OD was measured with a microplate reader (detection wavelength: 570 nm; reference wavelength: 630 nm), and the tumouricidal activity was determined. Tumouricidal activity

(%) = [1−(ODexperiment–ODeffector cells)/ODtarget cells] × 100%. Statistical analysis.  Analysis was performed using spss 11.5 statistics software (SPSS inc., Chicago, IL, USA), and data were expressed as mean ± SD. Group comparisons were carried out by t-tests. The significance level was set at the P-value of 0.05. Pearson correlation coefficient was selected for bivariate correlation analysis. Correlations between variables were evaluated using Spearman’s correlation coefficient (rho). Pembrolizumab price Flow cytometry plots of T cells, Th cells, NK cells and B lymphocytes from PBMCs were shown in Fig. 1. There were no marked differences

in the absolute numbers of check details peripheral blood T lymphocytes, NK cells or B lymphocytes among the three groups (P > 0.05 for each). In addition, there were no significant differences in T lymphocyte subsets or CD4+/CD8+ ratios noted among the three groups (Table 1) (P > 0.05 for each). As described in Methods, T lymphocytes were obtained from peripheral blood samples from 10 randomly selected members of each of the three subject groups. MTT assays were used to determine T cell proliferation. The stimulation index (SI) was the highest in group C (5.7 ± 1.9) and the lowest in group A (11.9 ± 2.8), and that in group B was 8.6 ± 2.6. There were significant differences in SI among the three groups (Table 2 and Fig. 2A) (P < 0.05). Bivariate correlation analysis revealed that the decrease in T lymphocyte stimulation index (SI) was age dependent, with a significant decrease in Cytidine deaminase individuals aged above 70 years, compared with the lower-age groups (r = −0.75; P < 0.0001) (Fig. 3A). As also described in Methods, CIK cells were prepared from PBMC samples of 10 randomly selected subjects from each of the three groups. These CIK cells were assessed for their tumouricidal activities. CIK tumouricidal activity was the highest in group C

(67.8 ± 10.1%) and the lowest in group A (43.8 ± 11.7%), and that in group B was 57.4 ± 10.3%. There were significant differences among the three groups (P < 0.05); CIK tumouricidal activity decreased with an increase in subject age (Table 2 and Fig. 2B). Bivariate correlation analysis revealed that the decrease in CIK tumouricidal activity was age dependent, with a significant decrease in individuals aged above 70 years, compared with the lower-age groups (r = −0.59; P < 0.001) (Fig. 3B). Ageing populations will present great challenges in the 21st century, and changes in immune function with increased age are closely related to senescence. In studies of immune-related senescence, various diseases, medical interventions, unhealthy lifestyles and other factors, except for ageing, that can affect immune function should be excluded.