Clinical significance of B7-H3 expression in circulating CD4+CD25high T cells, CD14+ monocytes, and plasma for the progression of HIV infection.

BACKGROUND: B7-H3 is an important immune checkpoint molecule that plays a negative role in immune regulation. This study was aimed to explore B7-H3 expression in HIV-infected patients and its clinical significance. METHODS: To explore the expression and clinical significance of B7-H3 in HIV-infected patients, we investigated the B7-H3 expression pattern and the correlation of B7-H3 expression with clinical parameters of HIV-infected patients with different levels of CD4+ T cells. To assess the role of B7-H3 in regulating the function of T cells in HIV infection, we performed a proliferation assay and T cell function test in vitro. RESULTS: B7-H3 expression in HIV-infected patients was significantly higher than that in healthy controls. mB7-H3 expression on CD4+CD25high T cells and CD14+ monocytes increased with disease progression. mB7-H3 expression on CD4+CD25high T cells and monocytes was negatively correlated with lymphocyte count, CD4+T cell count, and positively correlated with HIV viral load in HIV-infected patients. when the number of CD4+ T cells in HIV-infected patients was ≥ 200/µL, sB7-H3 and mB7-H3 expression levels on CD4+CD25high T cells and monocytes were negatively correlated with lymphocyte count, CD4+T cell count. sB7-H3 and mB7-H3 expression on monocytes were positively correlated with HIV viral load. B7-H3 inhibited the proliferation of lymphocytes and the secretion of IFN-γ in vitro, especially the ability of CD8+ T cells to secrete IFN-γ. CONCLUSIONS: B7-H3 played an important negative regulatory role in anti-HIV infection immunity. It could be used as a potential biomarker for the progression of HIV infection and a novel target for the treatment of HIV infection.

The exhaustion of lymphocytes is the main factor that decreases the sensitivity of QFT-GIT detection in silicosis.

BACKGROUND: Tuberculosis infection is a major complication of silicosis, but there is no study on whether silicosis can affect the sensitivity of QuantiFERON-TB Gold In-Tube (QFT-GIT) assays. This study will analyze the relationship between silicosis and QFT-GIT, determine the main factor of the QFT-GIT sensitivity decrease in silicosis and explore the methods to increase the sensitivity. METHODS: Silicosis patients with positive tubercle bacillus cultures were collected. The QFT-GIT, flow cytometry and blocking antibodies were used. RESULTS: The sensitivity of QFT-GIT in silicosis patients (58.46%) was significantly decreased and the expression of PD-1 on T cells and CD56+NK cells in pulmonary tuberculosis combined with silicosis were higher than normal tuberculosis patients and silicosis only patients. Further analysis found that the ratio of PD-1+CD4+T and IFN-γwere negatively correlated and blockaded the PD-1 pathway with antibodies can restore the sensitivity of QFT-GIT in silicosis. CONCLUSIONS: This is the first study to analyze the relationship between immune exhaustion and QFT-GIT in silicosis and found that the sensitivity of QFT-GIT was decreased by the expression of PD-1 on lymphocytes. Antibody blocking experiments increased the expression of IFN-γ and provided a new method to improve the sensitivity of QFT in silicosis. The study also found that silicosis can increase PD-1 expression. As PD-1 functions in infectious diseases, it will promote immune exhaustion in silicosis and lead to tuberculosis from latent to active infection. The study provided theoretical evidence for the diagnosis and immunotherapy of silicosis complications, and it has great value in clinical diagnostics and treatment.

The Immune Pathogenesis of Acute-On-Chronic Liver Failure and the Danger Hypothesis.

Acute-on-chronic liver failure (ACLF) is a group of clinical syndromes related to severe acute liver function impairment and multiple-organ failure caused by various acute triggering factors on the basis of chronic liver disease. Due to its severe condition, rapid progression, and high mortality, it has received increasing attention. Recent studies have shown that the pathogenesis of ACLF mainly includes direct injury and immune injury. In immune injury, cytotoxic T lymphocytes (CTLs), dendritic cells (DCs), and CD4+ T cells accumulate in the liver tissue, secrete a variety of proinflammatory cytokines and chemokines, and recruit more immune cells to the liver, resulting in immune damage to the liver tissue, massive hepatocyte necrosis, and liver failure, but the key molecules and signaling pathways remain unclear. The "danger hypothesis" holds that in addition to the need for antigens, damage-associated molecular patterns (DAMPs) also play a very important role in the occurrence of the immune response, and this hypothesis is related to the pathogenesis of ACLF. Here, the research status and development trend of ACLF, as well as the mechanism of action and research progress on various DAMPs in ACLF, are summarized to identify biomarkers that can predict the occurrence and development of diseases or the prognosis of patients at an early stage.

