Effects of Ageing on the Immune System: Infants to Elderly.

Physiological ageing is accompanied by decline in immune system function and immune alteration during ageing increases susceptibility to infections. We retrospectively analysed the data for complete blood count (CBC) and lymphocyte subsets from infant to elderly age groups to determine changes during ageing. Data from dual-platform flow cytometry and CBC were analysed to determine the percentage (%) and absolute cell counts (Abs) of peripheral blood lymphocyte subsets (CD3, CD4, CD8, CD19 and CD56+16+ cells) in infants (1 month to 1 year), children (1 year to 6 years), adolescents (12 years to 18 years), adults (21 years to 50) and elderly (70 years to 92 years). Differences in plasma cytokine levels in adults and elderly were also analysed using Randox system. Comparisons among age groups from infants through adults revealed progressive declines in the percentage of total lymphocytes and absolute numbers of T and B cells. The NK cells declined from infancy to adulthood but increased in elderly participants. The percentages of T cells increased with age from infant to adulthood and then declined. Pro-inflammatory cytokines, TNF-α and IL-6, were higher in elderly people compared to adults. The elderly group had significantly higher levels of monocyte chemoattractant protein-1 (MCP-1) and lower levels of epidermal growth factor (EGF) compared to adults. Our findings confirm and extend earlier reports on age-related changes in lymphocyte subpopulations and data generated from this study is useful for clinicians and researchers, patient management in various age groups for the interpretation of disease-related changes, as well as therapy-dependent alterations.