Fluid therapy in shock

The goal of treatment for all types of shock is the improvement of tissue perfusion and oxygenation. The mainstay of therapy for hypovolemic and septic shock is the expansion of the intravascular volume by fluid administration, including crystalloids, colloids, and blood products. Frequent physical examinations and monitoring enable the clinician to determine the adequacy of tissue oxygenation and thus the success of the fluid therapy.

Differential susceptibility to activation-induced apoptosis among peripheral Th1 subsets: correlation with Bcl-2 expression and consequences for AIDS pathogenesis

It has been proposed that HIV infection is associated with an imbalance in Th1 and Th2 subsets. Recent reports indicate that Th1 and Th2 effectors differ in their susceptibility to activation-induced apoptosis. To determine whether increased T cell apoptosis in HIV-infected patients contributes to alterations in cytokine synthesis, we performed single-cell analysis of type 1 and type 2 cytokine production by CD4 and CD8 T cells, simultaneously with detection of apoptosis. We demonstrate that a differential alteration in representation of Th1 subsets, rather than commitment of T cells to secrete Th2 cytokines, occurs throughout HIV infection. A significant decrease in the number of IL-2- or TNF-alpha-producing T cells was observed, whereas those producing IFN-gamma remained preserved. Furthermore, there is a gradient of susceptibility to activation-induced apoptosis (IL-2 < IFN-gamma < TNF-alpha) among the different Th1 subsets. This gradient was detected in both CD4 and CD8 subsets, as well as in control donors and HIV-infected patients, in whom the susceptibility to apoptosis of IL-2 and IFN-gamma producers was increased compared with controls. This differential intrinsic apoptosis susceptibility of Th1 effectors was found to be tightly regulated by Bcl-2 expression. In HIV-infected persons, disappearance of IL-2-producing T cells was a good indicator of disease progression and was correlated with the progressive shrinkage of the CD4+ CD45RA+ T cell compartment and a gradual increased susceptibility to activation-induced apoptosis of the IL-2-producing subset. This close relationship between the CD45RA/CD45R0 ratio, the level of type 1 cytokine production, and susceptibility to apoptosis should be considered in HIV-infected patients under antiviral or immune-based therapies.

Classification of cytokines according to the receptor code

A simple classification of cytokines is presented. It is based on voluminous information available from published papers of many outstanding researchers of the cytokines and their receptors and/or summarized by experts in this field. The cytokines are divided into 7 families according to their receptor code. Such arrangement of apparently different cytokines may explain the biological significance of pleiotropy and redundancy. Furthermore, it may stimulate the development of the comprehensive classification of cytokines together with classical hormones, neuromediators, neuromodulators and related substances that participate in complex biological communication system.

Cytokine amplification and inhibition of immune and inflammatory responses

Cytokines are soluble mediators of intercellular communication. They contribute to a chemical signalling language that regulates development, tissue repair, haematopoiesis, inflammation and the immune response. Potent cytokine polypeptides have pleiotropic activities and functional redundancy. They act in a complex network where one cytokine can influence the production of, and response to, many other cytokines. In the past 5 years this bewildering array of 100+ effector molecules and associated cell surface receptors has been simplified by study of three-dimensional cytokine and cytokine receptor structure: elucidation of convergent intracellular signalling pathways; and molecular genetics, especially targeted gene disruption to 'knockout' production of individual cytokines in mice. It is also now clear that much of the pathophysiology of infectious disease can be explained by the induction of cytokines and the subsequent cellular response. Cytokine and cytokine antagonists have also shown therapeutic potential in a number of chronic and acute diseases.

Independent regulation of cutaneous lymphocyte-associated antigen expression and cytokine synthesis phenotype during human CD4+ memory T cell differentiation

Although considerable attention has been paid to the development of cytokine synthesis heterogeneity during memory T cell differentiation, little information is available on how this function is coregulated with homing receptor expression. The development of skin-homing, CD4+ memory T cells in the human provides an excellent model for such investigation, since 1) the skin supports both Th1- and Th2-predominant responses in different settings, and 2) the skin-homing capability of human memory T cells correlates with and appears to depend on expression of the skin-selective homing receptor cutaneous lymphocyte-associated Ag (CLA). In this study, we used multiparameter FACS analysis to examine expression of CLA vs IFN-gamma, IL-4, and IL-2 synthesis capabilities among fresh peripheral blood CD4+ memory T cells, and Th1 vs Th2 memory T cells generated in vitro from purified CD4+ naive precursors by cyclic activation in polarizing culture conditions. Among normal peripheral blood T cells, CLA expression was essentially identical among the IFN-gamma- vs IL-4-producing CD4+ memory subsets, clearly indicating the existence of in vivo mechanisms capable of producing both Th1 vs Th2 skin-homing T cells. In vitro differentiation of naive CD4+ T cells confirmed the independent regulation of CLA and all three cytokines examined, regulation that allowed differential production of IFN-gamma-, IL-4-, and IL-2-producing, CLA+ memory subsets. These studies also 1) demonstrated differences in regulatory factor activity depending on the differentiation status of the responding cell, and 2) revealed CLA expression to be much more rapidly reversible on established memory cells than cytokine synthesis capabilities.

