Related Experiment Videos
Murine cytomegalovirus-induced macrophage dysfunction
Abstract:
Macrophages infected in vitro with murine cytomegalovirus (MCMV) manifest depressed phagocytic uptake of a variety of particles within hours after the initiation of infection. Analysis of kinetics of uptake of radiolabeled Staphylococcus aureus by MCMV-infected macrophages indicates that the diminished uptake results from a depression in the calculated maximum velocity of uptake (Vmax) with the apparent Michaelis constant (KM) remaining unaltered. This pattern of altered uptake is typical of that seen after manipulations that affect the surface interactions of macrophages with ingestible particles. Coincubation of macrophages and radiolabeled Staphylococcus with opsonizing antibody resulted in normalization of the phagocytic rates. The surface localization of the defective phagocytosis was further confirmed by light and scanning electron microscopy of the macrophages incubated with Staphylococcus or latex spherules. These data indicate that defective macrophage surface that interferes with the initial macrophage-particle interactions that initiate nonimmune phagocytosis.
Insights
Murine cytomegalovirus (MCMV) infection impairs macrophage phagocytosis by reducing uptake velocity, not binding affinity. This defect affects non-immune phagocytosis and can be overcome with antibody opsonization.
Area of Science:
- Immunology
- Virology
- Cell Biology
Background:
- Macrophages are crucial immune cells involved in phagocytosis.
- Murine cytomegalovirus (MCMV) is a common viral pathogen that infects macrophages.
- Viral infections can alter macrophage function, impacting host defense.
Purpose of the Study:
- To investigate the effect of MCMV infection on macrophage phagocytic activity.
- To elucidate the mechanism behind the observed depression in phagocytosis.
- To determine if the defect in phagocytosis is surface-mediated.
Main Methods:
- In vitro infection of macrophages with MCMV.
- Measurement of radiolabeled Staphylococcus aureus uptake kinetics.
- Analysis of Vmax and KM values.
- Light and scanning electron microscopy.
- Coincubation experiments with opsonizing antibody.
Main Results:
- MCMV-infected macrophages showed significantly reduced phagocytic uptake of particles.
- The diminished uptake was attributed to a decreased Vmax, while KM remained unchanged.
- Surface localization of the defect was confirmed via microscopy.
- Antibody opsonization normalized the phagocytic rates.
Conclusions:
- MCMV infection induces a defect in macrophage phagocytosis.
- The defect primarily affects the maximum velocity of particle uptake, indicating an issue with internal processing rather than initial binding.
- This impairment of non-immune phagocytosis is surface-related and can be modulated by immune factors like antibodies.