Distribution of activated T cells migrating through the body: a matter of life and death

CD146 T cells in lung cancer: its function, detection, and clinical implications as a biomarker and therapeutic target

CD146 alternatively called melanoma cell adhesion molecule (MCAM), is a biomarker and therapeutic target of clinical significance. It is found on different cells including the endothelial cells and lymphocytes which participate in heterotypic and homotypic ligand-receptor. This review concentrated on the CD146 expression T cells (or lymphocytes) centering on Treg in lung cancer. Here, we have also considered the vigorous investigation of CD146 mainly acknowledged new roles, essential mechanisms and clinical implications of CD146 in cancer. CD146 has progressively become a significant molecule, particularly recognized as a novel biomarker, prognosis and therapy for cancer. Hence, targeting CD146 expression by utilization of methanol extracts of Calotropis procera leaf may be useful for the treatment of carcinogenesis.

Negative regulation of Hif1a expression and TH17 differentiation by the hypoxia-regulated microRNA miR-210

MicroRNA-210 (miR-210) is a signature microRNA of hypoxia. We found robust increase (>100-fold) of miR-210 abundance in activated T cells, especially in the T_H17 lineage. Hypoxia synergized with T cell receptor (TCR)–CD28 stimulation to accelerate and increase the magnitude of Mir210 expression. Mir210 was directly regulated by HIF-1α, a key regulator of T_H17 polarization. Surprisingly, Hif1a was identified as a miR-210-target, suggesting negative-feedback by miR-210 to inhibit HIF-1α protein expression. Deletion of Mir210 promoted T_H17 differentiation under conditions with limited oxygen. In experimental colitis, miR-210 reduced Hif1a transcript abundance, reduced the proportion of cells producing inflammatory cytokines and controlled disease severity. Our study identifies miR-210 as an important regulator of T cell differentiation in hypoxia, which can limit immunopathology.

Oxygen tension regulates NK cells differentiation from hematopoietic stem cells in vitro

Natural killer (NK) cells are differentiated from hematopoietic stem cells (HSCs) which are located at the lowest end of an oxygen gradient within the bone marrow (BM). In this report, we investigated whether oxygen tension could affect NK cell differentiation from hematopoietic cells in vitro. We found that hypoxia led to an inhibition of differentiation in NK cells, and increased oxygen supply alleviated this inhibition and restored NK cell differentiation under hypoxic condition. Hypoxia-treated cells demonstrated reduced mRNA expression of transcription factors (TFs) that have important roles in NK cell differentiation, such as EOMES, T-bet, GATA-3 and ETS-1. Moreover, hypoxia-pretreated cells recovered mRNA expression of TFs when the oxygen tension was changed to normoxia. Our findings suggest that oxygen tension modulates in vitro differentiation of NK cells through the regulation of TF expression.

Rapid diagnosis of tuberculous pericarditis by ELISPOT assay

We describe a case in which the rapid diagnosis of tuberculous pericarditis was made using the Mycobacterium tuberculosis (MTB)-specific enzyme-linked immunospot (ELISPOT) assay on pericardial effusion mononuclear cells (PEMCs). The analysis of MTB-specific T-cells in PEMCs by ELISPOT may be useful for rapid decision-making in anti-tuberculous treatment.

Hypoxia-driven immunosuppression: a new reason to use thermal therapy in the treatment of cancer?

Hypoxia within the tumour microenvironment is correlated with poor treatment outcome after radiation and chemotherapy, and with decreased overall survival in cancer patients. Several molecular mechanisms by which hypoxia supports tumour growth and interferes with effective radiation and chemotherapies are now well established. However, several new lines of investigation are pointing to yet another ominous outcome of hypoxia in the tumour microenvironment: suppression of anti-tumour immune effector cells and enhancement of tumour escape from immune surveillance. This review summarises this important information, and highlights mechanistic data by which hypoxia incapacitates several different types of immune effector cells, enhances the activity of immunosuppressive cells and provides new avenues which help 'blind' immune cells to detect the presence of tumour cells. Finally, we discuss data which indicates that mild thermal therapy, through its physiologically regulated ability to alter vascular perfusion and oxygen tensions within the tumour microenvironment, as well as its ability to enhance the function of some of the same immune effector activities that are inhibited by hypoxia, could be used to rapidly and safely release the tight grip of hypoxia in the tumour microenvironment thereby reducing barriers to more effective immune-based therapies.

Reduced oxygen tension results in reduced human T cell proliferation and increased intracellular oxidative damage and susceptibility to apoptosis upon activation

Cell culture and in vitro models are the basis for much biological research, especially in human immunology. Ex vivo studies of T cell physiology employ conditions attempting to mimic the in vivo situation as closely as possible. Despite improvements in controlling the cellular milieu in vitro, most of what is known about T cell behavior in vitro is derived from experiments on T cells exposed to much higher oxygen levels than are normal in vivo. In this study, we report a reduced proliferative response and increased apoptosis susceptibility after T cell activation at 2% oxygen compared to in air. To explain this observation, we tested the hypothesis of an impaired efficacy of intracellular protective mechanisms including antioxidant levels, oxidized protein repair (methionine sulfoxide reductases), and degradation (proteasome) activities. Indeed, after activation, there was a significant accumulation of intracellular oxidized proteins at more physiological oxygen levels concomitant with a reduced GSH:GSSG ratio. Proteasome and methionine sulfoxide reductase activities were also reduced. These data may explain the increased apoptotic rate observed at more physiological oxygen levels. Altogether, this study highlights the importance of controlling oxygen levels in culture when investigating oxygen-dependent phenomena such as oxidative stress.

Patterns of leukocyte counts on admissions for acute heart failure--presentation and outcome--results from a community based registry

OBJECTIVE

To determine the correlation between differential white blood cell (WBC) count and characteristics and outcome of acute heart failure (AHF) syndromes.

BACKGROUND

Previous studies suggested that different white blood cell count patterns are related to outcome in patients with heart failure (HF) and other cardiovascular disorders.

METHODS

Data from all qualifying AHF admissions to a city hospital (n=340) was prospectively collected. Patients were followed from admission up to 6 months post-discharge. The relationship between patients' demographics, clinical and laboratory characteristics and outcome were assessed in relation to WBC count and lymphocyte to WBC ratio (LWR).

RESULTS

WBC count >10,100×10 (9)/L (upper tertile) on admission was associated with higher admission blood pressure, lower oxygen saturation, higher heart rate and increased troponin, with no impact on either short-term worsening HF or long-term adverse outcome. Lower LWR was associated with higher BUN and troponin and lower hemoglobin, but not with a distinct clinical presentation. The lower LWR tertile (≤13%) was associated with a 60% increase in worsening HF risk and a substantially higher 1 month (15% versus 2%) and 6 months mortality (23% vs. 3%) for lowest versus highest quartile (p<0.0001).

CONCLUSIONS

While increased WBC count is associated with a more "vascular presentation" and certain severity markers, it is not related to worse patient outcome. Low LWR (≤13%) is predictive of worse outcome and higher mortality. It is also associated with certain laboratory abnormalities, but not related to a specific clinical profile.

