Yan-jun Zhao

BACKGROUND: Recent studies have shown that neutrophils may display an antigen-presenting function and inhibit lymphocyte proliferation by expressing programmed cell death 1 ligand 1 (PD-L1). The current study was performed to investigate the effect of neutrophils and their pathophysiological significance during sepsis. METHODS: Neutrophil PD-L1 expression was determined in both septic mice (n = 6) and patients (n = 41). Neutrophils from septic mice were subtyped into PD-L1 and PD-L1 populations to determine their phenotypes and functions. Septic neutrophils were cocultured with lymphocytes to observe the effect of septic neutrophils on lymphocyte apoptosis. RESULTS: The PD-L1 level on neutrophils from septic mice was significantly up-regulated (21.41 ± 4.76%). This level increased with the progression of sepsis and the migration of neutrophils from the bone marrow to the blood and peritoneal cavity. The percentages of CD11a, CD62L, and C-C chemokine receptor type 2 were lower, whereas the percentages of CD16 and CD64 were higher on PD-L1 neutrophils than on PD-L1 neutrophils. The migratory capacity of PD-L1 neutrophils was compromised. Septic neutrophils induced lymphocyte apoptosis via a contact mechanism, and this process could be reversed by anti-PD-L1 antibody. PD-L1 was also up-regulated on neutrophils from patients with severe sepsis (14.6% [3.75%, 42.1%]). The levels were negatively correlated with the monocyte human leukocyte antigen-DR level and positively correlated with the severity of septic patients. Neutrophil PD-L1 was a predictor for the prognosis of severe sepsis, with an area of 0.74 under the receiver operating curve. CONCLUSIONS: PD-L1 is up-regulated on neutrophils during sepsis, which may be related to sepsis-induced immunosuppression.

Intercellular adhesion molecule-1 (ICAM-1) is a key adhesion molecule mediating neutrophil migration and infiltration during sepsis. But its role in the outcome of sepsis remains contradictory. The current study was performed to investigate the role of anti-ICAM-1 antibody in the outcome of polymicrobial sepsis and sepsis-induced immune disturbance. Effect of anti-ICAM-1 antibody on outcome of sepsis induced by cecal ligation and puncture (CLP) was evaluated by the survival analysis, bacterial clearance, and lung injury. Its influence on neutrophil migration and infiltration, as well as lymphocyte status, in thymus and spleen was also investigated. The results demonstrated that ICAM-1 mRNA was upregulated in lung, thymus, and spleen of CLP mice. Anti-ICAM-1 antibody improved survival and bacterial clearance in CLP mice and attenuated lung injury. Migration of neutrophils to peritoneal cavity was enhanced while their infiltration into lung, thymus, and spleen was hampered by ICAM-1 blockade. Anti-ICAM-1 antibody also prevented sepsis-induced apoptosis in thymus and spleen. Positive costimulatory molecules including CD28, CD80, and CD86 were upregulated, while negative costimulatory molecules including PD-1 and PD-L1 were downregulated following anti-ICAM-1 antibody administration. In conclusion, ICAM-1 blockade may improve outcome of sepsis. The rationale may include the modulated neutrophil migration and the reversed immunosuppression.

Millions of patients benefit from surgery and are exposed to surgical stress. However, ample studies suggest that surgical stress contributes to tumor recurrence or distant metastases. Surgical stress suppresses CD8+ T cells (CTL) function which is vital for eliminating the malignant cells. Anti-programmed cell death 1 (PD-1) therapy is an effective and safe treatment that increases survival rate of patients with multiple cancers, however, whether anti-PD-1 therapy is able to reverse the immunosuppression following surgery remains largely unknown. Using a surgical stress mice model, we found that surgical stress reduced CD8+ T cell total numbers in the spleen and impaired CTLs function. Surgical induced CD8+ T cells had impaired anti-tumor effects in a tumor bearing models. Blockade of PD-1 with specific antibody restored CD8+ T cell numbers and secretion ability. PGE2 expression was dramatically upregulated in the postoperative serum, and anti-PD-1 together with PGE2 inhibitor restored CTLs dysfunction induced by surgery. Collectively, blockade of PD-1 with monoclonal antibody may be an effective treatment during the postoperative period for restoring surgery-induced immunosuppression.

Objective To investigated whether the anti-CD54 antibody can protect the lung function and improve the immune function on septic mice.Methods Experimental sepsis was induced by cecal ligation and puncture (CLP).24 C57BL/6 mice were randomly divided into 4 groups:Sham group,CLP group(CLP+saline),Anti-CD54 group (CLP+Anti-CD54 antibody) and Isotype group (CLP +isotype antibody).Pathological morphology changes of lung tissue were observed.Wet/dry ratios and myekoperoxidase(MPO) activities of lung tissue were measured.The expression of tumor necrosis factor-α(TNF-α),interleukin(IL)-10 and IL-6 mRNA of lung tissue were detected by reverse transcriptive polymerase chain reaction (RT-PCR).The blood and peritoneal cavity lavage bacterial burden were assayed.The spleen and thymus were used to evaluate apoptotic level and their MPO activities were also measured.Results Compared with the CLP group and Isotype group,hematoxylin-eosin (HE) staining showed that the histological damages occurred in Anti-CD54 group were lower and expressed as interval slightly widened,no significant bleeding and a small amount of inflammatory cell infiltration.The RT-PCR results showed that the expression level of TNF-α(3.93±0.82) and IL-10 (2.83±0.55) mRNA in Anti-CD54 group were obviously lower than that of CLP group [(8.22±2.34),(6.05± 1.52)] and Isotype group [(8.54± 1.75),(5.56± 1.33)] (P＜0.05).The MPO level of thymus [(45 ± 10) U/mg],spleen [(39±8) U/mg] and lung [(64± 12) U/mg]tissue in Anti-CD54 group were lower than that of CLP group[(98±13),(78±12),(105±10) U/mg]and Isotype group[(88±20),(90±16),(110±16) U/mg] (P＜0.05).After treated with Anti-CD54 antibody (4.03 ±0.18),CLP mice lung showed lower wet-to-dry ratio compared with CLP group (4.95±0.18) and Isotype group(4.81±0.31) (P＜0.05).Compared to the CLP group[(76±18),(72 833±7 176)]and Isotype group [(69±18),(66 532±143 006)],the peritoneal cavity lavage (5±2) and blood (6±2) bacterial clearance were significantly elevated in anti-CD54 antibody group (P＜0.001).The terminal deoxynucleotidyl transferase mediated nick end labeling (TUNEL) assays of thymus (55±13) and spleen(45±17) in Anti-CD54 group were less than that of CLP group[(127±30),(130±25)]and Isotype group [(223±15),(110±42)](P＜0.01)respectively.Conclusions Anti-CD54 antibody showed therapeutic effects on septic mice,which may be related to improving pulmonary function,increasing blood and peritoneal clearance and inhibition of apoptosis of spleen and thymus. Key words: Sepsis;  Cecal ligation and puncture;  Neutrophil;  Intercellular adhesion molecule-1;  Immune function