What are T-Cells?
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If you’re one of those people following all the news on COVID-19 looking for a wee bit of hope (be careful, so-called “doomscrolling” isn’t good for your mental health) then you may well be worried about recent reports that antibodies to COVID-19 drop off rapidly after 2 or 3 months.
However, it’s not quite as bad as that, and the key to the situation may in fact be T-cells.
What are T-cells?
Our adaptive immune system uses two methods to attack infection.
Antibodies grab the virus before it can infect a cell and “kill” it. T-cells are the other prong. They identify infected cells and destroy them, preventing the virus from spreading through your system.
Like antibodies, T-cells are adaptive; they have to be programmed to recognize specific signs of infection. However, T-cell immunity seems to stick around for longer than antibodies.
There are two kinds of T-cells. Helper T-cells identify the virus, and killer T-cells destroy the cells. Helper T-cells are kind of like the dispatcher. They identify the virus and then tell the immune system to make more of the right kind of T-cells and antibodies.
Infected cells are identified by viral antigens that are left on the surface when the virus invades a cell.
T-Cells More Common than Antibodies to COVID
A recent study at the Karolinska institute in Sweden looked at people known to have had COVID-19 and discovered that for every one person with solid antibodies…there were two people with T-cells. Unfortunately, T-cell testing can’t be readily scaled up.
We can, however, use this as an extrapolation to guess real immunity levels in a population. And yes, having T-cells makes you immune; antibodies are better for keeping you from transmitting/carrying the virus, though, as they prevent cells from being infected in the first place. T-cells don’t do anything about free virus in your bloodstream, which you might pass on to others. T-cells going wrong is also what causes the cytokine storm often so deadly in COVID-19 patients.
More research is definitely needed, but it appears that the primary mediation of immunity to COVID-19 may not be B-cells, which make antibodies, but T-cells.
This does not affect vaccine production, but does mean we should focus on vaccines that elicit a good T-cell response. Drugs that boost T-cell production may also be helpful for treating patients.
And it certainly doesn’t mean you should assume you are immune after having COVID-19 once; although it does seem that we are not seeing the large number of reinfections six months into the pandemic that we would if people really only had immunity for two to four months.
T-cells are a key part of our immune system and they may be the silent warriors against COVID-19.