Blood Lymphocytes, Monocytes and NK Cells Modulate Their Expression of CD44, ICAM‐1, LFA‐1 and MHC Class II After Arrival Into Lymphoid Organs

Adhesion molecules expressed on surface membranes of lymphocytes and other leukocytes enable their entry into the lymphoid and other tissues. However, little is known about molecules that govern the transit of leukocytes through the parenchyma of lymphoid organs proper. We show that in comparison to blood leukocytes, the corresponding cells isolated from lymphoid organs, i.e., lymph nodes and spleen, have a significantly augmented expression of certain surface molecules. The helper and cytotoxic subsets of T cells, as well as B cells, display the increased expression of CD44, ICAM-1 and LFA-1, whereas B cells additionally show the augmented expression of MHC class II. In comparison with blood monocytes, splenic monocytes show the increased expression of ICAM-1 and MHC class II molecules. When compared with blood NK cells, splenic NK cells only show the increased expression of ICAM-1. The molecules, which we show to be up regulated upon the entry of leukocytes into lymphoid organs, could be involved in their retention within the tissue via cell-cell or cell-extracellular matrix interactions and in control of their transit through lymphoid tissues.

Homing imprinting and immunomodulation in the gut: role of dendritic cells and retinoids

Lymphocyte migration is at the heart of chronic inflammatory ailments, including inflammatory bowel disease (IBD). Whereas naïve lymphocytes migrate to all secondary lymphoid organs, they are mostly excluded from nonlymphoid peripheral tissues. Upon activation, lymphocytes change their pattern of adhesion receptors and acquire the capacity to migrate to extralymphoid tissues. Antigen-experienced T cells are subdivided into different subsets based on their expression of homing receptors that favor their accumulation in specific tissues, such as the skin and the gut mucosa. B cells and antibody-secreting cells (ASC) also show tissue-tropism, which is somewhat correlated with the class of immunoglobulin that they produce. In fact, IgA-ASC are located in mucosal tissues, where they produce IgA, the main class of antibodies found in secretions. Although IgA-ASC are usually considered as a homogeneous pool of cells, those located in the small bowel have some unique migratory characteristics, suggesting that they are generated under different conditions as compared to IgA-ASC in other mucosal compartments. Foxp3(+) regulatory T cells (T(REG)) can also exhibit tissue-specific migratory potential and recent evidence suggests that T(REG) can be imprinted with gut-specific homing. Moreover, foxp3(+) T(REG) are enriched in the small bowel lamina propria, where they can be generated locally. The present review addresses our current understanding of how tissue-specific homing is acquired and modulated on T cells, B cells, and ASC, with a special emphasis on the intestinal mucosa. Harnessing these mechanisms could offer novel, effective, and more specific therapeutic strategies in IBD.

Dendritic cell subsets in lymph nodes are characterized by the specific draining area and influence the phenotype and fate of primed T cells

Dendritic cells (DC) are important in differential T-cell priming. Little is known about the local priming by DC in the microenvironment of different lymph nodes and about the fate of the imprinted T cells. Therefore, freshly isolated rat DC from mesenteric lymph nodes (mLN) and axillary lymph nodes (axLN) were phenotyped and cultured with blood T cells in the presence of the superantigen Mycoplasma arthritidis mitogen (MAM). The phenotype, proliferation and apoptosis of the primed T cells were analysed. Our data show that a common DC population exists in both mLN and axLN. In addition, region-specific DC with an organotypical marker expression imprinted by the drained area were found. Coculture of T cells with DC from mLN or axLN resulted in a distinct shift in the CD4 and CD8 expression of T cells and their phenotype. Furthermore, when these differentially primed mLN and axLN T cells were injected into recipients, mLN-primed T cells survived longer in other lymphoid organs. The results show that the region-specific DC have a unique phenotype and an impact on the ratio of CD4 : CD8 T cells during an immune response in vivo.

Nanosystems for simultaneous imaging and drug delivery to T cells

The T-cell response defines the pathogenesis of many common chronic disease states, including diabetes, rheumatoid arthritis, and transplant rejection. Therefore, a diagnostic strategy that visualizes this response can potentially lead to early therapeutic intervention, avoiding catastrophic organ failure or prolonged sickness. In addition, the means to deliver a drug dose to those cells in situ with the same specificity used to image those cells would provide for a powerful therapeutic alternative for many disease states involving T cells. In this report, we review emerging nanosystems that can be used for simultaneous tracking and drug delivery to those cells. Because of their versatility, these systems--which combine specific receptor targeting with an imaging agent and drug delivery--are suited to both basic science and applications, from developing therapeutic strategies for autoimmune and alloimmune diseases, to noninvasive tracking of pathogenic T-cell migration.

Intramuscular rather than oral administration of replication-defective adenoviral vaccine vector induces specific CD8+ T cell responses in the gut

Gut-associated lymphoid tissue (GALT) is the primary replication site for HIV-1, resulting in a pronounced CD4(+) T cell loss in this tissue during primary infection. A mucosal vaccine that generates HIV-specific CD8(+) T cells in the gut could prevent the establishment of founder populations and broadcasting of virus. Here, we immunized mice orally and systemically with a chimpanzee derived adenoviral vector expressing HIV gag (AdC68gag) and measured frequencies of gag-specific interferon-gamma (IFN-gamma) producing CD8(+) T cells in the GALT. A single oral administration was inefficient at eliciting responses in the mesenteric lymph nodes and Peyer's Patches, while a single intramuscular administration elicited strong systemic and detectable mucosal responses. The gag-specific CD8(+) T cell responses were present in both acute and memory phases following intramuscular administration.

Multiplex cytokine profiling of initial therapeutic response in patients with chronic hepatitis C virus infection

Currently available prognostic tools are inadequate to discern the molecular basis of the heterogenic response in hepatitis C virus (HCV)-infected patients treated with the current standard of therapy. The expression and biological function of immune mediators have been shown to be critical in all phases of the immune response to HCV infection and likely therefore influence host response. Herein, a biometric multiplex serum cytokine assay was utilized to characterize the immunomodulatory effects of host response in 10 HCV patients. Serum levels of 17 cytokines were compared before and after 1 month of treatment and against controls. Overall serum cytokine levels were significantly higher in patients (P < 0.05) than controls. Additionally, viral titers decreased in all patients after 1 month of therapy, as did overall serum cytokine levels in the cohort (P < 0.05). To assess relationships between changes in cytokine levels and changes in viral titer, the cohort was divided into three statistically distinct subgroups based on changes in viral titers. Specific sets of cytokines decreased in each group: decreases in CCL4, interleukin (IL)-2, CXCL8, and IL-1beta correlated with the greatest drops in viral titer, decreases in IL-5, granulocyte colony stimulating factor (G-CSF), and CCL4 correlated with moderate drops in viral titer, and only CCL2 correlated with the lowest drops in viral titer. Interestingly, decreases in CCL4 levels correlated with decreases in viral titers in all patients. CCL4 controls leukocyte influx and thus propagates inflammation. In conclusion, these data raise the possibility that characteristic changes in host response modulate the therapeutic response, demonstrating the prognostic power of serum cytokine profiling in chronic HCV.

TCR engagement increases hypoxia-inducible factor-1 alpha protein synthesis via rapamycin-sensitive pathway under hypoxic conditions in human peripheral T cells

Peripheral T cells encounter rapid decrease in oxygen tension because they are activated by Ag recognition and migrate into inflammatory sites or tumors. Activated T cells, therefore, are thought to have such machineries that enable them to adapt to hypoxic conditions and execute immune regulation in situ. We have recently shown that survival of CD3-engaged human peripheral blood T cells is prolonged under hypoxic conditions and hypoxia-inducible factor-1 (HIF-1) and its target gene product adrenomedullin play a critical role for the process. It is also shown that hypoxia alone is not sufficient, but TCR-mediated signal is required for accumulation of HIF-1alpha in human peripheral T cells. In the present study, we showed that TCR engagement does not influence hypoxia-dependent stabilization but stimulates protein synthesis of HIF-1alpha, most possibly via PI3K/mammalian target of rapamycin system, and that expression of HIF-1alpha and its target genes is blocked by treatment with rapamycin. Since some of those gene products, e.g., glucose transporters and phosphoglycerokinase, are considered to be essential for glycolysis and energy production under hypoxic conditions and adequate immune reaction in T cells, this TCR-mediated synthesis of HIF-1alpha may play a pivotal role in peripheral immune response. Taken together, our results may highlight a novel aspect of downstream signal from Ag recognition by TCR and a unique pharmacological role of rapamycin as well.

