How Your Immune System Works & How to Improve It | Dr. Max Krummel

KEYPOINTS

• 01

  The immune system's core job is telling self from non-self

  Krummel retells a 1970s immunologist's analogy. WWII submarines carried two books of engine sounds, one for friendly subs (don't fire) and one for enemy subs. The immune system works the same way, and Krummel says the self/non-self question has turned out far richer than immunologists thought in the 1990s and 2000s. He calls today's view a 'new immunity.' It isn't a single fuel gauge running low for self and high for viruses.

• 02

  Your body becomes a genetic mosaic as you age

  Skin cells may pick up roughly 10,000–30,000 DNA mutations per cell per day from basic sun exposure, more than many other organs, which is one reason for sunscreen. Over years, neighboring cells stop being identical. Part of the immune system's role is surveillance: checking that cells are still 'the right thing' and acting when something is out of range, as with emerging cancers.

• 03

  Kids get sick often because everything is new to them

  A child's body has never seen flu or most other pathogens, so nearly every virus causes some illness. But young immune systems react strongly and clear infections quickly. Some childhood vaccines aren't given until about six months or later for developmental reasons. In late life, susceptibility rises again.

• 04

  The thymus trains T cells, then shrinks

  T cells are named for the thymus, where developing cells with an enormous range of possible receptors, on the order of 10^11, are screened. Cells too reactive to your own tissues, which might attack your pancreas or 'your big toe,' are weeded out to maintain tolerance. With age the thymus involutes and becomes tiny in older people, so it stops putting out new T cells. That's why there's interest in revitalizing it, for example to supply fresh tumor-specific T cells in cancer.

• 05

  Unapproved thymic peptides are hype for now

  Huberman notes that some people are already injecting non-FDA-approved thymus-derived peptides and says he doesn't recommend it. Krummel's general warning is that an idea that makes intuitive sense often fails. If an experiment has a 10% chance of working, you need at least ten tries, and probably more, to expect a result. Self-experimenters also generate anecdotes that get mistaken for data.

• 06

  Sleep loss likely hurts immunity partly through 'plumbing'

  Bags under the eyes and glassy eyes after poor sleep are well-established lymph-clearance problems that resolve after a night or two of good sleep. Krummel doesn't think lymph alone explains why one bad night makes you catch a cold, though. His speculative model is that cleanup processes, like macrophages clearing debris in the eye, work best when you aren't generating new metabolic 'grime.' It's like washing a windshield when you're not driving into flies.

• 07

  The brain can store and replay immune states

  In a mouse study Krummel describes, inflammatory bowel injury was induced with a sugar that damages the gut. Neurons firing in the insular cortex during that period were tagged. Re-activating those neurons after recovery made the gut immune system set itself up again as if newly injured. The implication is that memories, and possibly cues like smells, carry immune states. Krummel says it makes the idea that meditation can shift you toward less inflammatory states 'less and less wacky,' while warning that intuitive stories can mislead.

• 08

  Acute stress helps immunity; chronic stress harms it

  Huberman argues, and Krummel agrees, that the immune-enhancing effects of acute cortisol and stress have been overlooked next to the well-known harms of chronically high cortisol.

• 09

  Some autoimmunity may be a trade-off

  Genes that make the immune system overactive may persist because they help during pandemics. Huberman raises reports that mild psoriasis, which involves interleukin-17 and responds to anti-IL-17 drugs, may come with better resistance to infection. They present this as an intriguing reason why autoimmunity might be adaptive, not settled fact.