Table 3

Alterations in the innate and adaptive immune system of infants and older adults

CellChanges in healthy older adultsChanges seen in healthy infants
NeutrophilsIncreased incidence of neutropenia32
Altered cytokine production34
Impaired migration33
Reduced pathogen killing35
Increased apoptosis38
Reduced migratory ability55
Reduced degranulation57
Preserved phagocytosis88
Reduced NET generation60
Preserved ROS generation53
Macrophage/ monocytesReduced phagocytosis and production of free radicals89
Possible reduced efferocytosis90
Decreased ability to antigen present due to reduced expression of MHC class II91
Reduced ability to secrete inflammatory mediators after LPS stimulation92
Dendritic cellsRelative frequency controversial93
DC function maintained in healthy older adults94 but impaired in frail older adults95
Negative correlation between the number of plasmacytoid DC and age
NK cellsIncreased numbers but reduced cytotoxicity96 Reduced cytotoxicity97
NK cells from children are phenotypically different from adults in terms of cell surface receptors.98
Adaptive ImmunityReduced numbers of naïve T cells
T cell exhaustion
Decreased capacity to respond to novel antigens
Lower affinity antibodies
Reduced numbers of B cells99
Increased Tregs
Blunted humoral responses97
  • Table 3 gives an overview of cellular features of changing features of immunity in humans with ages. Features in neutrophils are expanded on later in the text.

  • DC, dendritic cell; LPS, Lipopolysaccaride; MHC, major histocompatibility complex; NET, neutrophil extracellular trap; NK, natural killer; ROS, reactive oxygen species; Treg, T regulatory lymphocyte.