IMMUNOPHENOTYPING OF BLOOD-LYMPHOCYTES IN CHILDHOOD - REFERENCE VALUES FOR LYMPHOCYTE SUBPOPULATIONS

Objective: Immunophenotyping of blood lymphocytes is an important tool in the diagnosis of hematologic and immunologic disorders, Because of maturation and expansion of the immune system in the first years of l ife, the relative and the absolute size of lymphocyte subpopulations v ary during childhood, Therefore we wished to obtain reference values f or the relative and the absolute size of all relevant blood lymphocyte subpopulations in childhood. Study design: We used the lysed whole bl ood method for analysis of lymphocyte subpopulations in 429 blood samp les from neonates (n = 20), healthy children (n = 358), and adults (n = 51). The following age groups were used: 1 week to 2 months (n = 13) , 2 to 5 months (n = 46), 5 to 9 months (n = 105), 9 to 15 months (n = 70), 15 to 24 months (n = 33), 2 to 5 years (n = 33), 5 to 10 years ( n = 35), and 10 to 16 years (n = 23). Results: Our results show that t he absolute number of CD19(+) B lymphocytes increases twofold immediat ely after birth, remains stable until 2 years of age, and subsequently gradually decreases 6.5-fold from 2 years to adult age, The CD3(+) T lymphocytes increase 1.5-fold immediately after birth and decrease thr eefold from 2 years to adult age, The absolute size of the CD3(+)/CD4( +) T-lymphocyte subpopulation follows the same pattern as the total CD 3(+) population, but the CD3(+)/CD8(+) T lymphocytes remain stable fro m birth up to 2 years of age, followed by a gradual threefold decrease toward adult levels, In contrast to B and T lymphocytes, the absolute number of natural killer cells decreases almost threefold in the firs t 2 months of life and remains stable thereafter. Our study also showe d that changes in the absolute size of lymphocyte subpopulations are n ot always consistent with changes in their relative size, This demonst rates that the relative counts of lymphocyte subsets do not reflect th eir actual size and are therefore of limited value. Conclusion: On the basis of this study we strongly recommend that immunophenotyping of b lood lymphocytes for the diagnosis of hematologic and immunologic diso rders be based on the absolute rather than on the relative size of lym phocyte subpopulations. Our data can be used as age-matched reference values for blood lymphocyte immunophenotyping.