Overexpression of Programmed Cell Death-1 (PD-1) Affects Circulatory Th1 and Th2 Cells in Patients with Cardiac Arrest in the Early Period After the Return of Spontaneous Circulation

0
0
0

Overexpression of Programmed Cell Death-1 (PD-1) Affects Circulatory Th1 and Th2 Cells in Patients with Cardiac Arrest in the Early Period After the Return of Spontaneous Circulation

Cardiac arrest (CA) is a critical global health issue associated with high morbidity and mortality. Even after the return of spontaneous circulation (ROSC), patients face systemic ischemia/reperfusion injury, which triggers sepsis-like syndromes and immune dysfunction, increasing susceptibility to infections and multi-organ failure. CD4+ T lymphocytes, particularly T-helper (Th) type 1 and Th2 cells, play pivotal roles in immune regulation and host defense. Th1 cells drive cellular immunity through interferon-gamma (IFN-γ) production, while Th2 cells promote humoral responses via interleukin-4 (IL-4). An imbalance in the Th1/Th2 ratio has been implicated in post-CA pathophysiology, yet the mechanisms underlying immune dysfunction remain poorly understood. This study investigates the role of programmed cell death-1 (PD-1), an inhibitory immune checkpoint receptor, in modulating Th1 and Th2 cell dynamics during the early post-ROSC phase.

Immune Dysregulation After Cardiac Arrest

After ROSC, systemic ischemia/reperfusion injury induces oxidative stress and inflammatory cascades that mimic sepsis. Patients exhibit immune suppression, characterized by reduced effector T cell activity and an increased risk of nosocomial infections. Previous studies using CA/cardiopulmonary resuscitation models and clinical observations highlight a disrupted Th1/Th2 balance, favoring Th2 responses. This imbalance compromises antimicrobial defenses and exacerbates organ injury. Th1 cells are critical for combating intracellular pathogens, while Th2 cells mediate anti-inflammatory responses. A skewed Th1/Th2 ratio contributes to prolonged immunosuppression, resembling patterns seen in sepsis.

PD-1, expressed on activated T cells, B cells, and natural killer cells, regulates immune tolerance by inhibiting T cell activation. In sepsis, PD-1 upregulation correlates with T cell exhaustion and poor outcomes. Similarly, CA survivors show elevated PD-1 expression on regulatory T (Treg) cells, suggesting its role in post-ROSC immune dysregulation. However, PD-1’s impact on Th1 and Th2 cells in CA patients remains unexplored.

Study Design and Methodology

This retrospective study enrolled 92 CA patients admitted to emergency departments between October 2018 and September 2019. Inclusion criteria required ROSC duration between 6 and 24 hours and a Glasgow Coma Scale score <8. Exclusion criteria included age <18 years, active infections, malignancies, immunosuppressant use, or immunodeficiencies. A control group of 40 age- and gender-matched healthy individuals was recruited.

Blood samples were collected from residual clinical tests and analyzed using flow cytometry (Gallios™, Beckman Coulter) and a multiplex cytokine assay (ProcartaPlex, Thermo Fisher). Th1 and Th2 cells were identified as CD3+CD8−IFN-γ+ and CD3+CD8−IL-4+ populations, respectively. PD-1 expression was quantified on these subsets using fluorochrome-conjugated antibodies (Supplementary Table 1). Plasma interleukin-6 (IL-6) and IL-10 levels were measured via Luminex assays.

Statistical analyses compared medians using the Mann-Whitney U test. Absolute Th1/Th2 counts, PD-1 expression percentages, and cytokine levels were analyzed.

Key Findings

1. Th1/Th2 Imbalance in Post-ROSC Patients

CA patients exhibited significantly reduced Th1 and Th2 cell counts compared to healthy controls:

  • Th1 cells: 5.72 [0.97, 25.94] cells/mL vs. 41.69 [21.75, 87.30] cells/mL (Z = −5.353, P < 0.001).
  • Th2 cells: 0.73 [0.26, 1.86] cells/mL vs. 0.97 [0.65, 2.33] cells/mL (Z = −2.142, P = 0.032).
  • Th1/Th2 ratio: 7.79 [3.58, 18.30] vs. 34.72 [15.06, 67.67] (Z = −5.674, P < 0.001).

Notably, Th1 depletion was more pronounced, skewing the balance toward Th2 dominance. However, no significant differences in Th1/Th2 ratios or cell counts were observed between 28-day survivors and non-survivors (P > 0.05) (Supplementary Tables 4 and 5).

2. Upregulated PD-1 Expression on Th1 and Th2 Cells

PD-1 expression was elevated in both subsets during the early post-ROSC phase:

  • PD-1+ Th1 cells: 29.95% [20.88, 41.90] vs. 24.00% [18.30, 29.73] in controls (Z = −2.696, P = 0.007) (Figure 1A).
  • PD-1+ Th2 cells: 29.30% [19.63, 39.60] vs. 24.65% [17.75, 29.10] in controls (Z = −2.659, P = 0.008) (Figure 1B).

PD-1 overexpression did not differ significantly between survivors and non-survivors (Figures 1C and 1D). This suggests that PD-1 upregulation is an early but non-prognostic marker of immune dysfunction.

3. Elevated Pro- and Anti-Inflammatory Cytokines

Plasma IL-6 (pro-inflammatory) and IL-10 (anti-inflammatory) levels were markedly higher in CA patients:

  • IL-6: 1.54 [−0.41, 4.16] vs. 0.24 [−4.61, 2.42] in controls (Z = −2.346, P = 0.019) (Supplementary Figure 3A).
  • IL-10: 3.95 [−2.30, 5.26] vs. −2.30 [−2.30, 4.60] in controls (Z = −2.149, P = 0.032) (Supplementary Figure 3B).

Survivors and non-survivors showed no significant cytokine differences, though non-survivors trended toward higher IL-10 levels.

Mechanistic Insights

PD-1’s role in post-CA immune dysfunction aligns with its known effects in sepsis. By binding to PD-L1/PD-L2, PD-1 inhibits T cell receptor signaling, reducing IFN-γ production (Th1 response) and enhancing IL-4 (Th2 response). This bias toward Th2 activity may impair pathogen clearance while promoting anti-inflammatory signaling, creating a “double-hit” of immunosuppression and unresolved inflammation.

IL-6 and IL-10 further reinforce this imbalance. IL-6 promotes Th2 differentiation, while IL-10 suppresses Th1 activity. Elevated cytokines correlate with adverse outcomes in CA and sepsis, reflecting systemic inflammation and compensatory anti-inflammatory responses.

Clinical Implications

PD-1 overexpression identifies a subset of CA patients with early immune exhaustion, offering a potential therapeutic target. Preclinical studies show PD-1 blockade restores T cell function and improves survival in sepsis. Similarly, CA patients might benefit from checkpoint inhibitors during post-ROSC care. However, timing is critical—excessive inflammation early after ROSC may necessitate cautious immunotherapy application.

Limitations and Future Directions

This study’s retrospective design limits causal inferences. The single-center cohort and lack of longitudinal data restrict generalizability. Future research should explore PD-1 dynamics over time and assess interventions like anti-PD-1 antibodies in CA models.

Conclusion

Overexpression of PD-1 on Th1 and Th2 cells, coupled with Th1/Th2 imbalance and elevated IL-6/IL-10 levels, characterizes early immune dysfunction in post-ROSC CA patients. These findings underscore PD-1’s role in post-CA immunosuppression and highlight avenues for immunotherapy.

DOI: https://doi.org/10.1097/CM9.0000000000001764

Was this helpful?

0 / 0