Two genetic loci, Ir-Z1 and ir-Z2, controlling the immune response to adjuvant-free bacterial β-D-galactosidase (Z) are present in inbred mouse strains SJL/J and CE/J, respectively. Each locus segregates as a single, autosomal gene: Ir-Z1 as dominant and ir-Z2 as recessive. The response is characterized by production of activating and precipitating IgG. Maximal levels of circulating IgG occur between 16 and 20 days after immunization with a single, 50-µg dose of enzyme. Failure of proteins other than Z to elicit an immune response indicates that the Ir-Z control is specific for determinant(s) of this enzyme. The immunogenicity of β-D-galactosidase preparations cannot be attributed to either the catalytic activity of the enzyme or adjuvant contamination. Non-responder mice acquire immunologic memory without detectable increase in circulating specific IgG under the same conditions that elicit antibody production in responder strains.
This work was supported by United States Public Health Grant AI-12626 from the National Institute of Allergy and Infectious Diseases.