Cross-reactive idiotypes in immunoglobulin A-deficient sera

Area of Science:

• Immunology
• Genetics

Background:

• Inbred mice strains immunized with antigens produce antibodies with similar V regions, leading to cross-reactive idiotypes (CRI).
• Immunoglobulin A (IgA)-deficient humans experience continuous intestinal immunization from dietary proteins.

Purpose of the Study:

• To investigate if IgA-deficient humans produce antibodies sharing CRI, similar to immunized mice.
• To analyze the cross-reactivity of anti-casein antibodies in IgA-deficient individuals.

Main Methods:

• Isolation of anti-casein antibodies from 16 IgA-deficient donors (Finnish and North American).
• Generation of autologous and heterologous anti-anti-casein reagents.
• Enzyme-linked immunosorbent assay (ELISA) inhibition assays to assess antibody cross-reactivity.

Main Results:

• Both autologous and heterologous anti-idiotypes bound anti-casein antibodies, with the heterologous reagent showing higher affinity for non-antigen-binding site determinants.
• Extensive cross-reactivity between anti-caseins was demonstrated using both reagents.
• A higher prevalence of shared CRI was observed in Finnish donors compared to North American donors.

Conclusions:

• Specific and commonly shared cross-reactive idiotypes (CRI) can be identified in IgA-deficient humans.
• Continuous gastrointestinal immunization in IgA-deficient individuals leads to the production of antibodies with shared CRI.
• The findings suggest a conserved immune response to dietary antigens in humans with IgA deficiency.