Avaliação do perfil de expressão das moléculas OX40, 4-1BB e CD40/CD40L no mieloma múltiplo / Evaluation of the expression profile of the molecules OX40, 4-1BB and CD40/CD40L in multiple myeloma

Introdução: O mieloma múltiplo é uma desordem clonal das células plasmocitárias e, responde por 10-15% das neoplasias hematológicas. Apresenta diversas alterações no sistema imune, caracterizadas por déficits na produção de anticorpos; alterações do perfil imunológico das células T; aumento da expressão do PD-L1; modificações no microambiente medular favorecendo o recrutamento de populações imunossupressoras como as Treg e disfunção nas células dendríticas. Manter um sistema imune ativo é fundamental para o controle da doença, pacientes com manutenção de células T efetoras apresentam maiores taxas de remissão e sobrevida. Receptores coestimuladores como o OX40, CD40/CD40L e 4-1BB, participam na ativação, proliferação e amplificação da resposta imune. Objetivo: Avaliar os níveis de linfócitos B e T e das moléculas coestimuladoras OX40, CD40, CD40L e 4-1BB no sangue e medula óssea dos pacientes com mieloma múltiplo. Métodos: Trata-se de estudo exploratório, realizado entre 2016 e 2019 no Hospital de Câncer de Pernambuco (HCP) e Laboratório de Pesquisa Translacional do Instituto de Medicina Integral Prof. Fernando Figueira (IMIP). Foram incluídas 40 pacientes, até 79 anos de idade, com diagnóstico de Mieloma Múltiplo. Coletas de sangue periférico e medula óssea foram realizadas ao diagnóstico. As mensurações dos níveis de expressão de proteínas de membrana CD20, CD3, OX40, CD40/CD40L foram detectadas pela técnica de Cytometric Bead Array por citometria de fluxo. A dosagem dos níveis solúveis de s4-1BB, sOX40 e sCD40L foi realizada por enzyme linked immunonoSorbent assay (ELISA). Foi realizada análise de curva Receiver Operating Characteristic (ROC) para determinar o melhor valor de acurácia de cada marcador estudado assim como, a ocorrência de óbito. A análise estatística foi realizada no programa GraphPadPrism v8.0. O nível de significância estatística foi de p<0,05. Resultados: Em sangue periférico, comparando-se pacientes e controles, verificou-se níveis menores de CD20 (p<0,0001) e CD20low (p<0,0001), CD40+ em leucócitos totais (p=0,0005), CD40+ em linfócitos (0,0006) e CD40/CD3+ (p<0,0001) no grupo de pacientes. Mas, em contrapartida, os pacientes apresentaram níveis mais elevados de OX40+ (p=0,0012), CD40L+ em leucócitos totais (p=0,002) e OX40+/CD3+ (p<0,0001). Os níveis séricos de s4-1BB (p=0,03) e sOX40 (p=0,01) estavam reduzidos no grupo de MM quando comparado aos controles. Na análise segundo o ISS, somente os níveis de expressão de CD40L+ em leucócitos (p=0,01) e de CD40+ em linfócitos (p=0,0045), mostraram níveis superiores nos pacientes com ISS1-2 em relação ao ISS-3. As medidas de expressão de OX40+ e CD40L+ em leucócitos totais eram inferiores nos casos com evolução para óbito (p<0,0006 e p=0,002, respectivamente). Os pacientes que apresentavam níveis de expressão de OX40 em leucócitos totais ≥2,93% tiveram maior sobrevida em relação àqueles com valores <2,93% (p=0,03), bem como aqueles com CD40L em leucócitos totais com valores ≥3,09% (p=0,001). Na análise da medula óssea, segundo o ISS, somente os níveis de expressão de OX40/CD3+, mostraram níveis superiores nos pacientes com ISS1-2 em relação ao ISS-3 (p<0,0017). Não foram observadas diferenças significativas entre os valores de expressão dos diversos marcadores em medula óssea, com relação ao desfecho óbito. Na análise de correlação de Spearman, os valores de CD20 em sangue e medula óssea, apresentam uma correlação moderada entre si (r=0,64 e p<0,0001). Conclusão: Os resultados deste estudo permitem concluir que existem alterações de mecanismos celulares envolvidos na regulação e ativação da resposta imune no MM quando comparados aos controles. A manutenção de níveis mais elevados de moléculas coestimuladoras (OX40 ≥2,93% e CD40L≥ 3,09%), foi preditiva de melhor sobrevida no MM

