The function of ST6GAL1 (ST6 beta-galactoside alpha-2,6-sialyltransferase 1, Ensembl gene identifier ENSG00000073849) is as follows. Transfers sialic acid from CMP-sialic acid to galactose- containing acceptor substrates. In B lymphocytes, generates neuraminidase-sensitive lymphocyte cell-surface differentiation antigens, such as CDw75, HB-6 and CD76 (PubMed:1730763). Sialylates complex-type N-glycans attached on the fragment crystallizable (Fc) of IgGs confering anti-inflammatory effector functions. Preferentially monosialylates the alpha(1->3) mannose antenna of Fc glycoforms with subsequent disialylation occurring at a much slower rate. {ECO:0000269|PubMed:1730763, ECO:0000269|PubMed:21081508, ECO:0000269|PubMed:23999306, ECO:0000269|PubMed:25733881, ECO:0000269|PubMed:27872474, ECO:0000269|PubMed:36280670, ECO:0000269|PubMed:37632720}.