Dynamic control of lymphocyte trafficking by fever-range thermal stress

Hyperthermia in Combination with Emerging Targeted and Immunotherapies as a New Approach in Cancer Treatment

Despite significant advancements in the development of novel therapies, cancer continues to stand as a prominent global cause of death. In many cases, the cornerstone of standard-of-care therapy consists of chemotherapy (CT), radiotherapy (RT), or a combination of both. Notably, hyperthermia (HT), which has been in clinical use in the last four decades, has proven to enhance the effectiveness of CT and RT, owing to its recognized potency as a sensitizer. Furthermore, HT exerts effects on all steps of the cancer-immunity cycle and exerts a significant impact on key oncogenic pathways. Most recently, there has been a noticeable expansion of cancer research related to treatment options involving immunotherapy (IT) and targeted therapy (TT), a trend also visible in the research and development pipelines of pharmaceutical companies. However, the potential results arising from the combination of these innovative therapeutic approaches with HT remain largely unexplored. Therefore, this review aims to explore the oncology pipelines of major pharmaceutical companies, with the primary objective of identifying the principal targets of forthcoming therapies that have the potential to be advantageous for patients by specifically targeting molecular pathways involved in HT. The ultimate goal of this review is to pave the way for future research initiatives and clinical trials that harness the synergy between emerging IT and TT medications when used in conjunction with HT.

Crosstalk of Inflammatory Cytokines within the Breast Tumor Microenvironment

Several immune and immunocompetent cells, including dendritic cells, macrophages, adipocytes, natural killer cells, T cells, and B cells, are significantly correlated with the complex discipline of oncology. Cytotoxic innate and adaptive immune cells can block tumor proliferation, and others can prevent the immune system from rejecting malignant cells and provide a favorable environment for tumor progression. These cells communicate with the microenvironment through cytokines, a chemical messenger, in an endocrine, paracrine, or autocrine manner. These cytokines play an important role in health and disease, particularly in host immune responses to infection and inflammation. They include chemokines, interleukins (ILs), adipokines, interferons, colony-stimulating factors (CSFs), and tumor necrosis factor (TNF), which are produced by a wide range of cells, including immune cells, such as macrophages, B-cells, T-cells, and mast cells, as well as endothelial cells, fibroblasts, a variety of stromal cells, and some cancer cells. Cytokines play a crucial role in cancer and cancer-related inflammation, with direct and indirect effects on tumor antagonistic or tumor promoting functions. They have been extensively researched as immunostimulatory mediators to promote the generation, migration and recruitment of immune cells that contribute to an effective antitumor immune response or pro-tumor microenvironment. Thus, in many cancers such as breast cancer, cytokines including leptin, IL-1B, IL-6, IL-8, IL-23, IL-17, and IL-10 stimulate while others including IL-2, IL-12, and IFN-γ, inhibit cancer proliferation and/or invasion and enhance the body's anti-tumor defense. Indeed, the multifactorial functions of cytokines in tumorigenesis will advance our understanding of cytokine crosstalk pathways in the tumor microenvironment, such as JAK/STAT, PI3K, AKT, Rac, MAPK, NF-κB, JunB, cFos, and mTOR, which are involved in angiogenesis, cancer proliferation and metastasis. Accordingly, targeting and blocking tumor-promoting cytokines or activating and amplifying tumor-inhibiting cytokines are considered cancer-directed therapies. Here, we focus on the role of the inflammatory cytokine system in pro- and anti-tumor immune responses, discuss cytokine pathways involved in immune responses to cancer and some anti-cancer therapeutic applications.