Cytokines in lung cancer

Cytokines are hormonE-like proteins and peptides involved in the signalling between cells during immune response. They are produced mainly by lymphocytes (lymphokines) and mononuclear phagocytes (monokines). They are involved in both cell-mediated and humoral immunity. Cytokines fall into a number of categories: interferons (IFNs), interleukins (ILs) and growth factors. It has been indicated in cancer immunology the following cytokines are particularly important: IFNs, TNF-alpha, IL-1, IL-2, IL-4, IL-6, IL-7, IL-9, IL-10, IL-12. Interferons (IFN-gamma in particular) in cooperation with TNF-alpha and IL-1 inhibit proliferation of tumor cells and by their synergic activity with IL-2 induce cytotoxicity of NK-cells. They activate mononuclear phagocytes and by B lymphocyte stimulation augment lysis of cancer cells. TNF-alpha has mainly cytotoxic activity, leading to hemorrhagic necrosis of tumors. It is also an endogenic pyrogen which is together with IL-1 responsible for pyretic status in neoplastic disease. IL-1 stimulates necrotizing activity of TNF-alpha and augments cachexia by anabolism of lipid induction. IL-2, IL-6 and IL-12 induce NK and LAK-cell cytotoxicity. IL-12 inhibits metastasis formation. IL-10, by inhibiting synthesis of cytokines may lead to tumor development.

Pathophysiology of fever. Part 1: The role of cytokines

Because of advanced molecular physiology techniques, there is new information about how fever affects the body. Now, fever is identified as a cascade of physiologic events, not just a single symptom. This article, the first in a set of two on the physiology of fever, focuses on the role of cytokines as the trigger for the physiologic cascade of fever. (Watch for Part 2 in the next issue of DCCN, which challenges the assumption that cooling interventions are appropriate for all febrile patients.

Glucocorticoids and Th-1, Th-2 type cytokines in rheumatoid arthritis, osteoarthritis, asthma, atopic dermatitis and AIDS

Endogenous or exogenous glucocorticoids play a key role in the control of the immune and inflammatory network. Regulation of the effects of the glucocorticoids depends on changes in therapeutic levels, but also, as recently discovered, on modifications of the binding characteristics of the glucocorticoid receptors of target cells. In rheumatoid arthritis (RA), chronic bronchial asthma, atopic dermatitis, in chondrocytes from osteoarthritic patients, and in advanced stages of HIV infection, there is a down-regulation of the glucocorticoid receptors. As a consequence, B cell immune proliferation is stimulated in RA, proteolysis is enhanced in osteoarthritis, the glucocorticoids' therapeutic effect is reduced in asthma and atopic dermatitis, and a chronic persistent increase of interferon alpha is seen in HIV. Finally, glucocorticoids are also capable of switching CD4 cells from a Th-1 to a Th-2 pattern. A decreased affinity of lymphocyte glucocorticoid receptors could hinder such a switch, with obvious clinical implications.

Leptin is a four-helix bundle: secondary structure by NMR

Leptin is a signaling protein that in its mutant forms has been associated with obesity and Type II diabetes. The lack of sequence similarity has precluded analogies based on structural resemblance to known systems. Backbone NMR signals for mouse leptin (13C/15N -labeled) have been assigned and its secondary structure reveals it to be a four-helix bundle cytokine. Helix lengths and disulfide pattern are in agreement with leptin as a member of the short-helix cytokine family. A three-dimensional model was built verifying the mechanical consistency of the identified elements with a short-helix cytokine core.

Impact of knockout mice in toxicology

Knockout mice obtained by homologous recombination technology may be valuable tools for in vivo investigations in toxicopathogenesis. A short review is given on the phenotype of mice with distinct deletions of cytokines and related genes. The application of these mice in pharmacological and toxicological research is discussed, with emphasis in endotoxic shock, hepatic toxicity, and myelotoxicity. The use of such knockout mice will be valuable for mechanistic studies in toxicology.

Does human toxoplasmosis involve an imbalance in T1/T2 cytokines?

The T1 (interferon-gamma, interleukin-12, interleukin-2) and T2 (interleukin-4, interleukin-10, interleukin-6) cytokine groups constitute two polar responses of the immune system. The T1 group is a predominantly cellular response, while the T2 group response is mainly humoral. The hypothesis forwarded here links these subgroups of induced cytokines to the various clinical forms of human toxoplasmosis. Ocular toxoplasmosis in immunocompetent patients could be attributed to a T1 hyper-response, whereas congenital toxoplasmosis, toxoplasmic encephalitis (in immunodeficient patients) and active chronic toxoplasmosis (with persistent lymphadenophathy) would be characterized by a predominantly T2 response. Confirmation that this kind of immunological imbalance effectively underlies the various clinical forms of toxoplasmosis would open the way for a new range of treatments based on immunomodulation.

