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Decreased Fc receptor expression on macrophages following simple hemorrhage as observed by scanning immunoelectron
Abstract:
Although it is known that macrophage (M phi) functions such as phagocytosis and antigen presentation are depressed following hemorrhage and resuscitation, the mechanism remains unknown. The aim of this study was to determine, using scanning immunoelectron microscopic techniques, whether there is any alteration in the Fc receptors on the M phi after hemorrhage. To study this, male C3H/HeN mice were bled to a mean blood pressure (BP) of 35 mm Hg and maintained at that pressure for 1 hr, then resuscitated with their own blood and adequate fluids. Twenty-four hrs later, Kupffer cells from livers and splenic adherent cells were isolated, incubated for 16 hr, and then exposed to polysterene beads conjugated with antimouse IgG that specifically binds to Fc receptors. The cells were then prepared for observation by scanning electron microscopy. At least 100 cells from each animal were examined. The number of Kupffer cells from posthemorrhage mice that exhibited specific receptor labeling was significantly decreased (41.0 +/- 2.6, P less than 0.05) compared with control (64.2 +/- 7.5). The number of splenic adherent cells from posthemorrhage mice exhibiting specific receptor labeling was also significantly decreased (35.7 +/- 2.5, P less than 0.01) compared with control (61.2 +/- 3.9). The internalization of markers was also seen in some cells. The cause of the decrease in receptor labeling following hemorrhage may be the loss, inactivation, and/or internalization of receptors. Thus the decreased number of functional macrophages may contribute to the depression of antigen presentation and to the enhanced susceptibility to sepsis following hemorrhage.
Insights
Hemorrhage and resuscitation decrease macrophage Fc receptors, impairing immune function. This study reveals reduced Fc receptor labeling on Kupffer and splenic cells post-hemorrhage, potentially explaining immune depression and sepsis susceptibility.
Area of Science:
- Immunology
- Cell Biology
- Physiology
Background:
- Macrophage (M phi) functions like phagocytosis and antigen presentation are known to be impaired after hemorrhage and resuscitation.
- The underlying mechanisms for this functional depression remain largely unknown.
Purpose of the Study:
- To investigate alterations in Fc receptors on macrophages following hemorrhage using scanning immunoelectron microscopy.
- To determine if changes in Fc receptors contribute to the observed functional deficits in macrophages.
Main Methods:
- Male C3H/HeN mice underwent induced hemorrhage to a mean blood pressure of 35 mm Hg for 1 hour, followed by resuscitation.
- Kupffer cells and splenic adherent cells were isolated 24 hours post-resuscitation.
- Cells were incubated and exposed to polystyrene beads conjugated with antimouse IgG to label Fc receptors, followed by scanning electron microscopy analysis.
Main Results:
- A significant decrease in Fc receptor labeling was observed on Kupffer cells from post-hemorrhage mice (41.0 +/- 2.6%) compared to controls (64.2 +/- 7.5%).
- Splenic adherent cells also showed a significant reduction in Fc receptor labeling post-hemorrhage (35.7 +/- 2.5%) compared to controls (61.2 +/- 3.9%).
- Internalization of Fc receptor markers was noted in some cells, suggesting receptor loss or inactivation.
Conclusions:
- Hemorrhage and resuscitation lead to a significant decrease in Fc receptor expression or accessibility on macrophages.
- This reduction in functional Fc receptors may contribute to the impaired antigen presentation and increased susceptibility to sepsis observed after hemorrhage.
- Potential mechanisms include receptor loss, inactivation, or internalization following hemorrhagic shock.