Distribution and clinical significance of circulating CD8+CD28- regulatory T cells in the peripheral blood of patients with pulmonary tuberculosis.

BACKGROUND: Regulatory T cells (Treg cells) in the peripheral blood of patients with pulmonary tuberculosis (PTB) may be closely related to the progression of PTB. In this study, the distribution characteristics and clinical importance of CD8+CD28- Treg cells in patients with tuberculosis were systematically analyzed, and the role and importance of CD8+CD28- Treg cells in influencing the immune response and progression of tuberculosis were discussed, which will provide immunological indices and reference values for the clinical diagnosis of tuberculosis. METHODS: Flow cytometry, sputum smears and computed tomography imaging were used to analyze the distribution characteristics of CD8+CD28- Treg cells in the peripheral blood of patients with PTB and the correlation between CD8+CD28-Treg cells and clinical and immune indices. RESULTS: The percentages of CD4+CD25high and CD8+CD28- Treg cells in the peripheral blood of patients with PTB were significantly higher than those in the healthy control (HC) group. Further analysis showed that the percentage of CD4+CD25highTreg cells in the Stage II group was significantly higher than that in the HC group. The percentages of CD4+CD25high and CD8+CD28- Treg cells increased significantly in patients in the Stage II group. The proportion of CD8+CD28- Treg cells was directly proportional to the degree of positivity in sputum smears, while CD4+CD25highTreg cells did not exhibit this trend. The correlations between the percentage of CD4+CD25high and CD8+CD28- Treg cells and the percentage of lymphocyte subsets were examined. The percentage of CD8+CD28- Treg cells was negatively correlated with the percentage of CD4+T cells and positively correlated with the CD8+T cell percentage in the HC and PTB groups. The percentage of CD4 + CD25highTreg cells was positively correlated with the percentage of CD4+T cells only in the PTB group. CONCLUSIONS: This study was the first to show that the proportion of CD8+CD28- Treg cells in the peripheral blood of patients with PTB was significantly increased, and the increase in CD8+CD28- Treg cells was related to the progression of PTB, which may affect the proportion of immune cell subsets by inhibiting the immune response, resulting in the progression of PTB.

Upregulation of PD-1 expression on circulating CD8+ but not CD4+ T cells is associated with tuberculosis infection in health care workers.

BACKGROUND: Health care workers (HCWs) are at risk for occupationally acquired Mycobacterium tuberculosis infection and tuberculosis (TB) disease due to repeated exposure to workplace tubercle bacilli. To determine whether continual mycobacterial stimulation correlates with increased expression of inhibitory T cell receptors, here we compared PD-1 receptor expression on surfaces of circulating T cells between naïve (uninfected) HCWs and HCWs with latent TB infection (LTBI). RESULT: Data collected from 133 medical workers who met study selection criteria were included in the final analysis. QuantiFERON-TB Gold In-​Tube (QFT-GIT) testing yielded positive results for 32 HCWs, for an overall LTBI rate of 24.1%. Multivariate analysis identified HCW length of service > 15 years as an independent risk factor for a positive QFT-GIT result. In addition, comparisons of blood T cell subgroup profiles between QFT- and QFT+ groups indicated QFT+ subjects possessed greater proportions of mature (TM), transitional memory (TTM) and effector memory (TEM) CD4+ T cell subgroups and lower proportions of naïve T cells (TN). Moreover, the QFT+ group percentage of CD8+ T cells with detectable surface PD-1 was significantly higher than the corresponding percentage for the QFT- group. Meanwhile, no statistical intergroup difference was observed in percentages of CD4+ T cells with detectible surface PD-1. CONCLUSIONS: Our data demonstrated that upregulated PD-1 expression on circulating CD8+, but not CD4+ T cells, was associated with latent TB infection of HCWs. As compared to other hospitals, occupational TB infection risk in our hospital was substantially mitigated by implementation of multitiered infection control measures.

Temporal and spatial characterization of negative regulatory T cells in HIV-infected/AIDS patients raises new diagnostic markers and therapeutic strategies.

