Effect of Age on Xenobiotic-Induced Autoimmunity

Area of Science:

• Immunology
• Gerontology
• Toxicology

Background:

• Aging is linked to increased spontaneous autoantibody production and chronic inflammation.
• The effect of aging on xenobiotic-induced autoimmunity is not well understood.
• Mercury-induced autoimmunity (HgIA) serves as a model for studying xenobiotic-induced autoimmunity.

Purpose of the Study:

• To investigate the impact of aging on mercury-induced autoimmunity (HgIA) in B10.S mice.
• To analyze age-related changes in autoantibody production following mercury exposure.
• To explore the immunological mechanisms underlying age-related alterations in HgIA.

Main Methods:

• Exposure of mice of different ages (3, 6, 12, 24 months) to mercury (HgCl₂) or phosphate-buffered saline (PBS).
• Monitoring of anti-nucleolar autoantibodies (ANoA) and anti-nuclear antibodies (ANA) titers.
• Flow cytometry analysis of T-cell populations (CD4⁺) and assessment of germinal center formation.

Main Results:

• Spontaneous ANA increased with age in PBS-treated mice.
• HgIA incidence and severity decreased in old-age mice compared to younger cohorts.
• Reduced immunoglobulin levels, anti-chromatin antibodies, and germinal center formation were observed in old mice.
• Age-related decline in CD4⁺ T cells was noted, with mercury exposure affecting T-cell differentiation differently in young versus old mice.

Conclusions:

• Aging enhances spontaneous autoimmunity but impairs the development of xenobiotic-induced autoimmunity.
• Immunosenescence, characterized by reduced immune cell function and antibody production, contributes to diminished HgIA in older mice.
• A subset of aged mice retains partial responsiveness to mercury, indicating a complex interplay between aging and environmental factors in autoimmunity.