Fight, Then Fix
Game · the immune system’s two shifts
▶ Play this chapter The script
Every line as it is spoken in the film, in order.
Scrape your knee, and within minutes your body starts a fight. But within a week, the fight is over, the mess is cleared and the new skin has regrown. The fight part usually gets the attention of modern medicine, but actually, much of what goes wrong with age happens during the cleanup process.
Dr. Bob had a simple picture for this. Your body was like an office. Office workers come in in the morning, work all day, leave tons of waste behind, and leave in the evening. Then in the evening, the cleaning crew comes to clean it all up so the office workers can start fresh again the following morning. Your body runs both types of shifts too, and the two locks in this film help decide which crew is on shift.
The first cells to arrive are neutrophils. They crawl toward the wound, swallow bacteria and kill them with bleach, the same active chemical that's in the bottle under your sink.
Cells on the attack burn sugar the fast, wasteful way, the way a sprinter burns through fuel.
Dr. Bob Melamede, in his own words · interview, 2011“We actually make free radicals that we focus in an effort to kill living entities that we don’t want living within us.”
That same sugar-burning chemistry that kills the bacteria also damages the healthy tissue around them with free radicals. You feel that cost as swelling, heat and pain.
Then the job changes. Some of the same macrophages switch roles. They eat the dead cells, send out signals that end the fight and help lay down new tissue. Some shift toward burning fat, though whether that drives the switch is still argued.
A few of the T cells that fought stay behind as memory cells, so the next infection gets beaten faster. They lean on fat too. In mice, nudging T cells toward burning fat made more of them become memory cells.
Ending a fight takes work. The body makes its own stop signals, and many of them are built from the same omega-3 and omega-6 fats it uses to make its own keys.
Dr. Bob Melamede, in his own words · Cannabis Hemp Conference & Expo, 2017“CB2 turns on fat burning. CB1 allows you to burn sugar safely. That’s why your brain needed it, because it’s so organized it’ll fry without it.”
CB1 sits mostly on nerves, and on the liver and fat that store fuel. CB2 was found in 1993 in the spleen, and it sits mostly on immune cells.
When CB2 turns on, immune cells generally calm down. They put out fewer alarm signals and fight less. In many disease models, mice bred without CB2 get worse inflammation.
CB1 can push the other way. In diabetic rats, the body's own keys turned CB1 on macrophages in the pancreas. That kept the inflammation going and killed insulin-making cells. Blocking CB1 outside the brain protected them.
In mouse liver studies, turning CB2 on macrophages switched on their recycling program, where a cell breaks down its own damaged parts. Work on that recycling process won the Nobel Prize in 2016.
Dr. Bob put it together this way. CB1 helps run the heavy machinery, CB2 starts the cleanup, and health means keeping both shifts working in a harmonious symphony since both processes happen at the same time.
If the cleanup starts too early, the infection wins. If it never starts, the fight keeps burning the tissue it was meant to protect.
A century ago, most people died of infections. Today most die of heart disease, cancer and other illnesses of age and inflammation.
Researchers call it inflammaging. As we get older, the fight switch never fully turns off.
Dr. Bob Melamede, in his own words · homeostasis talk, 2018“Free radicals are the friction of life, and endocannabinoids are the oil of life.”
Dr. Bob thought aging was mostly a cleanup crew falling behind, and that the body's own keys, along with the plant's, could help it catch up. Parts of that have good evidence in mice. In people, it's still a theory.
I can't sell you a pill for this, and I'd be wary of anyone who tries. The cleanup crew already responds to things you can do.
Much of the repair happens while you sleep. Exercise switches on recycling in your muscles, and fasting does it more widely. In addition to the plant's THC, a molecule in black pepper and cloves, beta-caryophyllene, turns the CB2 lock directly. In mice it's been shown to calm inflammation.
The fight and the cleanup are the whirlpool again, with fuel coming in and damage going out. Keep both moving, and you stay far from equilibrium for longer.
Sources
Every claim in this chapter with its grade: E established · M emerging (one or two studies, or animals only) · F framework.