Introduction: Multiple myeloma (MM) is a malignant plasma cell (PC) disorder, accounting for approximately 10-15% of all hematological cancers. Multiple myeloma presents several immune system alterations, characterized by deficits in antibody production, disruption of the T-cell immune profile, increased expression of cell death ligand 1 (PD-L1), changes in the bone marrow microenvironment favoring the recruitment of immunosuppressive populations such as Tregs and dysfunction in dendritic cells. It is important to preserve the integrity of the active immune system for the control of disease progression and patients with maintenance of T-cell cytotoxic activities improve rates of remission and overall survival. Co-stimulating receptors such as OX40, CD40/CD40L and 4-1BB, cooperate in the activation, proliferation, and amplification of the immune response. Objective: To evaluate T and B lymphocyte levels as well as co-stimulating molecules OX40, CD40, CD40L and 4-1BB in the blood and bone marrow of multiple myeloma patients. Methods: This is a cross-sectional and exploratory study, conducted between 2016 and 2019 at Pernambuco Cancer Hospital (HCP) and Translational Research Laboratory of Instituto de Medicina Integral Prof. Fernando Figueira (IMIP). Forty patients, up to 79 years of age, diagnosed with Multiple Myeloma were included. Peripheral blood and bone marrow samples were collected at diagnosis. Serum concentrations of CD20, CD3, OX40, CD40/CD40L were detected through the Cytometric Bead Array technique by flow cytometry, and the soluble forms of s4-1BB, sOX40 e sCD40L by enzyme linked immunosorbent assays. Receiver Operating Characteristic (ROC) curve analysis was performed to determine not only the best accuracy value of each studied marker but also, mortality. Statistical analysis was performed in the GraphPadPrism v8.0 program and the level of statistical significance was p <0.05. Results: In peripheral blood, comparing patients and controls, there were lower levels of CD20 (p<0.0001) and CD20low (p<0.0001), CD40+ in total leukocytes (p=0.0005), CD40+ in lymphocytes (0.0006) and CD40/CD3+ (p<0.0001) in the patient group. However, on the other hand, patients had higher levels of OX40+ (p=0.0012), CD40L+ in total leukocytes (p=0.002) and OX40+/CD3+ (p<0.0001). Serum levels of s4-1BB (p=0.03) and sOX40 (p=0.01) were reduced in the MM group compared to controls. According to the ISS, CD40L+ in leukocytes (p=0.01) and CD40+ in lymphocytes (p=0.0045) showed higher levels in patients with ISS1-2 compared to ISS-3. Regarding the outcome death, levels of OX40+ and CD40L+ in total leukocytes were lower (p<0.0006 and p=0.002, respectively). In survival analyses, patients who had OX40+ levels in total leukocytes ≥2.93% had higher survival compared to those with levels <2.93% (p=0.03), as well as those with CD40L+ in total leukocytes with values ≥3.09% (p=0.001). In the bone marrow only the OX40/CD3+ levels were higher in patients with ISS1-2 compared to ISS-3 (p<0.0017). No significant differences were observed between values of other bone marrow markers in relation to the outcome death. In Spearman's correlation analysis, CD20 levels in blood and bone marrow present moderate correlation between them (r=0.64 and p<0.0001). Conclusion: This study shows differences in cellular mechanisms involved in the regulation and activation of immune response in MM patients in comparison to healthy controls. The maintenance of higher levels of co-stimulating molecules (OX40 ≥2.93% and CD40L≥ 3.09%) is associated with better survival in multiple myeloma

Novel T cells with improved in vivo anti-tumor activity generated by RNA electroporation

