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Published on: September 5, 2016
Macrophages are required for influenza virus infection of human lymphocytes
Abstract:
Monocyte and lymphocyte surface-expressed viral antigens have been demonstrated after exposure of unseparated human mononuclear leukocytes to influenza virus in vitro. The current studies, using [35S]methionine pulse-labeled purified preparations of virus-exposed macrophages, depleted of lymphocytes, demonstrate that the presence of these viral proteins does represent new synthesis. However, purified lymphocytes, depleted of monocytes-macrophages and exposed to influenza virus, showed no detectable viral protein synthesis. In further experiments, unseparated mononuclear leukocytes were exposed to virus and subsequently separated by countercurrent centrifugal elutriation. Both macrophages and lymphocytes were then shown to synthesize influenza proteins. Cell-free control or influenza virus-infected macrophage-derived supernatant fluids did not facilitate influenza virus infection of the lymphocytes. The data suggest that macrophages are required for influenza virus infection of human lymphocytes, and raise the possibility that macrophage facilitation of an abortive infection of lymphocytes plays a role in the generation of effective immunity to viral antigens.
Insights
Macrophages are essential for human lymphocytes to become infected by influenza virus. This interaction may be key to developing immunity against viral antigens.
Area of Science:
- Immunology
- Virology
- Cell Biology
Background:
- Viral antigens on monocytes and lymphocytes were previously observed after exposing human mononuclear leukocytes to influenza virus.
- The origin of these viral proteins (new synthesis vs. external acquisition) remained unclear.
Purpose of the Study:
- To determine if macrophages are necessary for influenza virus infection of human lymphocytes.
- To investigate the role of macrophages in lymphocyte susceptibility to influenza virus.
Main Methods:
- Purified macrophages and lymphocytes were isolated from human mononuclear leukocytes.
- [35S]methionine pulse-labeling was used to detect new protein synthesis.
- Countercurrent centrifugal elutriation was employed for cell separation.
Main Results:
- Virus-exposed macrophages, depleted of lymphocytes, demonstrated new synthesis of viral proteins.
- Virus-exposed lymphocytes, depleted of monocytes-macrophages, showed no detectable viral protein synthesis.
- Both purified macrophages and lymphocytes synthesized influenza proteins when initially together, but not when separated without specific conditions.
Conclusions:
- Macrophages are required for human lymphocytes to become infected with influenza virus.
- Macrophage-facilitated, possibly abortive, infection of lymphocytes may contribute to generating immunity against viral antigens.
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