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Transfer of macrophage-derived mycobacterial antigens to dendritic cells can induce naïve T-cell activation
A Girvan1, F E Aldwell, G S Buchan
1Department of Microbiology, University of Otago, Dunedin, New Zealand.
Abstract:
Mycobacteria are capable of surviving and replicating in host macrophages, where they can release antigenic material into the environment. However, unlike dendritic cells (DCs), macrophages do not appear to be capable of activating naïve T cells. Therefore, this work investigated antigen transfer between macrophages and DCs. We generated culture supernatants from bacille Calmette-Guérin (BCG)-infected and uninfected macrophages and then determined whether DCs could present these extracellular mycobacterial antigens to T cells. Here, we show that DCs pulsed with antigens released from BCG-infected macrophages can stimulate primed T cells in vitro and initiate naïve T-cell responses in vivo. These results suggest that antigen transfer can occur between macrophages and DCs.
Insights
Macrophages transfer mycobacterial antigens to dendritic cells (DCs), enabling DCs to activate T cells. This antigen transfer is crucial for initiating immune responses against mycobacteria.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Mycobacteria survive within host macrophages, releasing antigens.
- Macrophages present antigens but cannot activate naive T cells.
- Dendritic cells (DCs) are professional antigen-presenting cells crucial for T cell activation.
Purpose of the Study:
- To investigate antigen transfer from macrophages to dendritic cells (DCs).
- To determine if DCs can present extracellular mycobacterial antigens to T cells.
- To understand the role of this transfer in initiating T cell responses.
Main Methods:
- Generated culture supernatants from bacille Calmette-Guérin (BCG)-infected and uninfected macrophages.
- Pulsed DCs with these macrophage-derived antigens.
- Assessed the ability of antigen-pulsed DCs to stimulate primed T cells in vitro.
- Evaluated the capacity of antigen-pulsed DCs to initiate naive T-cell responses in vivo.
Main Results:
- Dendritic cells pulsed with antigens from BCG-infected macrophages stimulated primed T cells in vitro.
- These DCs initiated naive T-cell responses in vivo.
- Demonstrated the presentation of extracellular mycobacterial antigens by DCs.
Conclusions:
- Antigen transfer occurs between macrophages and dendritic cells.
- This transfer facilitates the initiation of T cell-mediated immunity against mycobacteria.
- Highlights a novel mechanism for antigen presentation in mycobacterial infections.