The generation of T cells with maximal anti-tumor activities will significantly impact the field of T-cell-based adoptive immunotherapy. In this report, we found that OKT3/IL-2-stimulated T cells were phenotypically more heterogeneous, with enhanced anti-tumor activity in vitro and when locally administered in a solid tumor mouse model. To further improve the OKT3/IL-2-based T cell manufacturing procedure, we developed a novel T cell stimulation and expansion method in which peripheral blood mononuclear cells were electroporated with mRNA encoding a chimeric membrane protein consisting of a single-chain variable fragment against CD3 and the intracellular domains of CD28 and 4-1BB (OKT3-28BB). The expanded T cells were phenotypically and functionally similar to T cells expanded by OKT3/IL-2. Moreover, co-electroporation of CD86 and 4-1BBL could further change the phenotype and enhance the in vivo anti-tumor activity. Although T cells expanded by the co-electroporation of OKT3-28BB with CD86 and 4-1BBL showed an increased central memory phenotype, the T cells still maintained tumor lytic activities as potent as those of OKT3/IL-2 or OKT3-28BB-stimulated T cells. In different tumor mouse models, T cells expanded by OKT3-28BB RNA electroporation showed anti-tumor activities superior to those of OKT3/IL-2 T cells. Hence, T cells with both a less differentiated phenotype and potent tumor killing ability can be generated by RNA electroporation, and this T cell manufacturing procedure can be further optimized by simply co-delivering other splices of RNA, thus providing a simple and cost-effective method for generating high-quality T cells for adoptive immunotherapy.

Nuclear factor-κB pathway mediates the effects of CD137 signaling on NFATc1 expression in mice vascular smooth muscle cells / 中华心血管病杂志

<p><b>OBJECTIVE</b>To observe whether CD137 signaling could affect the nuclear factor of activated T cells c1 (NFATc1) expression through nuclear factor-κB (NF-κB) pathway in mice aortic vascular smooth muscle cells (VSMCs).</p><p><b>METHODS</b>Adherence methods for tissues explants were used for primary culture of mouse aortic VSMCs. The mRNA expression of CD137 and NFATc1 was detected by real-time quantitative PCR (RT-qPCR). The VSMCs protein expression of IκB-α, NF-κB p65, phospo-p65 and NFATc1 was determined by Western blot. The level of CD137 was measured by Flow Cytometry (FCM).</p><p><b>RESULTS</b>(1) The mRNA and protein expression of CD137 in VSMCs was significantly upregulated at 24 h after co-culture with TNF-α (10 ng/ml, all P < 0.05). (2) Compared with the control group, the level of p-NF-κB p65 in cytoplasm and nucleus was significantly increased (8.34 ± 0.28 vs. 1, P < 0.05, and 2.64 ± 0.42 vs. 1, P < 0.05) while the level of IκB-α was reduced (1 vs. 2.70 ± 0.28, P < 0.05) after co-treatment with agonist-CD137 mAb, above effects were partly blocked by adding specific NF-κB inhibitor PDTC (30 µmol/L: 1.15 ± 0.14 vs. 8.34 ± 0.28, P < 0.05, and 2.09 ± 0.12 vs. 2.64 ± 0.42, P < 0.05, and 1.78 ± 0.74 vs. 1, P < 0.05). (3) The mRNA (2.07 ± 0.09 vs. 1, P < 0.05) and protein (1.75 ± 0.07 vs. 1, P < 0.05) expression of NFATc1 was significantly upregulated by agonist CD137mAb compared with the control group, and these effects could be reversed by PDTC (1.15 ± 0.07 vs. 2.07 ± 0.09, P < 0.05, and 0.90 ± 0.11 vs. 1.75 ± 0.07, P < 0.05).</p><p><b>CONCLUSION</b>CD137 signaling could affect the NFATc1expression in VSMCs through NF-kappaB pathway.</p>

CD137 signaling regulates the expression of nuclear factor of activated T cells c1 through miR-145a-5p in ApoE(-)/(-) mice / 中华心血管病杂志