Human Th2-like cell clones induce IL-12 production by dendritic cells and may express several cytokine profiles

Previous studies have shown that human Th2 cells, unlike their murine counterparts, retain the ability to produce IFN-gamma upon activation in the presence of exogenous IL-12. Here we first extended this notion by showing that Th2-like cell clones (Th2C) are also capable of inducing IL-12 production by physiological antigen-presenting cells (APC); we next showed that these cells may express several distinct cytokine profiles depending upon the activation signal and the type of APC with which they interact. We have analyzed the production of IL-4, IL-5 and IFN-gamma by Th2C stimulated by either anti-CD3 mAb or exogenous IL-2, using peripheral blood monocytes or dendritic cells (DC) as accessory cells. We found that: (I) DC but not monocytes released IL-12 and promoted IL-12-dependent IFN-gamma production upon interaction with anti-CD3- or IL-2-stimulated Th2C and (II) ligation of CD3 was required for the production of IL-4 but not of IL-5 or IFN-gamma. Thus, depending upon the type of APC with which they interacted and the mode of activation, Th2C, expressed four distinct cytokine profiles: (i) IL-4 + IL-5, in response to anti-CD3 + monocytes; (ii) IL-4, IL-5 + IFN-gamma, in response to anti-CD3 + DC; (iii) IL-5 + IFN-gamma, in response IL-2 + DC; and (iv) IL-5 alone, in response to IL-2 + monocytes. The ability of human Th2-like cells to induce IL-12 production and to release the proinflammatory cytokines IFN-gamma and IL-5 upon IL-2-driven interactions with APC may contribute to explain how local infection exacerbates Th2-mediated diseases, like bronchial asthma and atopic dermatitis.

Polymorphonuclear leucocyte (PMN)-derived inflammatory cytokines--regulation by oxygen tension and extracellular matrix

The kinetics of IL-8, tumour necrosis factor-alpha (TNF-alpha) and IL-1 beta release by PMN adhered to fibronectin, laminin or plastic for 24 h in response to continuous stimulation with lipopolysaccharide (LPS; 50 ng/ml), N-formyl-Met-Leu-Phe (fMLP; 100 mM), or phorbol myristate acetate (PMA; 10 ng/ml), was investigated under altered oxygen tension conditions. Cell supernatants were sampled for cytokine content every 6 h and measured by ELISA. IL-8 was the most abundant cytokine, produced in a range of up to 5.4 ng/ml; TNF-alpha and IL-1 beta were produced in a range of up to 1 ng/ml. During normoxia, LPS was the most potent stimulus, inducing the release of each cytokine, while fMLP showed a less pronounced effect on IL-8 and IL-1 beta production and markedly inhibited TNF-alpha production. PMA markedly suppressed IL-8 and IL-1 beta release and failed to induce any release of TNF-alpha. Hypoxia had an overall inhibitory effect on cytokine release except for PMA-induced IL-1 beta release, and hypoxia/reoxygenation had a significant up-regulating effect except for a further inhibition of fMLP-induced release of TNF-alpha. Integrinmatrix protein ligation differentiated both spontaneous and externally induced cytokine release and its sensitivity to alteration in oxygen tension. Thus the process of PMN elaboration of inflammatory cytokines is controlled on multiple levels of signal transduction, differentiated by integrin-extracellular matrix interactions, and is sensitive to alterations in microenvironmental oxygen tension.

[Cytokines and their role in intercellular interactions]

Cytokines include interferons, colony-stimulating factors, interleukins and growth factors. 6 groups of cytokines are distinguished depending on the direction of their function. They provide regulation of intercellular interaction, initiate nonspecific inflammatory response, control growth and differentiation of hematopoietic and residential cells, activate the cells of the inflammatory infiltrate, stimulate hematopoiesis. Regulation of the cytokine activity is brought about at the level of their secretion, expression of the cytokines receptors as well as by means of other cytokines and soluble cytokine-binding factors and inhibitors. The use of cytokines and antibodies against them, receptor antagonists and soluble cytokine receptors is increasing for immunotherapy of various diseases.

Type 1 and type 2 cytokine dysregulation in human infectious, neoplastic, and inflammatory diseases

In the mid-1980s, Mosmann, Coffman, and their colleagues discovered that murine CD4+ helper T-cell clones could be distinguished by the cytokines they synthesized. The isolation of human Th1 and Th2 clones by Romagnani and coworkers in the early 1990s has led to a large number of reports on the effects of Th1 and Th2 on the human immune system. More recently, cells other than CD4+ T cells, including CD8+ T cells, monocytes, NK cells, B cells, eosinophils, mast cells, basophils, and other cells, have been shown to be capable of producing "Th1" and "Th2" cytokines. In this review, we examine the literature on human diseases, using the nomenclature of type 1 (Th1-like) and type 2 (Th2-like) cytokines, which includes all cell types producing these cytokines rather than only CD4+ T cells. Type 1 cytokines include interleukin-2 (IL-2), gamma interferon, IL-12 and tumor necrosis factor beta, while type 2 cytokines include IL-4, IL-5, IL-6, IL-10, and IL-13. In general, type 1 cytokines favor the development of a strong cellular immune response whereas type 2 cytokines favor a strong humoral immune response. Some of these type 1 and type 2 cytokines are cross-regulatory. For example, gamma interferon and IL-12 decrease the levels of type 2 cytokines whereas IL-4 and IL-10 decrease the levels of type 1 cytokines. We use this cytokine perspective to examine human diseases including infections due to viruses, bacteria, parasites, and fungi, as well as selected neoplastic, atopic, rheumatologic, autoimmune, and idiopathic-inflammatory conditions. Clinically, type 1 cytokine-predominant responses should be suspected in any delayed-type hypersensitivity-like granulomatous reactions and in infections with intracellular pathogens, whereas conditions involving hypergammaglobulinemia, increased immunoglobulin E levels, and/or eosinophilia are suggestive of type 2 cytokine-predominant conditions. If this immunologic concept is relevant to human diseases, the potential exists for novel cytokine-based therapies and novel cytokine-directed preventive vaccines for such diseases.

