Aquaporin-4 water channel expression by thymoma of patients with and without myasthenia gravis

Chan, K.H.; Kwan, J.S.C.; Ho, P.W.L.; Ho, S.L.; Chui, W.H.; Chu, A.C.Y.; Ho, J.W.M.; Zhang, W.Y.; Kung, M.H.W.

doi:10.1016/j.jneuroim.2010.07.016

« Previous Next »Journal of Neuroimmunology
Volume 227, Issue 1 , Pages 178-184, 8 October 2010

Aquaporin-4 water channel expression by thymoma of patients with and without myasthenia gravis

K.H. Chan
- University Department of Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong
- Neuroimmunology and Neuroinflammation Research Laboratory, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong
- Research Center of Heart, Brain, Hormone and Healthy Aging, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong
- Corresponding author. Department of Medicine, 4/F Professorial Block, Queen Mary Hospital, 102 Pokfulam Road, Hong Kong. Tel.: +852 2855 3315; fax: +852 507 2974 1171.
J.S.C. Kwan
- University Department of Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong
- Neuroimmunology and Neuroinflammation Research Laboratory, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong
P.W.L. Ho
- University Department of Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong
- Research Center of Heart, Brain, Hormone and Healthy Aging, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong
S.L. Ho
- University Department of Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong
- Research Center of Heart, Brain, Hormone and Healthy Aging, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong
W.H. Chui
- University Department of Surgery, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong
A.C.Y. Chu
- University Department of Surgery, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong
J.W.M. Ho
- University Department of Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong
W.Y. Zhang
- University Department of Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong
M.H.W. Kung
- University Department of Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong

Received 16 April 2010; received in revised form 17 May 2010; accepted 19 July 2010. published online 23 August 2010.

Abstract

Background

Neuromyelitis optica (NMO) is a serious idiopathic inflammatory demyelinating disorder characterized by acute transverse myelitis and optic neuritis. A significant proportion of NMO patients are seropositive for NMO-IgG, an autoantibody targeting aquaporin-4 (AQP4) water channel. Paraneoplastic NMO associated various tumors were recently reported.

Aim

We studied the expression of AQP4 by thymoma from patients with and without myasthenia gravis (MG).

Methods

Thymoma obtained from thymomectomy in patients with and without MG were studied by immunohistochemistry and western blot.

Results

Ten thymoma patients (9 with MG) and two control patients without thymoma or MG were studied. Immunohistochemistry revealed AQP4 immunoreactivity in cell membrane of thymoma cells from all ten thymoma specimens whereas thymic tissues from patients without thymoma or MG were negative for AQP4 immunoreactivity. Western blot revealed that lysates of nine of the ten thymoma specimens reacted with anti-human AQP4 antibody with a band of ~30kDa compatible with the molecular weight of AQP4. Interestingly, immunofluorescence revealed that IgG isolated from 2 NMO patients seropositive for NMO-IgG bound to cell membrane of thymoma cells from all ten thymoma specimens while IgG from healthy control subject did not.

Conclusion

Thymoma cells of patients with and without MG express AQP4. AQP4 autoantibodies from serum of NMO patients bound to AQP4 expressed on thymoma cell membrane.

Keywords: Neuromyelitis optica, Aquaporin-4 water channel, Aquaporin-4 autoantibodies, Thymoma, Myasthenia gravis, Paraneoplastic neurological disorders