[Programmed cell death protein 1 and its ligands regulate immune balance in allergic rhinitis]

Objective: To explore the expression and significance in regulating immune balance of programmed cell death protein 1 (PD-1) and its ligands PD-L1, PD-L2 in allergic rhinitis (AR). Methods: Eighty-two patients who received outpatient treatment due to high nasal reaction symptoms or were hospitalized due to nasal septum deviation and underwent nasal septum correction surgery in Department of Otorhinolaryngology Head and Neck Surgery of Renmin Hospital of Wuhan University from May 2018 to May 2019 were enrolled, including 42 males and 40 females, with the age ranging from 14 to 38 years old. Blood, inferior turbinate nasal mucosal tissue and relevant clinical data were collected. Patients were divided into AR group and control group due to clinical manifestation, skin prick test and detection of specific IgE (sIgE) in serum. Immunohistochemistry was used to detect the expression of PD-1 and its ligands in nasal mucosa of the two groups. Flow cytometry was used to detect the proportions of PD-1(+)CD4(+)T cells, PD-L1(+) myeloid dendritic cells (mDCs), PD-L2(+)mDCs and Th2 cells in peripheral blood of the two groups. The expression levels of total IgE, sPD-1, sPD-L1 and sPD-L2 in serum of the two groups were detected by ELISA. The measurement data of normal distribution or normal distribution after the logarithm conversion to Ln were compared by t test. Pearson correlation or Spearman correlation was used to analyze the correlation among the indicators. P<0.05 was considered statistically significant. Results: The expression of PD-1 and its ligands on the surface of immune cells in the nasal mucosa of the AR group was significantly higher than that of the control group. The ratio of PD-1(+)CD4(+)T cells, PD-L1(+)mDCs and Th2 cells in peripheral blood of AR group was significantly higher than that of the control group ((15.24±6.45)% vs (8.71±5.33)%, (8.79±2.01)% vs (5.74±2.90)%, (7.89±1.95)% vs (2.52±1.34)%, all P<0.05). There was no significant difference in the ratio of PD-L2(+)mDCs between the two groups. Correlation analysis found that the proportion of PD-1(+)CD4(+) T cells was positively correlated with the Visual Analogue Scale (VAS) score of AR, total IgE concentration and the serum sIgE concentration (r value was 0.501, 0.541, 0.608, respectively, all P<0.05). The proportion of PD-L1(+)mDCs was positively correlated with the VAS score of AR and the serum sIgE concentration (r value was 0.604, 0.563, respectively, all P<0.05). The proportion of Th2 cells in peripheral blood was positively correlated with the proportion of PD-L1(+)mDCs and PD-1(+)CD4(+)T cells (r value was 0.538, 0.623, respectively, all P<0.05). Serum total IgE, sPD-1 and sPD-L1 in the AR group were significantly higher than those in the control group ((6.34±1.38) ng/ml vs (4.89±1.10) ng/ml, (4.40±1.01) pg/ml vs (3.79±1.21) pg/ml, (3.88±0.25) pg/ml vs (3.57±0.23) pg/ml, all P<0.05), and there was no significant difference in sPD-L2 levels between the two groups. Correlation analysis showed that sPD-L1 was positively correlated with total IgE and sIgE concentration (r values was 0.32, 0.45, respectively, all P<0.05). Conclusions: PD-1 and PD-L1 are highly expressed on the surface of immune cells in peripheral blood and nasal mucosa of AR patients, and sPD-1 and sPD-L1 expression levels in peripheral blood of AR patients are increased. The PD-1/PD-L1 signaling pathway promote AR inflammatory response by inducing Th2 type immune response.