The CD8 memory T cell subsystem: integration of homeostatic signaling during migration

The ability of memory CD8 T cells to patrol non-lymphoid tissues represents an effective method whereby proficient immunosurveillance is achieved. From the analysis of memory CD8 T cell migration in vivo, it is clear that tissue-specific factors control trafficking and residence time within tissues. We propose that at least three pools of memory CD8 T cells exist based on migratory capabilities as dictated by their location in the body. Moreover, we hypothesize that the process of acquisition of homeostatic signals in specific tissues, such as the cytokines IL-7 and IL-15, regulates the mobility of memory T cells.

Overexpression of Bcl-xL in human breast cancer cells enhances organ-selective lymph node metastasis

Lymph node metastasis are the first prognostic factor in breast cancer diagnosis and an early event in metastatic spread. To assess the role of anti-apoptotic proteins in lymph node metastatic progression of human breast cancer cells we analyzed the metastatic activity of MDA-MB-435 cells transfected with the Bcl-xL gene, after orthotopic inoculation in Nude Balb/c and in SCID mice. The luciferase gene was introduced by permanent transfection in the 435/Bcl-xL and 435/Neo cells and used as a tumor marker to measure the number of tumor cells lodged in lymph nodes. We found that 435/Bcl-xL tumor cells had enhanced organ-specific metastatic activity, preferentially lodging in peripheral lymph nodes, where at 45 days post-implantation we found 7 x 10(6) +/- 6 x 10(6) 435/Bcl-xL.luc and 2 +/- 1.1 435/Neo.luc luciferase tagged tumor cell equivalents (TCEs). Metastases were abrogated in mice in which orthotopic tumors were induced with 435/Bcl-xL-antisense cells. Additionally, in vitro experiments show that in 435 cells Bcl-xL-antisense can override the emergence of resistance to apoptosis induced by TNF- alpha and TGF- beta in cells overexpressing Bcl-xL, increasing also adhesion to extracellular matrix proteins. These results point to the relevance of Bcl-xL overexpression inducing lymph node metastasis of breast cancer cells, and to the value of this gene as a target for therapy in order to prevent metastasis.

Autologous/syngeneic stem cell transplantation to treat refractory GvHD

Severe graft-versus-host disease (GvHD) refractory to corticosteroids responds poorly to experimental treatment and is often fatal. Attempts have been made to 'rescue' such patients by transfusing autologous cells in order to ablate the lymphoid component of the graft or to introduce regulatory cells capable of suppressing the GvHD. Here, we report details of eight patients with severe grade III-IV acute GvHD (n=7) or extensive chronic GvHD (n=1) who after failing a median of four lines of treatment were then treated with either autologous or syngeneic nucleated cell transfusions. Patients received standard conditioning (n=3), low intensity (n=2) or no conditioning (n=3) before the rescue procedure. In four of the five patients who received some form of conditioning, mixed chimerism or complete recipient hematopoiesis was restored. The GvHD resolved in four patients, of whom one died subsequently of multiorgan failure and two died of leukemia; one is still alive. A fifth patient had transient improvement in GvHD, which recurred when the corticosteroids were reduced. Three patients obtained no benefit from the procedure. We conclude that 'rescue' by transfusion of autologous or syngeneic nucleated cells may be valuable to treat severe refractory GvHD; the best approach to conditioning remains to be defined.

A co-transfer system in young prediabetic BB rats: reactivated autoreactive T cells can be partly controlled

A transfer model for studying both the development and prevention of diabetes in rats is described in detail. Diabetes was induced in BBDR rats by combining RT6-depletion with PolyI:C treatment. Autoreactive cells were isolated from acutely diabetic donors, reactivated in vitro and transferred intravenously into young (<34-day-old) BBDP rats. Accelerated diabetes occurred 13+/-3 days or 18+/-4 days after transfer of reactivated splenocytes or purified T cells (42/43 or 26/27 recipients, respectively). Freshly isolated mesenteric and splenic leukocytes from adult, healthy BBDR rats prevented spontaneous diabetes in BBDP rats, but were not able to prevent the accelerated diabetes when co-transferred with the autoreactive cells. By contrast, diabetes was significantly delayed (P<0.001) when protective cells were transferred 4 days prior to the autoreactive cells (16+/-3 days). In vivo tracking studies of the two types of transferred cells suggest different homing patterns which may explain this finding. The data suggest that leukocytes from BBDR contain cells with the ability to regulate reactivated autoreactive T cells in an autoimmune environment. This in vivo model of recurrent diabetes can therefore be used to define which type of cells are most effective in suppressing established autoimmune destruction of beta-cells.

Mechanisms of natural tolerance in the intestine: implications for inflammatory bowel disease

Tolerance, the regulated inability to respond to a specific immunologic stimulant, is a physiological event important to normal immune function. Just as loss of tolerance to self-proteins results in autoimmune diseases, we assert that loss of tolerance to commensal flora in the intestinal lumen leads to inflammatory bowel disease (IBD). Mechanisms through which the mucosal immune system establishes and remains hyporesponsive toward the presence of food proteins and commensal flora, which we define as natural tolerance, are discussed. In addition to the contributions by commensal flora, the innate host defense and the adaptive immune systems promote natural tolerance to sustain normal mucosal homeostasis. Understanding the molecular and cellular events that mediate natural tolerance will lead to more advanced insights into IBD pathogenesis and improved therapeutic options.

Dynamics of blood-borne CD8 memory T cell migration in vivo

Memory T cells are distributed throughout the body following infection, but the migratory dynamics of the memory pool in vivo is unknown. The ability of circulating microbe-specific memory T cells to populate lymphoid and nonlymphoid tissues was examined using adoptive transfer and parabiosis systems. While migration of memory CD8 T cells to lymph nodes and peritoneal cavity required G(i)-coupled receptor signaling, migration to the spleen, bone marrow, lung, and liver was independent of this pathway. Following parabiosis, memory T cells rapidly equilibrated into the lymphoid tissues, lung, and liver of each parabiont, implying most memory cells were not obligately tissue resident. Equilibration of memory cell populations was delayed in the brain, peritoneal cavity, and intestinal lamina propria, indicating controlled gating for entry into these tissues. In addition, memory cell migration to the lamina propria required beta7 integrins. Thus, the blood-borne T cell pool serves to maintain the homeostasis of tissue-based memory populations.

Extracellular Matrix Protein-dependent Apoptosis of T Cells in Women with a History of Recurrent Spontaneous Abortion

PROBLEM

The purpose of the study was to determine the role of T-cell apoptosis in extracellular matrix (ECM) environment in pregnancy maintenance in women with a history of recurrent spontaneous abortion (RSA).

