Target Molecules and their Respective Pathogenic and Protective Antibodies in Myasthenia Gravis.

Antibodies are becoming increasingly important agents both as a diagnostic tool
as well as therapeutic agents for human diseases. There is accumulating
evidence that autoreactive antibodies play key roles in neurodegenerative
diseases such as multiple sclerosis, Alzheimer*s disease, schizophrenia and
Parkinson*s Disease. However, so far these antibodies have only been poorly
characterised and in many diseases the autoantigens remain unknown. Presently,
myasthenia gravis (MG) is the best characterised antibody mediated disease and
we have cloned and produced one of the few recombinant human autoantibodies. A
technique published by Traggiai et al. in 2004 now tremendously simplifies
human B-cell cloning, therefore facilitating a broad range of new applications.

The aim of this study is to develop an immortalised B-cell line derived from MG
patients.
This antibody producing cell line will be used for different applications:
- The establishment of new passive transfer disease models for MG
- The identification of new autoantigens
- The development of neuroprotective antibodies

The goal of this study is to produce 6 B-cell producing cell lines which will
be used for the applications as described above in objectives. To reach this
goal we need 2 groups of donors of human material.
The first group of tissue donors consists of 30 MG patients undergoing a
thymectomy (robot-thymectomy with the Da Vinci robot according to standard
procedures). These patients will be asked to donate a part of the removed
thymus gland (2.5 x 2.5 cm), a muscle biopsy of an intercostal muscle (0,5 x
0,5 cm; taken during the operation) and blood (two tubes of 10 ml; collected
during the operation). From the thymus tissue B-cells will be isolated for
creating an immortalised cell line that will be used for the development of
neuroprotective antibodies. The muscle biopsies will be used to study the
disease specific changes at the neuromuscular endplate and to study the binding
of pathogenic antibodies to affected muscle tissue. The blood will be used for
isolation of lymphocytes, which will be studied and used for co-culturing
together with the isolated B-cells.
The second group of tissue donors consists of 30 control patients undergoing
another type of thoracic operation with the Da Vinci robot for a disorder that
is not related to MG, another autoimmune disease, or another disease affecting
the muscles, and will not get a thymectomy. These patients will be asked to
donate a muscle biopsy only. The muscle biopsy (0,5 x 0,5 cm of an intercostal
muscle) will be taken during the operation and will be used to study the
neuromuscular endplate of unaffected muscle tissue, the binding of pathogenic
antibodies to unaffected muscle tissue, to identify new autoantigens, and to
verify that eventually newly developed neuroprotective antibodies do not bind
to muscle tissue.

The thymectomy in MG patients is part of their regular treatment and will be
beneficial to them. Using the wasted material for this study will not change
the burden nor the risk for these patients.
Taking muscle biopsies (5 by 5 mm) from patients during an operation will
result in a negligible risk with minimal burden. The biopsy will be taken at
the place where, as part of the standard operation, a troquart (with a diameter
of 12 mm) is inserted in the intercostal space. An incision of the skin and
intercostal muscle is already made as part of the operation, so no extra
incision is made for the biopsy. As this is an open biopsy the risk is
negligible. Any eventual bleeding can be treated immediately.
As the blood sample of 20 ml will be taken from the venflon that is already in
place during the operation, the risk and burden are negligible.
The patients will not benefit from participating in this study.