Unraveling the immunopathogenesis of pemphigus with new research approaches: in-depth analysis of systemic and local T cell responses
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Philipps-Universität Marburg
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Abstract
The immune system functions as a sophisticated collaboration between the innate and
adaptive immunity capable of distinguishing self from non-self. A pivotal role in
governing adaptive immune responses is attributed to CD4+ T cells. With specificity for
a particular antigen, they facilitate the establishment of protective immunity targeted at
specific pathogens, but their actions can also inadvertently give rise to autoimmunity. One
such example is pemphigus, a rare autoimmune disease affecting skin and mucous
membranes. Pemphigus manifests as blister formations and erosions and is characterized
by the loss of immune tolerance to desmosomal cadherins, particularly desmoglein
(Dsg)1 and Dsg3. Autoreactive T cells provide help to B cells and thus play a central role
in driving the production of pathogenic IgG autoantibodies against these cadherins.
However, due to their low frequencies, detection of autoreactive T cells in pemphigus has
been challenging. Traditional methods like tritiated thymidine incorporation (3H-TdR) or
enzyme-linked immunospot (ELISpot) analysis have inherent limitations, including the
inability to distinguish specific cell populations or the need for an ab initio presumption
of the significance of certain cytokines. Newer experimental approaches, focused on
direct characterization and quantification of these T cells, are based on flow cytometry.
Some make use of MHC multimers others of surface activation markers. We aimed at
establishing a method of detecting autoreactive CD4+ T cells utilizing the transient
upregulation of CD154 (CD40L) upon stimulation with relevant antigens or
immunodominant epitopes, respectively. The CD154-method of antigen-specific T cell
detection is sensitive, time-efficient, and withal allows for specific phenotypic and
functional characterization of T cells when using a comprehensive panel of
immunological parameters. Herewith, we analyzed Dsg3-specific CD4+CD154+ T cells
from peripheral blood of patients with pemphigus vulgaris (PV) in comparison to healthy
control (HC), where the expression of CD154 on ex vivo expanded CD4+ T cells
positively correlated with Dsg3 titers in pemphigus patients. We could show clonal
expansion of CD4+CD154+ T cells in response to both, the full protein Dsg3 as well as
to various epitope-specific peptides, with P2 (extracellular domain 2 of Dsg3) appearing
to be particularly immunomodulatory in PV patients. Moreover, upregulation of IL-17
and IL-21 was seen to associate with antigen-specific activation in active stages of the
disease, further supporting the concept that immune activity in PV relies, at least partially,
on Dsg3-reactive Th17/Tfh17 cell subsets. Contrary to foregoing belief that in pemphigus
the subtype of T cells responsible for supporting autoreactive B cells is IL-4- and IL-5-producing Th2 cells. With newly discovered T cell populations such as Th9 cells, Th22
cells and many others, the inherent complexity of the pathomechanisms of pemphigus
will likely become even more evident, with different subsets presumably dominating at
different stages of the disease contributing to the complex interplay of immune
dysregulation in pemphigus.
Pemphigus is an autoimmune disease mediated by systemic immune responses, however,
the inflammation is localized in the peripheral effector tissues, namely mucosa and the
skin. More and more studies shed light on the importance of local tissue-resident
immunity in pemphigus. Yet, owing to hampered peripheral tissues’ accessibility and
difficulty in extracting the resident lymphocytes, blood remains a major source of
research material. Hence, we aimed at establishing a rapid easy-to-use protocol to isolate
a sufficient number of viable immune cells from small skin biopsies that can be directly
used for a deeper characterization such as comprehensive phenotyping and functional
studies of T cells. Since it is not yet clear what role local immunity plays in the disease's
pathogenesis and how important the balance among different T cell subsets in pemphigus
is, the need for further research to unravel its complexities is inherent. These newly
established methods, CD154 for detection of Dsg-reactive T cells and rapid isolation of
lymphocytes from skin and mucosa, aid to expedite the process and allow for closer
inspection of pemphigus’ pathogenesis. Moreover, the presented comprehensive
immunophenotyping of PV patients underlines the significance of Th17/Tfh17 cells, T
cell dysregulation, enhanced B cell activation, and elevated pro-inflammatory cytokines,
which collectively contribute to the autoimmune response observed in pemphigus. Thus,
these new findings not only provide deeper insights into the pathomechanism but may
also reveal improved treatment options for pemphigus patients in the future.
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Dates
Created: 2025Issued: 2025-08-06Updated: 2025-08-06
Faculty
Medizin
Publisher
Philipps-Universität Marburg
Language
eng
Data types
DoctoralThesis
Keywords
PemphigusHautB-ZellepemphigusT cellbloodBlutB cellskinT-Zelle
DDC-Numbers
610
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Alexandra Polakova (0000-0002-4792-9306): Unraveling the immunopathogenesis of pemphigus with new research approaches: in-depth analysis of systemic and local T cell responses. : Philipps-Universität Marburg 2025-08-06. DOI: https://doi.org/10.17192/z2025.0328.