Could T-cells provide more long-lasting COVID-19 immunity than antibodies?
As new coronavirus variants arise that may prove more resistant to antibodies, as well as the vaccines so far created to tackle them, researchers are investigating whether our bodies’ T-cell immune response could offer effective, longer-lasting protection from the disease.
We’ve spoken to Dr. Adam Laing and Dr. Tom Hayday, immunologists at King’s College London and Immunology leads at Melio, to find out more about this crucial part of our immune system.
What are T-cells?
Our immune system can be divided into two main parts: the innate immune system, and the adaptive immune system.
T-cells are one of the important white blood cells of the adaptive immune system, and play a central role in the immunity that occurs after we have been exposed to a bacterium, virus or other microorganism that can cause disease (a pathogen). They also play an important role in developing long lasting immunity following a vaccine.
“You have billions of T-cells in your body that are capable of recognising any potential pathogen you might encounter”, explains Dr Adam Laing, research associate at King's College London. “There are so many, in fact, that each one will likely never see the pathogen that it is specific for. On the chance that they do, the T-cells become activated and expand, producing clones of themselves.”
This clonal expansion is really important, as it gives you more T-cells that recognise the same thing allowing them to effectively fight off a specific infection. Following the successful clearance of an infection, these specific T-cells perform another extremely important role; They turn into long lasting memory cells that are able to rapidly respond to re-infection.
How do T-cells work?
T cells are generated from stem cells in your bone marrow that travel to your thymus, a gland near your heart, where they undergo what Adam describes as “their education”.
This education is how T cells gain the ability to recognise pathogens. “This is achieved via an elegant process whereby they randomly rearrange the genes that make up the T-cell receptor, the molecule that recognises foreign entities.” says Adam.
This near-random process poses a potential problem T-cells need to be educated so that they don’t attack our own bodies by mistake. To do that, the thymus tests each T-cell’s receptor by ‘asking’ it if it sees our body as a foreign entity. If it does, that T-cell is deleted.
“The good news is that this random generation of the T-cell receptor enables it to create specificity to anything, and SARS-CoV-2 – the coronavirus that can go on to cause the disease COVID-19 is a great example of this. Two years ago SARS-CoV-2 didn’t exist in humans, but now researchers know our bodies are able to mount an immune response to it, partly aided by our T-cells.”
Why are T-cells important?
According to Adam, the importance of T-cells cannot be overstated.
“For example, babies born without the gene that rearranges the T-cell receptor can’t generate working T-cells so don’t have any immune system response, leaving them at risk of developing all kinds of illnesses and diseases”, he says. “Another example is when HIV transitions into AIDS. If left untreated, the disease eliminates certain T-cells from the body leaving the person susceptible to all sorts of conditions, such as infections and malignancies.”
T-cells and COVID-19 immunity
Given the central role played by T-cells in the function of our immune system, can T-cells provide effective, long-lasting protection from COVID-19 in those who have caught the SARS-CoV-2 coronavirus?
“In the first instance, T-cells are important for identifying and eliminating virus infected cells”, explains Tom. “If you get infected with coronavirus, the cells that make up the lining of your lungs start to produce the virus. Your T-cells are able to identify infected cells and eliminate them, leaving healthy cells largely unharmed”
“More broadly, T-cells are also able to enhance effective antibody generation, plus they are where a lot of your immune system’s memory is stored. However, although we know T-cell memory can last for decades, at the moment we don’t yet know the durability of protection they give against COVID-19 because not enough time has passed for us to test this.”
T-cells and vaccines
Your body’s T-cell response to a COVID-19 vaccine is similar to its response to infection. Your body responds to the vaccine by mounting an immune response and triggers T-cells to reproduce and generate memory T-cells.
Your memory T-cells typically play a key role in long-term immunity against a disease. The same response is expected of the COVID-19 vaccines, however, it is too early to know how long your immune system will ‘remember’ the vaccine and therefore offer immunity. This is one reason why there may be a need for future ‘booster’ vaccinations.
Testing for COVID-19 immunity
“In an ideal world”, says Tom, “the body would mount a robust antibody response AND a robust T-cell response to infection, but what’s also becoming clearer through our research is that in some people – for example, cancer patients – normal immune response is disrupted and you don’t always see a robust response from either.”
This means that while T-cell response is important in fighting off coronavirus, it’s only half the story in the immune response, with antibody production (created by B-cells) being the other half.
“Taking a T-SPOT® COVID Test can tell you if you if you’ve been infected with the SARS-CoV-2 coronavirus and mounted a T-cell immune response, or if you’ve had a response to the COVID-19 vaccine, but for a fuller picture of your potential immunity to the virus you’d ideally take a COVID-19 antibody test as well”, says Tom.
Bolstering T-cell health
While it’s not yet possible to directly boost the health of your T-cells, there are plenty of ways to protect your general health and wellbeing that can have a positive effect on your immune system.
“Immune health is really important, but everyone is different and there is no one-size-fits-all approach to protecting our immune systems”, says Adam. “However, in general terms we do know that getting enough sleep, having a reasonable level of vitamin D and vitamin C, taking regular exercise, having a healthy BMI, eating a balanced diet and being sensible with your alcohol intake are all important ways of protecting your immune health.” But the most effective way to improve immunity is to get vaccinated.
Get your T-cell test from Melio
If you want to find out more about your COVID T-cell immune response, you can book a test directly via Melio, at a time that suits you.
A trained health professional at one of our partner clinics will perform the blood draw, and send the sample to one of our UKAS accredited labs. All test results are individually checked by one of our in-house doctors, who will also write you a personal medical report with any further advice and guidance you may need.
Book your T-SPOT® COVID Test blood test click here or use the chat button if you’d like talk to one of our specially trained advisors for more information.