Keratinocytes and cytokine/growth factors

Cytokines are polypeptide growth factors produced by most nucleated cells in the body, including epithelial cells, keratinocytes, and Langerhans cells in the skin. Cytokines can be classified into interleukins, tumor necrosis factors, chemokines, colony-stimulating factor, interferons, and growth factors. Like classic hormones, cytokines bind to specific receptors to transmit their messages to target cells. Cytokine receptors can be divided into three cytokine receptor superfamilies: the immunoglobulin superfamily, the hematopoietin family, and the tumor necrosis factor family. Following cytokine/cytokine-receptor binding (first messenger), a signal transduction pathway is initiated. Factors affecting homeostasis in the skin and oral mucosa include a delicate balance between cytokines/cytokine-receptors and their antagonists. An imbalance in these variables can influence the development of cutaneous and oral diseases-such as lichen planus, autoimmune disorders, and some neoplastic processes- and can affect wound healing. Potential uses of cytokines include cancer and antiviral therapy.

Characterization of type 1 and type 2 cytokine production profile in physiologic and pathologic human pregnancy

Antigen- and mitogen-stimulated cytokine production by peripheral blood mononuclear cells (PBMC) of 50 pregnant women and 31 age- and sex-matched non-pregnant controls were analysed to determine whether changes in cytokine production occur during normal and pathologic human gestation. The pregnant women, consecutively enrolled during a 3-month period, were undergoing a normal, non-pathologic pregnancy at the time of entry into the study, and underwent ultrasound examination to ascertain the exact week of pregnancy and the vitality of the fetus. Forty of the 50 pregnancies (80%) terminated physiologically with the birth of normal babies. Spontaneous abortions were observed in 5/50 (10%) women, and five women gave birth to newborns small for gestational age (SGA). A decrease in the production of IL-2 and interferon-gamma (IFN-gamma) accompanied by an increase in production of IL-4 and IL-10, was observed in normal pregnancy, with the lowest quantities of IL-2 and IFN-gamma and the highest quantities of IL-4 and IL-10 present in the third trimester of pregnancy. Statistically significant increased production of both IL-2 and IFN-gamma and reduced production of IL-10 characterized pathologic pregnancies and distinguished them from normal pregnancies. These preliminary data suggest that a type 2 cytokine profile may be associated with normal human pregnancy, whereas the lack of a dominant type 2 cytokine profile may be indicative of a pathologic pregnancy.

Type 1 and type 2 cytokine profiles in children exposed to or infected with vertically transmitted human immunodeficiency virus

In human immunodeficiency virus (HIV)-infected adults, cytokine production profiles switch from predominantly type 1 (interleukin-2 [IL-2] and gamma interferon [IFN-gamma]) to type 2 (IL-4 and IL-10) cytokines with disease progression. To test this hypothesis in vertically HIV-infected children, we measured cytokine transcription and production in rapid progressors (RPs), seroreverters (SRs), and those children exposed to HIV in utero (P0s). Production of type 1 and type 2 cytokines was measured in peripheral blood mononuclear cell cultures of 8 SR, 25 P0, and 11 RP children. Unstimulated cultures, irrespective of infection and stage of disease, produced similar levels of IL-2, IFN-gamma, IL-4, and IL-10. Upon stimulation with phytohemagglutinin (PHA) plus phorbol-12-myristate-13-acetate (PMA), RP children produced less IL-2 (P < 0.01) and IFN-gamma (P < 0.02) than SR children and also expressed significantly less IFN-gamma mRNA (P < 0.01) than SR children. RP children expressed significantly higher levels of IL-4 mRNA than P0 children (P < 0.03). There were no differences in the production of IL-10 by PHA-PMA-stimulated peripheral blood mononuclear cell cultures among the three groups of children. Our data with these pediatric patients suggest that a deficiency in mitogen-stimulated type 1 cytokine production and excess type 2 cytokine (IL-4) transcription correlate with disease progression. Additional studies with larger sample sizes are needed to test further the hypothesis of the type 1-to-type 2 cytokine switch in children infected with HIV.

Cytokine function: a study in biologic diversity

Cytokines are a group of hormone-like polypeptide mediators that play a variety of regulatory roles in both host defense and normal and abnormal homeostatic mechanisms. They may he produced by diverse cell types and exert their function on a variety of cells. Their effects (which may be suppressive or enhancing) are on cellular proliferation, differentiation, activation, and motility. In addition, cytokines can exert cytodestructive effects on infectious agents or tumor cells, either directly or by activating cells with cytodestructive potential. Any given cytokine may have many different biologic effects. However, two different cytokines may have similar or identical activities. Cytokines may be classified on the basis of their cell of origin, their spectrum of activity, the category of activity they influence, the cells that are their targets, or on specific features of their ligand-receptor interaction. The mode of action of many of the cytokines involves typical signal transduction events such as protein phosphorylation, and to date there is only limited understanding of the mechanisms that lead to one activity over another when a specific cytokine is involved in a specific biologic reaction. Nevertheless, elucidation of their role in other pathologic processes has provided insight into autoimmune and allergic diseases, as well as a variety of systemic disorders. Because of their broad spectrum of activity, cytokines have been used in a variety of therapeutic settings involving both infectious diseases and neoplasia. As the number of known cytokines continues to grow, it will be increasingly difficult for the non-"cytokinologist" to follow the exponentially expanding literature. Hopefully, this brief review will provide an overview that can serve as a framework for the understanding of this important area of biology and pathology.

