IgG Fc fragments containing α2,6-linked sialic acid only show a 10-fold increase in antiinflammatory activity compared to those containing both α2,3-and α2,6-linked sialic acids . In contrast, Fc fragments containing only α2,3-linked sialic acid show no antiinflammatory activity at all . It is crucial to ensure that the IgG antibodies used for antiinflammatory treatments have the appropriate sialic acid linkages through quality control.