T-CELL
IMMUNITY - SCI & TECH
News:
Omicron variants evolve
strategies to evade T cell immunity
What's
in the news?
●
Much like many other viruses that have
developed strategies to evade T cell-mediated clearance by humans, SARS-CoV-2
virus too has the ability to evade the CD8 T cells.
Key
takeaways:
●
While neutralising antibodies are
responsible for preventing infection, CD8
T cells play a huge role in reducing the viral load and clearing the infection
by detecting and killing infected cells. The CD8 T cells cannot prevent
infection.
MHC
I:
●
In a study recently published in the
Proceedings of the National Academy of Sciences (PNAS) found that the SARS-CoV-2 virus encodes multiple viral
factors that modulate major histocompatibility complex class I (MHC I)
expression in the host cells.
●
The MHC I plays an important role in
alerting the immune system to virally infected cells.
●
The MHC I molecules are expressed on the
surface of all infected cells.
SARS-CoV-2 and MHC I:
●
One of the common tricks that viruses use
to avoid killing is to inhibit MHC I
expression and presentation. SARS-CoV-2 is no exception.
●
The SARS-CoV-2 virus has evolved multiple
strategies to inhibit MHC I expression, which is not seen in the case of the
influenza virus.
●
The suppression of MHC I is specifically
seen in the infected cells and varies between different viral strains.
T
Cells:
●
T cells are part of the immune system and develop from stem cells in the bone
marrow.
●
They help protect the body from infection
and may help fight cancer. Also called T lymphocyte and thymocyte.
●
Rather than generically attack any
antigens, T cells circulate until they encounter their specific antigen.
Functions
of T Cells:
●
The most common context of T cells is fighting within infectious diseases.
●
They are used for adaptive immunity too. This includes responses to
allergens and tumors.
●
Also be responsible for inflammatory or autoimmune diseases.
Mechanism
of T Cells:
●
T cells originate in the bone marrow but
are matured in the thymus.
●
They bind to this antigen on the surface
of antigen-presenting cells (APCs).
Types
of T cells:
●
In general, there are three types of T cells such as
○
Cytotoxic
○
Helper and
○
Regulatory.
●
Cytotoxic
T-cells destroy infected cells.
●
Helper
T-cells send signals that direct other immune cells to fight
infection.