Evaluation of lymphocyte levels in a random sample of 218 elderly individuals from São Paulo city

BACKGROUND: Age-associated changes in the immune system cause decreased protection after vaccination and increased rates of infections and tumor development. METHODS: Lymphocyte percentages were compared by gender and age to establish differences between subtypes. Three mL blood samples were obtained from 218 randomly selected individuals (60-101 years old) who live in São Paulo city. Blood was lysed with Tris phosphate buffer and stained for 30 minutes with monoclonal antibodies (CD3PerCP, CD4FITC, CD8Pe, CD19Pe) for analysis by flow cytometry. Statistical analysis was by ANOVA. RESULTS: The percentage of CD4(+) T cells (p-value = 0.005) and the CD4/CD8 ratio (p-value = 0.010) were lower in men, whereas the percentage of CD8(+) T cells was lower (p-value = 0.002) in women; the percentage of B cells (CD19(+) ) was similar between groups. Individuals grouped by gender and age range and compared showed a drop in CD4(+) cells in 75 to 79-year-old men (female: 46.1% ± 8.1% and male: 38.8% ± 10.5%; p-value = 0.023). Also, the 80 to 84-year-old group of men had a higher percentage of CD8(+) (female: 20.8% ± 8.2%, and male: 27.2% ± 8.2%; p-value = 0.032). Low percentages of B cells were detected in men in the 75 to 79-year-old (p-value = 0.003), 85 to 89-year-old (p-value = 0.020) and older than 90 year old (p-value = 0.002) age ranges. CONCLUSION: Elderly men present with more changes in lymphocyte subsets compared to elderly women. These findings could demonstrate impairment in the immune response since the lower CD4(+) in men would provide less help to B cells (also lower in men) in terms of antibody production. In addition, the increase in CD8(+) cells in this group could represent chronic inflammation observed during the aging process.