The British Journal of Rheumatology, Vol 36, 1038-1044, Copyright © 1997 by British Society for Rheumatology
TC Hsu, TL Lee and GJ Tsay
Previously, we have demonstrated that ectocytosis, a unique cell
trafficking process to export a specific subset of cellular proteins in the
form of membrane vesicles, can be triggered from human skin fibroblasts
cultured in a three-dimensional collagen lattice upon stress relaxation.
The same culturing system was employed in the present study using
fibroblasts isolated from patients with systemic sclerosis (SSc). To see
whether any putative intracellular autoantigens causing SSc might escape
out of cells by way of ectocytosis, the same stress-relaxation method was
used to induce a synchronized ectocytosis among cultured cells. Membrane
vesicles released by scleroderma fibroblasts were subsequently isolated,
resolved on SDS-PAGE and immunoblotted with sera from 89 patients with
various autoimmune diseases and 11 normal volunteers. Three major
polypeptides with apparent mol. wts of 12-14, 32-34 and 70-80 kDa are
prominent bands on both SDS-PAGE and immunoblots. The 32-34 kDa polypeptide
has been further identified as a member of the annexin protein family,
while the 70-80 kDa protein has been shown to be topoisomerase I, as judged
by its reactivity to patients' sera and a rabbit polyclonal antibody, and
as also judged by a functional assay. In conclusion, our results suggest
that ectocytosis might be one of the potential pathways for cells to export
intracellular antigens and subsequently cause autoimmune reactions.
ORIGINAL PAPERS
Autoantigen components recognizable by scleroderma sera are exported via ectocytosis of fibroblasts
Department of Medicine, Chung Shan Medical and Dental College, Taichung, Taiwan.
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