Hyperthermic intraperitoneal chemotherapy and colorectal cancer: From physiology to surgery

The pursuit of this paper is to collect principal reviews and systematic reviews about hyperthermic intraperitoneal chemotherapy (HIPEC) and cytoreductive surgery (CRS) used in colorectal cancer (CRC). We focus on principal biological aspects of CRC, hyperthermia effects, and surgical procedures. We searched PubMed/MEDLINE for the principal reviews and systematic reviews published from 2010 to 2021 regarding the bimodal treatment (CRS + HIPEC) against local and advanced CRC. In the literature, from several studies, it seems that the efficacy of bimodal treatment with an accurate CRS can extend overall survival. Despite these studies, there are not still any straight guidelines more detailed and scheduled about the use of combined treatment in patients with CRC. Even if the concept is still not very clear and shared, after a careful evaluation of the published data, and after some technical and pathophysiological descriptions, we concluded that it is possible to improve the overall survival and quality of life and to reduce the tumor relapse in patients affected by locally advanced (pT4) CRC with peritoneal metastases.

Laser ablation: Heating up the anti-tumor response in the intracranial compartment

Immunotherapies, such as immune checkpoint inhibition (ICI), have had limited success in treating intracranial malignancies. These failures are due partly to the restrictive blood-brain-barrier (BBB), the profound tumor-dependent induction of local and systemic immunosuppression, and immune evasion exhibited by these tumors. Therefore, novel approaches must be explored that aim to overcome these stringent barriers. LITT is an emerging treatment for brain tumors that utilizes thermal ablation to kill tumor cells. LITT provides an additional therapeutic benefit by synergizing with ICI and systemic chemotherapies to strengthen the anti-tumor immune response. This synergistic relationship involves transient disruption of the BBB and local augmentation of immune function, culminating in increased CNS drug penetrance and improved anti-tumor immunity. In this review, we will provide an overview of the challenges facing immunotherapy for brain tumors, and discuss how LITT may synergize with the endogenous anti-tumor response to improve the efficacy of ICI.

Hyperthermia Targeting the Tumor Microenvironment Facilitates Immune Checkpoint Inhibitors

Immune checkpoint inhibitors (ICIs) have ushered in a new era of cancer therapy; however, ICIs are only effective in selective patients. The efficacy of ICIs is closely related to the tumor microenvironment. Fever for a long time was thought to directly regulate the immune response, and artificial “fever” from hyperthermia modulates the tumor immune microenvironment by providing danger signals with heat shock proteins (HSPs) as well as subsequent activation of immune systems. Encouraging results have been achieved in preclinical studies focused on potential synergetic effects by combining hyperthermia with ICIs. In this review, we summarized a cluster of immune-related factors that not only make hyperthermia a treatment capable of defending against cancer but also make hyperthermia a reliable treatment that creates a type I-like tumor microenvironment (overexpression of PD-L1 and enrichment of tumor infiltrating lymphocytes) in complementary for the enhancement of the ICIs. Then we reviewed recent preclinical data of the combination regimens involving hyperthermia and ICIs that demonstrated the combined efficacy and illustrated possible approaches to further boost the effectiveness of this combination.

In situ thermal ablation augments antitumor efficacy of adoptive T cell therapy

Purpose: The aim of this study is to investigate whether radiofrequency ablation (RFA) improves the efficacy of adoptive T cell immunotherapy in preclinical mouse cancer models.Method: Mice implanted subcutaneously (sc) with syngeneic colon adenocarcinoma or melanoma were treated with sub-curative in situ RFA (90 °C, 1 min). Trafficking of T cells to lymph nodes (LN) or tumors was quantified by homing assays and intravital microscopy (IVM) after sham procedure or RFA. Expression of trafficking molecules (CCL21 and intercellular adhesion molecule-1 [ICAM-1]) on high endothelial venules (HEV) in LN and tumor vessels was evaluated by immunofluorescence microscopy. Tumor-bearing mice were pretreated with RFA to investigate the therapeutic benefit when combined with adoptive transfer of in vitro-activated tumor-specific CD8⁺ T cells.Results: RFA increased trafficking of naïve CD8⁺ T cells to tumor-draining LN (TdLN). A corresponding increase in expression of ICAM-1 and CCL21 was detected on HEV in TdLN but not in contralateral (c)LN. IVM revealed that RFA substantially enhanced secondary firm arrest of lymphocytes selectively in HEV in TdLN. Furthermore, strong induction of ICAM-1 in tumor vessels was associated with significantly augmented trafficking of adoptively transferred in vitro-activated CD8⁺ T cells to tumors after RFA. Finally, preconditioning tumors with RFA augmented CD8⁺ T cell-mediated apoptosis of tumor targets and delayed growth of established tumors when combined with adoptive T cell transfer immunotherapy.Conclusions: These studies suggest that in addition to its role as a palliative therapeutic modality, RFA may have clinical potential as an immune-adjuvant therapy by augmenting the efficacy of adoptive T cell therapy.

