Cytolytic mechanisms and expression of activation-regulating receptors on effector-type CD8+CD45RA+CD27- human T cells

A maladaptive pleural environment suppresses preexisting anti-tumor activity of pleural infiltrating T cells

Introduction

Treatment options for patients with malignant pleural effusions (MPE) are limited due, at least in part, to the unique environment of the pleural space, which drives an aggressive tumor state and governs the behavior of infiltrating immune cells. Modulation of the pleural environment may be a necessary step toward the development of effective treatments. We examine immune checkpoint molecule (ICM) expression on pleural T cells, the secretomes of pleural fluid, pleural infiltrating T cells (PIT), and ability to activate PIT ex vivo.

Methods

ICM expression was determined on freshly drained and in vitro activated PIT from breast, lung and renal cell cancer. Secretomics (63 analytes) of activated PIT, primary tumor cultures and MPE fluid was determined using Luminex technology. Complementary digital spatial proteomic profiling (42 analytes) of CD45+ MPE cells was done using the Nanostring GeoMx platform. Cytolytic activity was measured against autologous tumor targets.

Results

ICM expression was low on freshy isolated PIT; regulatory T cells (T-reg) were not detectable by GeoMx. In vitro activated PIT coexpressed PD-1, LAG-3 and TIGIT but were highly cytotoxic against autologous tumor and uniquely secreted cytokines and chemokines in the > 100 pM range. These included CCL4, CCL3, granzyme B, IL-13, TNFα, IL-2 IFNγ, GM-CSF, and perforin. Activated PIT also secreted high levels of IL-6, IL-8 and sIL-6Rα, which contribute to polarization of the pleural environment toward wound healing and the epithelial to mesenchymal transition. Addition of IL-6Rα antagonist to cultures reversed tumor EMT but did not alter PIT activation, cytokine secretion or cytotoxicity.

Discussion

Despite the negative environment, immune effector cells are plentiful, persist in MPE in a quiescent state, and are easily activated and expanded in culture. Low expression of ICM on native PIT may explain reported lack of responsiveness to immune checkpoint blockade. The potent cytotoxic activity of activated PIT and a proof-of-concept clinical scale GMP-expansion experiment support their promise as a cellular therapeutic. We expect that a successful approach will require combining cellular therapy with pleural conditioning using immune checkpoint blockers together with inhibitors of upstream master cytokines such as the IL-6/IL-6R axis.

Radiotherapy plus camrelizumab affects peripheral CD8 T-cell differentiation subsets expressing PD-1, TIGIT, and CTLA-4 in esophageal squamous cell carcinoma

Our previous phase Ib trial (NCT03222440) showed that radiotherapy plus the anti-PD-1 antibody camrelizumab is a safe and feasible first-line therapy for locally advanced esophageal squamous cell carcinoma. In this study, we divided peripheral CD8 T-cell differentiation subsets into 4 subpopulations (naive T cells, central memory T cells, effector memory T cells, and CD45RA+ effector memory T cells). We then investigated the influence of radiotherapy plus camrelizumab therapy on the proportions of the 4 subsets and their PD-1, TIGIT, and CTLA-4 expression as well as their proliferative activity and compared the effects with those of concurrent chemoradiotherapy. Nineteen and 15 patients with esophageal squamous cell carcinoma who received radiotherapy plus camrelizumab therapy and concurrent chemoradiotherapy, respectively, were enrolled in this study. We isolated peripheral blood mononuclear cells from these patients before treatment and longitudinally after the delivery of 40 Gy radiotherapy. Flow cytometry was conducted to detect peripheral CD8 T-cell subsets and PD-1, TIGIT, CTLA-4, and Ki67 expression levels in patients with esophageal squamous cell carcinoma. We found that radiotherapy plus camrelizumab therapy did not change the proportions of the 4 subsets or the expression of CTLA-4, but this therapy decreased PD-1 expression by the 4 subsets and TIGIT expression by effector memory T cells, as well as significantly enhanced the proliferative activity of CD8 T cells, whereas concurrent chemoradiotherapy produced different effects. In addition, we further identified peripheral biomarkers that potentially predict the outcome of radiotherapy plus camrelizumab therapy.

Fixed drug eruptions, bullous drug eruptions, and lichenoid drug eruptions

Drug reactions are among the most common reasons for inpatient dermatology consultation. These reactions are important to identify because discontinuation of the offending agent may lead to disease remission. With the rising use of immunomodulatory and targeted therapeutics in cancer care and the increased incidence in associated reactions to these drugs, the need for accurate identification and treatment of such eruptions has led to the development of the "oncodermatology" subspecialty of dermatology. Immunobullous drug reactions are a dermatologic urgency, with patients often losing a significant proportion of their epithelial barrier; early diagnosis is critical in these cases to prevent complications and worsening disease. Lichenoid drug reactions have myriad causes and can take several months to occur, often leading to difficulties identifying the offending drug. Fixed drug eruptions can often mimic other systemic eruptions, such as immunobullous disease and Stevens-Johnson syndrome, and must be differentiated from them for effective therapy to be initiated. We review the clinical features, pathogenesis, and treatment of immunobullous, fixed, and lichenoid drug reactions with attention to key clinical features and differential diagnosis.

Exploiting NK Cell Surveillance Pathways for Cancer Therapy

Natural killer (NK) cells can evoke potent anti-tumour activity. This function is largely mediated through a battery of specialised cell-surface receptors which probe the tissue microenvironment for changes in surface and secretory phenotypes that may alert to the presence of infection or malignancy. These receptors have the potential to arouse the robust cytotoxic and cytokine-secreting functions of NK cells and so must be tightly regulated to prevent autoimmunity. However, such functions also hold great promise for clinical intervention. In this review, we highlight some of the latest breakthroughs in fundamental NK cell receptor biology that have illuminated our understanding of the molecular strategies NK cells employ to perceive malignant cells from normal healthy cells. Moreover, we highlight how these sophisticated tumour recognition strategies are being harnessed for cancer immunotherapies in the clinic.

Prevention strategies differentially modulate the impact of cytomegalovirus replication on CD8(+) T-cell differentiation in high-risk solid organ transplant patients

The present study aimed to determine whether antiviral prevention strategies against cytomegalovirus (CMV) infection used in high-risk D+R- solid organ transplanted patients can modulate the impact of CMV replication on CD8(+) T-cell differentiation. The different CD8(+) T-cell subpopulations were measured at a single point when at least one year had elapsed since transplantation. A total of 68 D+R- patients were included, of which 33 underwent pre-emptive therapy and 35 received prophylaxis. Multivariate analysis showed that CMV replication was associated with the expansion of CD28־ EMRA CD8(+) T cells in patients managed pre-emptively but not in patients under prophylaxis (21.4% vs. 3.6%). This finding is likely related to the higher frequency of CMV recurrence observed in patients under pre-emptive therapy compared to those under prophylaxis (75% vs. 14.3%; p < 0.001). In fact, multivariate analysis showed that having more than one replication episode was associated with a 17.2% increase (p = 0.001) in the percentage of CD28־ EMRA CD8(+) T cells compared to "no episode" and with a 10.9% increase with respect to "single episodes" (p = 0.025). Additionally, patients with IFNγ response to CMV (QuantiFERON-CMV Reactive) had a higher percentage of late-differentiated CD8(+) T cells than patients lacking this response. In summary, recurrent CMV replication in D+R- patients under pre-emptive therapy was associated with the expansion of CD28־ EMRA CD8(+) T cells, which might have a short-term beneficial effect related to the high functionality of this T-cell subpopulation. Nevertheless, we cannot rule out that this accumulation might have a long-term detrimental effect related to immunosenescence and inflammation.

