Résumé
BACKGROUND: Lymphocyte subset analysis in peripheral blood is widely performed to assess the immune status and to diagnose and monitor various diseases. Some lymphocyte subsets are known to change with age, but only a little data about age-related changes for these subsets in healthy individuals have been reported. So we attempted to review changes for these subsets with age. METHODS: Lymphocyte subset analysis was performed on 302 subjects, 189 males and 113 females with age group in all decades of life. Two color direct immunofluorescence flow cytometry (FCM) was done using a SimultestTM IMK-Lymphocyte kit (Becton Dickinson, USA), FACScanTM (Becton Dickinson, USA) and FACSCaliburTM (Becton Dickinson, USA). Lymphocyte subsets analysed were T (CD3+) and B cells (CD19+), helper/inducer T (CD4+) and suppressor/cytotoxic T cells (CD8+), and helper/suppressor (CD4+/CD8+) ratio and natural killer (NK) cells (CD3-CD16+/CD56+). The absolute numbers of each subset were calculated from the total lymphocyte counts. The data collected was analysed using SAS 6.12. A P-value of < 0.05 was considered significant. RESULTS: There were no statistically significant differences between male and female subjects. The percentage of CD4+ T cells, and the count of NK cells did not show any significant differences among the various age groups. The age-related changes observed in our study were as follows: 1) A decrease in the percentage of B cells; 2) A decrease in the counts of lymphocytes, T cells, B cells, CD4+ T cells and CD8+ T cells; 3) An increase in the percentage of NK cells; and 4) An increase in the CD4+/CD8+ ratio. CONCLUSIONS: A characteristic of the aging process shows a marked decrease in T and B cells. The age-related increase in the percentage of cells bearing NK markers can be interpreted as a compensatory consequence to cope with the deterioration of the immune system with age.