Human IgG1 (B-cell receptor) Fc peptide glycan analysis, LC-MS

Since few data are available on glycans expressed by human BCRs, we aimed to analyze the Fc glycans of membrane-bound IgG after BCR capture and tryptic digestion by LC-MS. For this purpose, human B-cell lines from Burkitt Lymphoma (Ramos) expressing IgG1-BCRs in the presence or absence of Fc glycans (FcG) were analyzed. The B-cell lines were generated by transduction of the BCR-negative MDL-AID KO cell line with N(297) or mutant Q(297) IgG-BCRs. The BCR sequences used were derived from single-cell sorted human B cells isolated from patients with the autoimmune disease rheumatoid arthritis. Two BCRs were directed towards citrullinated antigens (2G9 and 3F3), while a third BCR was directed against tetanus toxoid (D2). In addition, we analyzed the Fc glycan profile of IgG secreted (sIgG) by human Ramos B cells for comparison.