B Cell Levels in Centenarians, Semi-Supercentenarians, and Supercentenarians: Descriptive Analysis by Age, Sex, Cytomegalovirus Status, and Interleukin-6

This study aims to characterise the B cell compartment in a cohort of Sicilian centenarians by analysing absolute CD3−CD19+ lymphocyte counts, in association with age, sex, cytomegalovirus (CMV) serostatus, related to immune ageing, and interleukin (IL)-6 levels, representative of inflamm-ageing. It also investigates age-related changes in the CD4+/CD19+ ratio as a marker of immune ageing, reflecting shifts in immune homeostasis. B cell counts were assessed by flow cytometry on 53 Sicilians aged 19–110 years: 20 Adults, 15 Older adults, 11 long-living individuals, and 7 oldest centenarians. A multiple negative binomial regression was applied to evaluate the effects of age, sex, CMV serostatus, and Il-6 levels on values of B cells. The results showed a non-significant trend toward age-related decline without sex-based differences. A significant reduction in B cell count was observed in individuals with high anti_CMV titres, while IL-6 levels showed a borderline inverse correlation. CD4+/CD19+ ratio values showed an age-related increase. Our findings suggest that the age-related decline in B cell numbers may be mostly related to CMV infection and IL-6 values, without sex contribution. The age-related increase in the CD4+/CD19+ ratio, most pronounced in oldest centenarians, may represent a compensatory adaptation promoting immune regulation and chronic inflammation control.