Does hyperthermic preconditioning affect the rate of surgical site infection rate and inflammatory reaction in colorectal cancer patients? A prospective randomized clinical trial

OBJECTIVE

Hyperthermic preconditioning has been shown to protect against different insults in experimental studies. However, clinical studies assessing its effects remain limited. The aim of this study was to investigate the effects of hyperthermic preconditioning on the rate of surgical site infection and inflammatory reaction in patients undergoing elective colorectal cancer surgery.

MATERIAL AND METHODS

Patients with colorectal cancer, scheduled to undergo elective surgery were enrolled in this prospective randomized study. Patients were randomly assigned to either the hyperthermic preconditioning group or control group. Postoperative superficial and deep surgical site infection were recorded. Blood samples were collected from all the patients in the hyperthermic preconditioning group prior to the application of hyperthermia 12 h before surgery, immediately prior to surgery, and 4 h and 24 h postoperatively. For the control group, blood samples were obtained within the same periods without the application of hyperthermia. Levels of interleukin-1, IL-6, and tumor necrosis factor-α were measured from blood samples.

RESULTS

Twenty patients were randomized to the hyperthermic preconditioning group and 21 to the control group. No significant difference was found in deep or superficial surgical site infection between the groups. No significant difference in the tumor necrosis factor-α, interleukin-1, and IL-6 levels was found in serum samples collected before hyperthermia, during the operation, and postoperatively.

CONCLUSION

This study showed that hyperthermic preconditioning has no effect on the surgical site infection and cytokine response in patients undergoing elective surgical intervention for colorectal cancer.

A review of immune therapy in cancer and a question: can thermal therapy increase tumor response?

Immune therapy is a successful cancer treatment coming into its own. This is because checkpoint molecules, adoptive specific lymphocyte transfer and chimeric antigen T-cell (CAR-T) therapy are able to induce more durable responses in an increasing number of malignancies compared to chemotherapy. In addition, immune therapies are able to treat bulky disease, whereas standard cytotoxic therapies cannot treat large tumour burdens. Checkpoint inhibitor monoclonal antibodies are becoming widely used in the clinic and although more complex, adoptive lymphocyte transfer and CAR-T therapies show promise. We are learning that there are nuances to predicting the successful use of the checkpoint inhibitors as well as to specific-antigen adoptive and CAR-T therapies. We are also newly aware of a here-to-fore unrealised natural force, the status of the microbiome. However, despite better understanding of mechanisms of action of the new immune therapies, the best responses to the new immune therapies remain 20-30%. Likely the best way to improve this somewhat low response rate for patients is to increase the patient's own immune response. Thermal therapy is a way to do this. All forms of thermal therapy, from fever-range systemic thermal therapy, to high-temperature HIFU and even cryotherapy improve the immune response pre-clinically. It is time to test the immune therapies with thermal therapy in vivo to test for optimal timing of the combinations that will best enhance tumour response and then to begin to test the immune therapies with thermal therapy in the clinic as soon as possible.

Rationale of hyperthermia for radio(chemo)therapy and immune responses in patients with bladder cancer: Biological concepts, clinical data, interdisciplinary treatment decisions and biological tumour imaging

