CHANGES IN THE GALACTOSE CONTENT OF IGG DURING HUMORAL IMMUNE-RESPONSES

The Fc region of IgG bears two oligosaccharides of variable compositio n. The serum level of one variant which lacks terminal galactose and s ialic acid (agalactosyl IgG) is raised in a number of autoimmune disea ses and animal models thereof. Here it is shown that such changes in I gG glycosylation occur during non-pathological humoral immune response s. It was found that if specific pathogen free (SPF) CBA/Ca mice are t ransferred from a sterile to a conventional environment, their levels of total serum IgG rise whereas the degree of IgG galactosylation fall s. Next, mice were immunised with bovine serum albumin (BSA) in incomp lete Freund's adjuvant. As anti-BSA titres rose the antibodies became less galactosylated and later, as the titres fell, the antibodies beca me more galactosylated. By contrast, there was little or no variation in the relative galactosylation of total IgG. It is considered that th e galactosylation of IgG antibodies varies during an immune response.