An immunological approach for aging mechanism appears to be important. Lymphocyte subsets 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 few data about age-related reference ragnes for these subsets in healthy individuals have been reported. So we attempted to report reference ranges for these subsets in each age group and review changes of the results with age for the secondary studies about immune cell function as lymphocyte blast transformation and immunoglobulin gene rearrangement (VDJ) including recombination activating genes (RAG-1 and RAG-2).

Lymphocyte subset analysis was performed on 302 sugjects, 189 males and 113 females with age group of all decades of life. Two color direct immunofluorescene flow cytometry (FCM) was done using 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+), helper/suppressor (CD4+/CD8+) ratio and natural killer (NK) cells (CD3-CD16+/CD56+). The absolute numbers of each subset were calculaed from total lymphocyte counts. Data collected was analysed usting SAS 6.12. A P-value of <0.05 was considered significant.

We reported the counts and percentages of lymphocyte and these subsets in each age group. 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 the significant difference among the various age groups. The age-related changes observed in our study were as following: 1) a decrease in the percentages of T cells, B cells and CD8+ T cells; 2) a decrease in the counts of B cells and CD8+ T cells; 3) an increase in the percentage and count of NK cells; and 4) an increase in the CD4+/CD8+ ratio.

The characteristics of aging process appeared to be showing a marked decrease of lympocyte subsets T and B cells as well as T8 (CD8+). The age-related increase of the percentage of cells bearing NK marker can be interpreted as a compensatory consequence to cope with the decrease of T cells related to the thymic involution. These changes with age appeared to be for the secondary study about immune cell function as lymphocyte blast transformation and immunoglobulin gene rearrangement.