T cell zone resident macrophages silently dispose of apoptotic cells in the lymph node

Dendritic cells (DC) are the most potent antigen-presenting cells of the immune system. In lymph nodes (LN), they are also believed to dispose of apoptotic cells, a critical function usually achieved by macrophages (M) in other tissues. We report a population of tolerogenic M located in the T cell zone of LN. T zone M (TZM) are long lived M seeded after birth and slowly replaced by blood monocytes. We show that TZM but not DC act as the only professional scavengers clearing apoptotic cells in the LN T cell zone. Importantly, we demonstrate that TZM prevent the capture of apoptotic cells by DC and the associated potential noxious activation of T cell immunity. We thus propose a new model in which efferocytosis and T cell activation are uncoupled processes handled by TZM and DC respectively.

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Baratin M, Simon L, Jorquera A, Ghigo C, Dembele D, Nowak J, Gentek R, Wienert S, Klauschen F, Malissen B, Dalod M, Bajénoff M