Bladder cancer, the most common tumour of the urinary tract, ranks fifth among all tumour entities. While local treatment or intravesical instillation of bacillus Calmette-Guerin (BCG) provides a treatment option for non-muscle invasive bladder cancer of low grade, surgery or radio(chemo)therapy (RT) are frequently applied in high grade tumours. It remains a matter of debate whether surgery or RT is superior with respect to clinical outcome and quality of life. Surgical resection of bladder cancer can be limited by acute side effects, whereas, RT, which offers a non-invasive treatment option with organ- and functional conservation, can cause long-term side effects. Bladder toxicity by RT mainly depends on the total irradiation dose, fraction size and tumour volume. Therefore, novel approaches are needed to improve clinical outcome. Local tumour hyperthermia is currently used either as an ablation therapy or in combination with RT to enhance anti-tumour effects. In combination with RT an increase of the temperature in the bladder stimulates the local blood flow and as a result can improve the oxygenation state of the tumour, which in turn enhances radiation-induced DNA damage and drug toxicity. Hyperthermia at high temperatures can also directly kill cells, particularly in tumour areas which are poorly perfused, hypoxic or have a low tissue pH. This review summarises current knowledge relating to the role of hyperthermia in RT to treat bladder cancer, the induction and manifestation of immunological responses induced by hyperthermia, and the utilisation of the stress proteins as tumour-specific targets for tumour detection and monitoring of therapeutic outcome.

Interleukin-6 Induced "Acute" Phenotypic Microenvironment Promotes Th1 Anti-Tumor Immunity in Cryo-Thermal Therapy Revealed By Shotgun and Parallel Reaction Monitoring Proteomics

Cryo-thermal therapy has been emerged as a promising novel therapeutic strategy for advanced breast cancer, triggering higher incidence of tumor regression and enhanced remission of metastasis than routine treatments. To better understand its anti-tumor mechanism, we utilized a spontaneous metastatic mouse model and quantitative proteomics to compare N-glycoproteome changes in 94 serum samples with and without treatment. We quantified 231 highly confident N-glycosylated proteins using iTRAQ shotgun proteomics. Among them, 53 showed significantly discriminated regulatory patterns over the time course, in which the acute phase response emerged as the most enhanced pathway. The anti-tumor feature of the acute response was further investigated using parallel reaction monitoring target proteomics and flow cytometry on 23 of the 53 significant proteins. We found that cryo-thermal therapy reset the tumor chronic inflammation to an “acute” phenotype, with up-regulation of acute phase proteins including IL-6 as a key regulator. The IL-6 mediated “acute” phenotype transformed IL-4 and Treg-promoting ICOSL expression to Th1-promoting IFN-γ and IL-12 production, augmented complement system activation and CD86⁺MHCII⁺ dendritic cells maturation and enhanced the proliferation of Th1 memory cells. In addition, we found an increased production of tumor progression and metastatic inhibitory proteins under such “acute” environment, favoring the anti-metastatic effect. Moreover, cryo-thermal on tumors induced the strongest “acute” response compared to cryo/hyperthermia alone or cryo-thermal on healthy tissues, accompanying by the most pronounced anti-tumor immunological effect. In summary, we demonstrated that cryo-thermal therapy induced, IL-6 mediated “acute” microenvironment shifted the tumor chronic microenvironment from Th2 immunosuppressive and pro-tumorigenic to Th1 immunostimulatory and tumoricidal state. Moreover, the magnitude of “acute” and “danger” signals play a key role in determining the efficacy of anti-tumor activity.

Photothermal effect for localized desorption of primary lymphocytes arrayed on an antibody/DNA-based biochip

This work proposes a miniaturized system able to perform multiple cell capture followed by cell-type selective release from a biochip surface. Unlabelled lymphocytes were first specifically captured onto a DNA array by antibody-DNA conjugates. The immobilized cells were subsequently released under spatiotemporal control within local heating generated by intense Surface Plasmon Resonance (SPR) produced by laser illumination.

