Confirmation from Swedish study: Special T cells called helpers are detectable in the blood for at least 20 months after healing
How long does immunity last after Sars-CoV-2 infection?
Several studies have tried to answer this question and now good news comes from a Swedish paper published on Proceedings of the National Academy of Sciences (Pnas). According to a team of scholars from the University of Gothenburg, led by Anna Martner, some highly specialized T lymphocytes (called helper) are present in the blood of the healed. 20 months after infection. These lymphocytes facilitate the elimination of virus-infected cells.
I linfociti T helper
The scholars, in collaboration with colleagues from the Sahlgrenska University Hospital, analyzed 81 blood samples from healthcare personnel who contracted Covid in 2020, the first year of the pandemic.
After the disease, several types of Sars-CoV-2 specific T lymphocytes were detected in the participants’ blood, followed up with prolonged follow-up.
Most of the T cells disappeared from the blood of the healed after 10-12 weeks. With the exception of the T helper lymphocytes (Th1), present in the samples even after 20 monthsalmost two years, without however diminishing or weakening.
According to the authors, this discovery could explain why in reinfections the risk of serious illness and mortality is reduced compared to the first infection.
A vital aspect of immunity
Specifically, the researchers measured the reactivity of T cells to a part of Sars-CoV-2 (the so-called nucleocapside del virus), to observe the responses that are triggered after a natural infection. As mentioned, a subset of super specialized (Th1) T cells, which they promote the destruction of virus-infected cells, was active for at least 20 months after healing. Other types of T lymphocytes, active against Sars-CoV-2, disappeared from the blood about 2 months after the disease ended. While some T cell subsets disappear within weeks, highly specialized T cells remain stably present in the blood, suggesting that a vital aspect of functional protective immunity even years after Covid explained Anna Martner, associate professor of immunology at the Sahlgrenska Academy.
The memory cells
An English study, by King’s College London, instead examined the duration of the responses of memory B cells (memory B cells, Mbc) to Sars-CoV-2, after natural infection or vaccination. The main function of these cells (also called B lymphocytes) produce antibodies directed against specific antigens. The British authors analyzed blood samples from 52 donors recovered from Covid with varying severity of the disease, from asymptomatic to severe. In the work, published in the magazine Viral Immunology, the healed showed strong responses associated with B cells, which remained active for up to 6 months after healing, compared to IgG antibodies, which decreased over time. A similar survey, conducted on 14 post-vaccination donors, showed robust antibody responses against la proteina Spike del coronavirus, then dropped within a few weeks. Again, the activity of the B cells against the Spike protein showed a minor decline and the protective response was maintained for at least 6 months after vaccination.
July 23, 2022 (change July 23, 2022 | 17:41)
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