METHOD OF STUDY

Thirty-nine non-pregnant women with the history of RSA (anatomic, genetic, endocrine and microbiologic causes were excluded) and 22 healthy women with the previous successful pregnancy outcome were studied. In addition, 21 women with the history of RSA were also studied at the beginning of their next pregnancy. We studied apoptosis of peripheral blood T cells after culture with monoclonal antibody (mAb) OKT-3 alone or with mAb OKT-3 following ECM proteins: collagen IV (C-IV) or fibronectin (Fn). We used Cell Death Detection ELISA for studying cell death in cell population. In addition, apoptotic peripheral blood T cells were identified by annexin V-PE staining protocol using flow cytometry. CD29+ and CD95+ T-cell surface receptors were also analyzed by flow cytometry.

RESULTS

The significantly higher values of enrichment factor: mU of the sample (dying/dead cells) per mU of the corresponding control (viable cells) were observed after peripheral blood T-cell culture with C-IV (P = 0.0002) or Fn (P = 0.004) in samples of non-pregnant women with the history of RSA when compared with control women. The significantly higher values of enrichment factor were observed after peripheral blood T-cell culture with C-IV in samples of pregnant women with the history of RSA with successful pregnancy outcome when compared with pregnant women with the history of RSA with failed pregnancy outcome (P = 0.01). However, the percentage of apoptotic T cells stained by annexin V was significantly lower in non-pregnant RSA women compared with control (P = 0.0001). CD95 expression was significantly lower in non-pregnant RSA women compared with control (P = 0.01).

CONCLUSIONS

Apoptosis of T cells might be an interesting possible explanation of successful pregnancy outcome in women with the history of RSA.

Changes in immunological and virological parameters in HIV-1 infected subjects following leukapheresis

In order to assess immune responses during HIV-1 therapeutic immunization, a large number of blood mononuclear cells (PBMC) are needed. Clinical tolerance and safety, as well as changes in immunological and virological parameters, were assessed, following leukapheresis in HIV-1 infected subjects with CD4(+) cell count >200 x 10(6)/l. PBMC were collected using a Fenwal CS3000 cell separator in 29 subjects with mean CD4(+) cell counts of 503 x 10(6)/l (range 172-1,119) and viral load of 2.5 log(10) copies/ml (range <1.7-5.4). Twenty-four (83%) subjects were on antiretroviral therapy while 5 (17%) were untreated. The blood volume processed was 7 L over a period of 3 hours. A mean value (+/- standard error) of 82 +/- 26 x 10(9)/l lymphocytes was collected by a single apheresis in a mean volume of 200 +/- 1.8 ml, containing 9.0 +/- 1.3 x 10(9)/l CD4(+) and 10.2 +/- 1.3 x 10(9)/l CD8(+) cells. The leukapheresis procedures were well tolerated and no immediate or delayed side effects were observed within 90 days of follow-up. No changes from blood pre-leukapheresis values were detected for white blood cells, lymphocytes, monocytes, CD8(+), CD34(+), naive and memory CD4(+) cell counts immediately after, 1 h, 7 days, or within 90 days after leukapheresis. However, absolute CD4(+) cell counts and percentage significantly increased from pre-leukapheresis values after 1 h (530 +/- 43 vs. 700 +/- 75 cell x 10(6)/l; 32.6 +/- 1.6 vs. 36.9 +/- 1.9%; P < 0.001 for both paired t-tests) before returning to pre-leukapheresis levels on day 7. No significant changes in viral load from pre-leukapheresis levels in treated or untreated subjects were detected at any time points. We conclude that leukapheresis in HIV-1 infected subjects with CD4(+) cell counts >200 x 10(6)/l is safe and induces a transient increase in the absolute and percentage of CD4(+) cell count without enhancing viral replication.

Transforming growth factor-beta as a regulator of site-specific T-cell inflammatory response

A common immunopathological hallmark of many autoimmune inflammatory diseases is a T-cell invasion and accumulation at the inflamed tissue. Although the exact molecular and microenvironmental mechanisms governing such cellular invasion and tissue retention are not known, some key immunological principles must be at work. Transforming growth factor-beta (TGF-beta) is known to modulate some of these processes including homing, cellular adhesion, chemotaxis and finally T-cell activation, differentiation and apoptosis. The chronicity of such T-cell-driven inflammation probably involves an innate immunological response leading to a T-1 (Th/Tc), T-2 or T-3 (Th/Tr) T-cell adaptive immune response. Several studies suggest that the key to T-cell final destination resides on its and the antigen-presenting cell's phenotype as well as the coreceptor expression pattern and their signalling intensity. Recent observations suggest other equally important regulatory elements of T-cell inflammatory response that are sensitive to TGF-beta modulation. These include: (i) the stage of T-cell activation/differentiation; (ii) the chemotactic/adhesion molecule expression pattern; and (iii) the conditioning at the immunological synapse determining their sensitivity to known regulators such as TGF-beta. In this article, we focus on how the phenotype of the responding T cell and the T-cell receptor (TCR)-signalling intensity could drive the given inflammatory response. In particular, we discuss how TGF-beta can influence the process of T-cell migration and activation during such site-specific inflammation.

Reactivity of new adhesion molecules on lymphocytes from patients with chronic graft versus host disease

Reaction patterns of the 7th Human Leukocyte Differentiation Antigen Workshop blind panel adhesion molecules were studied on CD3/CD4, CD3/CD8, CD3/TCR gamma delta double positive T cells from peripheral blood of patients with chronic graft versus host disease (n = 8) and healthy controls (n = 4). Reactivity of 14 adhesion antibodies was tested by three-colour immunophenotyping. The mean proportion of CD3+ T cells (69 +/- 19%). CD3/CD8++ (31 +/- 13%) and CD3/TCR gamma delta++ (4 +/- 2%) T sub-populations of patients were comparable with the healthy controls. However, the mean percentage of CD3/CD4++ T cell subset in patients (14 +/- 12%) proved to be significantly decreased in comparison with the normal control value (34 +/- 16%) presumably due to secondary immunodeficiency. The workshop antibodies proved to be reactive with three T cell subsets expressing the examined antigens. Based on the results of the adhesion molecule workshop new CD categories have been introduced: CD156b as a transmembrane protein, CD167a as an epithelial tyrosin kinase receptor, CD168 as a receptor for hyaluronan mediated motility (RHAMM) and CD171 as a co-stimulatory adhesion molecule. There were significant differences in the expression of the CD167a and CD156b antigens on the CD3/CD4++ subset between the samples of patients compared with the controls characterizing the CD4+ T lymphocyte subpopulation in chronic graft versus host disease.

Red blood cells promote survival and cell cycle progression of human peripheral blood T cells independently of CD58/LFA-3 and heme compounds

Red blood cells (RBC) are known to modulate T cell proliferation and function possibly through downregulation of oxidative stress. By examining parameters of activation, division, and cell death in vitro, we show evidence that the increase in survival afforded by RBC is due to the maintenance of the proliferative capacity of the activated T cells. We also show that the CD3+CD8+ T cell subset was preferentially expanded and rescued from apoptosis both in bulk peripheral blood lymphocyte cultures and with highly purified CD8+ T cells. The ability of RBC to induce survival of dividing T cells was not affected by blocking the CD58/CD2 interaction. Moreover, addition of hemoglobin, heme or protoporphyrin IX to cultures of activated T cells did not reproduce the effect of intact RBC. Considering that RBC circulate throughout the body, they could play a biological role in the modulation of T cell differentiation and survival in places of active cell division. Neither CD58 nor the heme compounds studied seem to play a direct relevant role in the modulation of T cell survival.