T-cell receptor Vβ repertoire of CD8+ T-lymphocyte subpopulations in cutaneous leishmaniasis patients from the state of Rio de Janeiro, Brazil

In human cutaneous leishmaniasis (CL), the immune response is mainly mediated by T-cells. The role of CD8⁺ T-lymphocytes, which are related to healing or deleterious functions, in affecting clinical outcome is controversial. The aim of this study was to evaluate T-cell receptor diversity in late-differentiated effector (LDE) and memory CD8⁺ T-cell subsets in order to create a profile of specific clones engaged in deleterious or protective CL immune responses. Healthy subjects, patients with active disease (PAD) and clinically cured patients were enrolled in the study. Total CD8⁺ T-lymphocytes showed a disturbance in the expression of the Vβ2, Vβ9, Vβ13.2, Vβ18 and Vβ23 families. The analyses of CD8⁺T-lymphocyte subsets showed high frequencies of LDE CD8⁺T-lymphocytes expressing Vβ12 and Vβ22 in PAD, as well as effector-memory CD8⁺ T-cells expressing Vβ22. We also observed low frequencies of effector and central-memory CD8⁺ T-cells expressing Vβ2 in PAD, which correlated with a greater lesion size. Particular Vβ expansions point to CD8⁺ T-cell clones that are selected during CL immune responses, suggesting that CD8⁺ T-lymphocytes expressing Vβ12 or Vβ22 are involved in a LDE response and that Vβ2 contractions in memory CD8⁺T-cells are associated with larger lesions.

Identification and immunogenicity of two new HLA-A*0201-restricted CD8+ T-cell epitopes on dengue NS1 protein

Immunopathogenesis of dengue virus (DEN) infection remains poorly studied. Identification and characterization of human CD8(+) T-cell epitopes on DEN are necessary for a better understanding of the immunopathogenesis of dengue infection and would facilitate the development of immunotherapy and vaccines to protect from dengue infection. Here, we identified two new HLA-A*0201-restricted CD8(+) T-cell epitopes, DEN-4 NS1(990)(-998) and DEN-4 NS1(997)(-1005) that are conserved in three or four major DEN serotypes, respectively. Unexpectedly, we found that immunization of HLA-A*0201 transgenic mice with DEN-4 NS1(990)(-998) or DEN-4 NS1(997)(-1005) epitope peptide induced de novo synthesis of tumor necrosis factor (TNF)-α and IFN-γ, two important pro-inflammatory molecules that are hard to be detected directly without in vitro antigenic re-stimulation. Importantly, we demonstrated that CD8(+) T cells specifically activated by DEN-4 NS1(990)(-998) or DEN-4 NS1(997)(-1005) epitope peptide induced de novo synthesis of perforin. Furthermore, we observed that DEN-4 NS1(990)(-998) or DEN-4 NS1(997)(-1005)-specific CD8(+) T cells capable of producing large amounts of perforin, TNF-α and IFN-γ preferentially displayed CD27(+)CD45RA(-), but not CD27(-)CD45RA(+), phenotypes. This study, therefore, suggested the importance of synergistic effects of pro-inflammatory cytokines and cytotoxic molecules which were produced by dengue-specific CD8(+) T cells in immunopathogenesis or anti-dengue immunity during dengue infection.

Lung T-cell subset composition at the time of surgical resection is a prognostic indicator in non-small cell lung cancer

NSCLC arises in the complex environment of chronic inflammation. Depending on lung immune polarization, infiltrating immune cells may either promote or suppress tumor growth. Despite the importance of the immune microenvironment, current staging techniques for NSCLC do not take into consideration the immune milieu in which the neoplasms arise. T-cell subset content was compared between paired tumor-bearing and contralateral lungs, patient and control peripheral blood. The relationship between T-cell subset distribution and survival were evaluated. CD4 and CD8+ T cells were subsetted by CD45RA/CD27 and analyzed for expression of activation, adhesion, and homing markers. Strikingly, T-cell content was indistinguishable between lungs. Compared with peripheral blood, naïve CD4 and CD8 T cells were rare in BAL. CD4+ BAL T cells showed increased CD95 (higher apoptotic potential) and CD103 expression (epithelial adhesion), but decreased CD38 (activation) and CCR7 expression (lymph node homing). CD8+ BAL T cells showed increased CD103 expression and decreased CD28 expression (co-stimulation). Differences in CD28, CD95, and CCR7 expression were more pronounced within memory cells, while differences in CD4+ CD103 expression were more prominent in effector/memory cells. Of these populations, the absence of lung CD4 T cells with an effector-like phenotype (CD45RA+/CD27-) emerged as a predictor of favorable outcome. Patients with a low proportion (≤0.44%) had 90% 5-year survival (n = 10, median survival 2,343 days), compared with 0% (n = 9, median survival 516 days) of patients with a higher proportion. Further study is required to confirm this association prospectively and define the function of this subpopulation.

PD-1 expression on peripheral CD8+ TEM/TEMRA subsets closely correlated with HCV viral load in chronic hepatitis C patients

BACKGROUND

Tight correlation between host circulating CD8+ T cell-mediated immune response and control of viral replication is classical characteristic of long-term HCV infection. CD8+ T cell maturation/activation markers are expected to be associated with viral replication and disease progression in chronic HCV infection. The aim of the present study was to explore novel markers on CD8+ T cells with ability to evaluate HCV viral replication and disease progression.

METHODS

PBMCs were isolated from 37 chronic HCV-infected patients and 17 healthy controls. Distributed pattern of CD8+ T cells subsets and expression of PD-1, CD38, HLA-DR and CD127 were analyzed by flow cytometry. The correlation between expression of surface markers and HCV viral load or ALT was studied.

RESULTS

Declined naïve and increased TEMRA CD8+ T subsets were found in HCV-infected individuals compared with healthy controls. Percentage and MFI of PD-1, CD38 and HLA-DR on all CD8+ T cell subsets were higher in HCV-infected patients than healthy controls. In contrast, CD127 expression on CD8+ TCM showed an opposite trend as PD-1, CD38 and HLA-DR did. In chronic HCV infection, MFI of PD-1 on CD8+ TEM (p < 0.0001) and TEMRA (p = 0.0015) was positively correlated with HCV viral load while HLA-DR expression on non-naive CD8+ T cell subsets (p < 0.05) was negatively correlated with HCV viral load.

CONCLUSION

PD-1 level on peripheral CD8+ TEM/TEMRA was highly correlated with HCV viral load in chronic HCV-infected patients, which made PD-1 a novel indicator to evaluate HCV replication and disease progression in chronic hepatitis C patients.

HIV-1 matrix protein p17: a candidate antigen for therapeutic vaccines against AIDS

The success in the development of anti-retroviral therapies (HAART) that contain human immunodeficiency virus type 1 (HIV-1) infection is challenged by the cost of this lifelong therapy and by its toxicity. Immune-based therapeutic strategies that boost the immune response against HIV-1 proteins or protein subunits have been recently proposed to control virus replication in order to provide protection from disease development, reduce virus transmission, and help limit the use of anti-retroviral treatments. HIV-1 matrix protein p17 is a structural protein that is critically involved in most stages of the life cycle of the retrovirus. Besides its well established role in the virus life cycle, increasing evidence suggests that p17 may also be active extracellularly in deregulating biological activities of many different immune cells that are directly or indirectly involved in AIDS pathogenesis. Thus, p17 might represent a promising target for developing a therapeutic vaccine as a contribution to combating AIDS. In this article we review the biological characteristics of HIV-1 matrix protein p17 and we describe why a synthetic peptide representative of the p17 functional epitope may work as a vaccine molecule capable of inducing anti-p17 neutralizing response against p17 derived from divergent HIV-1 strains.

