Parameters of the Immune System and Vitamin D Levels in Old Individuals

Abstract

Aim: The increased number of individuals older than 80 years, centenarians, and supercentenarians is not a synonym for healthy aging, since severe infections, hospitalization, and disability are frequently observed. In this context, a possible strategy is to preserve the main characteristics/functions of the immune system with the aim to cause less damage to the organism during the aging process. Vitamin D acts on bone marrow, brain, breast, malignant cells, and immune system and has been recommended as a supplement. We aimed to evaluate whether immune parameters and vitamin D serum levels are correlated.

Methods: We evaluated some features of the immune system using the peripheral blood of individuals older than 80 years (n = 12) compared to young subjects (n = 10). In addition, we correlated these findings with vitamin D serum levels.

Results: Old individuals presented metabolic parameters of healthy aging and maintained preserved some features of immunity such as CD4/CD8 ratio, and low production of pro-inflammatory cytokines after stimulus. On the other hand, we observed increase in the frequency of myeloid-derived suppressor cells, reduction in circulating leukocytes, in the percentage of total CD8+, and in CD8+ Naïve T cells, in addition to increase in the percentage of CD8+ effector memory re-expressing CD45RA (EMRA) T cells. We found seropositivity for CMV in 97.7%, which was correlated with the decrease of CD8+ Naïve T cells and increase in CD8+ EMRA T cells. Vitamin D levels were insufficient in 50% of old individuals and correlated positively with total CD8+ T cells and negatively with CD8+ EMRA T cells.

Conclusion: In the studied population, longevity was correlated to maintenance of some immune parameters. Considering the limitations of the study as size of the sample and lack of functional assays, it was found that vitamin D in old individuals was correlated to some features of the immune system, mainly in the CD8 compartment.

Keywords: T cells; immunity; longevity; myeloid-derived suppressor cells; vitamin D.

Figure 1

Representative flow cytometry plots showing gate strategy for myeloid-derived suppressor cells (MDSC) frequency. Gate in live cells (FSC-A × SSC-A), doublets exclusion (SSC-H × SSC-W), gate in lineage negative cells (CD3⁻CD56⁻CD19⁻), gate in HLA-DR^low/neg cells, gate in CD33⁺CD11b⁺ cells. Gate in granulocytic (CD15⁺) and monocytic (CD14⁺) cells (A). Number of circulating leukocytes, MDSC (% MDSC) frequency, absolute number of MDSC, and frequency of monocytic and granulocytic MDSC in individuals of 20–30 years and 80+ years old individuals (B).

Figure 2

Representative flow cytometry plots showing gate strategy for the frequency of CD4⁺ and CD8⁺ T cells. Gate in live lymphocytes (FSC-A × SSC-A), doublets exclusion (SSC-H × SSC-W), gate in CD3⁺CD4⁺ T cells, gate in CD3⁺CD8⁺ T cells (A). Frequency of T lymphocytes CD3⁺CD4⁺, CD3⁺CD8⁺, and CD4/CD8 ratio in 20–30 and 80⁺ years old individuals. The CD4/CD8 ratio lower than 1 (0.542; blue square) (B).

Figure 3

Representative flow cytometry plots showing gate strategy for the frequency of CD4⁺ T cells phenotype. Gate in live lymphocytes (FSC-A × SSC-A), doublets exclusion (SSC-H × SSC-W), gate in CD3⁺CD4⁺ T cells, gate in CD45RA⁺CD27⁺ (Naïve) T cells, gate in CD45RA⁻CD27⁺ (central memory) T cells, gate in CD45RA⁻CD27⁻ (effector memory), gate in CD45RA⁺CD27⁻ (effector memory re-expressing CD45RA) T cells (A). Percentage (%) of CD4⁺ T cells phenotypes: Naïve (B), central memory (C), effector memory (D), effector memory RA re-expressing CD45RA (E) in 20–30 and 80+ years old individuals.

Figure 4

Representative flow cytometry plots showing gate strategy for the frequency of CD8⁺ T cells phenotype. Gate in live lymphocytes (FSC-A × SSC-A), doublets exclusion (SSC-H × SSC-W), gate in CD3⁺CD8⁺ T cells, gate in CD45RA⁺CD27⁺ (Naïve) T cells, gate in CD45RA⁻CD27⁺ (central memory) T cells, gate in CD45RA⁻CD27⁻ (effector memory), gate in CD45RA⁺CD27⁻ (effector memory re-expressing CD45RA) T cells (A). Percentage (%) of CD8⁺ T cells phenotypes: Naïve (B), central memory (C), effector memory (D), effector memory RA re-expressing CD45RA (E) in 20–30 and 80+ years old individuals.

Figure 5

Representative flow cytometry plots showing gate strategy for the frequency of proliferation in CD4⁺ and CD8⁺ T cells after stimulus with phytohemagglutinin (PHA) in culture. Gate in live cells (FSC-A × SSC-A), doublets exclusion (SSC-H × SSC-W), gate in CD3⁺CD4⁺ T cells, gate in the decrease of CFSE, gate in CD3⁺CD8⁺ T cells, gate in the decrease of CFSE (A). Percentage of CD3⁺CD4⁺ and CD3⁺CD8⁺ T cells proliferation after stimulus with PHA according to age: 20–30 and 80+ years old (B).

Figure 6

Cytokines produced by cells in culture under phytohemagglutinin stimulus according to age: 20–30 and 80+ years old.

Figure 7

Vitamin D [25(OH)D3] levels in young (n = 10; 20–30 years) and old (n = 12; 80–100 years) individuals.