BACKGROUND: Negative regulatory T cells (Tregs) not only deplete effector T cells but also inhibit the clearance of HIV during infection, which may allow Tregs to be used as informative diagnostic markers. To facilitate both diagnosis and treatment, a thorough understanding of these regulators by characterizing them on temporal and spatial scales is strongly required. METHODS: Hundred HIV-infected/AIDS patients, including 87 males, with an average age of 35.8 years, as well as 20 healthy controls, were enrolled. Flow cytometry was used to analyze CD3+T cells, CD4+T cells, and CD8+T cells to evaluate the immune status of the participants. Then, a group of representative negative regulatory T cells, including CD4+PD-1+T cells, CD4+PD-1high T cells, CD8+PD-1+T cells, and CD4+CD25high Tregs was also analyzed to explore their effects on disease progression and intercorrelation. RESULTS: The percentages of CD4+ PD-1+ T cells and CD4+ CD25high Tregs increased in patients with the same ultrahigh significance. Temporally, the patients with both intermediate-stage and late-stage disease had higher percentages of CD4+ PD-1+ T cells; however, the percentage of CD4+ CD25high Tregs only increased in the patients with late-stage disease. In addition, CD4+ PD-1+ T cells but not CD4+ CD25high Tregs were negatively correlated with the absolute CD4+ T cell count. Spatially, no correlations between CD4+ PD-1+ T cells and CD4+ CD25high Tregs were observed, which suggests these Tregs function differently during immunosuppression. CONCLUSIONS: This study characterized negative regulatory T cells in HIV-infected/AIDS patients at both temporal and spatial scales and found that CD4+ CD25+ Tregs and CD4+ PD-1+ T cells could be used as potential diagnostic markers for identifying different disease stages and monitoring disease progression.

Clinical characteristics and laboratory indicator analysis of 67 COVID-19 pneumonia patients in Suzhou, China.

BACKGROUND: Sudden exacerbations and respiratory failure are major causes of death in patients with severe coronavirus disease 2019(COVID-19) pneumonia, but indicators for the prediction and treatment of severe patients are still lacking. METHODS: A retrospective analysis of 67 collected cases was conducted and included approximately 67 patients with COVID-19 pneumonia who were admitted to the Suzhou Fifth People's Hospital from January 1, 2020 to February 8, 2020. The epidemiological, clinical and imaging characteristics as well as laboratory data of the 67 patients were analyzed. RESULTS: The study found that fibrinogen (FIB) was increased in 45 (65.2%) patients, and when FIB reached a critical value of 4.805 g/L, the sensitivity and specificity、DA, helping to distinguish general and severe cases, were 100 and 14%、92.9%, respectively, which were significantly better than those for lymphocyte count and myoglobin. Chest CT images indicated that the cumulative number of lung lobes with lesions in severe patients was significantly higher than that in general patients (P < 0.05), and the cumulative number of lung lobes with lesions was negatively correlated with lymphocyte count and positively correlated with myoglobin and FIB. Our study also found that there was no obvious effect of hormone therapy in patients with severe COVID-19. CONCLUSIONS: Based on the retrospective analysis, FIB was found to be increased in severe patients and was better than lymphocyte count and myoglobin in distinguishing general and severe patients. The study also suggested that hormone treatment has no significant effect on COVID-19.

Myeloid cell-like transcript 2 is related to liver inflammation and the pathogenesis of hepatitis B via the involvement of CD8+T cell activation.

This study analysed the biological significance of TLT-2 on CD8+T cells in hepatitis B patients and provided a theoretical basis for the potential role of TLT-2 as an immune regulator. Flow cytometry sorting, isobaric tags for relative and absolute quantitation and short hairpin RNAs were used to analyse the function of TLT-2 on CD8+T cells in hepatitis B patients. The TLT-2 expression levels in the acute hepatitis B and chronic hepatitis B groups were significantly higher than that in the healthy control group and were positively correlated with ALT and AST. The CD8+TLT-2+T cells exhibited stronger immune function and greater cell proliferation ability and secreted higher levels of cytokines than the CD8+TLT-2-T cells. An analysis of the proteome differences between the TLT-2+CD8+T and TLT-2-CD8+T cells revealed that TLT-2 affected CD8+T cell activation by regulating Granzyme B expression and by further action on the NF-κB signalling pathway. This study first elucidated the mechanism by which TLT-2 influences the activation of CD8+T cells, improved the understanding of the TLT-2 signalling pathway and clarified the role of the TLT-2+CD8+T cell subset in hepatitis B virus infection. The study proposed a novel subset of CD8+T cells that could be useful for understanding the immune function of patients with hepatitis B and further elucidating the pathogenesis of hepatitis B by analysing changes in this subpopulation with the goal of providing a new target for the treatment of hepatitis B.