Perforin and IL-2 upregulation define qualitative differences among highly functional virus-specific human CD8 T cells

The prevailing paradigm of T lymphocyte control of viral replication is that the protective capacity of virus-specific CD8⁺ T cells is directly proportional to the number of functions they can perform, with IL-2 production capacity considered critical. Having recently defined rapid perforin upregulation as a novel effector function of antigen-specific CD8⁺ T cells, here we sought to determine whether new perforin production is a component of polyfunctional CD8⁺ T cell responses that contributes to the control of several human viral infections: cytomegalovirus (CMV), Epstein-Barr virus (EBV), influenza (flu), and adenovirus (Ad). We stimulated normal human donor PBMC with synthetic peptides whose amino acid sequences correspond to defined CTL epitopes in the aforementioned viruses, and then used polychromatic flow cytometry to measure the functional capacity and the phenotype of the responding CD8⁺ T cells. While EBV and flu-specific CD8⁺ T cells rarely upregulate perforin, CMV-specific cells often do and Ad stimulates an exceptionally strong perforin response. The differential propensity of CD8⁺ T cells to produce either IL-2 or perforin is in part related to levels of CD28 and the transcription factor T-bet, as CD8⁺ T cells that rapidly upregulate perforin harbor high levels of T-bet and those producing IL-2 express high amounts of CD28. Thus, “polyfunctional” profiling of antigen-specific CD8⁺ T cells must not be limited to simply the number of functions the cell can perform, or one particular memory phenotype, but should actually define which combinations of memory markers and functions are relevant in each pathogenic context.

Although CD8⁺ T cells are thought to be largely responsible for the control of viral infections, exactly how they mediate protection is uncertain. One approach to assessing their protective capacity is to measure several of their functions simultaneously. Generally, it is believed the more functions a cell can perform, the better its potential to control viral replication. A multi-functional response including interleukin-2 (IL-2) production is currently valued as the key correlate of protection. We recently characterized a novel CD8⁺ T cell function: rapid perforin upregulation, which serves to contribute to and sustain the killing of virally infected host cells. In this study, we show that new perforin is abundant during adenovirus and cytomegalovirus infections, but scarcely detected in the context of influenza and Epstein-Barr virus. Importantly, perforin and IL-2 are rarely co-expressed. The significance of this relationship is that we can no longer assume the more functions a CD8⁺ T cell performs in response to a virus the better. Thus, when considering vaccine design, no single functional profile will likely be protective across all pathogens. Rather, vaccine-induced T cell responses may need to be “pathogen-specific”, as different T cell functional responses will be important for controlling different viral infections.

T-cell activation profiles in different granulomatous interstitial lung diseases--a role for CD8+CD28(null) cells?

Lymphocytes play a crucial role in lung inflammation. Different interstitial lung diseases may show distinct lymphocyte activation profiles. The aim of this study was to examine the expression of a variety of activation markers on T lymphocyte subsets from blood and bronchoalveolar lavage fluid (BALF) of patients with different granulomatous interstitial lung diseases and healthy controls. Bronchoalveolar lavage cells and blood cells from 23 sarcoidosis patients, seven patients with hypersensitivity pneumonitis and 24 healthy controls were analysed. Lymphocyte activation status was determined by flow cytometry. Lymphocytes were stained with antibodies against CD3, CD4, CD8, CD25, CD28, CD69, very late antigen-1 (VLA)-1, VLA-4 and human leucocyte antigen D-related (HLA-DR). In general, CD28, CD69 and VLA-1 expression on BALF CD4+ lymphocytes and HLA-DR expression on BALF CD8+ lymphocytes was different in patients with hypersensitivity pneumonitis and sarcoidosis patients with parenchymal involvement. This BALF lymphocyte phenotype correlated with carbon monoxide diffusing lung capacity (Dlco) values across interstitial lung diseases (ILD) (r2 = 0.48, P = 0.0002). In sarcoidosis patients, CD8+CD28(null) blood lymphocytes correlated with lower Dlco values (r = -0.66, P = 0.004), chronic BALF lymphocyte activation phenotype (r2 = 0.65, P < 0.0001), radiographic staging (stage I versus stage II and higher, P = 0.006) and with the need for corticosteroid treatment (P = 0.001). Higher expression of CD69, VLA-1 and HLA-DR and lower expression of CD28 on BALF lymphocytes suggests prolonged stimulation and chronic lymphocyte activation in patients with ILD. In sarcoidosis, blood CD8+CD28(null) cells might be a new biomarker for disease severity but needs further investigation.

Human late memory CD8+ T cells have a distinct cytokine signature characterized by CC chemokine production without IL-2 production

Late memory T cell skewing is observed in the setting of immune recovery after cord blood transplantation, and may be associated with inferior control of viral reactivation and cancers. Therefore, we sought to understand how late memory cells differ functionally from earlier stage memory T cells, and whether surface phenotypes associated with differentiation stages were predictably associated with functional signatures. Higher order cytokine flow cytometry allows characterization of human T cells based on complex phenotypic markers and their differential capacity to simultaneously secrete effector proteins, including cytokines and chemokines. We used 8-color, 10-parameter cytokine flow cytometry to characterize the functional activation of human late memory CD8(+) T cells defined by CD45RA and CD27 expression (CD27(-)CD45RA(+)). We assessed the 15 possible functional signatures of cells defined by production of IL-2, IFN-gamma, TNF-alpha, and MIP-1beta alone or in combination, following activation with Ags stimulating bypassing surface proteins (PMA:ionomycin) or through the TCR (e.g., viral Ags). Late memory CD8(+) T cells produced abundant amounts of CC chemokines (MIP-1beta, MIP-1alpha, and RANTES) but not IL-2. IL-2/IFN-gamma coproduction, characteristic of protective immune responses to viral infections, was absent in late memory CD8(+) T cells. These data demonstrate that functional cytokine signatures are predictably associated with CD8(+) maturation stages, and that the polarization of late memory CD8(+) T cells toward CC chemokine production and away from IL-2 production suggests a unique functional role for this subset.

Kinetics of host immune responses and cytomegalovirus resistance in a liver transplant patient

Among solid organ transplant (SOT) recipients, donor-seropositive/recipient-seronegative (D+/R-) cytomegalovirus (CMV) status is associated with the highest risk of ganciclovir-resistant CMV disease, which has been reported for patients receiving oral ganciclovir but not valganciclovir prophylaxis. We report a case of CMV breakthrough infection in a D+/R- liver transplant patient while he was receiving oral valganciclovir. Forty samples collected over 6 months were analyzed for the CMV viral load, lymphocyte counts, cytokine levels, and lymphocyte differentiation status. Genotypic resistance testing of the viral UL97 gene was performed when the patient failed to respond. CMV viremia occurred on day 50 post-transplant, and 5 samples taken between days 50 and 85 showed the wild-type UL97 genotype. The appearance of deletion 594-595 was observed from day 114 post-transplant. Viral loads declined when foscarnet was commenced and remained below 10,000 copies/mL when the lymphocyte count was greater than 1000/microL (P = 0.02). T cell responses revealed significant expansion of CD8+ terminal effector memory cells. CD4+ cells were largely populations of naïve and central memory cells. Circulating interleukin 10 (IL-10) levels correlated with the viral load (P < 0.0001). Seroconversion occurred on day 230. The CMV viral load in combination with lymphocyte counts and IL-10 may be a predictive marker for the risk of development of resistant CMV disease in D+/R- SOT patients.

Metastatic tumour cells favour the generation of a tolerogenic milieu in tumour draining lymph node in patients with early cervical cancer

OBJECTIVE

We compared the immune system state in metastatic tumour draining lymph nodes (mTDLN) and metastasis free TDLN (mfTDLN) in 53 early stage cervical cancer patients to assess whether the presence of metastatic tumour cells worsen the balance between an efficacious anti-tumour and a tolerogenic microenvironment.

METHODS

The immune system state was measured by immunophenotypic and functional assessment of suppressor and effector immune cell subsets.

RESULTS

Compared to mfTDLN, mTDLN were significantly enriched in CD4(+)Foxp3(+) regulatory T cells (Treg), which, in addition, exhibited an activated phenotype (HLA-DR(+) and CD69(+)). Treg in mTDLN were also significantly enriched in neuropilin-1 (Nrp1) expressing cells, a subset particularly potent in dampening T cell responses. mTDLN tended to be enriched in a population of CD8(+)Foxp3(+)T cells (operationally defined as CD8(+)Treg) that showed a suppressor potency similar to Treg under the same experimental conditions. Plasmacytoid dendritic cells (pDC) and myeloid DC (mDC) generally show distinct roles in inducing T cell tolerance and activation, respectively. In line with the excess of suppressor T cells, the ratio pDC to mDC was significantly increased in mTDLN. Immunohistochemical testing showed that metastatic tumour cells produced the vascular endothelial growth factor, a natural ligand for Nrp1 expressed on the cell surface of Nrp1(+)Treg and pDC, and therefore a potential mediator by which tumour cells foster immune privilege in mTDLN. Consistent with the overall tolerogenic profile, mTDLN showed a significant Tc2 polarisation and tended to contain lower numbers of CD45RA(+)CD27(-) effector memory CD8(+)T cells.

