In-depth human immune cellular profiling from newborn to frail

Area of Science:

• Immunology
• Gerontology
• Cellular Biology

Background:

• Immune system function declines with age, a process known as immunosenescence.
• Frailty, a state of increased vulnerability, is associated with immune changes but specific cellular differences remain unclear.
• Understanding immune cell composition across the lifespan, from newborns to frail elderly, is crucial for health assessments.

Purpose of the Study:

• To investigate age- and frailty-related changes in immune cell subtypes.
• To identify specific immune cell profiles associated with frailty.
• To establish an atlas of peripheral leukocyte subpopulations from newborn to frailty.

Main Methods:

• Analysis of human cord blood cells and peripheral blood from young adults, healthy old individuals, and frail old individuals.
• Flow cytometry was used to quantify 30 immune cell subsets based on surface markers.
• Correlation analysis was performed between the frailty index score and immune cell subpopulations.

Main Results:

• Frail individuals showed a higher CD4/CD8 ratio and increased proportions of CD4+ central memory T cells, CD8+ effector memory T cells, and specific B cell subsets (CD27- BSM, CD27+ BSM, age-associated B cells, CD38-CD24- B cells).
• Lower proportions of naïve CD8+ T cells and progenitor B cells were observed in frail individuals.
• The frailty index score correlated with naïve T cells, CD4/CD8 ratio, age-associated B cells, CD27- BSM cells, and CD4+ central memory T cells.

Conclusions:

• This study provides a comprehensive atlas of immune cell changes associated with aging and frailty.
• Specific immune phenotypes in frailty, including altered T and B cell populations, are identified.
• These findings may aid in understanding immunosenescence in frailty and inform future diagnostic and therapeutic strategies.