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Ontogeny of immunity in man
Acta Endocrinologica. Supplementum
|January 1, 1975
Summary
Human fetal immune system development shows early immunocompetence. Lymphoid development in the thymus precedes peripheral tissues, with exceptions in fetal liver cells responding to mixed lymphocyte reactions before thymus organization.
Area of Science:
- Immunology
- Developmental Biology
- Human Fetal Development
Background:
- Understanding the ontogeny of the human immune system is crucial for assessing fetal health and development.
- Experimental limitations in studying human fetal immunity necessitate reliance on in vitro analyses.
Purpose of the Study:
- To review recent findings on the ontogeny of human immunity.
- To explore the emergence of immunocompetence in fetal lymphoid tissues.
Main Methods:
- In vitro studies using deceased human fetuses.
- Analysis of lymphoid development in fetal thymus and peripheral tissues.
- Mixed lymphocyte culture (MLC) assays to assess cellular responses.
- Use of T-cell markers to map lymphocyte emergence.
Main Results:
- Fetal thymus lymphoid development generally precedes peripheral immunocompetence.
- Early fetal liver cells exhibit mixed lymphocyte reaction (MLR) responsiveness before thymus organization.
- MLR response to allogeneic cells precedes phytohaemagglutinin (PHA) response.
- B cells appear in fetal liver around 9 weeks gestation; immunoglobulin production is low until after birth.
- Evidence suggests a progression from IgM to IgA synthesis during fetal development.
Conclusions:
- Human fetal immune system demonstrates significant cellular and potential humoral immunocompetence early in development.
- The sequence of immune cell emergence and functional maturation varies, with exceptions to general lymphoid development patterns.