CONCLUSIONS

The increased recruitment of suppressor type cells concomitant with the scarcity of cytotoxic type cells suggests that in mTDLN the presence of tumour cells could tip the balance against anti-tumour immune response facilitating the survival of metastatic tumour cells and possibly contributing to systemic tolerance.

Identification of a particular HIV-specific CD8+ T-cell subset with a CD27+ CD45RO-/RA+ phenotype and memory characteristics after initiation of HAART during acute primary HIV infection

CD8(+) T cells play an important role in controlling viral infections. Defective CD8(+) T-cell responses during HIV infection could contribute to viral persistence. Early initiation of highly active antiretroviral therapy during acute primary HIV infection helps to preserve HIV-specific immune responses. Here, we describe a particular CD27(+) CD45RO(-)/RA(+) HIV-specific CD8(+) T cell in participants treated early during the primary infection. These cells, which were present at a very low frequency during primary HIV infection, increased markedly after early treatment, whereas their frequency remained unchanged in untreated participants and in participants treated later. These nonnaive antigen-experienced cells are in a resting state and have characteristics of long-lived memory cells. They also possess direct effector capabilities, such as cytokine production, and are able to proliferate and to acquire cytotoxic functions on reactivation. Our results suggest that these HIV-specific CD27(+) CD45RO(-)/RA(+) CD8(+) T cells, observed when early viral replication is inhibited, form a pool of resting cells with memory characteristics.

Phenotype and function of human T lymphocyte subsets: consensus and issues

In recent years, a tremendous effort has been devoted to the detailed characterization of the phenotype and function of distinct T cell subpopulations in humans, as well as to their pathway(s) of differentiation and role in immune responses. But these studies seem to have generated more questions than definitive answers. To clarify issues related to the function and differentiation of T cell subsets, one session of the MASIR 2008 conference was dedicated to this topic. Several points of consensus and discord were highlighted in the work presented during this session. We provide here an account of these points, including the relative heterogeneity of T cell subpopulations during infections with distinct pathogens, the relationship between phenotypic and functional T cell attributes, and the pathway(s) of T cell differentiation. Finally, we discuss the problems which still limit general agreement.

Flow cytometric detection of degranulation reveals phenotypic heterogeneity of degranulating CMV-specific CD8+ T lymphocytes in rhesus macaques

Flow-cytometric conditions for detection of lysosomal-associated membrane proteins (LAMPs) on the surface of recently degranulated cells were optimized for rhesus macaques and used to investigate the functional properties of rhesus cytomegalovirus (rhCMV)-specific CD8+ T lymphocytes with regards to cytotoxicity and interferon (IFN)-gamma secretion in six asymptomatic CMV-seropositive rhesus macaques. Unlike humans, the rhesus macaque LAMP-1 protein CD107a underwent little or no endocytosis over a six to 18 h stimulation period. Following in vitro stimulation, rhCMV-specific CD8+ T lymphocytes were heterogeneous with regards to the composition of cells positive for CD107a and/or IFN-gamma, time to reach peak degranulation, and kinetics of IFN-gamma secretion relative to degranulation. Responder CD8+ T lymphocytes that underwent degranulation without IFN-gamma production (CD107a+IFN-gamma-) were predominantly composed of terminally differentiated effectors (CD28-CD45RA+). Moreover, they had significantly lower frequencies of effector memory (CD28-CD45RA-) cells compared to the IFN-gamma-secreting cells that did or did not undergo degranulation (CD107a+IFN-gamma+ or CD107a-IFN-gamma+). The perforin content of effector CD8+ T lymphocytes was significantly greater than that of effector memory CD8+ T lymphocytes in rhesus macaques, suggesting that they were more cytolytic. Our findings suggest that the composition of rhCMV-specific CD8+ T lymphocytes with regards to CD107a+IFN-gamma- responders may be an important determinant of their ability to control CMV replication.

The co-expression of 2B4 (CD244) and CD160 delineates a subpopulation of human CD8+ T cells with a potent CD160-mediated cytolytic effector function

Within human CD8+ T lymphocytes, the CD27-CD45RAhigh or CD56+ phenotypes contribute to precisely define the cells with CTL effector function. Novel markers were demonstrated to correlate with CTL properties, such as the 2B4 (CD244) receptor, a member of the CD2 subset of the immunoglobulin superfamily or the glycosylphosphatidylinositol-anchored CD160 receptor. We performed a study of these markers to further define the population of effectors with CTL functions. Here we show that cytotoxic subpopulations defined by surface markers CD160, CD56 and CD57 are mostly contained in the 2B4+CD8+ T cell population. Expression of CD160 identifies two populations in the 2B4+ population. The 2B4+CD160+ subset expresses a bona fide CTL phenotype. The co-expression of 2B4 and CD160 defines T cells containing high amounts of perforin and granzyme B. During CTL ontogeny, an up-regulation of 2B4 and CD160 is observed from a naive to a terminally differentiated phenotype. Finally, we demonstrated that CD160 triggering failed to induce cytotoxicity per se, but costimulated CD3-redirected killing. We conclude that the co-expression of 2B4 and CD160 defines a CD8+ T lymphocyte subpopulation with high CTL activity.

Cyclooxygenase-2 inhibitor enhances the efficacy of a breast cancer vaccine: role of IDO

We report that administration of celecoxib, a specific cyclooxygenase-2 (COX-2) inhibitor, in combination with a dendritic cell-based cancer vaccine significantly augments vaccine efficacy in reducing primary tumor burden, preventing metastasis, and increasing survival. This combination treatment was tested in MMTV-PyV MT mice that develop spontaneous mammary gland tumors with metastasis to the lungs and bone marrow. Improved vaccine potency was associated with an increase in tumor-specific CTLs. Enhanced CTL activity was attributed to a significant decrease in levels of tumor-associated IDO, a negative regulator of T cell activity. We present data suggesting that inhibiting COX-2 activity in vivo regulates IDO expression within the tumor microenvironment; this is further corroborated in the MDA-MB-231 human breast cancer cell line. Thus, a novel mechanism of COX-2-induced immunosuppression via regulation of IDO has emerged that may have implications in designing future cancer vaccines.

Diversity of NKR expression in aging T cells and in T cells of the aged: the new frontier into the exploration of protective immunity in the elderly

Aging in the immune system is characterized by the contraction of the lymphocyte repertoire, exemplified by long-lived oligoclonal T cells that pervade the peripheral circulation. T-cell receptor (TCR) repertoire contraction likely explains the decline in immunity with chronological age as evidenced by the increased morbidity and mortality to common and new infections, and the low rates of protective responses to vaccination in the elderly. Interestingly, in vitro senescence models and cross sectional ex vivo studies have consistently demonstrated that senescent (or pre-senescent) T cells and T cells of the aged express unusually high densities of receptors that are normally found on natural killer (NK) cells, the killer cell immunoglobulin-like receptors (KIR) being the most diverse NK receptors (NKR). Molecular studies also show that T cells are programmed to express NKRs/KIRs, and T-cell clonal lineages express a variety of NKRs towards the end stages of their replicative lifespan. We propose that NKR/KIR induction in aging T cells is an adaptational diversification of the immune repertoire. We suggest that NKR/KIR expression in oligoclonal senescent and pre-senescent T cells is a compensatory adaptation to maintain immune competence despite the overall contraction in TCR diversity with aging. NKRs comprise a diverse superfamily of receptors. Mounting evidence for NKR/KIR signaling pathways in T cells divergent from those seen in NK cells indicate that senescent NKR(+)T cells are unique immune effectors. We suggest that appreciation of the functional diversity of these unusual NK-like T cells is central to the creative development of new strategies to enhance protective immunity in the aged.

