In fact, people who get mild cases of COVID often don’t even have enough antibodies in their bloodstream to be detected by lab tests, yet they have long-lasting immunity to the virus. The reason: Their T-cells – which are a type of white blood cell called T-lymphocytes – carry a much more detailed and complete memory of the shape of the virus compared to antibodies.
A recent study from Sweden, which has experienced more open spread of COVID-19 than other European nations, adds very credible support to this observation. Researchers asked the question: Do people with milder cases of COVID develop robust immunity, despite fewer symptoms or negative antibody testing or both? The answer is yes, according to their data.
Most studies on immunity to COVID have primarily focused on antibodies. But as we learned in recent months, antibodies tend to wane dramatically over time1, particularly in people with milder symptoms. Even if the antibodies are present, they are short-lived. In contrast, memory T-cells can persist for many years.
Based on research from SARS-CoV1 in animals, the T-cells protect against re-infection, which is what everyone wants.
NOTE – "milder symptoms" is a bit of a misnomer, as the term “mild” is subjective for sure. In this case, “mild” symptoms means lack of hospitalization or supplemental oxygen. For anyone who has ever had a bad flu, they would hardly consider feeling not quite horrible enough to go to the hospital as “mild” but with COVID, researchers use mild as a relative term. Keyword being relative. Mild COVID or regular flu – both can be intense. Most people don’t consider fever, coughing, headache, malaise and crushing fatigue as “mild” but when it comes to COVID, not requiring hospitalization is in many cases classified as “mild.”
That said, the paper describes how T-cells remember three distinctly different structural proteins on the COVID virus:
- Spike protein (familiar red knoblike structure depicted in so many visuals of this virus)
- Membrane protein (outer membrane of the virus)
- Nucleocapsid protein (the shell that protects the viral genetic “payload”)
Sometimes referred to as S, M, or N-proteins, the virus can mutate in any one of these proteins. However, keeping a cellular memory of all three, which is what T-cells do according to this paper, has the benefit of potential overlapping protection against new strains of the virus. In other words, if the S-protein mutates, the T-cell can still confer immunity via the M- or N-protein memory.
When naturally infected, a person’s T-cells hold memory of all three parts, whereas B-cells (antibodies) are specific to one protein. This can certainly explain why T-cell immunity is much longer lasting — because they contain a more complete model of what to fight against if exposed again.
Evidence continues to mount that T-cells are the main biological player in keeping us healthy when exposed to this virus.
This requires healthy, well-functioning T-cells that are ready to multiply (proliferate) when needed. SpectraCell Laboratoraies measures T-cell function (via proliferation assay) in its Immunidex test, which is a component of the more comprehensive Micronutrient Test.
(Cell, October 2020)
LINK to FREE FULL TEXT Robust T Cell Immunity in Convalescent Individuals with Asymptomatic or Mild COVID-19
1Ibarrondo et al. Rapid decay of anti-SARS-CoV-2 antibodies in persons with mild covid-19. NEJM 2020;383(11):1085-1087.