Related Experiment Videos
Macrophages, microglial cells, and HLA-DR antigens in fetal and infant brain
M M Esiri1, M S al Izzi, M C Reading
1Department of Neuropathology, Radcliffe Infirmary, Oxford.
Abstract:
Immunohistochemical reactions for macrophages, microglia, and HLA-DR antigens were tested on frozen sections of necropsy brain tissue from 20 fetuses and infants ranging in age from 18 weeks' gestation to 8 months post term. No primary central nervous system disease was present but there were four cases of sudden infant death syndrome (SIDS). Macrophages were detected in all the samples studied and were located in the germinal matrix zone, in perivascular spaces throughout the brain, and in the leptomeninges and subependymal layer. Well differentiated microglia were present in all cases examined after 35 weeks' gestation and less well ramified forms were seen at earlier stages of gestation. HLA-DR antigens were detected on a small number of macrophages, chiefly in a perivascular location, in all but three cases. The fewest reactive cells and the weakest reactions occurred in the youngest fetuses. One case of SIDS showed increased foci of microglia in perivascular white matter: this case and one other case of SIDS were the only cases with well ramified microglia that expressed HLA-DR antigens. These findings may be relevant to an understanding of local immune responses in fetal brain infections, including human immunodeficiency virus infection.
Insights
Macrophages and microglia are present in fetal brains, with immune responses varying by age. Human Leukocyte Antigen-DR (HLA-DR) antigen expression on these cells may indicate susceptibility to infections in developing brains.
Area of Science:
- Neuroscience
- Immunology
- Developmental Biology
Background:
- Immune cell presence and function in the developing human brain are not fully understood.
- Macrophages and microglia are key immune cells in the central nervous system.
Purpose of the Study:
- To investigate the presence and characteristics of macrophages, microglia, and HLA-DR antigen expression in fetal and infant brain tissue.
- To correlate immune cell findings with gestational age and sudden infant death syndrome (SIDS).
Main Methods:
- Immunohistochemistry was used to analyze brain tissue sections from 20 fetuses and infants (18 weeks gestation to 8 months post-term).
- Reactions for macrophages, microglia, and HLA-DR antigens were assessed.
Main Results:
- Macrophages were detected in various brain regions across all samples.
- Well-differentiated microglia appeared after 35 weeks gestation, with less developed forms seen earlier.
- HLA-DR antigens were found on some macrophages, primarily perivascularly, with weaker reactions in younger fetuses.
Conclusions:
- The study characterizes the ontogeny of macrophages and microglia in the human fetal brain.
- HLA-DR expression suggests potential immune surveillance and response capabilities even in early development.
- Findings may inform understanding of immune responses in fetal brain infections, including HIV.