Short, distorting summary: when it comes to antibodies, quality replaces quantity.
Most of our B cells, or the antibodies they produce, won’t actually react at all to SARS-CoV-2, or a vaccine that resembles it. That’s because our bodies are always churning out B cells at random, repeatedly futzing with their genetics so that they’ll make a diverse array of antibodies—billions or trillions in total—that can collectively recognize just about any microbe they might ever see. This process is haphazard and imprecise, though: When B cells are born, “they don’t have any particular pathogen in mind,” Gabriel Victora, an immunologist at Rockefeller University, told me. Instead of gripping firmly onto the virus’s surface, many antibodies might just “bounce on and off,” giving the pathogen ample time to wrest itself free, Bhattacharya said. It’s the best defense the body can slap together on short notice, having never met the bug before. Early antibodies are sort of the immune system’s best guesses at defense—the immunological equivalent of throwing spaghetti against a wall to see what sticks—which usually means we need a lot of them to truly pen the pathogen in place. They’re also fragile. Most antibodies don’t hang around for more than a few weeks before they degrade.
Such flimsy fighters aren’t terribly good investments for the long term. So while the subpar antibodies are duking it out on the front lines, the immune system will shuttle a contingent of young B cells into a boot camp, called a germinal center, where they can study up on the coronavirus. What happens inside these training camps is a battle royal in miniature: The cells crowd together and desperately vie for access to the resources they need to survive. Their weapons are their antibodies, which they wave frantically about, trying to latch on to chunks of dead coronavirus, while a panel of other immune cells judges them from afar. Only the most battle-ready among them—the ones whose antibodies grip most tightly onto the coronavirus—move on to the next round, and the losers perish in defeat. As Gommerman put it, “If they suck, they die.”
The harrowing cycle repeats itself over and over, and only gets more grim. Survivor B cells will xerox themselves, deliberately introducing errors into their genetic codes in the hopes that some of the mutations will enhance their antibodies’ chances of gluing themselves to the virus. The entire process is downright “Darwinian,” like a super-sped-up form of natural selection, Victora said. The weaklings are weeded out, leaving just the sharpest and strongest behind. It’s also very prolonged.
Researchers such as Ali Ellebedy, of Washington University in St. Louis, have found that these tournaments of culling continue for at least 12 to 15 weeks after people receive their COVID-19 vaccines, perhaps longer.If all of this is getting a little too Squid Game, consider the much rosier upshot: At the end of this process, our bodies are left with some truly primo antibodies, well poised to take up the mantle of protection as the first waves of mediocre defenders start to fall away.
Man, that would make a kickass episode of Cells at Work. (You seen that show, Dale?)
ReplyDeleteHave not, but will have to look. It's right in the familial wheelhouse where we can all watch and not be annoyed.
ReplyDeleteUnlike movie night, which is like trying to order pizza for fifty people...