not only patrols for invaders from without, but for rogue cells from within that could go cancerous.  Our immune system must recognize and destroy these rogue cells before their numbers grow too numerous and overwhelm our system.  Having learned that tumors collect oxidized fats, researchers at the Salk Institute determined that our killer T cells which patrol for cancer cells weaken when exposed to too much of these oxidized lipids.

Cancer cells are just our bodies’ own cells which genetically lose their brakes and keeping dividing beyond their boundaries until they wreak havoc both locally and farther away.  The changes within their genetics lead to changes on their surfaces which our immune system can recognize as tipoffs that they are no longer friendly cells.  CD8+ killer T cells get their name from their ability and role of killing either infected cells or these unfriendly cancer cells that they recognize.  Anything which hinders their recognition of unfriendly cells or their ability to destroy such cells would be detrimental to their function and therefore our health.

While millions of chemical reactions are occurring in our bodies at this very moment, many of them involving a process called oxidation, not all are good.  On one hand we oxidize foods for energy and we oxidize toxins to detoxify them.  On the other, if our fats or proteins become oxidized, they may not function properly or even cause further harm beyond their loss of function.  In the case of fats, also known as lipids, they may speed up or slow down other cellular reactions when they are oxidized.  Such oxidized lipids are, for example, associated with heart disease.

In this case, the oxidation of lipids in tumors appears to have a detrimental effect on the killer T cells known at CD8+ T cells.  When these damaged lipids accumulate in the killer T cell, the cell gets distracted from its cancer target to focus on the lipids.  The T cells accumulate the damaged lipids before they cause harm elsewhere, but this decreases activity against the tumor.

Much more research needs to be done but depending on the threshold for killer T cell inhibition, one has to wonder if body-wide oxidized lipids could increase one’s risk of cancer.  In functional medicine we often test what are called lipid peroxides which are simply oxidized lipids. They reflect signs of oxidative damage to cells and thus cell aging.  At what level would these circulating damaged lipids begin to increase cancer risk or is such a level only reached inside the tumor which collect lipid peroxides?  Optimizing our immune system for 2021 and beyond requires knowing more about this process and how we can modify it for our anti-cancer benefit.

Original Article:

Shihao Xu, Omkar Chaudhary, Patricia Rodríguez-Morales, Xiaoli Sun, Dan Chen, Roberta Zappasodi, Ziyan Xu, Antonio F.M. Pinto, April Williams, Isabell Schulze, Yagmur Farsakoglu, Siva Karthik Varanasi, Jun Siong Low, Wenxi Tang, Haiping Wang, Bryan McDonald, Victoria Tripple, Michael Downes, Ronald M. Evans, Nada A. Abumrad, Taha Merghoub, Jedd D. Wolchok, Maxim N. Shokhirev, Ping-Chih Ho, Joseph L. Witztum, Brinda Emu, Guoliang Cui, Susan M. Kaech. Uptake of oxidized lipids by the scavenger receptor CD36 promotes lipid peroxidation and dysfunction in CD8 T cells in tumors. Immunity, 2021; DOI: 10.1016/j.immuni.2021.05.003

Thanks to Science Daily:

Salk Institute. “‘Bad fat’ suppresses killer T cells from attacking cancer.” ScienceDaily. ScienceDaily, 10 June 2021. <www.sciencedaily.com/releases/2021/06/210610135647.htm>.