Germinal center-associated N-glycan remodeling correlates with reduced recombinant CD22 binding in human B cells.

CD22 (Siglec-2) is a key regulator of B-cell receptor (BCR) signaling during affinity maturation in the germinal center (GC) by setting the BCR signaling threshold, yet its candidate ligands on B cells and their dynamics during the light zone-dark zone (LZ-DZ) transition remain unclear. Here, we combined liquid chromatography-electrospray ionization mass spectrometry N-glycomics with recombinant CD22 (rCD22) pulldown and cell-surface binding assays in human tonsil B-cell subsets. rCD22 pulldown enriched α2,6-sialylated bisected and non-bisected N-glycan compositions, identifying these as candidate rCD22-binding glycan compositions under the pulldown conditions. Bisected sialylated N-glycan compositions increased approximately twofold in GC B cells compared with naïve B cells. In parallel, cell-surface binding of rCD22 was reduced in GC B-cell subsets despite largely stable CD22 expression. These findings identify an association between GC-associated N-glycan remodeling and reduced rCD22 binding. Direct binding and perturbation experiments are required to determine whether individual bisected glycoforms regulate CD22 interactions or signaling.