title: Platelet pro-aggregatory effects of CD40L monoclonal antibody.
abstract: An unexpected high incidence of thromboembolic complications has been described in patients with systemic autoimmune diseases treated with CD40L immunotherapy. Since activated platelets express CD40L, we aimed to investigate the effects of CD40L mAb in platelet aggregation induced by physiological stimuli. Optical aggregometry was performed on platelet-rich plasma and washed platelets obtained from systemic venous blood (0.38% citrate) of anesthetized pigs. CD40L mAb clone 5c8, used in clinical trials for autoimmune diseases, was used. In platelet-rich plasma, CD40L mAb neither induced platelet aggregation per se, nor significantly affected maximal aggregation or slope of ADP-induced aggregation curves. However, it dose-dependently inhibited spontaneous deaggregation observed in ADP-stimulated samples. This effect was not observed with an irrelevant isotype-matched immunoglobulin. The stabilizing effect on platelet aggregates was neither glycoprotein IIb/IIIa-mediated nor Ca2+-dependent but was abolished by acetylsalicylic acid pretreatment. F(ab')2 fragments did not stabilize ADP-induced platelet aggregates but inhibited the stabilizing effect of CD40L mAb. Similar results were obtained with washed platelets, although higher amplification of ADP-induced aggregation was observed. In conclusion, CD40L expression produced by physiological or pathophysiological platelet activation can sustain a pro-aggregatory effect of CD40L mAb by a mechanism involving mAb Fc domain. These results could help to explain the mechanism of CD40L mAb-induced thromboembolic complications.
authors.affiliation: Servei de Cardiologia, Hospital Universitari Vall d'Hebron, Pg. Vall d'Hebron 119-129, 08035 Barcelona, Spain.
authors.forename: Maribel
authors.initials: M
authors.lastname: Mirabet
authors.forename: José A
authors.initials: JA
authors.lastname: Barrabés
authors.forename: Adoración
authors.initials: A
authors.lastname: Quiroga
authors.forename: David
authors.initials: D
authors.lastname: Garcia-Dorado
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D001241:Aspirin / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects* / Q000502:physiology; D019013:CD40 Antigens / Q000276:immunology*; D023201:CD40 Ligand / Q000096:biosynthesis / Q000276:immunology*; D002118:Calcium / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000494:pharmacology; D066298:In Vitro Techniques; D010974:Platelet Aggregation / Q000187:drug effects*; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000037:antagonists & inhibitors; D013552:Swine; D013928:Thromboxane A2 / Q000096:biosynthesis
chemical_list: D000911:Antibodies, Monoclonal; D019013:CD40 Antigens; D002614:Chelating Agents; D007140:Immunoglobulin Fab Fragments; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D023201:CD40 Ligand; D013928:Thromboxane A2; D000244:Adenosine Diphosphate; D001241:Aspirin; D002118:Calcium