Fintetuning for antibodies
The strength of the immune reaction triggered by antibodies can be
regulated

Date:
July 14, 2023
Source:
Friedrich-Alexander-Universita"t Erlangen-Nu"rnberg
Summary:
Antibodies are crucial, not only for treating tumors and infections.

Sometimes, however, the immune reaction they trigger can be too
strong and end up causing more damage, for example in the case of
people infected with Covid-19. Problems such as these can often
be avoided by finetuning antibodies, according to new research.


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FULL STORY ========================================================================== Antibodies are crucial, not only for treating tumors and
infections. Sometimes, however, the immune reaction they trigger can
be too strong and end up causing more damage, for example in the case
of people infected with Covid-19. Problems such as these can often be
avoided by finetuning antibodies, as Prof. Dr. Falk Nimmerjahn from Friedrich-Alexander-Universita"t Erlangen-Nu"rnberg (FAU) and two of
his colleagues in the Netherlands and in the UK have now reported in thejournal_Nature_Immunology.

In his laboratories, the FAU researcher is carrying out research into immunoglobulin G, or IgG in short, that provides long-lasting protection against infection in the bodies of humans and animals. These biomolecules
that are often used in modern medicine consist of two long and two short
chains of proteins that link together to form a Y-shaped structure. For
many years, research and medicine has focused on the two top branches of
this Y for good reason: the two ends form a type of pocket which smaller structures on the surface of bacteria and other pathogens fit into,
similarly to a key in a lock.

Key-lock principle in immune system Just like a locksmith can produce
very many different locks and the matching keys by only making a few
slight changes, the immune system also produces very many different
structures at the ends of immunoglobulins that match to very many
different pathogens. After an infection with a specific bacterium or
virus, these IgG created during the immune reaction remain on patrol
within the body for a very long time and can react extremely rapidly in
the case of a renewed infection.

If the key fits the lock, the immunoglobulin attaches to the pathogen
and marks it for other immune specialists within the immune system. The antibody serves to mark tumor cells or pathogens to make them stand
out from the huge quantities of cells and harmless microorganisms that circulate throughout the body and take on important functions in the
bodies of humans and animals.

Using genetic glue to fight bacteria Once this stage has been
successfully completed, this is when the backbone of the Y-shaped
IgG comes into play. It is this backbone that Falk Nimmerjahn is now investigating closely at his Chair of Genetics. Macrophages, killer
cells and granulocytes take over in the end phase of the battle against
an infection.

"We have often observed cells working as a team, with granulocytes
taking on a suicidal role;" Falk Nimmerjahn explains. Attracted by the
antibody that has found its target, these cells burst, releasing their relatively sticky genetic material from their core. The bacteria that
the IgG previously identified as being harmful stick to this matter.

These microorganisms can be extremely dangerous, but have now been
rendered helpless, and are easy prey for the macrophages that have also
been attracted and can now consume the bacteria that the antibodies
have tracked down and marked. However, the macrophages are often rather aggressive and act with little consideration of possible consequences. If
time is running out in the race between life and death, collateral damage
is accepted as being unavoidable, and substances such as oxygen radicals
and other dangerous products that would normally be rendered harmless are released. For most patients this is of no consequence: The main priority
is survival, any resulting damage should be able to be repaired later.

One of the factors modulating the immune reaction involves small posttranslational modifications that are made to the backbone of the immunoglobulin after the antibody has been created. This involves,
for example, little sugar molecules that are attached to the backbone
of the immunoglobulin.

They seem to play a crucial role in the finetuning of the immune
reaction. "If the right components are missing, it makes the immune
reaction much more severe," explains Falk Nimmerjahn.

That can, however, have fatal consequences, for example if a viral
infection has already severely damaged tissue. If the control mechanism
on the backbone of the immunoglobulin is adjusted to only attach a little
sugar and therefore induce a strong reaction, that may cause dangerously
severe damage to an organ that is already stretched to its limit, such as
the lung in the event of a viral infection. According to Falk Nimmerjahn,
"the organism therefore adjusts its control mechanisms very exactly." In
cases such as this, the control mechanisms are set to trigger a weak
reaction with many chains of sugar.

Gaining an exact knowledge of this antibody tuning within the context
of an immune response is fundamental if we are to improve and increase patients' tolerance of antibodies used to treat tumors and autoimmune
diseases.

* RELATED_TOPICS
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Materials provided by Friedrich-Alexander-Universita"t_Erlangen-Nu"rnberg.

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========================================================================== Journal Reference:
1. Falk Nimmerjahn, Gestur Vidarsson, Mark S. Cragg. Effect of
posttranslational modifications and subclass on IgG activity:
from immunity to immunotherapy. Nature Immunology, 2023; DOI:
10.1038/s41590- 023-01544-8 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/07/230714114736.htm

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