Dissecting the mechanism underlying T cell receptor-mediated intercellular transfer of peptide-Major Histocompatibility complexes

Abstract: Cell surface molecules have been observed to pass from one cell to another as part of their
interaction. This phenomenon, known as trogocytosis, has been observed in many cell types,
particularly in the immune system. One receptor that is fundamental to the body`s defence
against many pathogens is the expressed polymorphic T cell receptor (TCR), which interacts
with major histocompatibility complex molecules loaded with antigenic peptides (pMHC). While
TCR-mediated trogocytosis of MHC complexes has been described in a number of publica-
tions, the underlying mechanisms as well as the fate of the acquired pMHC molecules remain
unclear. The aim of this thesis is to gain a better understanding of TCR-mediated trogocytosis
of pMHC.
The transfer of pMHC from donor to recipient cells was quantified by flow cytometry using both
fluorescent proteins covalently linked to the intracellular domain of pMHC and fluorescent an-
tibodies. We demonstrated that TCR-mediated trogocytosis of pMHC occurs across a species
barrier, as murine 58ab OT-1 T cells were able to acquire corresponding murine pMHC from
Chinese hamster ovary cells. This limited trogocytosis to one type of receptor-ligand interaction
and improved the reliability of our experimental system.
In the first part, we investigated the role of pMHC-TCR affinity on the efficacy of trogocytosis.
By generating a library of cell lines expressing pMHC with different LCMV gp33 peptides, we
were able to show a positive correlation between TCR-pMHC affinity and the efficiency of tro-
gocytosis.
In the second part, we investigated whether TCR-mediated trogocytosis depends on this TCR
signalling function or occurs independently. TCR-mediated pMHC trogocytosis was unaffected
by blocking TCR signalling with the Src kinase inhibitors PP2 or A77. Furthermore, efficient
trogocytosis could be achieved by cell lines expressing variants of CD3e, namely C80G and
K76T, which have been reported to block TCR signalling. Taken together, our data suggest
that TCR-mediated trogocytosis of pMHCs is independent of TCR signalling.
Lastly, we analysed the fate determinants of trogocytosed pMHC. The generation of pMHC as
single chain trimers with non-cleavable linkers increased the surface expression of acquired
pMHC compared to pMHC constructs with cleavable linkers. Trogocytosis of pMHC is known
to involve internalization of TCR-pMHC into intracellular vesicles, exposing this association to
the environment within the vesicles. As we have shown that non-cleavable linkers increase the
susceptibility of pMHC to acidification and proteases, we hypothesise, that this facilitates dis-
sociation of TCR and pMHC, leading to recycling of the pMHC

Object Details

• Location: Deutsche Nationalbibliothek Frankfurt am Main
• Extent: Online-Ressource
• Language: Englisch
• Notes: Universität Freiburg, Dissertation, 2025

Contributors, Places and Time

• Event: Veröffentlichung
• (where): Freiburg
• (who): Universität
• (when): 2025
• Creator: Zink, Alicia
• Contributor: Ehl, Stephan ; Rohr, Jan ; Hufnagel, Markus ; Albert-Ludwigs-Universität Freiburg. Medizinische Fakultät

Further information

• DOI: 10.6094/UNIFR/262844
• URN: urn:nbn:de:bsz:25-freidok-2628449
• Rights: Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Last update: 15.08.2025, 7:27 AM CEST