s36_ab6

Antineutrophil cytoplasmic autoantibodies penetrate into human polymorphonuclear leukocytes and modify their apoptosis

M. Deutsch¹, L. Guejes¹, N. Zurgil¹, O. Shovman², B. Gilburd², E. Afrimzon¹, Y. Shoenfeld

¹The Biophysical Interdisciplinary Jerome Schottenstein Center for the Research and the Technology of the Cellome, Department of Physics, Bar-Ilan University, Bar-Ilan; ² Department of Medicine B and the Research Unit of Autoimmune Diseases, Sheba Medical Center, Tel Hashomer, Israel

ABSTRACT
Objective
The interaction of extracellular anti-neutrophil cytoplasmic autoanti-bodies (ANCA) with neutrophilic granules may play an important role in the pathogenesis of ANCA-related disorders. It has been confirmed that apoptosis is an essential trigger associated with translocation of the cytoplasmic granules to the cell surface, and with the expression of ANCA antigens. Since cell penetration by autoantibodies and apoptosis may be associated processes, we tested the hypothesis that penetration of ANCA-autoantibodies into polymor-phonuclear leukocytes (PMNs) has an effect on apoptosis and thereby can influence surface antigen expression.

Methods
PMNs were isolated from the blood of healthy volunteers and incubated in the presence of anti-proteinase3 (PR3) enriched IgG or normal human IgG. For each period of incuba-tion (40 minutes or 12 hours) we evaluated: 1) PMN morphology by light microscopy (LM) and transmission electron microscopy (TEM) for general estimation of the apoptotic process, and 2) ANCA binding to the target antigen by immunogold electron microscopy (IgEM).

Results
Both normal and anti-PR3 IgG penetrate PMNs. The labeled PR3-ANCA were localized on PR3 granules, regardless of the granules' location within the cell, and in the sites where the PMN destruction processes were most expressed. The destructive processes showed extensive apoptotic char-acteristics, in contrast to PMNs pene-trated by normal IgG.

Conclusion
PR3 ANCA penetrate PMNs and, via the interaction between PR3-ANCA and PR3-containing granule components, initiate a modification of the apoptotic process.

Key words
Anti-neutrophil cytoplasmic autoantibodies (ANCA); polymorphonuclear leukocytes (PMN); apoptosis; anti-proteinase3 (PR3) IgG; normal human IgG.

Please address correspondence to: Prof. Yehuda Shoenfeld, MD, Department of Medicine "B" & the Research Unit of Autoimmune Diseases, Chaim Sheba Medical Center, (affiliated with Tel-Aviv University), Tel-Hashomer 52621, Israel.
E-mail: shoenfel@post.tau.ac.il
or
rtcellom@mail.biu.ac.il