<p><b>OBJECTIVE</b>To investigate if miR-145a-5p participates the modulation process of CD137 signaling on the expression of nuclear factor of activated T cells c1 (NFATc1) in ApoE(-)/(-) mice.</p><p><b>METHODS</b>Atherosclerotic plaque model was produced by perivascular carotid collar placement in ApoE(-)/(-) mice. After surgery, the mice were randomly divided into the following groups: CD137 activated group (CD137 group, n = 6), CD137 inhibited group (anti-CD137 group, n = 6) and control group (n = 6). The mRNA expression of miR-145a-5p in plaque and cells was measured by real-time quantitative PCR (RT-PCR). Immunofluorescence was used to observe the distribution of NFATc1 in plaque and the expression of NFATc1 at mRNA and protein levels were detected by qRT-PCR, Western blot, respectively. The mouse vascular smooth muscle cells (VSMCs) were isolated and transfected with miR-145a-5p mimics or inhibitors by Lipofectamine. The eukaryotic expression vector and luciferase vector including p3xFLAG-NFATc1, p3xFLAG-NFATc1-3'UTR, psicheck2-NFATc1, psicheck2-NFATc1-Mut were constructed through molecular cloning and homologous recombination techniques, 293T cells were transfected with the miR-145a-5p mimics or inhibitors and the protein level and fluorescence intensity were then measured, respectively.</p><p><b>RESULTS</b>In vivo or in vitro, the level of miR-145a-5p was significantly decreased (0.21 ± 0.06 vs. 1.00 ± 0.00, P < 0.05, 0.22 ± 0.07 vs. 0.50 ± 0.12, P < 0.05) while the opposite effects were observed in anti-CD137 group. NFATc1 expression was decreased or increased in VSMCs transfected with miR-145a-5p mimics or inhibitors, respectively (all P < 0.05). miR-145a-5p mimics decreased the expression of p3xFLAG-NFATc1-3'UTR and the fluorescence intensity (0.56 ± 0.08 vs. 1.00 ± 0.00, P < 0.05).</p><p><b>CONCLUSION</b>CD137 signaling participates the regulation process on the expression of NFATc1 through miR-145a-5p in ApoE(-)/(-) mice.</p>

Synergy between dendritic cell-based vaccine and anti-CD137 monoclonal antibody in the treatment of mouse renal cell carcinoma

Therapeutic efficacy of dendritic cell-based vaccine for renal cell carcinoma remains limited. In this study, we investigated whether anti-CD137 monoclonal antibody is capable of potentiating anti-tumor effect of dendritic cellbased vaccine. Experimental study. Research laboratory. Balb/c mice [8-10 weeks old]. A renal cell carcinoma model was established by subcutaneous injection of Renca tumor cells into Balb/c mice on day 0. After three days, tumor-bearing mice were treated with Renca tumor lysate-pulsed dendritic cells [i.e., dendritic cell-based vaccine], anti-CD137 monoclonal antibody, or combination of Renca tumor lysate-pulsed dendritic cells with anti-CD137 monoclonal antibody. Mice were killed on day 20 after tumor cell inoculation, and spleens were harvested for analysis of anti-tumor immune responses. The anti-tumor immune responses were analyzed by measuring proliferation and activity of T cells, which have the ability to kill tumor cells. The anti-tumor effect was assessed by measuring tumor size. The combination therapy with Renca tumor lysatepulsed dendritic cells and anti-CD137 antibody significantly increased T-cell proliferation and activity, and significantly inhibited tumor growth, compared with a single treatment with Renca tumor lysate-pulsed dendritic cells or anti-CD137 antibody. These results suggest that combination therapy can enhance anti-tumor effect by increasing T-cell proliferation and activity

The effect of CD137-CD137 ligand interaction on the expression of nuclear factor of activated T cells c1 in apolipoprotein E-deficient mice atherosclerotic plaque model / 中华心血管病杂志