Interleukin-2 receptor common gamma-chain signaling cytokines regulate activated T cell apoptosis in response to growth factor withdrawal: selective induction of anti-apoptotic (bcl-2, bcl-xL) but not pro-apoptotic (bax, bcl-xS) gene expression

Cytokine deprivation from activated T cells leads to apoptosis associated with down-regulation of the bcl-2 gene product. It is not clear, however, how cytokines other than interleukin-2 (IL-2) may affect this process and regulate the involvement of other apoptosis-modulating genes. We show that a group of cytokines including IL-2 (IL-2R gamma), prevent the apoptosis of IL-2-deprived activated T cells. This rescue involves the induction of the anti-apoptosis genes bcl-2 and bcl-xL), but causes little change in expression of bax and bcl-xS, which promote apoptosis. Furthermore, the prevention of apoptosis and induction of proliferation by the common gamma chain cytokines can be dissociated. Thus, when proliferation is blocked, the common gamma chain cytokines still induce up-regulation of bcl-2 relative to bax and retard apoptosis. These cytokines can thus regulate the persistence or removal of effector T cells by coordinating the balance between genes which promote and those which inhibit apoptosis, events which are probably mediated at least in part by signals through the common gamma chain. These data also implicate inappropriate T cell apoptosis resulting from a dysfunctional common gamma-chain as part of the pathophysiological defect in patients with X-linked severe-combined immunodeficiency (SCID).

Characterization of cytokine production in murine Trypanosoma cruzi infection by in situ immunocytochemistry: lack of association between susceptibility and type 2 cytokine production

Cytokine production in the spleens of mice infected with the protozoan parasite Trypanosoma cruzi was analyzed in three models which differ in the outcome of the infection. Using immunocytochemical techniques to detect cytokine-producing cells, the production of type 1 [interleukin-2 (IL-2) and interferon (IFN)-gamma], type 2 (IL-4, IL-5, IL-10), inflammatory [tumor necrosis factor (TNF)-alpha, IL-1 alpha, IL-6] and regulatory (transforming growth factor-beta) cytokines were examined. With the exception of IL-4 and IL-5, cells producing all of the cytokines assayed were detected in both the resistant and susceptible models of T. cruzi infection. Cells producing IL-4 and IL-5 were not detected until later in infection in the resistant mice (> 34 days), at about the time animals of the susceptible strain succumb to the infection. Mice of the susceptible model showed a slight delay in the appearance of cells producing the type 1 cytokines IL-2 and IFN-gamma and an earlier appearance of TNF-producing cells, in comparison to resistant mice. Cells producing IL-2 or IL-10 were transient in their appearance in the spleen while cells producing IL-1, IL-4, IL-5, IL-6, IFN-gamma, TNF, or TGF-beta were first detectable in either the acute or post-acute stage of the infection and persisted up to 700 days post infection in two different resistant models of the infection. Cells producing IFN-gamma, TNF-alpha and TGF-beta were particularly numerous even very late in the infection. Double-staining techniques were used to show that the vast majority of the IFN-gamma-producing cells in the spleen were CD4-, CD8- alpha/beta TCR+T cells. This study confirms the transience of IL-2 production in the acute stage of T. cruzi infection and the persistent and simultaneous production of type 1 and type 2 cytokines during the late-acute and chronic stages of the infection. Susceptibility or resistance to T. cruzi infection does not associate with a Th2 pattern of cytokine production in the three models examined in this study. The overlapping pattern of type 1 and type 2 cytokine-producing cells in both the acute and chronic stages of T. cruzi infection demonstrates that longterm infections do not necessarily lead to a dominance of either type 1 or type 2 cytokine production.

Review: nomenclature and biologic significance of cytokines involved in inflammation and the host immune response

This is a brief review of 42 cytokines and interleukins that are involved inflammatory and immune responses. The cytokines are listed in tables organized as hematopoietic growth factors, interferons, lymphokines, monokines, chemokines, and other cytokines. Information on each cytokine includes the most commonly used abbreviations, the former or alternative names and abbreviations of the cytokines, the cells that form the major sources of production of the cytokines, the major biologic actions of the cytokines, and references to recent reviews or primary literature. Minor biologic actions and minor cellular sources of the cytokines may not be listed. This review should be useful as a quick reference guide to the cytokines and interleukins.

Cutaneous reactions to recombinant cytokine therapy

Cytokines are critical to several fundamental homeostatic mechanisms such as fever, acute phase reactions, wound healing, hematopoiesis, inflammation, cellular and humoral immune responses, and tumor regression. As a result of advances in recombinant DNA technology, recombinant cytokines are available as therapeutic agents. They have been used for metastatic cancers and immunodeficiencies, as a therapy for naturally occurring or drug-induced anemias or leukopenias, and they have also been applied to some cutaneous disorders. Cytokine therapy can result in toxic reactions that affect many organ systems, especially the skin. These reactions are common and diverse, ranging from minor injection site reactions, pruritus, and flushing to life-threatening autoimmune disorders, severe erythroderma, or bullous skin reactions. This review focuses on the major cytokines that are in current clinical use or under investigation and describes the cutaneous complications of these agents.