The two faces of IL-6 in the tumor microenvironment

Within the tumor microenvironment, IL-6 signaling is generally considered a malevolent player, assuming a dark visage that promotes tumor progression. Chronic IL-6 signaling is linked to tumorigenesis in numerous mouse models as well as in human disease. IL-6 acts intrinsically on tumor cells through numerous downstream mediators to support cancer cell proliferation, survival, and metastatic dissemination. Moreover, IL-6 can act extrinsically on other cells within the complex tumor microenvironment to sustain a pro-tumor milieu by supporting angiogenesis and tumor evasion of immune surveillance. A lesser known role for IL-6 signaling has recently emerged in which it plays a beneficial role, presenting a fairer face that opposes tumor growth by mobilizing anti-tumor T cell immune responses to attain tumor control. Accumulating evidence establishes IL-6 as a key player in the activation, proliferation and survival of lymphocytes during active immune responses. IL-6 signaling can also resculpt the T cell immune response, shifting it from a suppressive to a responsive state that can effectively act against tumors. Finally, IL-6 plays an indispensable role in boosting T cell trafficking to lymph nodes and to tumor sites, where they have the opportunity to become activated and execute their cytotoxic effector functions, respectively. Here, we discuss the dual faces of IL-6 signaling in the tumor microenvironment; the dark face that drives malignancy, and the fairer aspect that promotes anti-tumor adaptive immunity.

IL-17 promotes neutrophil entry into tumor-draining lymph nodes following induction of sterile inflammation

Blood-borne neutrophils are excluded from entering lymph nodes across vascular portals termed high endothelial venules (HEVs) because of lack of expression of the CCR7 homeostatic chemokine receptor. Induction of sterile inflammation increases neutrophil entry into tumor-draining lymph nodes (TDLNs), which is critical for induction of antitumor adaptive immunity following treatments such as photodynamic therapy (PDT). However, the mechanisms controlling neutrophil entry into TDLNs remain unclear. Prior evidence that IL-17 promotes neutrophil emigration to sites of infection via induction of CXCL2 and CXCL1 inflammatory chemokines raised the question of whether IL-17 contributes to chemokine-dependent trafficking in TDLNs. In this article, we demonstrate rapid accumulation of IL-17-producing Th17 cells in the TDLNs following induction of sterile inflammation by PDT. We further report that nonhematopoietic expression of IL-17RA regulates neutrophil accumulation in TDLNs following induction of sterile inflammation by PDT. We show that HEVs are the major route of entry of blood-borne neutrophils into TDLNs through interactions of l-selectin with HEV-expressed peripheral lymph node addressin and by preferential interactions between CXCR2 and CXCL2 but not CXCL1. CXCL2 induction in TDLNs was mapped in a linear pathway downstream of IL-17RA-dependent induction of IL-1β. These results define a novel IL-17-dependent mechanism promoting neutrophil delivery across HEVs in TDLNs during acute inflammatory responses.

Stromal cells control soluble material and cellular transport in lymph nodes

Lymphocytes continuously patrol the secondary lymphoid organs (SLOs) of mammals in search for their cognate antigens. SLOs are composed of leucocytes (~95%) and lymphoid stromal cells (~5%) that form the structural framework of these organs. These sessile cells have been considered for decades as inert elements of the immune system. This simplistic view has dramatically changed in recent years, when it was discovered that these architectural cells are endowed with immuno-regulatory functions. Lymph nodes (LNs) are located at the interface between the blood and lymphatic systems, thus allowing tissue-derived antigen/antigen presenting cells (APCs) to gather with blood-derived lymphocytes. As a typical LN contains ~10 million of tightly packed cells, this accumulation of immune cells and information is probably not sufficient to foster the rare cellular interactions mandatory to the initiation of adaptative immune responses. Herein, I review some of the physicochemical elements of stromal cells that are used to transport and guide immune cells and soluble molecules within LNs.

Fever-range whole body thermotherapy combined with oxaliplatin: a curative regimen in a pre-clinical breast cancer model

PURPOSE

Studies were conducted to test whether fever-range whole body thermal therapy would boost the efficacy of oxaliplatin chemotherapy without substantial toxicity.

MATERIALS AND METHODS

The effect of mild heat (40 degrees C) on oxaliplatin cytotoxicity, cellular uptake, and platinum-DNA adduct formation was studied in vitro using the MTLn3 tumour cell line. In vivo oxaliplatin was administered at various doses and times before, during and after fever-range thermal therapy (6 h at 40 degrees C) to rats bearing an MTLn3 mammary adenocarcinoma. Tumour growth, survival, and toxicity were measured to determine treatment outcome.

