Autoantibodies in immune thrombocytopenia affect the physiological interaction between megakaryocytes and bone marrow extracellular matrix proteins.

GRODZIELSKI M; DI BUDUO C; GOETTE NP; LEV PR; SOPRANO P; HELLER PG; BALDUINI A; MARTA RF

Congreso; - LXII Reunión Anual de la Sociedad Argentina de Investigación Clínica. Reunión Conjunta de Sociedades de Biociencias.; 2017

Although autoantibodies from immune thrombocytopenia (ITP) interfere with megakaryocyte and platelet production, their effect on several aspects of megakaryocyte (MK) physiology has not been completely elucidated. After approval by the institutional Ethics Committees and written informed consent, blood samples from 14 ITP patients and controls were obtained and recalcified plasma, and IgG fractions, were prepared. Plasmatic autoantibodies were detected using PAKAUTO kit. Normal mature MKs were obtained after 13-day culture of human cord blood-derived CD34+ cells and incubated with recalcified plasma, or purified IgG, on type I collagen, fibrinogen and von Willebrand factor-coated surfaces to study different MK functions: MK adhesion by counting non-adhered cells, MK spreading by immunofluorecent staining with FITC-CD61, downstream signal activation of specific molecules by western blot and proplatelet formation by direct count on an inverted microscope. Data were analysed by Mann-Whitney test or, when the number of patients? samples were too small, individual values were compared to the normal range. All parameters evaluated were significantly affected in the presence of ITP plasmas bearing specific autoantibodies against the megakaryocytic glycoproteic (GP) receptors for type I collagen, fibrinogen and von Willebrand factor: GPIaIIa, GPIIbIIIa and GPIbIX, respectively. Purified IgG fractions reproduced the effect observed in the presence of plasma samples. Our results demonstrate that autoantibodies block the physiological interaction between MKs and these extracellular matrix proteins, and suggest they could alter normal MK functions within the bone marrow microenvironment, contributing to thrombocytopenia in ITP