Pregnancy dedifferentiates memory CD8+ T cells into hypofunctional cells with exhaustion-enriched programs
Jared M. Pollard, Grace Hynes, Dengping Yin, Malay Mandal, Fotini Gounari, Maria-Luisa Alegre, Anita S. Chong
Jared M. Pollard, Grace Hynes, Dengping Yin, Malay Mandal, Fotini Gounari, Maria-Luisa Alegre, Anita S. Chong
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Research Article Immunology Transplantation

Pregnancy dedifferentiates memory CD8+ T cells into hypofunctional cells with exhaustion-enriched programs

Abstract

Alloreactive memory, unlike naive, CD8+ T cells resist transplantation tolerance protocols and are a critical barrier to long-term graft acceptance in the clinic. We here show that semiallogeneic pregnancy successfully reprogrammed memory fetus/graft-specific CD8+ T cells (TFGS) toward hypofunction. Female C57BL/6 mice harboring memory CD8+ T cells generated by the rejection of BALB/c skin grafts and then mated with BALB/c males achieved rates of pregnancy comparable with naive controls. Postpartum CD8+ TFGS from skin-sensitized dams upregulated expression of T cell exhaustion (TEX) markers (Tox, Eomes, PD-1, TIGIT, and Lag3). Transcriptional analysis corroborated an enrichment of canonical TEX genes in postpartum memory TFGS and revealed a downregulation of a subset of memory-associated transcripts. Strikingly, pregnancy induced extensive epigenetic modifications of exhaustion- and memory-associated genes in memory TFGS, whereas minimal epigenetic modifications were observed in naive TFGS. Finally, postpartum memory TFGS durably expressed the exhaustion-enriched phenotype, and their susceptibility to transplantation tolerance was significantly restored compared with memory TFGS. These findings advance the concept of pregnancy as an epigenetic modulator inducing hypofunction in memory CD8+ T cells that has relevance not only for pregnancy and transplantation tolerance, but also for tumor immunity and chronic infections.

Authors

Jared M. Pollard, Grace Hynes, Dengping Yin, Malay Mandal, Fotini Gounari, Maria-Luisa Alegre, Anita S. Chong

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Figure 1

Pregnancy induces a hypofunctional phenotype in memory OVA-specific TFGS.

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Pregnancy induces a hypofunctional phenotype in memory OVA-specific TFGS...
(A) Bar graph showing percentage of P vs. R + P mice achieving successful full-term pregnancies; n = 35–49 mated mice per group. Additionally, there was a 100% success rate in sensitized mice subjected to a second pregnancy (n = 12). P values were determined by χ2 test of independence. (B) Bar graph showing number of viable pups at birth (litter sizes) of P vs. R + P mice female mice achieving successful full-term pregnancies; n = 31–39 per group. Each dot indicates individual mice. (C) Experimental design. Female B6 mice were mated with transgenic 2W-OVA.B/c mice, with or without sensitization to 2W-OVA.B/c via skin graft 30 days prior (R+P and P, respectively). Unmated mice with or without skin graft rejection were included as controls (naive [N] and rejection [R], respectively). (D) Representative pseudocolor plots showing OVA:Kb-specific CD8+ T cells (TFGS). Each dot indicates an individual mouse. (E) Normalized total recovery of TFGS at postpartum days 0–3. Data acquired from 2 or more biologically independent experiments; n = 20–38 per group. P values were determined by Kruskal-Wallis 1-way ANOVA with Dunn’s post hoc test. (F and G) Radar plot showing phenotypic profile of TFGS (F) or non-TFGS (G) based on markers of activation, memory, and coinhibition. Data are normalized to the highest and lowest MFI for each marker expressed by TFGS or non-TFGS from all 4 experimental groups. Symbols color coded as in D. Expression is represented as normalized percentage of the highest/lowest-expressing group (based on all OVA+TFGS and non- TFGS) for each marker. (H) UMAP with experimental groups (left) and FlowSOM clustering (right) reveals distinct phenotypic subsets in TFGS. (I) Stacked bar graph showing FlowSOM cluster distributions for each experimental group. (J) UMAP with heatmap overlays to show expression of each phenotypic marker on TFGS at single-cell resolution. Data represent mean ± SEM. Gating strategy, statistical analysis, and representative histograms of this flow data set are in Supplemental Figure 1, A–C. *P < 0.05; ****P < 0.0001.