Table 1

Age-associated changes in the immune system

Innate
 NeutrophilsReduced function including chemotaxis, microbial killing and phagocytosis.
 MacrophagesDefective chemotaxis, cytokine production and phagocytosis
 DCsChange in the balance of plasmacytoid DCs and myeloid DCs
 Natural killer cellsDecreased proliferationReduced production of TNF-α, IL-2, IL-12 and IL-2R
Adaptive
 B cellsReduced B cell lymphopoiesis; reduced CD4+ T cell help; reduced quantity and quality of antibodies
 CD4+ T cellsReduced IL-2 production; dampened co-stimulation
 CD8+ T cellsReduced repertoire; increased frequencies of memory cells
 TregsIncreased frequencies

  • For more information, please see McKay et al89 and references therein.

  • DCs, dendritic cells; IL, interleukin; TNF, tumour necrosis factor.