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In Situ Detection of Autoreactive CD4 T Cells in Brain and Heart Using Major Histocompatibility Complex Class II Dextramers
Published on: August 1, 2014
Ultrastructural location of major histocompatibility complex (MHC) class II positive perivascular cells in
M B Graeber1, W J Streit, D Büringer
1Center for Neurologic Diseases, Brigham and Women's Hospital, Boston, Massachusetts.
Insights
Researchers identified a new cell type in the human brain's blood vessels, called perivascular cells, which express major histocompatibility complex (MHC) class II antigens and may play a role in brain immunity.
Area of Science:
- Neuroimmunology
- Cerebral Microvasculature Research
Background:
- Major histocompatibility complex (MHC) antigens are crucial for immune responses.
- Their expression in the brain, particularly on vascular cells, is not fully understood.
Purpose of the Study:
- To investigate the expression and characteristics of MHC class I and II antigens in the human brain vasculature.
- To identify and characterize specific cell populations associated with MHC class II immunoreactivity in normal brain tissue.
Main Methods:
- Immunocytochemistry (light and electron microscopy) on surgical and postmortem human brain biopsy tissue.
- Use of monoclonal antibodies against MHC class I, MHC class II, human macrophages (EBM11), and alpha-smooth muscle actin.
Main Results:
- MHC class II immunoreactivity in normal human brain vasculature is localized to distinct perivascular cells.
- These cells share macrophage antigens but not smooth muscle actin, distinguishing them from pericytes and microglia.
- Perivascular cells exhibit specific morphology, frequency, and distribution within the cerebral microvasculature.
Conclusions:
- Perivascular cells expressing MHC class II antigens are a normal component of the human cerebral microvasculature.
- These cells may be involved in immunological reactions at the blood-brain interface.
Abstract:
The expression of major histocompatibility complex (MHC) class I and II antigens was studied in surgical and postmortem brain biopsy tissue using light and electron microscopic immunocytochemistry. In addition, monoclonal antibodies directed against human macrophages (EBM11) and alpha-smooth muscle actin were applied. It is shown that blood vessel-associated MHC class II immunoreactivity in histologically normal human brain can be localized to a distinct class of cells, termed perivascular cells, which share macrophage but not smooth muscle cell antigen. This immunophenotype, the location in the perivascular space as well as the morphology, frequency and tissue distribution distinguish perivascular cells from pericytes and intraparenchymal microglia. It is suggested that MHC class II positive perivascular cells are a normal constituent of the human cerebral microvasculature. The potential role of these cells in immunological reactions occurring at the blood-brain interface is discussed.
