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Intravital Microscopy of the Spleen: Quantitative Analysis of Parasite Mobility and Blood Flow
Published on: January 14, 2012
Intravital microscopy comparing T lymphocyte trafficking to the spleen and the mesenteric lymph node
Mitchell H Grayson1, Richard S Hotchkiss, Irene E Karl
1Division of Allergy and Immunology, Washington University School of Medicine, St. Louis, Missouri 63110, USA. wheeze@allergist.com
Insights
T cell rolling velocity in lymph nodes depends on specific adhesion molecules. However, spleen T cell accumulation differs, influenced by unique vascular mechanics rather than these molecules.
Area of Science:
- Immunology
- Cell Biology
- Microcirculation
Background:
- Lymphocyte trafficking is crucial for immune surveillance.
- Leukocyte-alpha(4)-integrin (CD49d), L-selectin, and MAdCAM-1 mediate lymphocyte rolling in lymph nodes.
- The mechanisms of T cell emigration to the spleen are not well understood.
Purpose of the Study:
- To investigate the role of L-selectin and CD49d in T lymphocyte rolling velocity in the spleen.
- To characterize the microvascular environment of T cell adherence in the spleen.
- To compare T cell trafficking mechanisms between the spleen and other lymphoid organs.
Main Methods:
- Real-time intravital confocal microscopy in murine models.
- Utilized FITC-dextran and TIE2-GFP mice to define splenic microvasculature.
- Analyzed T lymphocyte rolling velocities and adherence patterns.
Main Results:
- T cell rolling velocity in mesenteric lymph node high endothelial venules (HEVs) depends on L-selectin and CD49d.
- Spleen T lymphocyte rolling velocity is independent of L-selectin and CD49d.
- T cell adherence in the spleen occurs in non-endothelialized white pulp regions with high shear rates.
Conclusions:
- T cell trafficking to the spleen employs distinct mechanisms compared to other secondary lymphoid organs.
- The spleen's unique vascular architecture and mechanical properties significantly influence T cell accumulation.
- These findings highlight the importance of the spleen's blood-filtering function in immune cell homing.
Abstract:
Lymphocyte rolling velocity is determined largely by interactions between leukocyte alpha(4)-integrin (CD49d) and L-selectin and mucosal addressin cell adhesion molecule-1 (MAdCAM-1) in mesenteric postcapillary venules and Peyer's patch high endothelial venules (HEVs). The role of these interactions in other tissue sites of lymphocyte emigration is not known. With the use of real-time intravital confocal microscopy, we found that rolling velocities of T lymphocytes in the murine mesenteric lymph node (MLN) HEV also depend on L-selectin and CD49d. However, in the murine spleen, rolling velocities of T lymphocytes are not influenced by the loss of L-selectin and CD49d. With the use of FITC-dextran and TIE2-GFP mice, we further defined the microvascular compartments of the spleen and showed that adherence of T cells is localized to regions in the white pulp that are not lined by endothelial cells and have shear rates similar to bone marrow sinusoids. These results establish that T cell trafficking to the spleen differs from trafficking to other secondary lymphoid organs and suggest that the mechanical properties of the blood-filtering role of the spleen are important in T cell accumulation in the organ.
