Skin B cells in the progression from cutaneous lupus to systemic lupus

In this study we aim to identify the immunological mechanisms underlying the
break of tolerance checkpoints in Systemic Lupus Erythematosus (SLE).
Autoimmune diseases are characterized by dysfunction of the immune system in
which an immune response is mounted against ones* own tissue causing disease.
Many autoimmune diseases are autoantibody-mediated, meaning that antibodies
cause tissue inflammation and damage.1 Antibodies are produced by plasma cells,
the terminal differentiation stage of B cells. Systemic lupus erythematosus
(SLE) is a prototypical autoimmune disease in which autoantibodies cause
systemic inflammation and damage.
In healthy individuals, production of autoantibodies is prevented in a process
called immune tolerance. Tolerance in B cells consists of several checkpoints
throughout B cell development. A tolerance checkpoint is defined as the stage
in B cell development where a block in maturation occurs. Though the tolerance
checkpoints in early B cell development have been quite well-characterized, the
checkpoints after B cell activation are not yet defined and understood, though
they are crucial in prevention of autoimmune diseases.
Although developments in recent years have led to identification of B cell
activation pathways with increased activity in SLE, how and where tolerance is
broken in SLE is not well understood, due to a lack of access to an early or
pre-disease state.
In this study, we propose to take a novel approach by determining the
transition of cutaneous lupus erythematosus (CLE) to systemic disease (SLE).
CLE is a skin disorder that can occur as isolated disease limited to the skin.
However, depending on the subtype of CLE, up to 40% of CLE patients progress to
SLE, and thus can be used as a unique approach to study the development of
systemic autoimmunity.
We hypothesize that the skin is an initial site where B cell checkpoints are
broken, but still locally confined in CLE. Maturation of the immune response in
the skin can ultimately lead to systemic disease (SLE).

In this proposal, we therefore aim to characterize in detail the cutaneous B
cell response in patients with isolated CLE (CLE only) and patients with
systemic and cutaneous disease (SLE/CLE).
Primary Objectives:
1. Characterize autoreactive B cells in CLE and SLE
2. Identify mechanisms for B cell tolerance breakthrough and plasma cell
differentiation in transition of CLE to SLE

This is an interventional, cross-sectional, single center study in which
biomaterial (sera, plasma, PBMCs, skin biopsies) will be collected from the
patients at a single timepoint.

In this study biopsies and a blood sample will be obtained combined with a
routine visit to our clinic. Isolated immune cells will be analysed using
spectral flow cytometry, in vitro cultures, and single cell RNA sequencing to
construct a comprehensive overview of molecular alterations of B cells from SLE
and CLE patients.

Peripheral blood will be drawn from 25 patients with isolated CLE and 25
patients with combined CLE/SLE.
Four skin biopsies will be collected of these patients: (2 x 4 mm) unaffected
skin and (2 x 4 mm) affected skin for both groups (25 in each group).

Two four mm skin biopsies will be obtained from lesional skin and non-lesional
skin at a routine visit to the clinic. There are no high risks to be expected
with this approach. There is only a (very low) risk (<5%) of a wound infection
after biopsy. No direct benefit from participation is expected for this study.