The CD160+ CD8high cytotoxic T cell subset correlates with response to HAART in HIV-1+ patients

We investigated the circulating cytotoxic CD160+ CD8(high) subset in correlation to antiviral immunity and response to highly active antiretroviral therapy (HAART) in HIV+ subjects. The study included 45 treatment-naive patients receiving HAART for 18 months, retrospectively defined as good (n=29) and transient (n=16) responders. HIV-specific CD8 T lymphocyte levels were measured by IFNgamma production in response to p17 Gag, in the presence of immobilized anti-CD160 mAb. We report a significantly increased baseline level of CD160+ CD8(high) subset in good therapy responders. CD160+ CD8(high) subset correlates with CD4+ T cell count, immune activation, and viral load. CD160+ CD8(high) lymphocytes contain a high amount of Granzyme B and include virus-specific T lymphocytes in HIV-1+ subjects. Co-stimulation through CD160 molecules enhances IFNgamma production in response to p17 Gag. Therefore, the CD160+ CD8(high) subset may be useful for monitoring of virus-specific cellular immunity and predicting response to antiretroviral therapy in chronic HIV-1 infection.

Effector, memory and naïve CD8+ T cells in peripheral blood and pleural effusion from lung adenocarcinoma patients

The proportions of naïve, memory and effector CD8+ T cells in peripheral blood and pleural effusion from lung adenocarcinoma patients were studied. CD8+ T subsets were identified by using a combination of the following antibodies: anti-CD45RA, anti-CD45RO, anti-CD27 and anti-CD28, as well as antibodies to other markers. Fas-positive cells were determined in each CD8+ T subset. Also, the intracellular cytokine patterns of CD4+ and CD8+ lymphocytes from pleural effusion were analysed. In naïve, memory and effector CD8+ T subsets no significant differences were observed in peripheral blood between healthy donors and cancer patients. In contrast, a high proportion of cells with memory phenotype (CD45RA-CD45RO+CD27+CD28+) and a low proportion of cells with effector phenotype (CD45RA+CD45RO-CD27-CD28-) were found in pleural effusion with respect to peripheral blood (P<0.001). The altered proportions of CD8+ T subsets in pleural effusion were not mediated by type 2 cytokines produced by CD4+ or CD8+ lymphocytes. In the effector CD8+ T subset, from peripheral blood as well as from pleural effusion, a low percentage of perforin-expressing cells was observed compared to granzyme A-expressing cells. Additionally, a high percentage of naïve CD8+ T cells expressing Fas was found. Our data suggest that: (i) terminal-differentiation process of CD8+ T cells is blocked, and (ii) early Fas-expression in CD8+ T cells, which was reflected even in peripheral blood, may lead to apoptosis of naïve cells when they reach the effector stage. All these processes may contribute to the inadequate antitumour immune response found in lung carcinoma patients.

Human CD8+ T cells specific for influenza A virus M1 display broad expression of maturation-associated phenotypic markers and chemokine receptors

To define the role of memory T cells in a non-persistent viral infection, we have delineated the phenotype of memory CD8+ T cells specific for influenza A virus (FluA; matrix protein M158-66) based on the expression of several memory/effector lineage markers and relevant chemokine receptors. We found a majority of FluA-specific CD8+ T cells expressed CD27 and CD28, and variably expressed CD45RA, CD62L, CD94 and granzyme A. A majority of FluA-specific CD8+ T cells expressed high levels of CXCR3, and moderate levels of CCR5 and CXCR4, whereas a limited proportion expressed CCR7, CCR6 and CXCR5. A phenotypic profile based on these observations showed that there are both immature and mature memory CD8+ T cells specific for FluA.

Coordination of activating and inhibitory signals in natural killer cells

NK cells are equipped with multiple activating and inhibitory cell surface receptors whose engagement regulate NK cell effector function (i.e. cytotoxicity as well as chemokine and cytokine production). Several components (adaptors, effector molecules) that participate to NK cell signalling pathways have been described. Yet, the spatio-temporal organisation of these pathways is still poorly understood. In addition, the mechanisms that integrate several simultaneous input signals in NK cells remain to be elucidated.

Expression of inhibitory KIR is confined to CD8+ effector T cells and limits their proliferative capacity

A subset of effector/memory CD8(+) T cells expresses natural killer cell receptors (NKR). Expression of inhibitory NKR at that stage of T cell differentiation is poorly understood. Interestingly, recent studies in mice indicated that transgenic expression of an inhibitory NKR induced the accumulation of memory T cells by inhibiting activation-induced cell death (AICD). To further understand the role of inhibitory NKR on T cells, we characterized the subset of human peripheral T cells expressing the inhibitory NKR, CD158b, and studied the modulation of antigen-driven T cell expansion by an endogenous inhibitory NKR. We found that CD158b expression was confined to a population of CD8(+)TCRalphabeta(+) effector T cells as defined by a CD45RA(+)CCR7(-) phenotype and high constitutive expression of granzyme B1. Few cells expressed the activating form CD158j in the absence of CD158b. Functionally, engagement of CD158b by MHC ligands diminished early TCR signaling, as well as AICD. However, the reduced AICD did not rescue cells for proliferation, since T cell expansion in the presence of CD158b triggering was impaired. Expression of inhibitory NKR on effector CD8(+) T cells may explain in part the poor replicative capacity of T cells at that stage of differentiation.

Altered trafficking of CD8+ memory T cells after implantation of rapamycin-eluting stents in patients with coronary artery disease

Aim of this study was to investigate the effects of implantation of different coronary drug-eluting stents on trafficking of central (T(CM)) or effector (T(EM)) memory T cells in the coronary sinus of patients with coronary artery disease (CAD) undergoing percutaneous coronary revascularization. Thirty-two patients presenting with stable coronary disease and angiographically proven stenosis of left descending coronary artery were randomly assigned to treatment with rapamycin-eluting, paclitaxel-eluting or bare metal stents. Heparinized blood samples were obtained from the coronary sinus either before or 20 min after stent implantation. Mononuclear cells were stained with mAbs specific for CD3, CD4, CD8, CD45R0, and CD27 molecules. Analysis of surface phenotype was performed by four-color flow cytometry and data on both CD4+ and CD8+ T(CM) and T(EM) cells were expressed either as absolute cell numbers/microL of blood or as percentages relative to the corresponding total memory T cell populations in the individual patients. We found that the number of CD8+ T(EM), as defined by CD3+CD45R0+CD8+CD27- phenotype, was significantly reduced in patients receiving a rapamycin-eluting stent as compared with basal values. Conversely, the number of CD8+ T(CM) (CD3+CD45R0+CD8+CD27+) was increased in the same treatment group after the revascularization procedure. No changes in the absolute number of CD4+ and CD8+ total (T(CM) plus T(EM)) memory T cells before and after the procedure were observed. These findings suggest that rapamycin eluted from medicated coronary stents rapidly induce a redistribution of memory CD8+ T lymphocyte subsets, with a significant decrease of T(EM) and a corresponding increase of T(CM) increase circulating within the coronary sinus. This anti-inflammatory effect could partially explain the reduction of coronary in-stent restenosis rate associated with the clinical use of this type of device.

Lessons from the study of T-cell differentiation in persistent human virus infection

Confusion surrounds the current classification of memory and effector T-cell subsets and there is a lack of consistency in the use of these terms between human and murine studies. The development of peptide-HLA tetrameric complexes ("tetramers") that accurately identify virus-specific T cells and can be used with a range of cell surface and intra-cellular markers has provided further insights in our understanding of the process of T-cell differentiation, or post-thymic development. We propose that T-cell differentiation subsets in human viral infection should be regarded as distinct from the current definitions of memory and effector cells; further work is needed to reveal the role of the differentiation process in anti-viral immunity.

