ab21317

Specificity of antinuclear and antiphospholipid antibodies in sera of patients with autoimmune lymphoproliferative disease (ALD)

V. Pittoni, M. Sorice¹, A. Circella¹, R. Cangemi, L. Conti², U. Ramenghi³, G.M. Gandolfo², U. Dianzani⁴, G. Valesini

Dipartimento di Clinica e Terapia Medica Applicata, Cattedra di Reumatologia, ¹Dipartimento di Medicina Sperimentale e Patologia, and ²Servizio di Patologia Clinica, Istituto Regina Elena, Universitá di Roma "La Sapienza", Rome; ³Dipartimento di Scienze Pediatriche e dellÕAdolescenza and ⁴Dipartimento di Scienze Mediche, Universitá del Piemonte Orientale Novara, Italy.

ABSTRACT
Objective
A human lymphoproliferative syndrome characterized by a defect of the Fas-mediated apoptosis pathway in the absence of a fas gene mutation (Autoimmune Lymphoproliferative Disease) has recently been described and characterized by autoimmune phenomena. The aim of this study was to investigate the presence of antinuclear and antiphospholipid antibodies and to define their specificity in 5 pediatric patients with this syndrome.

Methods
Antinuclear antibodies were investigated by Western Blot and IIF performed under standard as well as apoptotic conditions. The fine specificity of antiphospholipid antibodies was dissected by an ELISA for anti-b2-glycoprotein I, anti-prothrombin, anti-annexin V and anti-protein S antibodies, and by immunostaining on thin layer chromato-graphy plates for antiphospholipid molecule antibodies.

Results
This study showed that the autoantibodies found in these patients targeted a broad spectrum of nuclear antigens which undergo redistribution from the nucleus to the cytoplasm and plasma membrane during the course of the apoptotic process. This reactivity does not comprise known specificities such as anti-extractable nuclear antigens or anti-dsDNA. Antiphospholipid antibodies were also found in these sera. A further characterization of the antiphospholipid antibodies showed the presence of a heterogeneous response with antibodies directed to negatively-charged phospholipids and antibodies targeting coagulation-related proteins (b2-GPI, prothrombin, annexin V) which are considered relevant antigens in the antiphospholipid syndrome.

Conclusions
These results suggest that lack of tolerance due to a defect of Fas-mediated apoptosis allows the survival of B and T clones involved in the antinuclear and antiphospholipid immune responses.

Key words
Fas, apoptosis, autoimmune lymphoproliferative syndrome, antiphospholipid antibodies, antinuclear antibodies.

This study was supported by Telethon, Project w.E. 1170; FISM (Federazione Italiana Sclerosi Multiple).
Please address correspondence and reprint requests to: Prof. Guido Valesini, Cattedra di Reumatologia, Policlinico Umberto I, V.le del Policlinico 155, 00161 Rome, Italy. E-mail: guido.valesini@uniroma1.it