CD75/ST6GAL1
CD75 defines the α2,6-sialylated carbohydrate determinants generated by ST6GAL1, a type II Golgi membrane sialyltransferase encoded by the ST6GAL1 gene. Rather than a conventional receptor, CD75 marks the sialylated N-glycans that ST6GAL1 creates by transferring sialic acid in α2,6 linkage to galactose residues. Expression is characteristic of mature resting B cells, and CD75 staining is a classic B cell marker in immunophenotyping. The enzyme is induced during B cell activation and contributes to germinal center reactions, where α2,6-sialylation provides ligands for CD22 and tunes B cell receptor signaling. ST6GAL1 is also produced by epithelial and endothelial cells and circulates in serum as a secreted form.