The nomenclature of chemokines

Migration of leukocytes to injured tissues is a hallmark of inflammation. The recruitment phase of cells can be subdivided into three steps: the rolling phase, the firm adhesion phase, and the transendothelial migration phase. Each step is mediated by a complex interplay of endothelial/leukocyte surface molecule interactions (mostly of selectin and integrin families) as well as a group of small, secreted peptides, called chemokines. Chemokines activate on the one hand, the leukocytes to express the appropriate adhesion molecules and on the other hand, they lead to transendothelial migration via chemotaxis (migration along a gradient in solution) and haptotaxis (migration along a gradient bound to extracellular martrices or cell membranes). The structure, biology and pathobiology of the more than 22 known members of this group of soluble mediators, with a particular emphasis on their past and present nomenclature, is the topic of this minireview.

Pro-inflammatory cytokines in a ruminant model: pathophysiological, pharmacological, and therapeutic aspects

Infection evokes complex changes which are thought to be caused by production and release of pro-inflammatory cytokines such as tumour necrosis factor (TNF-alpha), interferons (INFs), and interleukins (ILs). They regulate local inflammatory reactions, but may also gain access to the circulation and induce systemic effects collectively known as the Acute Phase Response. To improve our understanding of the pathophysiology of pro-inflammatory cytokines in ruminants, studies have been performed with TNF-alpha, IL1-alpha/beta, and IFN-alpha/ gamma as well as with cytokine-inducers in dwarf goats. In relation to therapy, the following aspects may be of interest: a) Cytokine therapy given before or just after microbial challenge induces in vivo antimicrobial activity. Moreover, cytokines potentiate in vivo the antimicrobial activity of antibiotics, b) Cytokines may act as biological response modifiers for enhancing specific immunity to vaccines, and c) Cytokines may affect drug absorption, disposition, and metabolite formation in disease states. Although studies of the actions of corticosteroids, nonsteroidal anti-inflammatory and antipyretic agents, antibodies to endotoxin, TNF-alpha, or IL-1, synthetic E. coli lipid A precursors, hydrazine, isoniazid, chloroquine, polymyxin B, bicyclic imidazoles, hydroxamates, and tyrosine kinase inhibitors in endotoxaemic animals have shed further light on inflammatory processes, clinical studies in this field are urgently required to evaluate their beneficial effect.

Stimulus and cell-specific expression of C-X-C and C-C chemokines by pulmonary stromal cell populations

Chronic inflammatory responses in the lung rely on the continual recruitment of leukocytes to the site of inflammation. Recent data have demonstrated a possible role for stromal cell-derived chemokines in leukocyte recruitment. In the present study we examined the production of interleukin (IL)-8 and ENA-78, members of the C-X-C family of chemokines, and macrophage inflammatory protein (MIP)-1 alpha and MIP-1 beta, members of the C-C chemokine family, from pulmonary smooth muscle and endothelial cells. The production of IL-8 and ENA-78 was induced by early response cytokines, IL-1 and tumor necrosis factor (TNF), but not by immune-associated cytokines, IL-4, IL-10, or interferon (IFN)-gamma. In contrast, the production of MIP-1 alpha and MIP-1 beta by pulmonary vascular smooth muscle cells increased when stimulated by immune-associated cytokines as well as with IL-1 beta and TNF. The level of MIP-1 alpha production induced in smooth muscle cells by the immune-associated cytokines, IL-4, IFN-gamma, and IL-10 ranged from 0 to 340 pg/ml. The production of MIP-1 beta in response to the immune-associated cytokines IL-4, IFN-gamma, and IL-10 in smooth muscle cells ranged from 260 to 940 pg/ml. Human pulmonary artery endothelial cells did not generate MIP-1 alpha or MIP-1 beta in response to graded doses of any of the cytokines. These data demonstrate differential induction of C-X-C and C-C chemokines from nonimmune stromal cell populations.(ABSTRACT TRUNCATED AT 250 WORDS)

Basophil and eosinophil activation by CC chemokines

Recent studies have shown that CC chemokines act on monocytes, lymphocytes, eosinophils and basophils, but not neutrophils, with distinct target cell selectivities, possibly explaining the selective attraction and activation of these cell types in different types of chronic inflammation and allergic disease. Functional and desensitization studies on basophils and eosinophils indicate the expression of at least three distinct G-protein-coupled CC chemokine receptors (three on basophils and two on eosinophils), which exert partially selective and partially overlapping ligand specificities and also appear to mediate distinct functions despite similar signal transduction pathways. Functional studies with all known six human CC chemokines show that each cytokine has a distinct spectrum of bioactivities and target cell profile. Interestingly, overall sequence homologies between the chemokines are not predictive for the cell function or cell type that a particular chemokine will preferentially activate, and thus discrete sequence motifs may be important for activating the different CC chemokine receptors. Using different chemokine mutants and hybrids between chemokines, the functional importance of selected individual amino acids and short motifs are now being analysed. These structure-function studies could also lead to antagonists that have more disease-selective anti-inflammatory properties than currently available drugs.

