Sustained immune youth risks autoimmune disease in the aging host

Area of Science:

• Immunology
• Gerontology
• Autoimmunity

Background:

• Immune responses protect against infection and cancer but risk autoimmune diseases increases with age.
• Many autoimmune diseases, including giant cell arteritis, peak in incidence in later life.
• Aging is traditionally viewed as leading to immune decline, yet autoimmunity rises.

Purpose of the Study:

• To investigate if aging predisposes individuals to autoimmunity.
• To explore the role of sustained immune competence in the progression of autoimmune diseases.
• To re-evaluate the concept of immune aging as a protective mechanism against autoimmunity.

Main Methods:

• Discussion and synthesis of existing research on immune responses in aging and autoimmunity.
• Focus on the autoimmune vasculitis giant cell arteritis as a model disease.
• Analysis of the role of stem-like memory CD4+ T cells (T_SCM) and antigen-presenting cells in disease pathogenesis.

Main Results:

• Disease progression in giant cell arteritis is driven by age-inappropriate immune competence.
• Stem-like memory CD4+ T cells (T_SCM) near lesions provide a continuous source of pathogenic T cells.
• Impaired peripheral tolerance, due to antigen-presenting cells lacking inhibitory ligands and neoantigens, promotes autoimmunity.

Conclusions:

• Sustained immune competence ('immune youthfulness') in aging can be detrimental, leading to autoimmunity.
• Immune aging may represent a beneficial adaptation, balancing self- and non-self-antigen reactivity.
• This challenges the notion that immune decline solely explains age-related disease, highlighting a paradox in immune aging.