RESULTS

Heating halved the oxaliplatin IC-50 dose for MTLn3 cells. Cellular uptake of platinum and platinum adducts increased by 34% and 36%, respectively, with heat. In vivo, 50% of all rats given 10 mg/kg oxaliplatin 24 h before thermal therapy were completely immunologically cured, while a further 11% regressed their primary tumour but ultimately succumbed to metastases, and 17% experienced a limited response with increased survival. The curative response occurred only in a narrow range of doses, with most cures at 10 mg/kg. Thermochemotherapy-treated, but uncured, animals had delayed incidence and slowed growth of metastases. Anti-tumour efficacy was greatest, and toxicity was least, when oxaliplatin was administered 12 or 24 h before fever-range whole body thermal therapy.

CONCLUSIONS

When properly dosed and scheduled, oxaliplatin thermochemotherapy achieved permanent eradication of all primary and metastatic tumours in 50% of animals, seemingly through an immune response. Successful clinical translation of this protocol would yield hitherto unseen cures and substantial improvement in quality of life.

Tumour infiltrating host cells and their significance for hyperthermia

Much information can be gained by investigating the consequences of hyperthermia on individual cell populations in vitro, however the precise effects of such a therapeutic modality in vivo depend on the tumour microenvironment and the cellular composition therein. Although the direct cytotoxic effects of hyperthermia on tumour tissue can lead to an immediate reduction in tumour volume, long-term benefits to local and distal tumour recurrence will very much depend on the induction of immunity and the capacity of effector cells to traffic to tumours and elicit their cytotoxic functions. The immunological sequelae to hyperthermia are even more important in those instances when large tumour volumes preclude the delivery of appropriate thermal damage. The development of protective anti-tumour immunity requires a plethora of interactions and responses, the vast majority of which can be influenced by temperatures that are consistent with fever-like temperatures (39 degrees -40 degrees C), as well as hyperthermia treatment (<41 degrees C). This article reviews current knowledge relating to the effects of hyperthermia treatment on aspects of the induction and manifestation of immunological responses that are most pertinent to the development and maintenance of protective anti-tumour immunity.

Fine-tuning immune surveillance by fever-range thermal stress

An effectively orchestrated immune response to infection and disease depends on efficient trafficking of lymphocytes across vascular beds at distinct tissue sites. Local inflammation and systemic fever increase immune surveillance to immune-relevant sites throughout the body. During the initiation phase of inflammation, this tightly regulated process improves leukocyte trafficking to the secondary lymphoid organs where they undergo activation and expansion in response to cognate antigen. In the resolution phase following the clearance of the invading pathogen, lymphocyte entry is rapidly returned to baseline conditions. Specialized blood vessels termed high endothelial venules (HEVs) have emerged as critical 'hotspots' controlling the rate of lymphocyte entry into lymphoid organs during both phases of inflammation. In this review, we will examine the remarkably tight regulation of lymphocyte trafficking across HEVs conferred by inflammatory cues associated with the thermal element of fever. These studies have revealed a novel role for interleukin-6 (IL-6) trans-signaling in eliciting systemic effects on lymphocyte trafficking patterns to fine-tune immune surveillance.

Thermal facilitation of lymphocyte trafficking involves temporal induction of intravascular ICAM-1

OBJECTIVE

Fever is associated with improved survival, although its beneficial mechanisms are poorly understood. Previous studies indicate that the thermal element of fever augments lymphocyte migration across high endothelial venules (HEVs) of lymphoid organs by increasing the intravascular display of a gatekeeper trafficking molecule, intercellular adhesion molecule-1 (ICAM-1). Here, we evaluated the spatio-temporal relationship between the thermal induction of intravascular ICAM-1 and lymphocyte trafficking.

METHODS

Intravascular ICAM-1 density was quantified by immunofluorescence staining in mice exposed to fever-range whole-body hyperthermia (39.5+/-0.5 degrees C). ICAM-1-dependent lymphocyte trafficking was measured in short-term homing assays.