<p><b>OBJECTIVE</b>To investigate the effects of CD137-CD137L interaction on the nuclear factor of activated T cells c1 (NFATc1) in apolipoprotein E knockout (ApoE(-/-)) mice.</p><p><b>METHODS</b>Atherosclerotic plaque model was produced by rapid perivascular carotid collar placement in ApoE(-/-) mice. In vivo, the expression of NFATc1 in mice plaque and lymphocytes was detected by immunohistochemical and flow cytometry, respectively. In vitro, the NFATc1 mRNA and protein expressions in cultured lymphocytes of ApoE(-/-) mice were measured by RT-PCR and flow cytometry, respectively.</p><p><b>RESULTS</b>In vivo, after stimulating CD137-CD137L signal pathway, the expression of NFATc1 was significantly upregulated in the atherosclerotic plaques and lymphocytes. In vitro, the mRNA and protein expressions of NFATc1 in cultured leukocytes of ApoE(-/-) mice were also significantly increased, the maximal effect appeared post 20 µg/ml anti-CD137 mAb-stimulation and reached maximum at 24 h at any concentrations. Anti-CD137L mAb significantly downregulated the mRNA and protein expressions of NFATc1 in lymphocytes of ApoE(-/-) mice, maximal effect appeared at 20 µg/ml anti-CD137L mAb and reached minimum at 24 h.</p><p><b>CONCLUSION</b>CD137-CD137L interactions can modulate the expression of NFATc1 in this ApoE(-/-) mice atherosclerotic plaque model.</p>

Antileukemic effects in vitro of new co-stimulatory molecule CD137 / 中国实验血液学杂志

This study was aimed to investigate the expression characteristics of new co-stimulatory molecule CD137 (4-1BB) on human T lymphocytes and antileukemic effects of monoclonal antibody hCD137mAb in stimulating the T lymphocyte proliferation, promoting the cytokine secretion, enhancing the cell killing effect and so on. The expression of CD137 on normal T lymphocytes treated with phytohemagglutinin (PHA) was detected by FACS and indirect immunofluorescence. In HL-60 and T lymphocyte system in vitro, the effect of hCD137mAb and PHA on T lymphocyte proliferation was tested by MTT colorimetric assay. The IFN-gamma and IL-4 expression levels on the surface of T cells were detected by FACS and indirect immunofluorescence. In vitro mixed lymphocyte tumor cell culture (MLTC) system, the function of hCD137mAb enhancing toxicity killing leukemic cells at different effect-target ratio were studied. The results showed that almost no expression of hCD137 was found in T cells without PHA stimulation, but after activation of T cells by PHA, the expression gradually increased with a peak at 7th day (FACS 56.4%+/-1.98%, indirect immunofluorescence 52.8%+/-2.01%). CD137mAb alone could not stimulate T cell proliferation (proliferation index 1.002+/-0.011), but could enhance PHA stimulating activity (proliferative index of 2.161+/-0.102) about 2-folds (proliferation index 4.705+/-0.133). Moreover, hCD137mAb increased expression of IFN-gamma high by about 3-fold in presence of PHA, but did not effect on IL-4. The hCD137mAb markedly enhanced T cell killing activity on HL-60 cell line and its co-stimulatory effect was best at the effect-target ratio of 40:1 with increasing of killing percentage by about 2-fold. It is concluded that the new co-stimulatory molecule CD137 has significant antileukemic effect, use of hCD137mAb is an effective, safe and simple immunization strategy for leukemia therapy, this study provides some experimental basis for clinical immunotherapy with CD137 mAb.

Expression of 4-1BB and 4-1BBL in thymocytes during thymus regeneration

4-1BB, a member of the tumor necrosis factor receptor (TNFR) superfamily, is a major costimulatory receptor that is rapidly expressed on the surface of CD4+ and CD8+ T cells after antigen- or mitogen-induced activation. The interaction of 4-1BB with 4-1BBL regulates immunity and promotes the survival and expansion of activated T cells. In this study, the expression of 4-1BB and 4-1BBL was examined during regeneration of the murine thymus following acute cyclophosphamide-induced involution. Four-color flow cytometry showed that 4-1BB and 4-1BBL were present in the normal thymus and were preferentially expressed in the regenerating thymus, mainly in CD4+CD8+ double-positive (DP) thymocytes. Furthermore, the CD4loCD8lo, CD4+CD8lo and CD4loCD8+ thymocyte subsets, representing stages of thymocyte differentiation intermediate between DP and single-positive (SP) thymocytes, also expressed 4-1BB and 4-1BBL during thymus regeneration but to a lesser degree. Interestingly, the 4-1BB and 4-1BBL positive cells among the CD4+CD8+ DP thymocytes present during thymus regeneration were TCR(hi) and CD69+ unlike the corresponding controls. Moreover, the 4-1BB and 4-1BBL positive cells among the intermediate subsets present during thymus regeneration also exhibited TCRhi/int and CD69+/int phenotypes, indicating that 4-1BB and 4-1BBL are predominantly expressed by the positively selected population of the CD4+CD8+ DP and the intermediate thymocytes during thymus regeneration. RT-PCR and Western blot analyses confirmed the presence and elevated levels of 4-1BB and 4-1BBL mRNA and protein in thymocytes during thymus regeneration. We also found that the interaction of 4-1BB with 4-1BBL promoted thymocyte adhesion to thymic epithelial cells. Our results suggest that 4-1BB and 4-1BBL participate in T lymphopoiesis associated with positive selection during recovery from acute thymic involution.

