Katherine J. Wu writes:

To locate some of the world’s most superpowered cells, look no further than the human immune system. The mission of these hometown heroes is threefold: Memorize the features of dangerous microbes that breach the body’s barriers. Launch an attack to bring them to heel. Then squirrel away intel to quash future assaults.

The immune system is comprehensive, capable of dueling with just about every microbe it meets. It’s archival, ace at memorizing the details of its victories and defeats. It might be complicated, but it is also, simply put, cool as hell.

Now, a year into a pandemic, our immune systems face a new challenge. The coronavirus has picked up mutations that boost its ability to hop from human to human and thwart some of the antibodies that have reliably conquered it before. The protection offered by vaccines appears riddled with holes. Viruses evolve fast—faster than humans ever could. If the pandemic is a race, the coronavirus seems, at times, on the verge of lapping us.

But the immune system is not doomed to be discombobulated by a never-ending barrage of shape-shifting variants. For every trick the virus plays, the immune system arguably has an equally impressive one. Vaccines remain an essential ally, armoring the body before it encounters the virus. And although the variants have opened up gaps in that chain mail, the pliancy built into our bodies can at least buy time to repair them.

“Yes, we should be concerned,” Ali Ellebedy, an immunologist at Washington University in St. Louis, told me. “But I think we should also be optimistic.”

When any infectious interloper hits, the body’s first responders—the less specialized cells of the innate immune system—rush in to wallop it. Those cells also gather information on the invader and ferry it to the lymph nodes, where they parade pieces of the pathogen in front of the body’s longer-term defenders, the cells of the adaptive immune system.

Among these adaptive cells are B cells, each wired to recognize a slightly different hunk of foreign matter. During their development, individual B cells will mix and match segments of genes that encode antibodies, generating billions or trillions of unique combinations. The result is a multitude of Y-shaped molecules that can collectively “respond to any foreign pathogens they see,” says Kim Jacobson, an immunologist at Monash University in Australia. The focus of these antibodies is so laser-sharp that they can differentiate even the individual nooks and crannies that decorate a virus’s surface. [Continue reading…]