THE REPERTOIRE OF SERUM IGM IN NORMAL MICE IS LARGELY INDEPENDENT OF EXTERNAL ANTIGENIC CONTACT

Antigen-free (AGF) and germ-free (GF) mice, although essentially free of serum IgG, maintain normal levels of circulating IgM. Using a quant itative immunoblot assay, we have now analyzed the repertoire of serum IgM from AGE GF, and specific pathogen-free (SPF) BALB/c mice, on lar ge panels of natural antigens from homologous tissues and bacteria. Th e reactivity profiles were very similar in the three groups of mice. M ultiparametric statistic evaluation of the data showed that BALB/c ani mals, SPE GF, and AGF mice constitute an homogeneous group with simila r immunoreactivity profiles when compared to C57BL/6. Differences betw een immunoreactivity profiles of GF and AGF mice were observed, but we re not statistically significant. These results suggest that the serum IgM repertoire of normal mice is strictly regulated and selected by e ndogenous ligands.