Enhanced antitumor immunity in mice deficient in CD69

We investigated the in vivo role of CD69 by analyzing the susceptibility of CD69-/- mice to tumors. CD69-/- mice challenged with MHC class I- tumors (RMA-S and RM-1) showed greatly reduced tumor growth and prolonged survival compared with wild-type (WT) mice. The enhanced anti-tumor response was NK cell and T lymphocyte-mediated, and was due, at least in part, to an increase in local lymphocytes. Resistance of CD69-/- mice to MHC class I- tumor growth was also associated with increased production of the chemokine MCP-1, diminished TGF-beta production, and decreased lymphocyte apoptosis. Moreover, the in vivo blockade of TGF-beta in WT mice resulted in enhanced anti-tumor response. In addition, CD69 engagement induced NK and T cell production of TGF-beta, directly linking CD69 signaling to TGF-beta regulation. Furthermore, anti-CD69 antibody treatment in WT mice induced a specific down-regulation in CD69 expression that resulted in augmented anti-tumor response. These data unmask a novel role for CD69 as a negative regulator of anti-tumor responses and show the possibility of a novel approach for the therapy of tumors.

Compartmentalisation between gut and lung mucosae in a model of secondary immunodeficiency: effect of thymomodulin

Compartmentalisation of mucosal immune response seems to be the result mainly of the preferential migration of activated cells back to their inductive sites. The aim of this report was to demonstrate, in a model of secondary immunodeficiency in Wistar rats (severely protein deprived at weaning and refed with casein 20%; group R21), that the oral administration of Thymomodulin (group:R21TmB) has different effects on gut and BALT (Bronchus-associated lymphoid tissue). Tissue sections (5 mu) were studied by immunohistochemistry 1). The oral administration of Thymomodulin restores only in gut Lamina propria (LP) the IgA B and CD4 T cell populations to control levels. The CD8a and CD25 subpopulations do not vary in gut as they return to control levels when refed with 20% casein diet. All the populations mentioned above remained decreased even after receiving Thymomodulin by the oral route. However, the same behaviour was observed for the TCR delta T cells that were decreased and return to normal levels in both mucosae by the effect of the immunomodulator; 2) when studying the iIEL (intestinal intraepithelial lymphocytes) CD8 alpha, CD25 and TCR gamma delta T cells, that were increased in R21, return to control levels in R21TmB. In BALT intraepithelium CD8 alpha and CD25 T cells remained decreased, while only TCR gamma delta T cells (increased in R21) return to control values.

CONCLUSIONS

1) there exists a compartmentalisation between both mucosae, as T CD4+ and IgA B+ cells are restored by TmB only in gut; 2) only those iIEL involved in inflammation (CD8 alpha+/CD25+ and TCR gamma delta+/CD25+) are normalised by means of the Thymomodulin 3) however, in BALT,only TCR gamma delta+ T cells are restored 4) the oral administration of the present immunomodulator may be useful as a therapeutic agent, although the preferential survival in the tissue of initial stimulation is the major factor in the preferential distribution of activated cells.

T cell reactivity to MHC class II-bound self peptides in systemic lupus erythematosus-prone MRL/lpr mice

The epitopes recognized by pathogenic T cells in systemic autoimmune disease remain poorly defined. Certain MHC class II-bound self peptides from autoimmune MRL/lpr mice are not found in eluates from class II molecules of MHC-identical C3H mice. Eleven of 16 such peptides elicited lymph node cell and spleen cell T cell proliferation in both MRL/lpr (stimulation index = 2.03-5.01) and C3H mice (stimulation index = 2.03-3.75). IL-2 and IFN-gamma production were detected, but not IL-4. In contrast to what was seen after immunization, four self peptides induced spleen cell proliferation of T cells from naive MRL/lpr, but not from C3H and C57BL/6.H2(k), mice. These peptides were derived from RNA splicing factor SRp20, histone H2A, beta(2)-microglobulin, and MHC class II I-A(k)beta. The first three peptides were isolated from I-E(k) molecules and the last peptide was bound to I-A(k). T cell responses, evident as early as 1 mo of age, depended on MHC class II binding motifs and were inhibited by anti-MHC class II Abs. Thus, although immunization can evoke peripheral self-reactive T cells in normal mice, the presence in MRL/lpr mice of spontaneous T cells reactive to certain MHC-bound self peptides suggests that these T cells actively participate in systemic autoimmunity. Peptides eluted from self MHC class II molecules may yield important clues to T cell epitopes in systemic autoimmunity.

The fate of effector T cells in vivo is determined during activation and differs for CD4+ and CD8+ cells

Effector T cells generated in the mesenteric lymph nodes (mLN) are known to accumulate in mLN and the tissue drained by them after circulating in the blood. Their accumulation is due less to preferential entry into mLN but more to preferential proliferation within mLN. The factors regulating the proliferation of effector T cells in vivo are unclear, and it is unknown whether they are different for CD4(+) and CD8(+) effector T cells. Rat T cells from mLN or peripheral lymph nodes (pLN) were stimulated polyclonally via the TCR and CD28 and injected i.v. into congenic recipients. Using three-color flow cytometry and immunohistochemistry, they were identified in mLN, pLN, and blood over time, and proliferation was determined by measuring bromodeoxyuridine incorporation. Only effector mLN T cells showed a significantly increased proliferation rate after entry into mLN compared with that in pLN (2.4 +/- 1.8% vs 0.8 +/- 0.4%). Proliferation among the injected cells was higher when they had contact with dendritic cells within mLN (9.0 +/- 4.3%) than when they did not (4.1 +/- 2.1%). Furthermore, effector mLN T cells which were observed 56 days after injection maintained the capacity for preferential proliferation within mLN. Interestingly, CD4(+) effector mLN T cells proliferated at a higher rate (4.8 +/- 0.7%), remaining in mLN, whereas CD8(+) effector mLN T cells proliferated at a lower rate (3.3 +/- 1.0%) and were able to leave the mLN into the blood. Elucidating the factors regulating the proliferation of effector T cells in vivo will help to modify their distribution for therapeutic purposes.

Lymphocyte apoptosis after exhaustive and moderate exercise

Apoptosis or programmed cell death is a process of fundamental importance for regulation of the immune response. Several reasons suggest that apoptosis is involved in exercise-induced alterations of the immune system such as postexercise lymphocytopenia. Healthy volunteers performed two treadmill exercise tests; the first was performed at 80% maximal oxygen uptake until exhaustion (exhaustive exercise) and the second 2 wk later at 60% maximal oxygen uptake with the identical running time (moderate exercise). Blood samples were taken before, immediately after, and 1 h after the test. Lymphocytes were analyzed for apoptotic and necrotic cells by using FITC-labeled annexin V-antibodies and nuclear propidium iodide uptake, respectively. In addition, apoptotic/necrotic cells were measured after a 24-h incubation of lymphocytes in the presence of camptothecin or phytohemagglutinin. Finally, plasma membrane expression of CD95-receptor and CD95-receptor ligand was investigated. Immediately after the exhaustive exercise, the percentage of apoptotic cells increased significantly, whereas it remained unchanged after the moderate exercise. Similar results were obtained after 24-h incubation of lymphocytes in medium alone or in the presence of camptothecin, but not with phytohemagglutinin. We found an upregulation of CD95-receptor expression after both exercise tests. However, only after exhaustive exercise a characteristic shift in CD95 expression profile toward cells with a high receptor density was observed. Expression of the CD95-receptor ligand remained unchanged after both exhaustive and moderate exercise. These results suggest that apoptosis may contribute to the regulation of the immune response after exhaustive exercise. Whether this mechanism can be regarded either as beneficial, i.e., deletion of autoreactive cells, or harmful, i.e., suppression of the immune response, awaits further investigations.

