Anticuerpos antifosfolípidos y proteína Z / Antiphospholipid antibodies and Z protein

La proteína Z (PZ) constituye una proteína plasmática, vitamina K dependiente. Se une a trombina, promoviendo la unión de ésta a las vesículas fosfolipídicas, uniéndose además por sí misma a estas superficies en presencia de calcio. Medimos la concentración de PZ plasmática, en pacientes con anticuerpos antifosfolipídicos (aFL). Se estudiaron 53 pacientes con aFL, a 33 de ellos se les dosificó, además de la PZ, anticuerpos antiprotrombina (anti-II) y antibeta 2 glicoproteína 1 (aß2GP1). El grupo testigo estaba constituido por 36 sujetos normales. Los pacientes con aFL, presentaron niveles disminuidos de PZ, con una significancia estadística de p < 0.0001. Los niveles de PZ se encontraron disminuidos, independientemente de la presencia o ausencia de anti-II o antibeta 2 glicoproteína 1. Concluimos que los pacientes con aFL presentan niveles plasmáticos de PZ reducidos, sin relacionarse con la especificidad antigénica de los anticuerpos antifosfolipídicos. Es aún desconocido si esta alteración puede deberse a una acelerada depuración de la proteína, a inhibición de su síntesis o a la presencia de anticuerpos específicos anti-PZ

Anticuerpos anti-beta, glicoproteína I y niveles plasmáticos de la proteína de unión a C4b / Antibodies against beta glycoprotein I and C4b binding protein plasmatic levels

Autoantibodies directed to beta2 glycoprotein I (a beta 2 GPI) are frequently found in patients with antiphospholipid antibodies (aPL). They are more strongly associated with clinical manifestations of the antiphospholipid syndrome then a PL. It has been shown that beta2 GPI and C4b bibding protein (C4bBP) share certain homology. In a previous study we have shown that anticardiolipin antibodies were associated with a plasma decrease of C4bBP. The aim of the present study was to evaluate in 131 patients with a PL whether the decrease in C4bBP is related to the presence of abeta2 GPI. Lower C4bBP levels (mean +- SD) in the group of patients having abeta2 GPI (n=57) were observed when compared with the normal group (n=44), (74.3 porciento +-28.1 vs 94.6 porciento +-20.9,p<0.005).This difference was more significant consideing the IgG isotype. The group of patients with positive abeta2GPI-igG (n=41) had lower values of C4bBP (70.1 porciento +- 26.8) than both the normal group (p<0.005) and the group of patients with negative abeta2 IgG (n=90, 86.0 porciento +- 30.5 porciento, p<0.05). C4bBP deficiency (level <70 porciento) was also morefrequent in the group abeta 2GPI-IgG (+) (63.4 porciento) then in the group abeta2GPI-IgG 8-) (34.4 porciento, p<0.005). Moreover, patients with a PL and previews venous thrombosis (n=32) showed lower C4bBP values (75.1 porciento +- 27.9) compared with the normal group (p<0.05). As this time, the mechanisms responsibles for the C4bBP decrease are not known. Our findings on the close relationship between abnormalitiesin the C4bBP/protein S system and the presence of abeta2GPI could explain the major thrombotic risk in patients havingthese autoantibodies