Lymphocyte subsets in healthy children from birth through 18 years of age: The pediatric AIDS clinical trials group P1009 study

Background: Peripheral blood lymphocyte subsets need to be determined in a large, urban, minority-predominant cohort of healthy children to serve as suitable control subjects for the interpretation of the appearance of these cells in several disease conditions, notably pediatric HIV-1 infection. Objective: We sought to determine the distribution of lymphocyte subsets in healthy urban-dwelling infants, children, and adolescents in the United States. Methods: Lymphocyte subsets were determined by means of 3-color flow cytometry in a cross-sectional study of 807 HIV-unexposed children from birth through 18 years of age. Results: Cell-surface marker analysis demonstrated that age was an extremely important variable in 24 lymphocyte subset distributions measured as percentages or absolute counts-eg, the CD4 (helper) T cell, CD8 (cytotoxic) T cell, CD19 B cell, CD4CD45RACD62L (naive helper) T cell, CD3CD4CD45RO (memory helper) T cell, CD8HLA-DRCD38 (activated cytotoxic) T cell, and CD8CD28 (activation primed cytotoxic) T cell. The testing laboratory proved to be an important variable, indicating the need for using the same laboratory or group of laboratories to assay an individual's blood over time and to assay control and ill or treated populations. Sex and race-ethnicity were much less important. Conclusion: The results of this study provide a control population for assessment of the effects of HIV infection on the normal development and distribution of lymphocyte subsets in children of both sexes, all races, and all ethnic backgrounds from birth through 18 years of age in an urban population. This study's findings will also prove invaluable in interpreting the immune changes in children with many other chronic diseases, such as primary immunodeficiency, malignancy, rheumatoid arthritis, and asthma.