Influence of FcγRIIA H131R polymorphism on platelet activation induced by HIT antibodies. (A) Serotonin release assay performed with washed platelets from FcγRIIA 131HH (n = 5) and 131RR donors (n = 5) incubated with HIT plasma sample containing a high titer of activating PF4-specific antibodies (A405nm = 2.7 in enzyme-linked immunosorbent assay), and different concentrations of unfractionated heparin. (B-D) Lag times measured with PRP and washed platelets (WP) from 70 healthy donors according to FcγRIIA H131R genotype (RR: n = 15; HR: n = 32; HH: n = 23). The median values are indicated as solid lines. Aggregation tests were performed with unfractionated heparin (0.5 IU/mL). HIT plasma was tested using the serotonin release assay as described above (B), 5B9 was tested at 18 μg/mL (C), and collagen was tested at 0.5 μg/mL (D). The Mann-Whitney U test was performed to compare lag times in relation to FcγRIIA H131R polymorphism; P values are displayed.
