Pediatric ITP patient plasma has increased IgG antibodies against the TF antigen. (A) O-glycan Core 1 synthesis pathway. ST3Gal1 mediates sialylation and capping of the TF antigen. (B) Principal component analysis plot of IgG antibodies binding to a 95-member O-glycan array differentiating healthy plasma (lime green circles) from pediatric ITP plasma (green triangles). (C) Heat map of O-glycans that significantly contribute to separation of IgG antibody-O-glycan binding from healthy (lime green) vs pediatric (green) ITP plasma. (D) Data in panel B shown from decreasing to increasing fold change of normalized binding fluorescence intensity in ITP patient plasma. TF antigen and its sialylated form are noted as a red bar. (E) Structures of O-glycans that significantly contribute to differentiating healthy vs pediatric ITP plasma. TF-antigen (O-5) and its sialylated form (O7) is highlighted in the red box. (F) IgG antibody binding in pediatric patients with ITP to desialylated (O-5) and sialylated (-O-7) Core 1 structure (TF antigen). (F) For comparison of the 2 groups, moderated Student t tests were used to compare healthy vs ITP, and P values were adjusted by using the Benjamini-Hochberg method. *P < 0.05, **P < .01.