Temporal changes in the distribution of thoracic duct lymphoblasts to synovium and other tissues of rats with adjuvant-induced arthritis

The distribution of lymphoblasts(lymphocytes in cell cycle) obtained from the central lymph of donor rats and transferred adoptively to syngeneic recipients has been shown previously to be influenced by the presence of arthritis in either donor or recipient rats. The intent of the present study was to examine patterns of distribution of lymphoblasts in the early period after transfer, when extravasation of donor lymphoblasts was expected to occur. Thoracic duct lymphoblasts labelled in vitro with [125I]-iododeoxyuridine were detected in recipient rats by external radiometry and autoradiography. Irrespective of donor status, fewer donor lymphoblasts accumulated in the feet of normal recipients when compared to arthritic recipients at 15 min, 2 h and 24 h after cell transfer.When recipients of similar disease status were compared, the percentages of injected lymphoblasts from normal and arthritic donors recovered in the feet were similar at 15 min and 2 h after transfer. The proportions of lymphoblasts recovered in the feetat 24 h after injection declined in normal recipients and arthritic recipients of cells from normal donor rats. Importantly,this decline did not occur when both the donor and the recipient were arthritic. In the hindpaws, donor lymphoblasts were located predominantly in the bone marrow, except in transfers between arthriticrats, when at 24 h they were predominantly in the synovium. At 15 min, lymphoblasts were detected within the lumen of vessels within synovium, whereas by 2 h extravasation of these cells was evident. In conclusion, lymphoblasts accumulate more readily in hindfeet that are inflamed. In the early hours after injection, lymphoblasts from normal and arthritic donors are recruited equally, but these early levels are only maintained for 24 hin the combination of arthritic donor and arthritic recipient. Adramatic change in the proportion of lymphoblasts located in synoviumat this later time suggests that a dynamic process of relocation,retention and/or local cell division maintains the numbers of arthritic donor cells in the latter combination.

Kinetics of B, CD4 T, and CD8 T cells infused into humans: estimates of intravascular:extravascular ratios and total body counts

Little is known about the rate of T and B cell traffic from blood to extravascular compartments or about the steady-state distribution of T and B cells between intravascular and extravascular compartments in humans. We quantitated circulating T and B cell subsets before and during the first 24 h after the infusion of an allogeneic or syngeneic peripheral blood stem cell graft (containing approximately 10(10) lymphocytes) into 10 patients conditioned with chemotherapy and/or total body irradiation. For all lymphocyte subsets measured, <15% of the infused cells were present in the blood at the end of the 0.5-h infusion and <3% of the infused cells were present in the blood 1 h later. Thereafter, CD4 T cell counts plateaued at approximately 1% and CD8 T cell counts at < or = 0.4% of the infused cells, whereas B cell counts declined slowly (1.5% of the infused B cells were present in the blood at 2 h and 0.3% at 24 h postinfusion). We conclude that the rate of lymphocyte traffic from blood to extravascular spaces can be extraordinary (approximately 10(10) lymphocytes can leave blood within 0.5 h) and that at steady state the blood contains approximately 1% total body CD4 T cells, < or = 0.4% total body CD8 T cells, and approximately 1.4% total body B cells. By inference, an average-size person may carry a total of approximately 4.1 x 10(11) CD4 T cells, > or = 4.5 x 10(11) CD8 T cells, and approximately 1.0 x 10(11) B cells.

What role for FTY720, a novel immunosuppressive agent, in canine nonmyeloablative hematopoietic stem cell transplantation?

BACKGROUND

Stable mixed donor/host hematopoietic chimerism was almost uniformly achieved in dogs given 200 cGy total body irradiation (TBI) before, and a short course of immunosuppression after, transplantation of marrow from dog leukocyte antigen-identical littermates, but was transient when the TBI dose was decreased to 100 cGy. Here, we examined whether stable engraftment could be achieved in five dogs given FTY720 (days -5 and -4), followed by 100 cGy TBI, dog leukocyte antigen-identical marrow grafts, and mycophenolate mofetil/cyclosporine.

RESULTS AND CONCLUSIONS

Although all five dogs showed initial engraftment, four dogs rejected their grafts within 11 weeks, whereas one dog was euthanized on day 17 due to enteritis. This was not different from the control dogs not given FTY720 (P=0.32). Thus, FTY720 failed to enhance allogeneic engraftment in this model, perhaps due to in vivo T-cell depletion of the graft resulting from sequestration of donor lymphocytes in host central lymphoid tissues.

Differential regulation of two alternatively spliced isoforms of hypoxia-inducible factor-1 alpha in activated T lymphocytes

Cell adaptation to hypoxia is partially accomplished by hypoxia-inducible transcription factor-1 (HIF-1). Here we report the hypoxia-independent up-regulation of HIF-1 alpha subunit in antigen receptor-activated T cells. This is explained by a selective up-regulation of alternatively spliced mRNA isoform I.1 that encodes the HIF-1 alpha protein without the first 12 N-terminal amino acids. We show that both short (I.1) and long (I.2) HIF-1 alpha isoforms display similar DNA binding and transcriptional activities. Major differences were observed between these two HIF-1 alpha isoforms in their expression patterns with respect to the resting and activated T lymphocytes in hypoxic and normoxic conditions. The T cell antigen receptor (TCR)-triggered activation of normal ex vivo T cells and differentiated T cells results in up-regulation of expression of I.1 isoform of HIF-1 alpha mRNA without an effect on constitutive I.2 HIF-1 alpha mRNA expression. The accumulation of I.1 HIF-1 alpha mRNA isoform in T lymphocytes is also demonstrated during cytokine-mediated inflammation in vivo, suggesting a physiological role of short HIF-1 alpha isoform in activated lymphocytes. The TCR-triggered, protein kinase C and Ca(2+)/calcineurin-mediated HIF-1 alpha I.1 mRNA induction is protein synthesis-independent, suggesting that the HIF-1 alpha I.1 gene is expressed as an immediate early response gene. Therefore, these data predict a different physiological role of short and long isoforms of HIF-1 alpha in resting and activated cells.

Differential effects of physiologically relevant hypoxic conditions on T lymphocyte development and effector functions

Direct measurements revealed low oxygen tensions (0.5-4.5% oxygen) in murine lymphoid organs in vivo. To test whether adaptation to changes in oxygen tension may have an effect on lymphocyte functions, T cell differentiation and functions at varying oxygen tensions were studied. These studies show: 1) differentiated CTL deliver Fas ligand- and perforin-dependent lethal hit equally well at all redox conditions; 2) CTL development is delayed at 2.5% oxygen as compared with 20% oxygen. Remarkably, development of CTL at 2.5% oxygen is more sustained and the CTL much more lytic; and 3) hypoxic exposure and TCR-mediated activation are additive in enhancing levels of hypoxia response element-containing gene products in lymphocyte supernatants. In contrast, hypoxia inhibited the accumulation of nonhypoxia response element-containing gene products (e.g., IL-2 and IFN-gamma) in the same cultures. This suggests that T cell activation in hypoxic conditions in vivo may lead to different patterns of lymphokine secretion and accumulation of cytokines (e.g., vascular endothelial growth factor) affecting endothelial cells and vascular permeabilization. Thus, although higher numbers of cells survive and are activated during 20% oxygen incubation in vitro, the CTL which develop at 2.5% oxygen are more lytic with higher levels of activation markers. It is concluded that the ambient 20% oxygen tension (plus 2-ME) is remarkably well suited for immunologic specificity and cytotoxicity studies, but oxygen dependence should be taken into account during the design and interpretation of results of in vitro T cell development assays and gene expression studies in vivo.

