Double diffusion in gel tests with Paul-Bunnell antibodies of infectious mononucleosis sera

Double diffusion tests in gel were employed for studies of reactions between infectious mononucleosis sera and extracts of bovine, sheep and equine erythrocyte stromata. The extracts were obtained by ultrasonication of stromata prepared from trypsin-digested erythrocytes. The reaction with bovine stroma extract was composed, in many instances, of two lines. A single line was observed in reactions with sheep and equine stroma extracts. This line merged into a reaction of partial or complete identy with one of the lines formed with bovine stroma extract. Evidence was obtained that some infectioous mononucleosis sera may contain heterophile (Paul-Bunnell) antibodies belonging to IgG class in addition to those of IgM nature.