T Cell Zone Resident Macrophages Silently Dispose of Apoptotic Cells in the Lymph Node

authors

• Baratin Myriam
• Simon Lea
• Jorquera Audrey
• Ghigo Clement
• Dembele Doulaye
• Nowak Jonathan
• Gentek Rebecca
• Wienert Stephan
• Klauschen Frederick
• Malissen Bernard
• Dalod Marc
• Bajenoff Marc

abstract

In lymph nodes (LNs), dendritic cells (DCs) are thought to dispose of apoptotic cells, a function pertaining to macrophages in other tissues. We found that a population of CX3CR1(+) MERTK+ cells located in the T cell zone of LNs, previously identified as DCs, are efferocytic macrophages. Lineage-tracing experiments and shield chimeras indicated that these T zone macrophages (TZM) are long-lived macrophages seeded in utero and slowly replaced by blood monocytes after birth. Imaging the LNs of mice in which TZM and DCs express different fluorescent proteins revealed that TZM-and not DCs-act as the only professional scavengers, clearing apoptotic cells in the LN T cell zone in a CX3CR1-dependent manner. Furthermore, similar to other macrophages, TZM appear inefficient in priming CD4 T cells. Thus, efferocytosis and T cell activation in the LN are uncoupled processes designated to macrophages and DCs, respectively, with implications to the maintenance of immune homeostasis.

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