Study on control of graft-versus-host disease by blocking CD137-CD137L ligand costimulatory pathway in mice / 中华血液学杂志

<p><b>OBJECTIVE</b>To explore the in vitro effect on control of graft-versus-host disease (GVHD) and its mechanism in mice by blockade of CD137-CD137L pathway.</p><p><b>METHODS</b>Responder spleen cells from BALB/c donor mice (H-2(d)) were incubated with stimulator spleen cells from C57BL/6 ( H-2(b)) recipient mice, with or without anti-CD137L mAb. Lethally irradiated C57BL/6 mice were transplanted with donor bone marrow cells plus primary MLC spleen T cells. Group A (Allo-BMT control group): allo-BMT mice not receiving any prevention measures for GVHD. Group B (CsA + MTX control group): CsA and MTX given to C57BL/6 mice after transplantation. Group C (experimental group): donor spleen cells from BALB/c mice treated with anti-CD137L mAb. The percentages of CD3+ CD8+ T and CD3+ CD4+ T cells in the three groups were detected by flow cytometry, and the level of cytokines (IFN-gamma, IL-2, IL-10, IL-4) by RT-PCR.</p><p><b>RESULTS</b>The incidence of GVHD in group C was 70%, while in group A and group B were 100%. The survival rate was higher and the median survival time was longer of group C than that of group A and B (P < 0.01). All mice in group A died of aGVHD within 15 ds, while 30% of mice in group C survived more than 30 ds. Symptoms and histological signs of GVHD in group C were the mildest among the three groups. The percentage of CD3+ CD8+ T cells and the levels of IFN-gamma were significantly lower (P < 0.01), and the levels of IL-10 were significantly higher in group C than those in group A and B (P < 0.01).</p><p><b>CONCLUSION</b>Treatment of donor T cells with anti-CD137L mAb in vitro may relieve GVHD, thereby improve the survival time and survival rate, which maybe related to increasing Th1 cytokine (IFN-gamma) and decreasing Th2 cytokine (IL-10) as well as reducing CD3+ CD8+ T cells.</p>

Regulation of Bcl-2 expression in ageing T cells by CD137 and CD28 / 南方医科大学学报

<p><b>OBJECTIVE</b>To observe the effect of the costimulatory molecules CD137 and CD28 on Bcl-2 expression in T cells of mice with D-galactose-induced aging and natural aging.</p><p><b>METHODS</b>Seven-week-old male BALB/c mice were injected daily with D-galactose (120 mg/kg) for 5 months to induce subacute aging, and 16-month-old male BALB/c mice served as the natural aging group. The spleen T cells of were isolated from the rats and stimulated in vitro with conA+IgG, conA+CD137 mAb or conA+CD28 mAb for 48 h. Bcl-2 expression of T cells was detected by flow cytometry and semi-quantitative RT-PCR.</p><p><b>RESULTS</b>In the subacute aging group, Bcl-2 protein expression rate in the T cells stimulated with conA+IgG, conA+CD137 mAb and conA+CD28 mAb were (24.4-/+1.5)%, (34.4-/+2.4) %, and (45.1-/+2.7) %, which were (19.6-/+2.0) %, (26.3-/+1.9) %, and (48.5-/+2.2) % in the natural aging group, respectively. In vitro stimulation with conA+IgG, conA+CD137 mAb and conA+CD28 mAb resulted in expression rate of bcl-2 mRNA in the T cells of 0.309-/+0.039, 0.547-/+0.036, and 0.780-/+0.041 in the subacute aging group, and 0.283-/+0.038, 0.535-/+0.041, and 0.771-/+0.063 in the natural aging group, respectively.</p><p><b>CONCLUSION</b>CD137 and CD28 can promote bcl-2 expression at both mRNA and protein level in T cells in aging mice, which may be one of the mechanisms through which CD137 and CD28 molecules inhibit aging T cell apoptosis and maintain their function.</p>

