Characterizing sites 1 and 2 using HIT sera.

(A) ELISA studies with wildtype PF4 (), NHHH (⋄), and HP34RHHH (■) complexed to heparin for 14 HIT serum samples. Insert shows the comparative binding of the 14 HIT sera to the 2 mutant proteins demonstrating high correlation. (B) ELISA studies with wildtype PF4 NHHH and HHT38QHH complexed to heparin of 41 HIT sera. For each HIT serum, reactivity with NHHH and with HHThr38GlnHH was normalized for binding to wildtype PF4 complexed to heparin. Reactivity of less than 50% compared with wildtype PF4 is shown in the gray area; the white boxed area shows the samples with less than 50% antigenicity for both the site 1 and site 2 mutations.