The biological functions of LGR5 in promoting non-small cell lung cancer progression.

BACKGROUND: The Leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5), which is used as a marker of adult stem cells and colorectal cancer stem cells (CSCs), is closely associated with the progression of non-small cell lung cancer (NSCLC). This study aimed to identify the clinical significance and biological function of LGR5 in NSCLC. METHODS: Quantitative reverse transcription polymerase chain reaction (RT-PCR) was applied to detect the expression of LGR5 and stemness-related genes in 22 NSCLC patients, and the clinical significance of LGR5 in NSCLC progression was estimated by statistical analysis. LGR5 overexpressing A549- and H1299-transfected cells were established, and CCK-8 and clone formation assays were used to test the proliferation ability. A wound-healing assay was utilized to clarify the migration ability. The invasion ability was confirmed via the Transwell assay kit. RESULTS: LGR5 expression was markedly higher in NSCLC tissues than in the matched adjacent normal tissues, and had a trend to associate with tumor size, lymph node metastasis, and TNM stage. The proliferation rates, clone formation rates, wound healing rates, number of invasive cells, and the NOTCH1 expression of the LGR5 overexpressing groups, were significantly higher than those of the control groups. CONCLUSIONS: LGR5 plays an essential role in NSCLC tumorigenesis and is closely associated with the proliferation, metastasis, and invasion of NSCLC cells. LGR5 may promote NSCLC progression via NOTCH1 and could be a new target for gene-targeted therapies for NSCLC.

Clinical Significance of B7-H3 Expression During the Progression of Hepatitis B Virus Infection.

B7-H3, one of the costimulatory members participating in checkpoint pathway, has been shown to be upregulated after hepatitis B virus (HBV) infection. To further explore the clinical significance of dynamic B7-H3 expression during the progression of HBV infection, we systematically investigated the expression pattern of B7-H3 and the correlation of B7-H3 expression with the ratio of T lymphocyte subsets and clinical parameters at different stages in the course of the disease. Flow cytometry and enzyme-linked immunosorbent assay data showed that soluble form of B7-H3 (sB7-H3) was positively correlated with the frequency of Treg cells in acute hepatitis B (AHB), chronic hepatitis B (CHB), and hepatocellular carcinoma patients with HBV infection (HBV-HCC). Membrane form of B7-H3 (mB7-H3) expressed on Treg cells and monocytes was positively correlated with the frequency of Treg cells in CHB. SB7-H3 had relationship with mB7-H3 expressed on Treg cells and monocytes at different stages during HBV infection, except for HBV-HCC. MB7-H3 expressed on Treg cells was positively correlated with that on monocytes in AHB, CHB, HBV-liver cirrhosis, and HBV-HCC. The B7-H3 expression was positively correlated with aspartate aminotransferase and alanine aminotransferase levels in CHB and sB7-H3 level was higher in late tumor/node/metastasis (TNM) stage in HCC. Higher mB7-H3 expression was associated with greater tumor size, later TNM stage, and worse prognosis in HBV-HCC indicated by immunohistochemistry. Taken together, these results suggested that B7-H3 might contribute to the progression of HBV infection by triggering inhibitory signals in effector T cells and it was closely associated with the progression and poor prognosis during HBV infection. B7-H3 could be utilized as a potential clinical indicator and a potential target for therapeutic strategies against HBV infection.

Risk factors of latent tuberculosis infection and immune function in health care workers in Suzhou, China.

BACKGROUND: The Chinese government has pay attention about tuberculosis infection among medical staff in infectious disease hospitals, but the effects have not yet been reported. This study will explore latent infection and immune function in the medical staff and systematically analyze the associated influencing factors. METHODS: Ninety-four medical staffs were enrolled and 20 medical staffs were defined as low risk group and others were high risk group. We used IFN-γ release assay and flow cytometry to analyze the latent TB infection status and immune function. Logistic regression analyses were performed to identify the independent risk factors of latent TB infection. RESULTS: This study explored and compared the infection status of medical workers and found that the rate of positive TB-IGRA results was higher among high risk group than in low risk group. Working environment, occupational history and work type were risk factors for TB infection in hospital. This study also found that high risk group had higher IFN-γ expression and a lower ratio of CD4+ to CD8+ T cells and further analysis found that this immune disorder is associated with wards and occupations. CONCLUSIONS: This study through rigorous sample collection and analysis found the risk factors of latent tuberculosis infection in health care workers. This finding may provide a theoretical basis to be used by the countries with a high TB burden to further improve their strategies for the prevention of TB infections in hospitals and may give an indication for improving the personal health of medical staff in infectious disease hospitals.