T cell subsets and in vitro immune regulation in "infectious" transplantation tolerance

CD4-targeted mAb therapy results in permanent acceptance of cardiac allografts in rat recipients, in conjunction with features of the infectious tolerance pathway. Although CD4(+) T cells play a central role, the actual cellular and molecular tolerogenic mechanisms remain elusive. This study was designed to analyze in vitro alloimmune responses of T lymphocytes from CD4 mAb-treated engrafted hosts. Spleen, but not lymph node, cells lost proliferative response against donor alloantigen in MLR and suppressed test allograft rejection in adoptive transfer studies, suggesting compartmentalization of tolerogenic T cells in transplant recipients. A high dose of exogenous IL-2 restored the allogeneic response of tolerogenic T cells, indicating anergy as a putative mechanism. Vigorous proliferation of the tolerogenic T cells in in vivo MLR supports the existence of alloreactive lymphocytes in tolerogenic T cell repertoire and implies an active operational suppression mechanism. The tolerogenic splenocytes suppressed proliferation of naive splenocytes in vitro, consistent with their in vivo property of dominant immune regulation. Finally, CD45RC(+) but not CD45RC(-) T cells from tolerant hosts were hyporesponsive to alloantigen and suppressed the proliferation of normal T cells in the coculture assay. Thus, nondeletional, anergy-like regulatory mechanisms may operate via CD4(+)CD45RC(+) T cells in the infectious tolerance pathway in transplant recipients.

The intestinal mucosa as a target for dietary polyunsaturated fatty acids

Several studies have reported beneficial effects of dietary polyunsaturated fatty acids (PUFA) on various aspects of both human and animal health, and particular reference has been made to their effects on systemic immune responses. Both immune stimulation and immune suppression have been reported, with the outcome dependent on the type of PUFA, the target cell, as well as the immune competence of the cells before exposure. The systemic and the mucosal immune systems are discrete entities, which have evolved specific approaches in the defense of the host. The latter comprises several interconnected tissues, which communicate with one another through the action of soluble mediators and the trafficking of cellular components. After the oral mucosa, the intestinal epithelium and its associated gut-associated lymphoid tissue are the primary targets of dietary components. Absorption of dietary PUFA and its incorporation into intestinal tissues has been well studied, but the consequences of these events in relation to local immune responses have received little attention. This article describes some of the immune mechanisms operating at this barrier and, where possible, pinpoints areas for which a modulatory role for PUFA has already been demonstrated. Although not an exhaustive treatise of the subject, it is hoped that this review will foster research into the specific interaction between dietary PUFA and cell populations comprising the intestinal barrier.

Intracellular cytokine repertoire in different T cell subsets from patients with sarcoidosis

BACKGROUND

Pulmonary sarcoidosis is characterised by a mononuclear alveolitis with a predominance of CD4+ T cells and macrophages. We determined the intracellular expression of interferon (IFN)gamma, interleukin (IL)-2, tumour necrosis factor (TNF)alpha, IL-4, IL-5 and IL-10 in CD4+ and CD8+, naive and memory lymphocytes from blood and bronchoalveolar lavage (BAL) fluid using three colour flow cytometry.

METHODS

Eighteen untreated patients with pulmonary sarcoidosis were evaluated and stratified according to whether they had acute or chronic disease.

RESULTS

Significantly more T cells expressed Th1 than Th2 type cytokines in both BAL fluid and peripheral blood samples, regardless of clinical presentation. Significantly greater proportions of T cells secreted Th1 type cytokines in BAL fluid than in peripheral blood. Th1 type cytokines were more frequently expressed by peripheral and alveolar T cells in acute disease than in chronic disease. There were no significant differences between CD4+ and CD8+ T cells. Concerning naive and memory lymphocytes, significantly higher CD45RO:CD45RA ratios were found in BAL fluid than in blood, and increased expression of Th2 type cytokines was found in peripheral compared with alveolar memory T cells.

CONCLUSIONS

Our data support the immunopathogenetic concept of Th1/Th2 imbalance and compartmentalisation in pulmonary sarcoidosis and suggest that the cytokine patterns change during the course of disease. Expression of Th2 type cytokines in memory lymphocytes is decreased in the alveolar compartment compared with peripheral blood.

Naive and memory T cells migrate in comparable numbers through the normal rat lung: only effector T cells accumulate and proliferate in the lamina propria of the bronchi

T cells reach the lung via the pulmonary and bronchial arteries that supply the alveolar and bronchial regions. Although these regions are differentially affected by T cell-mediated diseases, the migration of T-cell subsets in these two regions has not been studied. Naive, memory, and effector T cells were injected into congenic rats and traced in sections of normal lung. All three T-cell subsets were found in large numbers in the alveolar region and exited again quickly. Only effector T cells accumulated in the lamina propria of the bronchi. Further, 72 h after injection 6% of the effector T cells still proliferated in the lung, whereas apoptotic effector T cells were only observed 1 h after injection (0.2%). Thus, not only effector and memory but also naive T cells continuously migrated through the lung. The preferential accumulation of effector T cells in the bronchial lamina propria may explain why some diseases preferentially affect the bronchial region.

Intracellular cytokine repertoire in different T cell subsets from patients with sarcoidosis

BACKGROUND

Pulmonary sarcoidosis is characterised by a mononuclear alveolitis with a predominance of CD4+ T cells and macrophages. We determined the intracellular expression of interferon (IFN)γ, interleukin (IL)-2, tumour necrosis factor (TNF)α, IL-4, IL-5 and IL-10 in CD4+ and CD8+, naive and memory lymphocytes from blood and bronchoalveolar lavage (BAL) fluid using three colour flow cytometry.

METHODS

Eighteen untreated patients with pulmonary sarcoidosis were evaluated and stratified according to whether they had acute or chronic disease.

RESULTS

Significantly more T cells expressed Th1 than Th2 type cytokines in both BAL fluid and peripheral blood samples, regardless of clinical presentation. Significantly greater proportions of T cells secreted Th1 type cytokines in BAL fluid than in peripheral blood. Th1 type cytokines were more frequently expressed by peripheral and alveolar T cells in acute disease than in chronic disease. There were no significant differences between CD4+ and CD8+ T cells. Concerning naive and memory lymphocytes, significantly higher CD45RO:CD45RA ratios were found in BAL fluid than in blood, and increased expression of Th2 type cytokines was found in peripheral compared with alveolar memory T cells.

CONCLUSIONS

Our data support the immunopathogenetic concept of Th1/Th2 imbalance and compartmentalisation in pulmonary sarcoidosis and suggest that the cytokine patterns change during the course of disease. Expression of Th2 type cytokines in memory lymphocytes is decreased in the alveolar compartment compared with peripheral blood.

Cytokines and chemokines in the immune response to hepatitis C infection

Over 170 million people are infected with the hepatitis C virus worldwide, resulting in a large disease burden and significant mortality. Hepatitis C virus is rarely cleared in the acute phase of the infection and most patients become chronically infected; a proportion of these patients develop progressive liver disease and fibrosis. The outcome of infection depends on the immune responses of both the innate and cognate immune systems, and these in turn are orchestrated by networks of cytokines and chemokines. There is evidence that a vigorous type 1 immune response to viral proteins is required for viral elimination, and the recruitment of such effector cells to the liver is dependent on the local activity of specific inducible chemokines. Multiple factors determine the ability of the hepatitis C virus to survive host immune responses, including an ability to alter the cytokine profile secreted by T cells and to cause resistance to the effects of antiviral cytokines such as interferon. In the present review, we briefly cover the important advances made in this area over the past 12 months.

