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Related: Editorials & Other Articles, Issue Forums, Alliance Forums, Region ForumsCovid-19 Immunity May Rely on a Microscopic Helper: T Cells
IF YOU WANT to know if youve ever been infected with SARS-CoV-2, the natural thing to do is to get a blood test. These look for antibodiesproteins that signal your body has encountered a virus, and could perhaps be protected from catching it again. But recently, a study published in Nature Medicine introduced a worrying complication. Researchers in Chongqing, China, followed 37 people who had tested positive for the virus but didnt show symptoms during their illnessin other words, who were asymptomaticand tested their blood regularly. They found those antibodies didnt always last for long: In some cases, after two to three months, they were barely detectable. Thought a positive antibody test was your ticket out of this thing? Its not so simple. Simple, after all, is not a word immunologists would ever use to describe their field.
Marcus Buggert, an immunologist at the Karolinska Institute in Sweden, had noticed a similar pattern among patients there: cases where people who tested positive for the virus quickly lost their antibodies or never appeared to muster those forces at all. That wasnt a big surpriseantibodies had also waned in patients who recovered from SARS. But to Buggert, who studies T cellspart of an orchestra of cells that perform in the bodys immune responsethe symphony appeared incomplete. Research from SARS offered hints that, even if antibodies faded, some people retained immune cells that recognized the virus. Sometimes, those responses could last for years. For SARS-CoV-2, similar dimensions of the immune response could have bearing on how immunity works and how to design a vaccine. Just because you cant detect antibodies in their blood doesnt mean theres no immune response, Buggert says.
Antibodies are a critical component of immunityespecially the ones that neutralize the virus by homing in on the proteins that comprise it. They glom onto their target and prevent the virus from infecting cells. A good vaccine will try to replicate that kind of natural protection. Neutralizing antibodies are the holy grail, says Sallie Permar, a vaccine researcher at Duke University. There are few to no viral vaccines where were not shooting for that as an end point.
But antibody levels are only part of the immunity story. While antibodies may wane past the limit of detection, that doesnt mean they go away entirely. And even a very low level could be protective. Whats important when youve been exposed to the virus is how quickly you can ramp up those antibodies, Permar says. That involves a whole army of cells, which store knowledge of each new pathogen they encounter. There are B cells, which help coax those virus-specific antibodies into existence, plus killer T cells, which can learn to obliterate infected cells. Helper T cells help orchestrate the whole process. You have multiple arms of the immune response, says Donna Farber, an immunologist at Columbia University who studies respiratory viruses. Its like the Army, the Navy, and the Air Force. If one branch stands down, the body hasnt necessarily lost its germ-fighting capacity.
https://www.wired.com/story/covid-19-immunity-may-rely-on-a-microscopic-helper-t-cells/
Cracklin Charlie
(12,904 posts)The appearance of T-cells on the immune response team seems like great news.