Characterization of virus-specific CD8(+) effector T cells in the course of HIV-1 infection: longitudinal analyses in slow and rapid progressors

Studies in humans have provided evidence that CD8(+) T cells exhibit distinct phenotypical and functional properties dependent on virus specificity. It is not known how these T-cell phenotypes develop over the course of infection. Dynamics and properties of T cells specific for human immunodeficiency virus (HIV), cytomegalovirus (CMV), and Epstein-Barr virus (EBV) in HIV infection were investigated in relation to viral load. In rapid progressors, HIV-specific CD8(+) T cells were less differentiated early in infection and did not develop a more differentiated phenotype. In slow progressors, perforin expression of HIV-specific CD8(+) T cells slightly increased over time. HIV and EBV loads were detectable in all individuals, while CMV load could not be detected. Thus, in individuals with progressive HIV infection, HIV-specific T cells are less differentiated already early in infection. This apparent block in differentiation may be partly caused by chronic viremia or lack of CD4(+) T-cell help.

Neoadjuvant therapy changes the lymphocyte composition of tumor-draining lymph nodes in cervical carcinoma

BACKGROUND

The objective of the current study was to illustrate the influence of neoadjuvant therapy on the local immune response in patients with cervical carcinoma.

METHODS

Uninvolved tumor-draining lymph nodes (TDLN) (n=158 lymph nodes), including internal, external, and common iliac lymph nodes as well as obturator, presacral, and aortic lymph nodes from 15 nontreated (NT) patients, 4 chemotherapy (CT)-treated patients, and 19 chemoradiation (CR)-treated patients, were analyzed for lymphocyte subset distribution and for the proliferative response of T cells to polyclonal activation and interferon-gamma (IFN-gamma) production. Lymphocyte subsets in peripheral blood also were assessed.

RESULTS

TDLNs from CR-treated patients contained higher proportions of CD8+ cells and natural killer cells than NT and CT-treated patients (P values ranged from <0.05 to <0.01). TDLNs from CR-treated patients were enriched in activated-type CD4+ cells (HLA-DR+, CD134+, CD62L-, and CD25+ at an intermediate expression level; P values ranged from <0.05 to <0.01) and activated-type CD8+ cells (CD62L-, P<0.001) compared with NT patients. Concomitantly, there was a reduction in the proportion of naïve-type CD4+ and CD8+ cells (CD45RA+/CD62L+) (P<0.01 and <0.05, respectively). CR treatment increased the proportion of both CD4+ and CD8+ cells prone to produce IFN-gamma. All TDLNs contained suppressive CD4+ T regulatory (Treg) cells (CD25+ and CD152+ at a high expression level) whose frequency and suppressive activity was not influenced by the treatment. Therapy-induced changes in TDLN were mirrored only in part by respective alterations in peripheral blood.

CONCLUSIONS

To our knowledge, the current study is the first to show that neoadjuvant therapy produces an enhancing effect on the immune competency of TDLNs from patients with cervical carcinoma.

CD4+ T-cell–directed antibody responses are maintained in patients with psoriasis receiving alefacept: results of a randomized study

BACKGROUND

Alefacept, human LFA-3/IgG(1) fusion protein, selectively reduces memory-effector (CD45RO(+)) T cells, a source of the pathogenic mediators of psoriasis.

OBJECTIVE

To evaluate the effect of alefacept on immune function, T-cell-dependent humoral responses to a neoantigen (PhiX174) and recall antigen (tetanus toxoid) were assessed.

METHODS

Patients with psoriasis were randomized to the control group or to receive alefacept (7.5 mg intravenously weekly for 12 weeks). The alefacept group received PhiX174 immunizations at weeks 6, 12, 20, and 26 and tetanus toxoid at week 21; control subjects received PhiX174 at weeks 6 and 12 and tetanus at week 10.

RESULTS

Mean anti-PhiX174 titers were comparable in both groups. There was no difference in the percentage of responders (anti-PhiX174 IgG >/=30% of the total anti-PhiX174) between the alefacept group and the control group (86% and 82%, respectively; P =.73). The percentage of patients with anti-tetanus toxoid titer increases >/=2 times baseline also was similar (alefacept, 89%; control 91%).

CONCLUSION

A single 12-week course of alefacept did not impair primary or secondary antibody responses to a neoantigen or memory responses to a recall antigen. The selective immunomodulatory effect of alefacept against a potentially pathogenic T-cell subset is associated with maintenance of a significant aspect of immune function (antibody response) to fight infection and respond to vaccinations.

Ex vivo characterization of human CD8+ T subsets with distinct replicative history and partial effector functions

After antigenic challenge, naive T lymphocytes enter a program of proliferation and differentiation during the course of which they acquire effector functions and may ultimately become memory cells. In humans, the pathways of effector and memory T-cell differentiation remain poorly defined. Here we describe the properties of 2 CD8+ T-lymphocyte subsets, RA+CCR7-27+28+ and RA+CCR7-27+28-, in human peripheral blood. These cells display phenotypic and functional features that are intermediate between naive and effector T cells. Like naive T lymphocytes, both subsets show relatively long telomeres. However, unlike the naive population, these T cells exhibit reduced levels of T-cell receptor excision circles (TRECs), indicating they have undergone additional rounds of in vivo cell division. Furthermore, we show that they also share effector-type properties. At equivalent in vivo replicative history, the 2 subsets express high levels of Fas/CD95 and CD11a, as well as increasing levels of effector mediators such as granzyme B, perforin, interferon gamma, and tumor necrosis factor alpha. Both display partial ex vivo cytolytic activity and can be found among cytomegalovirus-specific cytolytic T cells. Taken together, our data point to the presence of T cells with intermediate effector-like functions and suggest that these subsets consist of T lymphocytes that are evolving toward a more differentiated effector or effector-memory stage.

Identification of non-naïve CD4+CD45RA+ T cell subsets in adult allogeneic haematopoietic cell transplant recipients

The study of thymic-dependent pathways of T cell reconstitution in T cell replete haematopoietic cell transplant (HCT) recipients in previous studies was complicated by the transfer of naïve CD4(+)CD45RA(+) T cells with the stem cell graft. However, direct quantification of thymic output has been enabled by measurement of T cell receptor excision circles (TREC). We analysed T cell reconstitution using T cell phenotyping and TREC quantification in 12 T cell-replete HCT recipients 6-53 years of age during the first 12 months post transplant. We have identified a novel subpopulation of CD4(+)CD45RA(+) T cells in the peripheral blood of these HCT recipients with expansions of this subset being more pronounced in older recipients. The recovery of classical naïve CD4(+)CD45RA(+) T cells was dependent on thymic output whereas this novel CD4(+)CD45RA(+) subpopulation arose independently of thymic output and displayed effector function and phenotype. These results suggest that CD4(+)CD45RA(+) effector populations exist, similar to the CD8(+)CD45RA(+) effector subset, and that the CD45RA antigen should not be used alone to define naïve CD4(+) T cells when monitoring T cell reconstitution in T cell replete HCT recipients. Furthermore, these results raise important questions regarding the role of the thymus in regulating T cell homeostasis in older HCT recipients and normal individuals.

