Strong activation of anti-bacterial T cells linked to severe COVID-19


Date:
September 28, 2020
Source:
Karolinska Institutet
Summary:
A type of anti-bacterial T cells, so-called MAIT cells, are strongly
activated in people with moderate to severe COVID-19 disease,
according to a new study.



FULL STORY ==========================================================================
A type of anti-bacterial T cells, so-called MAIT cells, are strongly
activated in people with moderate to severe COVID-19 disease, according
to a study by researchers at Karolinska Institutet in Sweden that is
published in the journal Science Immunology. The findings contribute
to increased understanding about how our immune system responds against COVID-19 infection.


==========================================================================
"To find potential treatments against COVID-19, it is important to
understand in detail how our immune system reacts and, in some cases,
perhaps contribute to worsening the disease," says Johan Sandberg,
professor at the Department of Medicine, Huddinge, at Karolinska
Institutet and the study's corresponding author.

T cells are a type of white blood cells that are specialized in
recognizing infected cells, and are an essential part of the immune
system. About 1 to 5 percent of T cells in the blood of healthy people
consist of so-called MAIT cells (mucosa-associated invariant T cells),
which are primarily important for controlling bacteria but can also be recruited by the immune system to fight some viral infections.

In this study, the researchers wanted to find out which role MAIT cells
play in COVID-19 disease pathogenesis. They examined the presence and
character of MAIT cells in blood samples from 24 patients admitted to Karolinska University Hospital with moderate to severe COVID-19 disease
and compared these with blood samples from 14 healthy controls and 45 individuals who had recovered from COVID-19. Four of the patients died
in the hospital.

The results show that the number of MAIT cells in the blood decline
sharply in patients with moderate or severe COVID-19 and that the
remaining cells in circulation are highly activated, which suggests they
are engaged in the immune response against SARS-CoV-2. This pattern of
reduced number and activation in the blood is stronger for MAIT cells
than for other T cells. The researchers also noted that pro-inflammatory
MAIT cells accumulated in the airways of COVID-19 patients to a larger
degree than in healthy people.

"Taken together, these analyses indicate that the reduced number of MAIT
cells in the blood of COVID-19 patients is at least partly due increased accumulation in the airways," Johan Sandberg says.

In convalescent patients, the number of MAIT cells in the blood recovered
at least partially in the weeks after disease, which can be important
for managing bacterial infections in individuals who have had COVID-19, according to the researchers. In the patients who died, the researchers
noted that the MAIT cells tended to be extremely activated with lower expression of the receptor CXCR3 than in those who survived.

"The findings of our study show that the MAIT cells are highly engaged
in the immunological response against COVID-19," Johan Sandberg says. "A
likely interpretation is that the characteristics of MAIT cells make them engaged early on in both the systemic immune response and in the local
immune response in the airways to which they are recruited from the blood
by inflammatory signals. There, they are likely to contribute to the fast, innate immune response against the virus. In some people with COVID-19,
the activation of MAIT cells becomes excessive and this correlates with
severe disease." This research was supported by the Swedish Research
Council, the Swedish Cancer Society, the Swedish Heart-Lung Foundation,
the Knut and Alice Wallenberg Foundation, Nordstjernan AB and Karolinska Institutet.


========================================================================== Story Source: Materials provided by Karolinska_Institutet. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Tiphaine Parrot, Jean-Baptiste Gorin, Andrea Ponzetta, Kimia
T. Maleki,
Tobias Kammann, Johanna Emgaard, Andre' Perez-Potti, Takuya Sekine,
Olga Rivera-Ballesteros, Sara Gredmark-Russ, Olav Rooyackers,
Elin Folkesson, Lars I. Eriksson, Anna Norrby-Teglund, Hans-Gustaf
Ljunggren, Niklas K.

Bjo"rkstro"m, Soo Aleman, Marcus Buggert, Jonas Klingstro"m,
Kristoffer Straalin, Johan K. Sandberg. MAIT cell activation
and dynamics associated with COVID-19 disease severity. Science
Immunology, 2020; 5 (51): eabe1670 DOI: 10.1126/sciimmunol.abe1670 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200928152855.htm

--- up 5 weeks, 6 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)