Individual seroconversion profiles from 6 representative patients, 3 with HIT and 3 exhibiting seroconversion without HIT, shown in relation to the platelet count profile. For the 3 patients with HIT, the profiles shown include (A) isolated IgG response (red), (B) predominant IgA (green) with IgG response, and (C) predominant IgG with IgA immune responses. For the 3 antibody-positive patients without HIT, the profiles shown include (D) predominant IgG with IgA immune response, (E) predominant IgA with IgG and IgM (blue) responses, and (F) predominant IgM with IgA response. “Predominant” immunoglobulin responses refers only to relative OD values and should not be taken to infer differences in relative concentrations of antibodies. For patients A, B, and C, the asterisks (*) designate the beginning of the platelet count decline indicating HIT. DVT indicates deep vein thrombosis; and PE, pulmonary embolism.