Granulocytes may weaken immune response in connection with COVID-19


Date:
August 30, 2021
Source:
University of Helsinki
Summary:
Information on granulocytes sheds light on the mechanisms associated
with COVID-19 and other infectious diseases.



FULL STORY ==========================================================================
Most of the white blood cells in humans are neutrophils, which have
received a lot of attention during the coronavirus pandemic due to their numbers growing in conjunction with covid-19. However, their role in
the disease remains partially unknown.


========================================================================== Low-density granulocytes (LDG) are a type of neutrophils whose number has
been observed to grow particularly in connection with certain autoimmune diseases and cancers, such as rheumatoid arthritis, melanoma, liver cancer
and breast cancer. Increased levels of these granulocytes have also been associated with septicaemia, but their general role and functioning in infectious diseases are yet to be comprehensively described.

The emergence of the SARS-CoV-2 virus and the ensuing pandemic has
demonstrated a need to investigate mechanisms of acute respiratory
infections in more detail. In a recently completed study, researchers
from the University of Helsinki studied LDG levels in patients suffering
from acute covid-19. The goal was to determine the role, if any, of LDGs
in the disease.

The results were published in the PLOSPathogens journal.

A total of 34 hospitalised patients and 21 outpatients with mild symptoms
were included in the study. The researchers used flow cytometry to
measure LDG levels, detecting a significant increase in LDGs in the
blood of acute covid-19 patients compared to healthy control subjects.

"LDGs are cells associated with the innate immune response, and they fight acute infections. However, their effect on the progression of covid-19
appears to take place through an inhibiting effect on the proliferation
and division of T lymphocytes, consequently potentially suppressing part
of the adaptive immune response against the virus," says Luz Cabrera,
doctoral student at the University of Helsinki.

Four LDG sub-types observed in the study The researchers identified
several sub-types of LDGs in the acute covid-19 patients, with
four different LDG populations displaying distinctive stages of
development. According to the researchers, the stages most likely reflect emergency myelopoiesis, that is, the production of granulocytes in the
bone marrow.

The researchers linked the elevated LDG levels to an increased neutrophil demand and, consequently, their activation in the circulation. This
matches an inflammatory process where neutrophil progenitors, or immature neutrophils, are produced at a rapid rate.

The researchers consider the immunosuppressive capacity of neutrophils demonstrated in the study a significant find, observed when they were
isolating LDGs from the patients. When isolated in the laboratory,
the cells began to secrete substances which inhibit T lymphocytes from dividing.

"Low T lymphocyte levels are one of the major severity indicators for
covid-19.

A more effective immune response can be the difference between a milder
disease and more severe one," Cabrera says.

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


========================================================================== Journal Reference:
1. Luz E. Cabrera, Pirkka T. Pekkarinen, Maria Alander, Kirsten H. A.

Nowlan, Ngoc Anh Nguyen, Suvi Jokiranta, Suvi Kuivanen, Anu Patjas,
Sointu Mero, Sari H. Pakkanen, Santtu Heinonen, Anu Kantele, Olli
Vapalahti, Eliisa Keka"la"inen, Tomas Strandin. Characterization
of low- density granulocytes in COVID-19. PLOS Pathogens, 2021;
17 (7): e1009721 DOI: 10.1371/journal.ppat.1009721 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210830140243.htm

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