The antigenicity of asialylated IgG: its relationship to rheumatoid factor.

Native IgG of human or rabbit origin, from which terminal sialic acid is removed by immobilized neuraminidase, undergoes changes in structure and antigenicity. Such asialylated rabbit IgG's tend to agglutinate, and are immunogenic in autologous hosts. The sialic acid content of rheumatoid factor (RF) isolated from the serum of a rheumatoid patient and identified as IgG and IgM, was also found to be lower than that of normal IgG and IgM. These findings indicate that carbohydrate residues influence the secondary structure of IgG and suggest an enzymic mechanism for the genesis of RF.