Role of immune activation and cytokine expression in HIV-1-associated neurologic diseases

Central nervous system (CNS) involvement is common during human immunodeficiency virus type-1 (HIV-1) infection. The neurologic disease of the CNS most frequently observed during acquired immunodeficiency syndrome (AIDS) is HIV-1-associated cognitive/motor complex or AIDS dementia complex (ADC), which is most likely a direct consequence of HIV-1 infection of the CNS. The peripheral nervous system (PNS) is also affected in HIV-1-infected individuals and there are several features of immune- and cytokine-related pathogenesis in both the CNS and PNS that are reviewed. Several lines of evidence demonstrate aspects of immune activation in the CNS and peripheral nervous system (PNS) of HIV-1-infected individuals. The relative paucity of HIV-1 expression in contrast to widespread functional and pathologic changes in the CNS and PNS of AIDS patients, and the lack of evidence of productive infection of HIV-1 in neuronal cells in vivo lead to the possibility of indirect or immunopathogenic mechanisms for HIV-1-related neurologic diseases. Proposed mechanisms of neuronal and glial cell damage are injury of oligodendrocytes by tumor necrosis factor-alpha (TNF-alpha) released from activated macrophage/microglia, calcium-dependent excitoneurotoxicity induced by gp120 HIV-1 envelope protein, N-methyl-D-aspartate (NMDA) receptor-mediated neurotoxicity by quinolinic acid (a product of activated macrophages), cell injury by HIV-1-specific cytotoxic T cells, and apoptosis of oligodendrocytes or neurons triggered by interaction between cell surface receptors and HIV-1 gp120 protein. Common to those mechanisms is the dependence on cellular activation with expression of proinflammatory cytokines (TNF-alpha, interleukin-1). Amplification of activation signals through the cytokine network by macrophage/astrocyte/endothelial cell interactions, and cell-to-cell contact between activated macrophages and neural cells by upregulation of adhesion molecules dramatically enhances the toxic effect of macrophage products. Expression of immunosuppressive cytokines such as interleukin-4, interleukin-6, and transforming growth factor-beta is also increased in the CNS and PNS of HIV-1-infected patients. This may serve as neuroprotective and regenerative mechanism against insults to nervous system tissue.

Effects of 15-deoxyspergualin in vitro and in vivo on cytokine gene expression

Reverse transcriptase-polymerase chain reaction showed that interleukin 3, IL-4, IL-5, IL-6, interferon-gamma and stem cell factor mRNA expression were higher in 15-deoxyspergualin-treated spleen cells than in control spleen cells. Increased IL-2 and IFN-gamma mRNA expression were observed in 15-deoxyspergualin-treated bone marrow cells. On the other hand, increased platelet counts in BALB/c-->C3H/He bone marrow chimeras were observed from days 20 to 33 in our previous work, when they were treated with 15-deoxyspergualin from days 14 to 25. In contrast, marked leukocytopenia and anemia were simultaneously observed, although a marked leukocytosis and a rapid recovery of anemia were observed on day 33 and thereafter. To analyze effects of 15-deoxyspergualin on hematopoiesis and the immune system, we examined mRNA expression in bone marrow and spleen cells from BALB/c-->C3H/He bone marrow chimeras treated with 15-deoxyspergualin from days 14 to 25. Reverse transcriptase-polymerase chain reaction showed that IL-3, IL-4, IL-6, stem cell factor, granulocyte colony-stimulating factor, and granulocyte/macrophage colony-stimulating factor mRNA expression were higher in 15-deoxyspergualin-treated chimeras than in control chimeras, indicating that these cytokines are responsible for an enhancement of hematopoiesis. It was conceivable that IL-6 supported thrombopoiesis in concert with other cytokines. On the contrary, increased IFN-gamma, IL-2, IL-3, IL-4, and IL-10 mRNA expression may play an immunosuppressive role in vivo.

The role of cytokines in the pathogenesis of Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is characterised by an accumulation of cells ('LCH cells') with the same phenotypic features as normal Langerhans cells found in skin and other organs. The pathogenesis of LCH is unknown but there is increasing evidence to implicate the involvement of lymphokines and proinflammatory cytokines in the tissue damage seen in this disorder. Apart from histiocytes, the lesions contain giant cells, macrophages, neutrophils, eosinophils, lymphocytes, plasma cells and occasional mast cells that are the hallmark of an inflammatory process. The role of cytokines in the recruitment of haemopoietic cells within inflammatory lesions has only recently been recognised. In this article, we review the possible role of cytokines in the pathogenesis of LCH, and provide an overview of the methods currently used to detect and quantitate them. An appreciation of the type, distribution and amount of different cytokines released within lesions can provide clues to the possible aetiology of LCH. Using immunoassays, in situ hybridisation and RT-PCR, increased amounts of IL-1, IL-3, IL-4, IL-8, GM-CSF, TNF alpha, TGF beta and LIF have been demonstrated in LCH lesions. Lymphocytes constitutively produce GM-CSF and IL-3 and, to a lesser degree, IL-1, IL-4 and LIF whilst histiocytes produce TNF alpha, IL-1 beta and GM-CSF.