More significance of TB-IGRA except for the diagnose of tuberculosis.

OBJECTIVE: Tuberculosis (TB)-interferon gamma release assay (IGRA) test has the characteristics of short time, high specificity, and high sensitivity, but it lacks the correlation research between TB-IGRA test results and body's immune cells, disease progression and prognosis, which is explored in this study. DESIGN: A retrospective study was carried out on positive TB-IGRA patients who were infected with TB and diagnosed at our hospital from January 2014 to June 2015. The TB-IGRA, routine blood test, T-cell subgroup data were collected for statistical analysis. RESULTS: TB-IGRA results were in positive proportion to the lymphocytes, CD4+ T cells and CD4+ CD28+ T cells, whereas negative to the Treg cells. Patient with unilateral pulmonary lesion had higher TB-IGRA than those with bilateral pulmonary lesions. After the stimulation of TB-specific antigen, the proportion of CD4+ IFN-γ+ and CD8+ IFN-γ+ T Tcells were both increased and the CD4+ IFN-γ+ T had positive correlation with the value of TB-IGRA. CONCLUSIONS: IFN-γ was tested with TB-IGRA in patients with TB by the specific TB T cells and correlated with the lymphocytes, while the lymphocytes also closely related to the host's anti-TB immunity and disease outcome. Hence the result of TB-IGRA could reflect the specific anti-TB immunity ability of the host, disease progression and prognosis. This study further expands the application scope of TB-IGRA technology in the diagnosis of TB and lays a foundation for clinical practice to understand the immunity state of the patients with TB and the application of auxiliary clinical immunity regulators.

The Expression of B7-H3 in Circulating CD4+CD25high T Cells, Circulating CD14+ Monocytes and Plasma during Hepatitis B Virus Infection Progression.

BACKGROUND: B7-H3 is frequently upregulated in response to autoantigens and pathogens during host T cell immune responses. However, the role of B7-H3 which express in CD14+ monocytes and CD4+CD25high T cells had not been investigated. METHODS: Cytometry and ELISA were used in this study. RESULTS: The study showed that B7-H3 expression in CD14+ monocytes, CD4+CD25high T cells, and plasma was significantly increased in AHB, CHB, HBV-LC, and HBV-HCC group. In CHB group, the expression of B7-H3 was positively correlated with the ALT and AST levels. CONCLUSIONS: B7-H3 expression in peripheral CD14+ monocytes, CD4+CD25high T cells, and plasma changed with HBV infection progression and had a significant correlation with liver function in CHB. B7-H3 expression could be utilized as a potential clinical indicator to determine the extent of liver injury.

New attempt in tuberculosis treatment: autologous cytokine-induced killer after chemotherapy treatment failure in a case of multi-drug resistant tuberculosis (MTB).

A 32-year-old woman was diagnosed as pulmonary tuberculosis 15 years ago and recurred several times due to long-term nonstandard treatment. Drug sensitivity test indicated that multidrug-resistant tuberculosis had emerged and we determined relevant therapeutic schedule according to this result. However, it didn't show any amelioration of the disease after 3-month chemotherapy. We formulated 3-course CIK immunotherapy based on patient's condition. After 3 courses of immunotherapy, we found obvious amelioration of the patient's condition. And there was no recurrence during the follow-up in the past 3 years. Therefore, we considered that the CIK immunotherapy is an effective method for tuberculosis treatment and recurrence prevention. (Sarcoidosis Vasc Diffuse Lung Dis 2017; 34: 97-99).

Expression of PD-L1 on CD4+CD25+Foxp3+ Regulatory T Cells of Patients with Chronic HBV Infection and Its Correlation with Clinical Parameters.