Expansion of CMV-specific CD8+CD45RA+CD27- T cells in B-cell chronic lymphocytic leukemia

In patients with B-cell chronic lymphocytic leukemia (B-CLL), the absolute number of T cells is increased. Although it has been suggested that these T cells might be tumor specific, concrete evidence for this hypothesis is lacking. We performed a detailed immunophenotypic analysis of the T-cell compartment in the peripheral blood of 28 patients with B-CLL (Rai 0, n = 12; Rai I-II, n = 10; Rai III-IV, n = 6) and 12 healthy age-matched controls and measured the ability of these patients to mount specific immune responses. In all Rai stages a significant increase in the absolute numbers of CD3+ cells was observed. Whereas the number of CD4+ cells was not different from controls, patients with B-CLL showed significantly increased relative and absolute numbers of CD8+ cells, which exhibited a CD45RA+CD27- cytotoxic phenotype. Analysis of specific immune responses with tetrameric cytomegalovirus (CMV)-peptide complexes showed that patients with B-CLL had significantly increased numbers of tetramer-binding CMV-specific CD8+ T cells. The rise in the total number of CD8+ cytotoxic T cells was evident only in CMV-seropositive B-CLL patients. Thus, our data suggest that in patients with B-CLL the composition of T cells is shifted toward a CD8+ cytotoxic cell type in an effort to control infections with persistent viruses such as CMV. Moreover, they offer an explanation for the high incidence of CMV reactivation in CLL patients treated with T cell-depleting agents, such as the monoclonal antibody (mAb) alemtuzumab (Campath; alpha-CD52 mAb). Furthermore, because in CMV-seronegative patients no increase in cytotoxic CD8+ T cells is found, our studies do not support the hypothesis that tumor-specific T cells account for T-cell expansion in B-CLL.

Frequencies of circulating cytolytic, CD45RA+CD27-, CD8+ T lymphocytes depend on infection with CMV

Viral infections may cause serious disease unless the adaptive immune system is able to clear the viral agents through its effector arms. Recent identification and functional characterization of subpopulations of human CD8(+) T cells has set the stage to study the correlation between the appearance of particular subsets and common viral infections during childhood, i.e., EBV, CMV, varicella-zoster virus (VZV), and the attenuated measles-mumps-rubella (MMR) vaccine strains. In a cohort of 220 healthy children we analyzed lymphocytes and subpopulations of CD4(+) and CD8(+) T cells. The presence of the cytolytic CD45RA(+)CD27(-) subset of CD8(+) T cells correlated with prior CMV infection as defined by seroconversion (p < 0.0001). The number of this CD8(+) T cell subset remained stable during follow-up over 3 years in 40 children. The CD45RA(+)CD27(-) subset of CD8(+) T cells first appeared during acute CMV infection and subsequently stabilized at an individual set-point defined by age and immunocompetence. The functional importance of these cells in CMV surveillance was reflected by their increased numbers in immunosuppressed pediatric kidney transplant patients. Preferential expansion of CD8(+)CD45RA(+)CD27(-) cytolytic T cells seems unique for CMV.

Human CD8 T cells of the peripheral blood contain a low CD8 expressing cytotoxic/effector subpopulation

Heterogeneity of lymphocyte populations demonstrates the diversity of cellular immune responses and provide a better understanding of the immune system. CD3+ CD8+ T cells exhibit a low CD8 expressing (CD8low) population in flow cytometric analysis of peripheral blood T cells. In healthy donors, this population consists of 0.2-7.0% of all CD8 T cells. The majority of the CD8low T cell population showed an elevated expression of CD25, CD45RA, and CD95L, and low levels of CD28, CD62L and CD45RO. Circulating CD8low T cells resemble cytotoxic effector cells because they express cytolytic mediators and are able to execute cytotoxicity. A restricted T cell receptor profile with increased Vbeta9, Vbeta14 and Vbeta23 expression was observed and the CD8low T cell population contain Epstein-Barr virus-specific T cells. Therefore, the CD8low population represent a subset of activated CD8 effector T cells, resulting most probably from a continuous and/or balanced immune response to intracellular pathogens.

Effector CD8+CD45RO-CD27-T cells have signalling defects in patients with squamous cell carcinoma of the head and neck

A subset of circulating T cells (CD8(+)CD45RO(-)CD27(-)) with a naïve phenotype, but mediating effector function, is considered to play an important role in host antitumour defence. To investigate the attributes of these effector T cells in patients with squamous cell carcinoma (SCC) of the head and neck cancer, venous blood was obtained from 39 individuals with cancer and 45 normal controls (NC). Peripheral blood mononuclear cells were isolated, stained with labelled monoclonal antibodies specific for CD8, CD45RO, CD45RA, CD62L, CD27, TCR-zeta as well as isotype controls and examined by multicolour flow cytometry. Annexin V binding to CD8(+) T cells and PMA/ionomycin-induced IFN-gamma expression were also evaluated in patients and NC. The proportions of CD45RA(+)CD45RO(-) (naïve) and CD45RA(-)CD45RO(+) (memory) cells were found to be comparable within the CD8(+) T-cell subset. However, relative to NC, the frequency of effector CD8(+)CD45RO(-)CD27(-) cells was strikingly increased in all SCC patients regardless of the disease status (P=0.0003). The proportion of these cells was found to increase with age in both patients and NC. In NC, stimulated IFN-gamma expression was largely restricted to CD8(+)CD45RO(-)CD27(+) cells, while in patients CD8(+)CD45RO(-)CD27(-) expressed IFN-gamma after ex vivo stimulation. Expression of the TCR-associated zeta chain was decreased or absent in freshly isolated CD8(+)CD45RO(-)CD27(-) T cells in patients (P<0.0001). Annexin V was found to bind to a higher proportion of circulating CD8(+) T cells in patients than NC (P<0.006), and significantly more Annexin V(+) T cells were present in the effector (P<0.0059) than the naïve subset within the CD8(+)CD45RO(-) compartment. The data indicate that the expanded CD8(+)CD45RO(-)CD27(-) T cells, which contain precursors of IFN-gamma-producing T cells, are zeta-negative and sensitive to apoptosis in the circulation of patients with HNC.

Involvement of CD27/CD70 interactions in antigen-specific cytotoxic T-lymphocyte (CTL) activity by perforin-mediated cytotoxicity

CD27 molecules are shown to be essential in the regulation of the death, activation and differentiation of T and B cells. However, the influence of CD27 on cytotoxic T-cell function remains obscure. Autologous EBV transformed B-cell lines (LCL), which highly express CD27 ligand CD70, here stimulated T cells and induced the cytotoxic T-lymphocyte (CTL) activity via T-cell antigen receptors (TCR). The cytotoxicity against LCL was diminished when anti-CD70 blocking MoAb was added initially in the culture. Resting T cells killed more CD70-transfected P815 cells than wild type P815 cells in the presence of anti-CD3 MoAb as measured by a 4-h 51Cr release assay, and the cytotoxicity of both of the cell populations completely disappeared in the presence of concanamycin A (CMA). The expression of the perforin by the LCL-induced CTL in the presence of anti-CD70 blocking MoAb was diminished as compared with that without the blockage of CD27/CD70 interactions. The CTL induced by LCL did not kill Fas-transfected WR cells. CD27 signalling in the T cells did not affect Fas ligand (FasL) mRNA expression, LAK activity and IFN-gamma synthesis in humans. Our data demonstrate that CD27/CD70 interactions enhance the cytotoxicity of CTL in the induction phase through enhancement of killing activity induced via the perforin-dependent mechanism, but not via the Fas/FasL system.

Proliferation requirements of cytomegalovirus-specific, effector-type human CD8+ T cells

Two prototypic types of virus-specific CD8(+) T cells can be found in latently infected individuals: CD45R0(+)CD27(+)CCR7(-) effector-memory, and CD45RA(+)CD27(-)CCR7(-) effector-type cells. It has recently been implied that CD45RA(+)CD27(-)CCR7(-) T cells are terminally differentiated effector cells and as such have lost all proliferative capacity. We show in this study, however, that stimulation of CMV-specific CD45RA(+)CD27(-)CCR7(-) T cells with their cognate peptide in concert with either CD4(+) help or IL-2, IL-15, or IL-21 in fact induces massive clonal expansion. Concurrently, these stimulated effector T cells change cell surface phenotype from CD45RA to CD45R0 and regain CCR7, while effector functions are maintained. Our data imply that CD45RA(+)CD27(-)CCR7(-) effector-type T cells contribute to immunity not only by direct execution of effector functions, but also by yielding progeny in situations of viral reinfection or reactivation.