Red blood cells inhibit activation-induced cell death and oxidative stress in human peripheral blood T lymphocytes

Red blood cells (RBCs) are known to perform one prominent function: to carry and deliver oxygen to the tissues. Earlier studies, however, suggested a role for RBCs in potentiating T-cell proliferation in vitro. Here it is shown that the presence of RBCs in cultures of stimulated human peripheral blood lymphocytes strengthens T-cell proliferation and survival. Analysis of phosphatidylserine externalization and DNA fragmentation showed that RBCs inhibit T-cell apoptosis. This inhibition correlated with a reduction in CD71 but not CD95 expression. RBCs enhanced T-cell proliferation and survival upon activation with phytohemagglutinin and with OKT3 antibodies. Studies aimed at characterizing the cellular and molecular basis of the protection afforded to T cells by RBCs showed that (1) optimal protection required intact RBCs and red cell/T-cell contact but not monocytes; (2) RBCs markedly reduced the level of intracellular reactive oxygen species; and (3) RBCs inhibited the formation of protein-bound acrolein, a peroxidation adduct in biologic systems. Overall, these data indicate that human RBCs protect T cells from activation-induced cell death, at least in part by reducing the pro-oxidant state, and suggest a role for RBCs as conceivable modulators of T-cell homeostasis.

Homing of in vitro-generated donor antigen-reactive CD4+ T lymphocytes to renal allografts is alpha 4 beta 1 but not alpha L beta 2 integrin dependent

The extravasation and sequestration of Ag-reactive T lymphocytes into vascularized organ allografts depend on a cascade of complex interactions among circulating lymphocytes, endothelial cells, and extracellular matrix proteins. Ag-activated donor-specific CD4 T cells are major initiators and effectors in the allograft rejection response. Interfering with the intragraft homing of activated CD4 T cells may represent a novel therapeutic approach in transplant recipients. We have developed a FACS-based short-term homing assay that allows tracing in vitro-generated Ag-reactive CD4 T cells after adoptive transfer in test rat recipients. Allospecific cell lines were preincubated with anti-alpha(4)beta(1) or anti-alpha(L)beta(2) mAb, because of enhanced expression of both integrin receptors after alloactivation. The pretreated Lewis(BN) lymphocytes were carboxyfluorescein diacetate succinimidyl ester labeled and adoptively transferred into Lewis rat recipients of Brown Norway kidney allografts. The injection of equal numbers of PKH-26-labeled untreated cells allowed quantitative comparison of both populations in the same animal. Ex vivo treatment with anti-alpha(4)beta(1) mAb diminished intragraft infiltration of adoptively transferred T cells by 85% in a donor-specific fashion. In contrast, treatment with anti-alpha(L)beta(2) mAb did not affect intragraft cell sequestration. Hence, blocking alpha(4)beta(1) integrin interactions represents a novel strategy in preventing local intragraft recruitment of Ag-reactive CD4 T cells in transplant recipients.

Immunological principles of adverse drug reactions: the initiation and propagation of immune responses elicited by drug treatment

Adverse drug reactions account for between 2 to 5% of all hospital admissions and can prevent the administration of an otherwise effective therapeutic agent. Hypersensitivity or immune-mediated reactions, although less common, tend to be proportionately more serious. There is convincing evidence to implicate the immune system in the pathogenesis of hypersensitivity reactions. Our understanding of the way in which the immune system recognises drugs is based on the hapten hypothesis; the onset of hypersensitivity involves drug bioactivation, covalent binding to proteins, followed by uptake, antigen processing and T cell proliferation. Central to this hypothesis is the critical role of drug metabolism, with the balance between metabolic bioactivation and detoxification being one important component of individual susceptibility. The purpose of this review is to classify drug hypersensitivity reactions in terms of their clinical presentation, and also to consider recent advances in our understanding of the chemical, biochemical and, in particular, cellular immunological mechanisms of hypersensitivity. The following topics are reviewed: (i) drug disposition and cellular metabolism; (ii) mechanisms of antigen processing and presentation; (iii) the role of cytokines and co-stimulatory molecules in the induction and maintenance of a polarised immune response; and (iv) the application of the hapten hypothesis, danger hypothesis and serial triggering model to drug hypersensitivity. A greater understanding of the mechanism(s) of hypersensitivity may identify novel therapeutic strategies and help to combat one of the more severe forms of adverse reactions to drugs.

Identical T-cell expansions in the colon mucosa and the synovium of a patient with enterogenic spondyloarthropathy

Intestinal T lymphocytes activated by antigen are suspected to play a key role in enterogenic spondyloarthropathies (SpA). Therefore, we aimed to identify and functionally characterize T-cell clones that are coexpanded in the intestinal mucosa and the synovium. Colon, peripheral blood, and synovium of a patient with enterogenic SpA were screened for clonal T-cell expansions by TCRB-CDR3 length analysis and sequencing. T-cell clones expanded in vivo were isolated from archived synovial cells by targeted T-cell cloning and characterized for phenotype, cytokine production, and antigen specificity. The synovial TCRBV18(+) T-cell repertoire of the patient was dominated by 2 CD8(+) T-cell clones using related CDR3. Both clones were expanded throughout the colon and were present in the peripheral blood. Upon in vitro stimulation with PDB/ionomycin, they showed predominantly interferon gamma and interleukin (IL)-4 but also tumor necrosis factor alpha and IL-10 production and did not specifically lyse autologous T-cell blasts, B-cell lines, or other autologous or allogeneic target or CD1d-transfected cells. These findings strongly suggest that T lymphocytes activated by antigen in the intestinal mucosa contribute to joint inflammation in enterogenic SpA by recognition of antigens specific for the inflamed synovium.

Activation induces rapid and profound alterations in the trafficking of T cells

Activation and differentiation of lymphocytes have profound effects on their trafficking. Whereas naive T cells recirculate through lymphoid organs, activated cells localize predominantly in other compartments. Here, we report that changes in migratory properties of T cells occur immediately upon activation via the TCR. One hour stimulation is enough to target T cells into lung and liver following i.v. injection. The high localization within lung and liver and the lack of recirculation through lymphoid tissues are key features of activated lymphocytes. the source, in vitro as well as in vivo activated lymphocytes show this behavior, which is not caused by increased cell size. Accumulation in the lung requires protein synthesis and is partly mediated by LFA-1, in contrast to the acquisition of liver "homing" properties. Intravital microscopy reveals firm adhesion of activated cells within periportal sinusoids of the liver. Selective homing to other organs, such as skin or mucosa, was not observed, regardless of the cell's origin. These data indicate that activation quickly switches the trafficking program of lymphocytes from recirculation to sequestration; it is tempting to speculate that especially the induced trapping in the liver has a distinct role in limiting systemic T cell responses.

T-lymphocyte-epithelial-cell interactions: integrin alpha(E)(CD103)beta(7), LEEP-CAM and chemokines

The epithelia are the avascular layers of cells that cover the environment-exposed surfaces of the body. It appears that T cells localize to selected sites in or adjacent to epithelia via the selective expression of adhesion molecules and chemokine receptors on T cells. These bind to counter-receptors and to chemokines expressed by epithelial cells. Recently, there has been an advance in our understanding of the interaction of the alpha(Ebeta7) integrin with its epithelial cell ligand, E-cadherin. In addition, a new adhesion molecule has been identified on non-intestinal epithelial cells, termed lymphocyte-endothelial-epithelial-cell adhesion molecule (LEEP-CAM). Finally, there have been advances in our understanding of the role of skin- or gut-epithelia-derived chemokines in regulating activated T cell homing to these sites.