Antigenic similarities among mammalian immunoglobulins.

Cross-reactions between immunoglobulins from twelve mammalian species were observed by immunoelectrophoresis with antisera prepared in rabbits against the purified IgG of each species. The Fc fragments of the IgG from man, pig, goat, sheep and cow were compared by examination of the cross-reactions before and after absorption of the antisera with the various IgG. Eight antigenic determinants could be detected; some of them were species-specific, others were shared by IgG from two or more species. A close resemblance was found between goat, sheep and cow IgG.