[conspire] Some light reading about…mast cells

[Deirdre Saoirse Moen]

When I took immunology, we didn't really get time to cover mast cells very much except to say that they were responsible for cytokines. So, eventually having time to catch up on readings necessitated by all the Covid papers I've digested, I started reading more about them.

They're kind of a source of heparin and histamine, and send out over 1000 different cell mediators.

And if your mast cells decide to be jerks, you can get some very weird symptoms, many of which are fatal.

https://en.wikipedia.org/wiki/Mast_cell

A few of the mediators sent out:

* ATP (aka the basic energy currency of the body)
* histamine (for all your anaphylactic shock needs, not to mention lesser allergy reactions)
* serotonin (to get that brain stuff done)
* TNF-alpha (tumor necrosis factor) to respond to a detected intrusion
* Interleukin 4, which helps T-Helper cells mature.
* Proteases, which help snip peptides apart into their components.

So you can imagine with all this stuff they do, being a Swiss Army Knife kind of cell, dysfunctions of mast cells could have wide-ranging and weird side effects.

Dr. Lawrence Afrim's book, Never Bet Against Occam: Mast Cell Activation Disease and the Modern Epidemics of Chronic Disease and Medical Complexity is a fascinating read for an educated layperson. Many chapters are presented in House-like puzzles, as they unfolded case-wise.

https://www.amazon.com/Never-Bet-Against-Occam-Activation/dp/0997319615

Anyhow, I mention it not because it's necessarily worth reading, but because there was one interesting point: that, for many people with mast cell disease, an aspirin (specifically aspirin, not ibuprofen) dose plus a histamine H1 blocker (e.g., loratadine) made them feel a lot better. Some also needed an H2 blocker (e.g., famotidine, which is found in Pepcid). Some needed a lot stronger meds.

The damage in ARDS from Covid comes from the cytokine storm, which is your immune system over-reacting, as led by mast cells.

So the Covid papers on this suggest that:

* these blockers don't necessarily help once you're in the hospital (at least in terms of outcome at a population level)
* they don't work directly on the outer coat for SARS-CoV-2

…but they may help if used pre-hospitalization, which hasn't been studied well. Animal models are promising, a few case studies are encouraging, but no one's paying for heavy research on an off-patent med.

-- 
  Deirdre Saoirse Moen
  deirdre at deirdre.net