This study examined how natural torpor reshapes the immune system in a hibernating mammal, the thirteen-lined ground squirrel. The authors combined single-cell RNA sequencing (scRNA-seq) with quantitative image analysis of splenic tissues to define both morphological and transcriptional changes across immune cell types during torpor. The work aims to identify cellular programs that mediate reversible immune suppression and to highlight molecular targets with potential translational relevance.
The investigators used single-cell transcriptomics to profile immune cell populations from spleen and paired these data with quantitative image analysis to assess tissue-level architecture. These complementary approaches enabled mapping of lineage-specific numerical changes alongside gene expression programs in situ. Specific experimental parameters, sample sizes, and analytic thresholds are reported in the preprint supplementary material but are not reproduced here.
Quantitative imaging revealed a marked contraction of the splenic white pulp during torpor. This architectural change reflected selective depletion of regions normally enriched for adaptive immune cells. The white-pulp contraction was accompanied by relative preservation of red-pulp and innate compartments, indicating an overall reorganization of splenic microanatomy consistent with energy conservation.
Image analysis and single-cell counts showed preferential numerical loss of adaptive lymphocyte niches, notably B cell- and T cell-rich areas. In contrast, innate myeloid populations were numerically preserved or relatively enriched. Thus, torpor produces a hierarchical shift in immune cellular composition that favors innate surveillance over adaptive abundance, likely reflecting energetic priorities during prolonged low-metabolic states.
Across diverse immune lineages, scRNA-seq revealed a conserved transcriptional program consistent with metabolic downscaling. Key features of this program included suppression of glycolytic pathways, downregulation of cell-cycle progression genes, reduced RNA-processing and translational signatures, and decreased expression of glucose transporters. In parallel, induction of cold-shock RNA-binding proteins was observed, suggesting a coordinated molecular response to the low-temperature, low-energy torpor state.
Although B cells retained lineage-defining features, they underwent both numerical reduction and transcriptional contraction. These changes were linked to remodeling of follicles within the splenic white pulp. The data indicate that follicular architecture and B cell programs are specifically reconfigured during torpor, consistent with an adaptive compartment that can be scaled down and subsequently restored.
T cells adopted a quiescent, stress-resistant transcriptional state during torpor. Importantly, this quiescence was not accompanied by enrichment of apoptotic programs, suggesting that T cells are preserved in a non-proliferative but viable condition rather than being eliminated. This preservation of lineage identity despite metabolic suppression implies capacity for rapid functional recovery on arousal.
Innate cell populations—including myeloid lineages—were relatively numerically preserved in the torpid spleen. Transcriptionally, these innate cells exhibited restrained activation programs rather than inflammatory upregulation, consistent with a role in low-energy tissue surveillance rather than active immune defense. This pattern supports the concept that innate surveillance is maintained at low cost during torpor.
The combined morphological and transcriptional data support a model in which torpor imposes a coordinated, multi-tiered, and reversible immune suppression. Hierarchical programs selectively downscale energy-intensive adaptive responses while maintaining essential innate infrastructure. Cells across lineages retain identity, enabling restoration of pre-torpor immune states after arousal. The authors characterize this state as energy-conserving yet protective of key immune capacity.
The authors highlight that the identified molecules and pathways mediating torpor-driven immune suppression could inform development of targeted interventions for human diseases. Specifically, they suggest potential relevance for therapies against autoimmune conditions, certain cancers, and infectious diseases by leveraging pathways that reversibly suppress or modulate immune activity. The preprint reports no competing interests. Detailed experimental parameters and supplementary analyses are available in the source document but are not reiterated here.