RESULTS

A linear relationship was observed between the duration of heat treatment and intravascular ICAM-1 density in HEVs with maximal responses requiring sustained (i.e., five hours) thermal stress. Circulating lymphocytes were found to sense incremental changes in ICAM-1 on HEVs, such that trafficking is proportional to the intravascular density of ICAM-1. We further identified a hydroxamate-sensitive shedding mechanism that restores ICAM-1 expression to homeostatic levels following the cessation of thermal stress.

CONCLUSIONS

The time-dependent response to thermal stress indicates that ICAM-1 density governs the efficiency of lymphocyte interactions with HEVs in vivo. These studies highlight the dynamic role of the microcirculation in promoting immune surveillance during febrile inflammatory responses.

Hyperthermia on immune regulation: a temperature's story

Over the last decade the linkage between hyperthermia, heat shock proteins and fever with the body's immune system has been well investigated. The immunomodulatory function of hyperthermia has been found to be quite sensitively regulated by temperature, as different levels of heating can bring different modulatory effect on different sensitive targets. Understanding these intrinsic mechanisms could bring new inspirations on the design of clinical trials combining local tumor hyperthermia with immunotherapy in cancer patients. This review will attempt to tell the story about the effect of temperature on immune regulation, with special emphasis on the clinical application of hyperthermia and the feasibility of combining it with immunotherapy in the clinic.

Sickness behavior, its mechanisms and significance

Recent studies have begun to clarify the pathogenesis of sickness behavior. Cytokines released by macrophages, dendritic cells and mast cells act on the brain to trigger behavioral changes in infected animals. The major cytokines, interleukin-1, tumor necrosis factor alpha, and others, all act on the hypothalamus to provoke alterations in the normal homeostatic condition. These include elevated body temperature, increased sleep, and loss of appetite as well as major alterations in lipid and protein metabolism leading to significant weight loss. Some of these changes are clearly directed towards enhancing the normal immune responses. The benefits of others such as appetite loss are unclear. It is also important to recognize that other animals may recognize sickness behavior as a sign of weakness and mark the victim out for targeting by predators. As a result, some prey species may work very hard to mask their sickness, a response that serves to complicate veterinary diagnosis.

Exercise-induced redistribution of T lymphocytes is regulated by adrenergic mechanisms

Acute exercise is known for causing considerable changes in leukocyte counts and function. In this paper we report that differentiated changes in T-lymphocyte distribution occur in lymphoid and non-lymphoid organs depending on the type and the intensity of exercise. Using fluorescent cell tracking we observed a release of T-cells from the spleen while lung, bone marrow and Peyer's patches served as target organs. The number of T-cells in the blood rose after intensive running while lymphopenia occurred after swimming exercise. Changes in number of labelled T-cells were neither found in the lymph nodes nor in the thymus regardless of exercise protocol. Following an alpha- or beta-blockade, the exercise-induced release of T-cells from the spleen and the accumulation of T-cells in the lung were inhibited while the enhancement of T-cells in the Peyer's patches was not affected. The administration of epinephrine partially mimicked the effects of exercise and resulted in a release of T-cells from both, the spleen and the liver, as well as in an increase of circulating blood T-cells. In conclusion, exercise induces a substantial re-distribution of T-cells within lymphoid and non-lymphoid organs. The migrating properties of T-cells could be partially explained by adrenergic mechanisms associated with exercise while the involvement of certain homing receptors remains to be shown. Our results suggest that the accumulation of T-cells in both, lung and Peyer's patches, may enhance the immune vigilance in these compartments which serve as the body's major defence barriers.

Regulation of a lymphocyte-endothelial-IL-6 trans-signaling axis by fever-range thermal stress: hot spot of immune surveillance

