CD163+ red pulp macrophages interact with marginal metallophilic macrophages during blood-stage malaria to maintain splenic architecture.

The spleen harbors distinct macrophage subsets that support circulatory homeostasis and initiate immune responses, but the ontogeny and long-term dynamics of these populations remain incompletely understood. Here, we identified a transcriptionally and developmentally distinct CD163-expressing red pulp macrophage (CD163high RPM) population that arose from yolk sac progenitors and occupied a vascular-associated niche. Using fate-mapping models, we showed that CD163- RPMs were progressively replenished by monocytes during aging, whereas CD163high RPMs were mainly self-maintaining. During blood-stage malaria, CD163high RPMs were rapidly depleted, failed to recover despite parasite clearance, and were replaced by CD163- monocyte-derived RPMs. Single-cell RNA sequencing and genetic mouse models revealed that CD163 deficiency exacerbated structural disintegration of the marginal zone and selectively impaired marginal metallophilic macrophage (MMM) recovery, underscoring a CD163-dependent RPM-MMM crosstalk. This study reveals that the sustained loss of a specialized, yolk sac-derived CD163high RPM subset rewires splenic architecture and inter-macrophage crosstalk long after malaria resolution.