4-1BB gene expression in peripheral blood mononuclear cells from orthotopic liver transplant recipients with graft acceptance / 中华医学杂志(英文版)

<p><b>OBJECTIVE</b>To investigate the gene expression of 4-1BB in peripheral blood mononuclear cells (PBMCs) and the possible significance of the 4-1BB pathway after clinical orthotopic liver transplantation (OLT).</p><p><b>METHODS</b>4-1BB mRNA levels in PBMCs from 22 OLT patients were analyzed by RT-PCR. 4-1BB protein expressed on the surface of CD(4)(+) and CD(8)(+) T cells were detected by flow cytometry, and visualized with direct immunofluorescence and confocal fluorescence microscopy. Patients with primary liver cancer (PLC) and healthy volunteers served as controls. Six cases of recently performed liver transplantation were also observed in this study.</p><p><b>RESULTS</b>4-1BB mRNA was detected in PBMCs from both liver transplant patients with long-term graft acceptance (22 cases) and from transplant patients on day 1 to day 3 post-transplantation (6 cases), but was not found in PBMCs from transplant patients on day 7 to day 30 post-transplantation (6 cases). 4-1BB mRNA was also not found in samples from 8 of the healthy controls and 7 of the PLC patients, though very low expression was detected in the other 4 healthy volunteers and 6 PLC patients. Simultaneously, 4-1BB protein was expressed at nearly undetectable levels on CD(4)(+) and CD(8)(+) T cells from healthy controls, PLC patients, as well as OLT patients within the first month post-transplantation (6 cases). However, 4-1BB expression was found on the surface of CD(4)(+) and CD(8)(+) T cells from liver transplant patients with long-term graft acceptance. Direct immunofluorescent staining and confocal fluorescence microscopy clearly revealed evidence of 4-1BB protein on cell membranes of CD(4)(+) and CD(8)(+) T cells from liver transplant patients with long-term graft acceptance. Simultaneously, a significantly higher percentage of CD(3)(+) CD(25)(+) T cells were found in liver transplant patients with long-term graft acceptance group as compared with the healthy control group (P < 0.05). The expression of 4-1BB protein on T cells did not correlate with the survival time of OLT patients postoperation.</p><p><b>CONCLUSIONS</b>This study demonstrates that although patients remain in stable condition after liver transplantation under the treatment of immunosuppressants, activated T cells are present to some extent and 4-1BB protein may be involved in this process. Effector T-cells can exert permanent immunoresponses against grafts under these circumstances. Therefore, we conclude that a new immune response balance is established under the combination of both treatment with immunosuppressants and natural immune responses against alloantigens. Manipulation of the 4-1BB/4-1BBL pathway may provide a therapeutic technique for prolonging graft survival.</p>

Constitutive expression of 4-1BB on T cells enhances CD4+ T cell responses

4-1BB, a transmembrane molecule, member of the tumor necrosis factor receptor superfamily, is an important costimulatory molecule in the immune response, plays a key role in the clonal expansion and survival of CD8(+)T cells. In this study, we investigated 4-1BB regulation of CD4(+)T cell responses using 4-1BB transgenic (TG) mice that constitutively expressed 4-1BB on mature T cells. We first showed that CD4(+)T cells of 4-1BB TG mice had more sustained proliferative capacity in response to TCR/4-1BB stimulation in vitro compared to WT mice. Secondly, 4-1BB TG mice exhibited a more elevated contact hypersensitivity (CHS) response mediated by CD4+ Th1 cells due to more vigorous expansion of and apoptotic inhibition of CD4(+)T cells. Finally, CD4(+)T cells of 4-1BB TG mice had a heightened capacity for T cell priming. Overall, our results demonstrate the involvement of 4-1BB in CD4(+)Th1 cell responses by regulating the clonal expansion and survival of CD4(+)T cells as seen in CD8(+)T cells.