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MHC class II expression by beta2 integrin (CD18)-positive microglia, macrophages and macrophage-like cells in rabbit
Wenbing Huang1, Coral G Chamberlain, Richard Y Sarafian
1School of Medical Sciences (Anatomy and Histology) and Bosch Institute, University of Sydney, Sydney, NSW 2006, Australia.
Abstract:
The aim of this study was to investigate the developmental expression of major histocompatibility complex class II (MHCII) by microglia and macrophages and their relationship to blood vessels in the retina, a representative tissue of the central nervous system. Such information is crucial to understanding the role of these cells in immune surveillance. Wholemount preparations of retinas from late embryonic, postnatal and adult rabbits were subjected to three-colour fluorescence microscopy using beta2 integrin (CD18) and MHCII antibodies and biotinylated Griffonia simplicifolia B4 isolectin labelling of blood vessels. CD18+ cells consistently exhibited characteristics of macrophages or microglia in the vascularized and non-vascularized regions of the retina, respectively. At all ages, MHCII was expressed by a high proportion of cells in the vascularized region, which contained macrophage-like 'parenchymal cells' as well as typical perivascular macrophages. MHCII expression by ramified microglia, first detected on postnatal day 30, was lower in the peripheral retina and intermediate in the avascular region of the myelinated streak. The observed localization of MHCII+ cells in relation to blood vessels and location-dependent differences in MHCII expression point to the possibility that these cells may be distributed strategically within the retina to provide multiple lines of defence against immune challenge arriving via the retinal vasculature.
Insights
This study reveals how major histocompatibility complex class II (MHCII) is expressed by retinal immune cells, like microglia and macrophages, and their relation to blood vessels. This finding is key for understanding immune surveillance in the central nervous system.
Area of Science:
- Neuroscience
- Immunology
- Ophthalmology
Background:
- Microglia and macrophages are key immune cells in the central nervous system.
- Major histocompatibility complex class II (MHCII) expression is crucial for immune cell function and antigen presentation.
- Understanding the retinal immune cell landscape is vital for neuroinflammation and ocular disease research.
Purpose of the Study:
- To investigate the developmental expression of MHCII by retinal microglia and macrophages.
- To determine the relationship between MHCII-expressing cells and retinal blood vessels.
- To elucidate the role of these cells in retinal immune surveillance.
Main Methods:
- Whole-mount rabbit retinas from different developmental stages (embryonic, postnatal, adult) were analyzed.
- Three-color fluorescence microscopy was employed using antibodies for beta2 integrin (CD18) and MHCII.
- Biotinylated Griffonia simplicifolia B4 isolectin was used to label blood vessels.
Main Results:
- CD18+ cells identified as macrophages/microglia in vascularized/non-vascularized retinal regions.
- MHCII was highly expressed by cells in vascularized regions, including parenchymal and perivascular macrophages.
- MHCII expression by ramified microglia emerged postnatally, with location-dependent differences in expression levels.
Conclusions:
- MHCII expression in retinal immune cells is developmentally regulated and spatially distinct.
- The strategic localization of MHCII+ cells relative to blood vessels suggests a role in monitoring immune challenges via retinal vasculature.
- These findings provide insights into the immune surveillance mechanisms of the retina.
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