J. Arvieux et al., DEVELOPMENT OF AN ELISA FOR AUTOANTIBODIES TO PROTHROMBIN SHOWING THEIR PREVALENCE IN PATIENTS WITH LUPUS ANTICOAGULANTS, Thrombosis and haemostasis, 74(4), 1995, pp. 1120-1125
Some lupus anticoagulants (LA) have been shown to be directed against
phospholipid-bound prothrombin. While developing an ELISA to detect an
ti-prothrombin autoantibodies in patient serum or plasma, no or very l
ow signal was observed using human prothrombin immobilized on plain po
lystyrene plates. In contrast, the same LA-positive samples bound spec
ifically to prothrombin coated on gamma-irradiated plates, depending o
n the radiation dose, in the absence of added calcium and phospholipid
. Optimization of the assay required the addition of 0.1% Tween 20 to
the buffers. Antibody specificity for immobilized prothrombin was asce
rtained by competition using liposome-bound prothrombin, since fluid-p
hase prothrombin competed poorly. Seventy-seven of 139 patients (55.4%
) with LA related to a variety of underlying diseases possessed anti-p
rothrombin antibodies (27 IgG, 35 IgM and 15 both isotypes), either is
olated or more often associated with anti-beta(2) glycoprotein I (beta
(2)GPI) antibodies. These included 67-71% of the patients with systemi
c lupus erythematosus and related disorders, primary antiphospholipid
antibody syndrome or drug-induced LA (autoimmune groups), but only 19-
20% of those with infection or malignancy (p <0.001). As previously sh
own for anti beta(2)GPI antibodies, IgG(2) was the predominant IgG sub
class reactive with prothrombin. Thus, autoimmune patients with LA. ha
ve a high incidence of antibodies to beta(2)GPI and prothrombin, the b
inding of which could similarly require high antigen density and/or ex
posure of cryptic epitopes resulting from protein interaction with an
irradiated (i. e. more anionic) polystyrene surface.