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Longitudinal survey of lymphocyte subpopulations in the first year of life
E de Vries1, S de Bruin-Versteeg, W M Comans-Bitter
1Department of Immunology, Erasmus University Rotterdam, The Netherlands.
Insights
This study tracked lymphocyte changes in infants for one year, revealing distinct developmental patterns for T, B, and NK cells. Findings offer crucial insights into infant immune system maturation and interpreting immune disorders.
Area of Science:
- Immunology
- Developmental Biology
- Pediatrics
Background:
- Establishing age-matched reference values for lymphocyte subpopulations typically relies on cross-sectional data, contrasting with longitudinal patient monitoring.
- Infant immune system development requires a detailed understanding of lymphocyte dynamics from birth through the first year of life.
Purpose of the Study:
- To conduct a comprehensive longitudinal analysis of lymphocyte subpopulation changes in healthy infants from birth to one year of age.
- To identify early developmental markers, maturation indicators, and activation markers within infant lymphocyte populations.
- To establish a baseline for interpreting immune function and potential disorders in infants.
Main Methods:
- Longitudinal study design following 11 healthy infants from birth to 1 year of age.
- Detailed analysis of lymphocyte subpopulations, including T cells, B cells, and NK cells.
- Assessment of specific markers such as CD45RA, CD45RO, CD38, CD1c, and CD5.
Main Results:
- T and B lymphocytes increased at 1 and 6 weeks, respectively; NK cells declined post-birth.
- Naive T lymphocytes (CD45RA+) expanded, while memory T lymphocytes (CD45RO+) showed adult-like counts but lower expression.
- Infant lymphocytes, particularly T and B cells, exhibited high CD38 expression, potentially linked to metabolic needs and primary immune responses. Elevated CD1c+ and CD5+ B lymphocytes were observed.
- The study provides a detailed longitudinal profile of infant lymphocyte development, highlighting key changes and marker expressions.
Conclusions:
- This longitudinal survey clarifies lymphocyte development in infants, detailing changes in T cells, B cells, and NK cells during the first year.
- The findings contribute to a better understanding of immune maturation and aid in the accurate interpretation of immune data from infants.
- Specific markers like CD1c, CD5, and CD38 may indicate untriggered B lymphocytes in infants, offering diagnostic potential.
Abstract:
Age-matched reference values for lymphocyte subpopulations are generally obtained via cross-sectional studies, whereas patients are followed longitudinally. We performed a detailed longitudinal analysis of the changes in lymphocyte subpopulations in a group of 11 healthy infants followed from birth up to 1 y of age, with special attention for early developmental markers, markers of maturation, and markers of activation. We found that T and B lymphocytes increased at 1 and 6 wk of age, respectively. In contrast, NK cells showed a sharp decline directly after birth, suggesting that they are more important during pregnancy than thereafter. CD45RA+--mainly CD4+--naive T lymphocytes were high at birth, and increased further during the first year of life; they form a large expanding pool of cells, ready for participation in primary immune responses. The absolute counts of CD45RO+ memory T lymphocytes were similar in infants and adults, albeit with a lower level of expression of CD45RO on infant T lymphocytes. Almost all infant T lymphocytes expressed CD38 throughout the first year of life. The abundant expression of CD38 on an infant's T lymphocytes might be related to a greater metabolic need of the large population of naive untriggered cells that are continually involved in primary immune responses during the first year of life. The high B lymphocyte counts in infants mainly concerned CD38+ B lymphocytes throughout the first year of life. Also, the relative frequencies of CD1c+ and CD5+ B lymphocytes were higher throughout the first year of life than in adults. Therefore, CD1c, CD5, and CD38 could be markers of untriggered B lymphocytes. In conclusion, our longitudinal survey of T and B lymphocytes, NK cells, and their subpopulations during the first year of life helps to complete the picture of lymphocyte development in infants. This information contributes to the correct interpretation of data from infants with possible immune disorders.
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