- MFranceschi C et al. Inflamm-aging: an evolutionary perspective on immunosenescence. Ann N Y Acad Sci 2000;908:244–54. (The idea and the name: a low, lasting inflammation that rises with age) link
- FRobert (Bob) Melamede, PhD. Backward-looking and forward-looking: a far-from-equilibrium reading of the endocannabinoid system. His framework, not scientific consensus.
- FHartfield J. Your immune system has two speeds: full-throttle attack and zen-like repair. justinhartfield.com, 2025. (Dr. Bob’s framing of the two shifts.) link
- EKlebanoff SJ. Myeloperoxidase: friend and foe. J Leukoc Biol 2005;77:598–625. (Neutrophils make hypochlorous acid, the active chemical of household bleach, to kill what they swallow; the same chemistry injures tissue) link
- EO'Neill LAJ, Kishton RJ, Rathmell J. A guide to immunometabolism for immunologists. Nat Rev Immunol 2016;16:553–65. (Attacking cells run on fast glycolysis; resting, memory and regulatory cells lean on fat oxidation) link
- FBob Melamede, PhD. Interview, 2011 (recording; the quotes at 2:40 and 4:51). His framework.
- ESerhan CN. Pro-resolving lipid mediators are leads for resolution physiology. Nature 2014;510:92–101. (Resolvins, protectins, maresins and lipoxins: stop signals made from omega-3 and omega-6 fats) link
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- FBob Melamede, PhD. Talk at the Cannabis Hemp Conference & Expo, 2017 (recording; the quotes at part 2, 4:28, 6:52 and 10:10, and part 3, 11:33). His framework.
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- MJourdan T et al. Activation of the Nlrp3 inflammasome in infiltrating macrophages by endocannabinoids mediates beta cell loss in type 2 diabetes. Nat Med 2013;19:1132–40. (Zucker diabetic fatty rats; a CB1 blocker that stays outside the brain protected the insulin-making cells) link
- MDenaës T et al. The cannabinoid receptor 2 protects against alcoholic liver disease via a macrophage autophagy-dependent pathway. Sci Rep 2016;6:28806. (Mice: CB2 on liver macrophages switches on autophagy; without it, no protection) link
- EThe Nobel Prize in Physiology or Medicine 2016: Yoshinori Ohsumi, for his discoveries of mechanisms for autophagy. link
- ELeading causes of death: 1900 (death-registration states, rates per 100,000; NCHS, Leading Causes of Death 1900–1998) and 2023 (NCHS Data Brief 521, Mortality in the United States, 2023). In 1900 the three leading causes were infections; in 2023, heart disease and cancer. link
- FBob Melamede, PhD. Cannabinoids: homeostasis regulators, from cells to society. Talk, 2018 (recording; the quotes at 2:17, 8:21 and 10:29). His framework (the mouse finding he describes is Varvel & Lichtman 2002).
- EBesedovsky L, Lange T, Haack M. The sleep-immune crosstalk in health and disease. Physiol Rev 2019;99:1325–80. (Sleep supports repair and keeps inflammation in check; short sleep raises it) link
- EHe C et al. Exercise-induced BCL2-regulated autophagy is required for muscle glucose homeostasis. Nature 2012;481:511–5. (Mice: a run switches on autophagy in muscle and heart) link
- MAlirezaei M et al. Short-term fasting induces profound neuronal autophagy. Autophagy 2010;6:702–10. (Mice: a day or two without food raises autophagy in liver and brain) link
- MGertsch J et al. Beta-caryophyllene is a dietary cannabinoid. PNAS 2008;105:9099–104. (Binds CB2 at 155 nM; in mice, cut inflammation, but not in mice without CB2) link
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- MManuzak JA et al. Heavy cannabis use associated with reduction in activated and inflammatory immune cell frequencies in antiretroviral therapy-treated HIV-infected individuals. Clin Infect Dis 2018;66:1872–82. (198 people; an association, clinical meaning unclear) link