Role of 4-1BB (CD137) in the functional activation of cord blood CD28(-)CD8(+) T cells

The CD28(-) subset of CD8(+) T cells is associated with cytotoxic T lymphocyte (CTL) effector function. We investigated a potential role for 4-1BB, a costimulatory molecule structurally related to members of the tumor necrosis factor (TNF) receptor family, in the generation and functional activation of CD28(-) CTLs by using human cord blood (CB) cells composed exclusively of naive CD8(+) T cells with few or no CD28(-) CTLs. The 4-1BB was induced preferentially on the CB CD28(-)CD8(+) T cells when CD28 down-regulation was induced by interleukin 15 (IL-15) and IL-12 stimulation. Anti-4-1BB costimulation induced dramatic phenotypic changes in the CD28(-) CTLs, including restoration of CD28 expression as well as that of memory markers such as CD45RO and CC chemokine receptor 6 (CCR6). Anti-4-1BB costimulation also promoted long-term survival of CD28(-) CTLs, which were sensitive to activation-induced cell death upon anti-CD3 stimulation. The memory-type CD28(+) CTLs induced by anti-4-1BB costimulation acquired a greatly enhanced content of granzyme B, a cytolytic mediator, and enhanced cytotoxic activity as compared with CD28(-) CTLs. Strong cytotoxicity of memory-type CTLs to a 4-1BB ligand-expressing Epstein-Barr virus (EBV)-transformed B-cell line was almost completely abrogated by 4-1BB-Fc, a soluble form of 4-1BB, suggesting involvement of 4-1BB in cytolytic processes. Taken all together, our results suggest that 4-1BB plays a role in the differentiation of effector memory CTLs.

Direct evidence for interferon-gamma production by effector-memory-type intraepidermal T cells residing at an effector site of immunopathology in fixed drug eruption

Effector-memory T cells are strategically placed to epithelial tissues to provide frontline immune protection against pathogens. Their detrimental effects, however, have been rarely examined because of difficulty in sampling these T cells in pathological settings. Our previous studies suggested persistence of a similar subset of intraepidermal CD8(+) T cells at high frequencies in the lesions of fixed drug eruption, a localized variant of drug-induced dermatoses. In situ activation of this subset resulting in localized epidermal injury can be traced in the lesions after antigen challenge by paired immunohistochemical staining, reverse transcriptase-polymerase chain reaction in situ, and flow cytometry of dispersed cells. Here we show that effector-memory T cells were greatly enriched in these intraepidermal CD8(+) T cells, but not dermal and circulating counterparts, and that they constitutively express an early activation marker CD69 even before challenge. Surprisingly, a large proportion of these T cells expressed immediate effector function as evidenced by the rapid production of high levels of interferon-gamma in situ with much faster kinetics than their counterparts at the mRNA and protein levels after challenge. This was followed by localized epidermal injury. The intracellular cytokine assay ex vivo shows that the great majority of these dispersed T cells produce interferon-gamma. This study provides the first in situ description of the detrimental effects specifically mediated by effector-memory T cells residing at the effector site of immunopathology.

Molecular Mechanism of the Activation-Induced Cell Death Inhibition Mediated by a p70 Inhibitory Killer Cell Ig-Like Receptor in Jurkat T Cells

In this study we investigated the molecular mechanism of the activation-induced cell death (AICD) inhibition mediated by a p70 inhibitory killer cell Ig-like receptor (KIR3DL1, also called NKB1) in Jurkat T cells. Using stable Jurkat transfectants that express KIR or CD8-KIR fusion proteins we have shown for the first time that KIR inhibits, in a ligation-independent manner, the AICD induced by PHA, PMA/ionomycin, or anti-CD3 Ab. The AICD inhibition mediated by KIR appears to result from the blockade of Fas ligand induction upon activation of the Jurkat transfectants. Moreover, the membrane-proximal 20 aa of the KIR cytoplasmic tail were determined to play a crucial role in this process. Since the membrane-proximal portion of the KIR cytoplasmic tail contains a putative protein kinase C (PKC) substrate site, we investigated the molecular interaction between KIR and PKC. Immunoprecipitation analysis demonstrated that KIR constitutively bound both to PKCalpha, a conventional Ca(2+)-dependent PKC, and to PKCtheta, a novel Ca(2+)-independent PKC. Furthermore, an in vitro kinase assay revealed that PKC activation was blocked after PHA stimulation in Jurkat transfectants expressing KIR. These observations were supported by the finding that a recombinant KIR cytoplasmic tail also appeared to inhibit PKCalpha activation in vitro. Taken together these data strongly suggest that KIR inhibits the AICD of T cells by blocking Fas ligand induction upon stimulation, in a process that seems to be accomplished by PKC recruitment to the membrane-proximal PKC binding site and subsequent inhibition of PKC activation against the activating stimuli.

Impaired effector function of hepatitis C virus-specific CD8+ T cells in chronic hepatitis C virus infection

The cellular immune response contributes to clearance of hepatitis C virus (HCV) and persists for decades after recovery from infection. The immunological basis for the inefficiency of the cellular immune response in chronically infected persons is not known. Here, we used four HLA-A2 tetramers, specific for two HCV core and two HCV NS3 epitopes, to investigate at the single-cell level effector function and phenotype of HCV-specific CD8+ T cells in 20 chronically infected and 12 long-term recovered patients. Overall, HCV-specific, tetramer+ T cells were more frequently found in PBMCs of chronically infected patients than in those of recovered patients. However, when compared with HCV-tetramer+ T cells of recovered patients, they displayed an impaired proliferative capacity. As a result of the impaired proliferative capacity, HCV-specific T cell lines derived from chronically infected patients displayed less peptide-specific cytotoxicity than those from recovered patients. In addition, proliferation and ex vivo IFN-gamma production of HCV-tetramer+ cells, but not influenza-virus-specific T cells, were defective in chronically infected patients and could not be restored by in vitro stimulation with peptide and IL-2. At least three distinct phenotypes of HCV-specific CD8+ T cells were identified and associated with certain functional characteristics. In addition, impairment of proliferative, cytokine, and cytotoxic effector functions of tetramer+ T cells in viremic patients was associated with weak ex vivo HCV-specific CD4+ T cell responses. Thus, the defective functions of HCV-specific CD8+ T cells might contribute to viral persistence in chronically infected patients, and knowledge on their reversibility may facilitate the development of immunotherapeutic vaccines.

Generation of CD4(+)CD45RA(+) effector T cells by stimulation in the presence of cyclic adenosine 5'-monophosphate-elevating agents

After TCR cross-linking, naive CD4(+)CD45RA(+) T cells switch to the expression of the CD45RO isoform and acquire effector functions. In this study we have shown that cAMP-elevating agents added to anti-CD3- and anti-CD28-stimulated cultures of T lymphocytes prevent acquisition of the CD45RO(+) phenotype and lead to the generation of a new subpopulation of primed CD4(+)CD45RA(+) effector cells (cAMP-primed CD45RA). These cells displayed a low apoptotic index, as the presence of dibutyryl cAMP (dbcAMP)-rescued cells from CD3/CD28 induced apoptosis. Inhibition of CD45 splicing by dbcAMP was not reverted by addition of exogenous IL-2. cAMP-primed CD45RA cells had a phenotype characteristic of memory/effector T lymphocytes, as they showed an up-regulated expression of CD2, CD44, and CD11a molecules, while the levels of CD62L Ag were down-regulated. These cells also expressed the activation markers CD30, CD71, and HLA class II Ags at an even higher level than CD3/CD28-stimulated cells in the absence of dbcAMP. In agreement with this finding, cAMP-primed CD45RA cells were very efficient in triggering allogenic responses in a MLR. In addition, cAMP-primed CD45RA cells produce considerable amounts of the Th2 cytokines, IL-4, IL-10, and IL-13, whereas the production of IFN-gamma and TNF-alpha was nearly undetectable. The elevated production of IL-13 by neonatal and adult cAMP-primed CD45RA cells was specially noticeable. The cAMP-dependent inhibition of CD45 splicing was not caused by the production of immunosuppressor cytokines. These results suggest that within the pool of CD4(+)CD45RA(+) cells there is a subpopulation of effector lymphocytes generated by activation in the presence of cAMP-elevating agents.