Regulatory T cells (Tregs) play a pivotal role in suppressing specific antiviral immune responses during the progression of chronic hepatitis B virus infection (CHB) as well as tumorigenesis. Programmed death-1 ligand-1 (PD-L1) expressed on Tregs can transduce an inhibitory signal into effector T cells through interacting with programmed death-1 (PD-1). However, in CHB patients, the clinical significance of PD-L1 expression on Tregs has not been clearly described. This study investigated the frequency of circulating Tregs and PD-L1 expression on Tregs and analyzed their correlations with clinical parameters. The data show that both the frequency of CD4+CD25+FoxP3+ Tregs and PD-L1 expression on Tregs in the peripheral blood increased significantly in CHB patients when compared with healthy controls. At the same time, it is shown that PD-L1 expression on Tregs was positively correlated with the percentage of Tregs in CHB patients. Moreover, the results demonstrated that both Treg frequency and PD-L1 expression on Tregs positively correlated with the levels of alanine aminotransaminase (ALT) and aspartate aminotransferase (AST), both of which are indicators of the extent of liver injury. Taken together, these findings suggest that PD-L1 on Tregs might contribute to progression of hepatitis B virus infection through mediating the inhibitory function of Tregs. Thereby, blockade of interaction between Treg-expressing PD-L1 and PD-1 on effector T cells may be adopted as a potential therapeutic approach in CHB.

The role of LGR5 and ALDH1A1 in non-small cell lung cancer: Cancer progression and prognosis.

The Leucine rich repeat containing G protein coupled receptor 5 (LGR5), may be a candidate marker of non-small cell lung cancer (NSCLC) cells with stem cell-like properties. Aldehyde dehydrogenase 1A1 (ALDH1A1) is one of NSCLC stem cell markers. To identify the relationship of LGR5 and ALDH1A1 in NSCLC, we analyzed the expression of LGR5 and ALDH1A1 in NSCLC samples, and determined their clinical significance. We performed quantitative RT-PCR for LGR5 and ALDH1A1 expression in 24 NSCLC patients, and showed that LGR5 and ALDH1A1 mRNA were frequently increased in NSCLC tissues in comparison to that in adjacent normal tissues (p = 0.0005 and p < 0.0001, respectively). Besides, the expression of LGR5 and ALDH1A1 mRNA has a significant correlation (r = 0.416, P = 0.0483). The expression of LGR5 and ALDH1A1 in 109 NSCLC tumors and 50 adjacent normal tissues were detected by immunohistochemistry. Positive LGR5 and ALDH1A1 expression was defined in 28.4% and 41.3% of the NSCLC tumors, respectively. Further analysis indicated that 24 of these LGR5⁺ (24/31) samples expressed ALDH1A1(r = 0.3883, p < 0.0001), we also found co-localization of LGR5 and ALDH1A1 in tumor tissue samples. LGR5 and ALDH1A1 expression was significantly associated with higher pathological TNM stage of the disease (stage I + II and III + IV) (P = 0.0311 and p = 0.0221, respectively), the co-expression of LGR5 and ALDH1A1 was associated with nodal status (p = 0.0424). High expression of LGR5 or ALDH1A1 was related to poor prognosis (P = 0.0125 and p = 0.0410, respectively), and NSCLC patients with co-expression of LGR5 and ALDH1A1 had a poorer prognosis than the others (P = 0.0011). Both of them can be an independent risk factor of a poorer prognosis (P = 0.016 and P = 0.024, respectively). The expression of LGR5 and ALDH1A1 were closely associated with the tumorigenicity, metastasis and poor prognosis of NSCLC, and LGR5⁺ cells in NSCLC were likely to be the cancer cells with stem cell-like properties due to the significant correlation between LGR5 and ALDH1A1.

Generation and characterization of two novel monoclonal antibodies produced against human TLT-2 molecule.

Trem-like transcript 2 (TLT-2), one of the TREM family members, which is expressed on B cells, T cells, and macrophages, plays a critical role in immune response mechanism. In this study, two novel mouse anti-human TLT-2 monoclonal antibodies (MAbs) were prepared using hybridoma technology and their immunological characteristics were determined. The results showed that the two MAbs (clones 10F5 and 8C10) were both IgG1 (κ) and bound specifically to human TLT-2. Furthermore, 10F5 and 8C10 seemed to recognize a different site (epitope) of TLT-2 by competition assay. MAb 10F5 was proven in Western blot analysis to specifically bind to denatured TLT-2 protein while both MAbs were proven in dot blot analyses and immunofluorescence to specifically bind to natural TLT-2 protein. In addition, crosslinking of TLT-2 with MAb 8C10 markedly blocked TLT-2 positive signal and T cell proliferation. Taken together, these two monoclonal antibodies might be of great value as tools for further exploration of the expression and function of TLT-2.