Age-related changes of immunophenotypically immature lymphocytes in normalhuman peripheral blood

The presence of phenotypically immature lymphocytes in umbilical cord blood has been a controversial topic. Moreover, their changes with age have not been systematically evaluated. In the present study, relative and absolute numbers of CD34+, CD10+CD19+ and CD4+CD8+ cell subsets were determined in u mbilical cord blood from 12 full-term normal newborns, 43 children aged 1 m onth to 6 years, and 10 young adults. The samples were processed by whole-b lood lysis and monoclonal antibody staining, and cells were analyzed by flo w cytometry. Immature cells were present in cord blood and progressively de clined in both absolute and percentage numbers with age, each according to a particular curve, reaching youth Values roughly at age 2-4 years. These r esults demonstrate that phenotypically immature cells normally circulate at low levels in peripheral blood, mostly at birth and during infancy, but al so during youth. (C) 1999 Wiley-Liss, Inc.