Ontogeny of lymphocyte function in the equine fetus

Area of Science:

• Equine immunology
• Fetal immunology
• Lymphocyte development

Background:

• Assessing fetal immune system development is crucial for understanding neonatal health and disease.
• The equine immune system's ontogeny, particularly in utero, requires further elucidation.

Purpose of the Study:

• To determine the gestational age at which pony fetuses develop functional T and B lymphocytes.
• To quantify immunoglobulin M (IgM) and IgG levels in fetal and neonatal equine serum.

Main Methods:

• In vitro phytolectin and allogeneic lymphocyte stimulation assays were performed on cells from various fetal tissues.
• Radioimmunoassay was used to quantify IgM and IgG concentrations in fetal and neonatal serum samples.

Main Results:

• Phytolectin-responsive cells appeared in thymus (80 days), peripheral blood (120 days), lymph node (160 days), and spleen (200 days).
• Mixed lymphocyte culture-responsive cells were detected in thymus (100 days) and spleen (200 days).
• Both IgM and IgG were detectable before 200 days of gestation, with higher and more variable IgG levels in neonatal foals.

Conclusions:

• Functional T lymphocytes are present in pony fetuses by 100 days of gestation.
• Functional B lymphocytes are present by 200 days of gestation.
• Equine fetuses achieve immunocompetence before birth, highlighting significant in utero immune maturation.