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. 2006 Nov 29:3:10.
doi: 10.1186/1742-4933-3-10.

Ageing is associated with a decline in peripheral blood CD56bright NK cells

Shivani M Chidrawar  1 , Naeem Khan, Y L Tracey Chan, Laxman Nayak, Paul A H Moss
Affiliations

Ageing is associated with a decline in peripheral blood CD56bright NK cells

Shivani M Chidrawar et al. Immun Ageing. .

Abstract

Background: Natural killer (NK) cells are cytotoxic lymphocytes that lack CD3 and express variable levels of CD16, CD56 and CD57. In recent years NK cells have been categorised into two major groups based on the level of CD56 expression. This phenotypic classification correlates with functional activity as CD56bright NK cells are the major cytokine producing subset whereas CD56dim NK cells exhibit greater cytotoxic activity. Previous studies have revealed a reduction in total NK cell numbers in association with ageing and this study sought to determine the potential influence of ageing on the number of NK cell subsets within peripheral blood.

Results: The number of NK (CD56+CD3-) cells within peripheral blood did not change with increasing age. The number of CD56dim NK cells also remained stable with ageing. In contrast the absolute number of CD56bright NK cells within peripheral blood declined by 48% with ageing from a mean of 15.6/microl in individuals aged 20-40 years to 8.1/microl in those aged 60+ years (p = 0.0004).

Conclusion: The number of CD56bright NK cells within peripheral blood declines with age. As this population plays a central role in cytokine secretion during the innate immune response this decline may contribute to impaired immune regulation in elderly individuals.

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Figures

Figure 1
Figure 1
Identification of CD56bright and CD56dim NK cells. Peripheral blood lymphocytes were stained with CD3, CD56 and CD16 mABs and analysed. The CD3negative lymphocyte population was initially gated and then analysed for CD56 and CD16 expression. Gates A and B allow enumeration of the CD56bright and CD56dim NK cell population respectively.
Figure 2
Figure 2
The effect of age on peripheral blood NK cells. These graphs illustrate (a) the number of NK cells μl/blood and (b) the percentage of lymphocytes that NK cells represent within samples in each age group; 20–40(n = 25) 40–60(n = 23) and 60 + (n = 67). The mean values within each respective cohort group are marked. Statistical analysis was carried out as described in the Methods; p values between groups are displayed and results are summarised further in table 1.
Figure 3
Figure 3
The effect of age on peripheral blood CD56bright and CD56dim NK cell number. These graphs illustrate (a) the number of CD56dim NK cells μl/blood and (b) the percentage of CD56bright NK cells μl/blood within samples in each age group; 20–40(n = 25) 40–60(n = 23) and 60 + (n = 67). The mean values within each respective cohort group are displayed. Statistical analysis was carried out as described in the Methods and p values between groups are shown. These results are summarised together with the percentage of the lymphoid pool occupied by CD56bright and CD56dim cells and are displayed in table 2.
Figure 4
Figure 4
The percentage of total peripheral blood lymphocytes represented by CD56bright and CD56dim NK cells with advancing age. This graph illustrates the percentage of the total peripheral blood lymphoid pool represented by CD56bright and CD56dim NK cell subsets. These results are also documented in tables 1 and 2.
See this image and copyright information in PMC

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