Peripheral Blood Lymphocyte Subsets in Adolescents: a Longitudinal Analysis from the REACH Project

Flow cytometry analysis of lymphocyte subset markers was performed for a group of sexually active, human immunodeficiency virus (HIV)-negative adolescents over a 2-year period to establish normative data. Data were collected in the REACH Project (Reaching for Excellence in Adolescent Care and Health), a multicenter, longitudinal study of HIV-positive and high-risk HIV-negative adolescents. Two- and three-color flow cytometry data were collected every 6 months for these subjects. We determined the effects of gender, race, and age on the following lymphocyte subset markers: total CD4⁺ cells, CD4⁺ naïve cells, CD4⁺ memory cells, all CD8⁺ cells, CD8⁺ naïve cells, CD8⁺ memory cells, CD16⁺ natural killer cells, and CD19⁺ B cells. Gender was the demographic characteristic most frequently associated with differences in lymphocyte subset measures. Females had higher total CD4⁺ cell and CD4⁺ memory cells counts and lower CD16⁺ cell counts than males. Age was associated with higher CD4⁺ memory cell counts as well as higher CD8⁺ memory cell counts. For CD19⁺ cells, there was an interaction between age and gender, with males having significantly lower CD19⁺ cell counts with increasing age, whereas there was no age effect for females. Race and/or ethnicity was associated with differences in total CD8⁺ cell counts and CD8⁺ memory cell counts, although both of these associations involved an interaction with gender.