Cytokines and acute phase proteins in rheumatoid arthritis

Cytokines are extracellular signalling glycoproteins that play an important pathological role in rheumatoid arthritis (RA) where they mediate acute inflammation, chronic inflammation and connective tissue destruction. In RA the macrophage-derived cytokines such as interleukin-1 (IL-1), interleukin-6 (IL-6), interleukin-8 (IL-8), tumour necrosis factor (TNF), colony stimulating factors (CSFs) and growth factors play a key role in amplifying and perpetuating inflammation. IL-1 and TNF activate cartilage and bone degrading enzymes, while IL-8 recruits inflammatory cells into the joint. IL-1 and TNF play an important role in the acute phase response in that they potently induce IL-6, itself the major mediator and regulator of hepatic synthesis of acute phase proteins (APPs). The acute phase response is signalled by the rapid elevation of APPs such as C-reactive protein (CRP) and serum amyloid A (SAA) in the blood, and these can be used as good surrogate markers of disease activity. In health, the activity of cytokines such as IL-1 or TNF is checked by inhibitory molecules such as receptor antagonist molecules or soluble receptor molecules. In disease, cytokine activity appears to be relatively unopposed, leading to the recent development of cytokine inhibitory molecules as potential anti-RA therapies. However, while cytokines are mediators of disease, they probably do not provide the initial stimulus for RA to develop, although polymorphisms in TNF, IL-1 and IL-1 receptor antagonist genes which have been recently found may represent important genetic modifying factors of disease severity in RA.

Autocrine and paracrine functions of cytokines in malignant lymphomas

Cytokines play important roles in the pathogenesis of lymphomas via an autocrine or a paracrine mechanism, or both. The characteristic clinical and histopathological features of malignant lymphomas may be due in part to elevated serum or tissue levels of cytokines. Determination of the effects of cytokines on the growth or differentiation of lymphoma cells is often complicated by the fact that more than one cytokine is responsible, and by the failure of anti-cytokine antibodies or antisense oligonucleotides to block the proliferation in vitro of lymphoma cells. However, it appears that IL-6 and/or IL-9 may play a prominent role in the tumor cell proliferation of Hodgkin's disease (HD), anaplastic large-cell lymphoma, or immunoblastic lymphoma. IL-6 may also be responsible for the plasmacytoid differentiation of lymphoma cells in polymorphic immunocytoma. The histopathological changes as a result of paracrine effects are most noticeable in HD. The malignant (H-RS) cells of HD have been shown to express IL-1, IL-5, IL-6, IL-9, TNF-alpha, M-CSF, TGF-beta, and CD80, and, less frequently, IL-4 and G-CSF. These cytokines may be responsible for the increased cellular reaction and fibrosis observed in tissues involved by HD and for the immunosuppression found in patients with HD. In contrast to H-RS cells, most non-HD lymphoma cells do not produce cytokines in excess amounts and reveal only a minimal cellular reaction. Exceptions include T-cell-rich B-cell lymphoma, angiocentric T-cell lymphoma, and angio-immunoblastic lymphadenopathy (AILD-like T-cell lymphoma. IL-4 is responsible for the T-cell reaction in T-cell-rich B-cell lymphoma, whereas IL-6 accounts for the plasma cell reaction in AILD-type T-cell lymphoma. The authors extensively review the role of cytokines in lymphomas because this may lead to major advances in the understanding of the molecular processes involved in the histopathogenesis of lymphomas.

[Cytokines and solid tumors]

Various cytokines can be used in the treatment of solid tumours. They are factors of proliferation and/or differentiation of haematopoiesis or immunopoiesis, and they stimulate the effector cells of anti-tumoral response. The various steps in the preclinical and clinical development of a cytokine in the field of oncology are detailed, taking IL-2 as an example. The results of the clinical trials reported (essentially with INF and IL-2) are presented and discussed.

What's new in the role of cytokines on osteoblast proliferation and differentiation?

This review assesses recent data concerning the role of cytokines produced by a variety of cells in bone on osteoblast function. The following themes are presumed: (1) osteoblasts are mesenchymal cells which act as either the major cellular agents of bone formation or as modulators of bone resorption by osteoclasts. The regulation of osteoblast proliferation and differentiation may involve a negative feedback process resulting in phenotype suppression; (2) cytokines including platelet-derived growth factors (PDGF), parathyroid hormone-related proteins (PTHrP), bone morphogenic proteins (BMP), transforming growth factor beta (TGF beta), fibroblast growth factors (FGF), insulin-like growth factors (IGF), epidermal growth factors (EGF), interleukin-1 and 6, tumour necrosis factors (TNF), interferon and haematopoietic growth factors have effects on osteoblast differentiation and proliferation but their effectiveness may not be identical in vitro and in vivo; (3) finally, therapeutic strategies for cytokine use in clinical practice are considered.

Cytokines: clinical potentials for the allergic patient

Classic allergic responses occur as a result of mast cell-bound IgE being cross linked by allergen, causing degranulation and activation with release of multiple biologically active mediators. Such mediators may have a direct effects on target tissues and/or promote the inflammatory milieu typical of late-phase responses. The production of IgE is a normal T-cell dependent antibody response. It is the specificity for allergens that is aberrant, resulting in a hypersensitivity state. Recent work has demonstrated that small molecular weight substances called cytokines are responsible for many immunological activities such as IgE production, mast cell and eosinophil maturation, and proinflammatory mediators that directly contribute to the pathology of late-phase allergic responses. Differences are being sought in the relative production of various cytokines that can be correlated with disease activity. This should find clinical use in diagnosis, prognosis, and/or monitoring of specific immunotherapy. Additionally, therapeutic agents are being sought that have various agonist/antagonist properties to correct aberrant cytokine production. Such agents likely will have a central role in future therapy for allergic diseases.