Increased inhibitory surface marker PD-1 expression in CD4⁺T cells and Th2⁺T cells in allergen-specific immunotherapy

Recent evidence has shown that T cell exhaustion is implicated in Allergen-specific Immunotherapy (AIT). However, how T cell exhaustion plays a role in AIT is far from clear. Our study aimed to investigate T cell exhaustion associated with allergen exposure during AIT in mice. Ovalbumin (OVA) - sensitized C57BL/6J asthma mouse and AIT mouse models were constructed. Quantitative real-time PCR (qRTPCR) and flow cytometry were used to monitor the occurrence of local and systemic CD4⁺ T cells and Th2⁺T cells exhaustion in OVA-sensitized mice. The inhibitory surface marker programmed cell death protein 1 (PD-1) on CD4⁺ T cells and Th2⁺T cells was significantly upregulated in AIT mice compared with asthmatic and control mice. The level of PD-1 on the surface of CD4⁺T cells of asthma mice was significantly higher than that of control mice. The inhibitory surface marker cytotoxic T lymphocyte-associated protein 4 (CTLA-4) on CD4⁺ T cells and Th2⁺T cells showed no significant difference between the AIT, asthma and control mice. Collectively, our study indicated that the expression of PD-1 on CD4⁺ T cells and Th2⁺T cells was increased in AIT. Allergen exposure promotes the expression of PD-1 on the surface of CD4⁺ T cells. T cell exhaustion plays an important role in AIT.