The pleiotropic cytokine, interleukin-6 (IL-6), has emerged in recent years as a key regulator of the transition from innate to adaptive immunity through its ability to modulate leukocyte recruitment at inflammatory sites. This review highlights a newly identified role for IL-6 trans-signaling, initiated by an agonistic complex of IL-6 and a soluble form of IL-6 receptor alpha, in heightening immune surveillance of peripheral lymphoid organs during febrile inflammatory responses. Inflammatory cues provided by the thermal component of fever trigger IL-6 trans-signaling to act at discrete levels in the multistep adhesion cascade that governs the entry of blood-borne lymphocytes across 'gatekeeper' high endothelial venules (HEVs) in lymph nodes and Peyer patches. IL-6 trans-signaling-dependent mechanisms have been elucidated during thermal stimulation of primary tethering and rolling of lymphocytes along the lumenal surface of HEVs as well as during secondary firm arrest of lymphocytes in HEVs prior to their migration into the underlying parenchyma. These mechanisms profoundly increase the probability that lymphocytes that continuously patrol the body will engage in productive encounters with target antigens sequestered within lymphoid organs. Findings that the lymphocyte-HEV-IL-6 trans-signaling biological axis functions as a thermally-sensitive alert system that promotes immune surveillance provide insight into one of the unresolved mysteries in immunology regarding the benefits of mounting a febrile reaction during inflammation.

Primary immune surveillance: some like it hot

The thermal element of fever has been found to be beneficial in models of infectious disease. The contributions of fever-range temperatures to the efficacy of the adaptive immune response have only begun to be delineated. There is accumulating evidence that fever-range thermal stress bolsters primary immune surveillance of lymph nodes and Peyer patches by augmenting lymphocyte extravasation across specialized vessels termed high endothelial venules. Molecular mechanisms have recently come to light by which the thermal component of fever alone may promote lymphocyte trafficking, and thereby the probability of mounting a defense against microbial infection. Acquired knowledge of the molecular changes associated with thermal stress may allow for the development of novel therapies for a variety of disease processes.

Fever-range thermal stress promotes lymphocyte trafficking across high endothelial venules via an interleukin 6 trans-signaling mechanism

Fever is an evolutionarily conserved response during acute inflammation, although its physiological benefit is poorly understood. Here we show thermal stress in the range of fever temperatures increased the intravascular display of two 'gatekeeper' homing molecules, intercellular adhesion molecule 1 (ICAM-1) and CCL21 chemokine, exclusively in high endothelial venules (HEVs) that are chief portals for the entry of blood-borne lymphocytes into lymphoid organs. Enhanced endothelial expression of ICAM-1 and CCL21 was linked to increased lymphocyte trafficking across HEVs. A bifurcation in the mechanisms controlling HEV adhesion was demonstrated by evidence that the thermal induction of ICAM-1 but not of CCL21 involved an interleukin 6 trans-signaling pathway. Our findings identify the 'HEV axis' as a thermally sensitive alert system that heightens immune surveillance during inflammation by amplifying lymphocyte trafficking to lymphoid organs.

Hurdles to lymphocyte trafficking in the tumor microenvironment: implications for effective immunotherapy

An important consideration in the development of T cell-based cancer immunotherapy is that effector T cells must efficiently traffic to the tumor microenvironment in order to control malignant progression. T cell trafficking to target tissues is orchestrated by dynamic interactions between circulating lymphocytes and endothelial cells lining blood vessels. It is informative, in this regard, to compare and contrast the molecular mechanisms governing lymphocyte extravasation at distinct vascular sites: (1) high endothelial venules (HEV) of secondary lymphoid organs, which are portals for efficient trafficking of naive and central memory T lymphocytes; (2) non-activated endothelium of normal tissues that mediate relatively low basal levels of trafficking but are rapidly transformed into HEV-like vessels in response to local inflammatory stimuli; and (3) vessels within the intratumoral region and the surrounding peritumoral areas. These vessels can be distinguished by differential expression of hallmark trafficking molecules that function as molecular beacons directing lymphocyte migration across vascular barriers. This article reviews evidence that recruitment of effector T cells to the intratumoral microenvironment is impeded by sub-threshold expression of trafficking molecules on tumor microvessels. Emerging data support the thesis that when considered from the perspective of extravasation, vessels embedded within the intratumoral microenvironment of established tumors do not exhibit stereotypical characteristics of a chronic inflammatory state. A major challenge will be to develop therapeutic approaches to improve trafficking of effector T lymphocytes to tumor sites without skewing the balance in favor of a chronic inflammatory milieu that facilitates tumor maintenance and progression.