Human bone marrow non-B, non-T cells produce interleukin 4 in response to cross-linkage of Fc epsilon and Fc gamma receptors

Eosinophils, Basophils, and Neutrophils in Bullous Pemphigoid

Bullous pemphigoid (BP) is an autoimmune blistering skin disease, of which the incidence has increased in recent years. BP is characterized by circulating IgG and IgE autoantibodies against the hemidesmosomal proteins BP180 and BP230. Although autoantibodies trigger inflammatory cascades that lead to blister formation, effector cells and cell-mediated autoimmunity must also be considered as important factors in the pathogenesis of BP. The aim of this review is to outline the current knowledge on the role of eosinophils, basophils, and neutrophils in BP.

Basophils and their effector molecules in allergic disorders

Basophils are the rarest granulocytes which represent <1% of peripheral blood leukocytes. Basophils bear several phenotypic similarities to tissue-resident mast cells and therefore had been erroneously considered as blood-circulating mast cells. However, recent researches have revealed that basophils play nonredundant roles in allergic inflammation, protective immunity against parasitic infections and regulation of innate and acquired immunity. Basophils are recruited to inflamed tissues and activated in an IgE-dependent or IgE-independent manner to release a variety of effector molecules. Such molecules, including IL-4, act on various types of cells and play versatile roles, including the induction and termination of allergic inflammation and the regulation of immune responses. Recent development of novel therapeutic agents has enabled us to gain further insights into basophil biology in human disorders. In this review, we highlight the recent advances in the field of basophil biology with a particular focus on the role of basophils in allergic inflammation. Further studies on basophils and their effector molecules will help us identify novel therapeutic targets for treating allergic disorders.

Basophils, a neglected minority in the immune system, have come into the limelight at last

Basophils, the rarest granulocytes, were identified by Paul Ehrlich more than 140 years ago, much earlier than the discovery of T and B cells. Unfortunately, basophils were often mixed up with tissue-resident mast cells because of some phenotypic similarities between them and considered erroneously as minor relatives or blood-circulating precursors of mast cells. Moreover, basophil research was hindered by the rarity of basophils and the paucity of useful analytical tools, and therefore basophils had often been neglected in immunological studies. A series of studies using newly developed tools, including basophil-depleting antibodies and genetically engineered mice deficient only in basophils, have clearly defined previously unrecognized roles of basophils, that are distinct from those played by tissue-resident mast cells. In this mini-review, we highlight recent advances in our understanding of basophil functions, particularly focusing on their roles in the regulation of innate and acquired immunity, allergic reactions, autoimmunity and protective immunity against parasitic infections, mainly based on animal studies. Further studies on human basophils would facilitate the development of new strategies for the treatment of basophil-associated disorders.

Clinical Outcomes and Immune Metrics in Intratumoral Basophil-Enriched Gastric Cancer Patients

BACKGROUND

Accumulation of basophils has been reported in several malignancies. In gastric cancer, the relation between tumor-infiltrating basophils and patient overall survival and chemotherapeutic responsiveness still remains obscure.

OBJECTIVE

We aimed to investigate the postoperative prognostic and predictive significance of basophils to survival outcomes and chemotherapeutic responsiveness in resectable gastric cancer.

METHODS

The study enrolled two independent patient data sets with 448 gastric cancer patients overall. Basophils were evaluated with the use of immunohistochemistry (IHC) staining, and the correlation with clinicopathological characteristics, survival outcomes, and responsiveness to fluorouracil-based adjuvant chemotherapy (ACT) were investigated. Additionally, IHC was applied to characterize immune contexture in gastric cancer.

RESULTS

In either the discovery or validation data sets, accumulated basophils indicated poorer prognosis, and tumor-infiltrating basophils were identified as an independent adverse prognostic factor by multivariate analysis. Furthermore, tumor-infiltrating basophils determined significantly inferior therapeutic responsiveness to fluorouracil-based ACT in patients with stage III tumors. In addition, the abundance of basophils was correlated with an immunoevasive contexture characterized by M2-polarized macrophage infiltration. Moreover, our findings indicated elevated interleukin-4 expression but decreased interferon-γ expression in the high-basophils subgroup.

CONCLUSIONS

Tumor-infiltrating basophils in gastric cancer were identified as an independent adverse prognosticator, and also predicted inferior chemotherapeutic responsiveness, which identified those patients in need of much more individualized postoperative adjuvant therapy and more stringent follow-up. Furthermore, the infiltration of basophils was associated with immunoevasive tumor microenvironment, which might be a potential immunotherapeutic target for gastric cancer.

Recent advances in understanding basophil-mediated Th2 immune responses

Basophils, the least common granulocytes, represent only ~0.5% of peripheral blood leukocytes. Because of the small number and some similarity with mast cells, the functional significance of basophils remained questionable for a long time. Recent studies using newly-developed analytical tools have revealed crucial and non-redundant roles for basophils in various immune responses, particularly Th2 immunity including allergy and protective immunity against parasitic infections. In this review, we discuss the mechanisms how basophils mediate Th2 immune responses and the nature of basophil-derived factors involved in them. Activated basophils release serine proteases, mouse mast cell protease 8 (mMCP-8), and mMCP-11, that are preferentially expressed by basophils rather than mast cells in spite of their names. These proteases elicit microvascular hyperpermeability and leukocyte infiltration in affected tissues, leading to inflammation. Basophil-derived IL-4 also contributes to eosinophil infiltration while it acts on tissue-infiltrating inflammatory monocytes to promote their differentiation into M2 macrophages that in turn dampen inflammation. Although basophils produce little or no MHC class II (MHC-II) proteins, they can acquire peptide-MHC-II complexes from dendritic cells via trogocytosis and present them together with IL-4 to naive CD4 T cells, leading to Th2 cell differentiation. Thus, basophils contribute to Th2 immunity at various levels.

Basophil-derived IL-4 plays versatile roles in immunity

Recent studies demonstrated that basophils play crucial and non-redundant roles in the immune system, in spite of the fact that they are the rarest granulocytes and represent less than 1 % of peripheral blood leukocytes. In response to various stimuli, basophils release effector molecules stored in their cytoplasmic granules, including chemical mediators and proteases, and also secrete cytokines and chemokines. In this review, we will focus on the physiological and pathological roles of basophil-derived IL-4. Basophils can readily produce large quantities of IL-4 and are therefore the important source of IL-4. Basophil-derived IL-4 has been shown to regulate other immune cells, including T cells, B cells, group 2 innate lymphoid cells, monocytes, and macrophages. It also acts on non-hematopoietic cells such as fibroblasts and endothelial cells. Those cells stimulated with basophil-derived IL-4 contribute to the positive or negative regulation of a variety of immune responses in health and disease, including protection against parasitic and bacterial infections, allergy, and autoimmune diseases. Thus, basophil-derived IL-4 plays versatile roles in immunity.

The skin is an important bulwark of acquired immunity against intestinal helminths

IL-4–producing basophils promote the trapping of N. brasiliensis in the skin during secondary infection, a process critical for limiting the spread of infection to the lungs.

Once animals have experienced a helminthic infection, they often show stronger protective immunity against subsequent infections. Although helminthic infections are well known to elicit Th2-type immune responses, it remains ill-defined where and how acquired protection is executed. Here we show that skin-invading larvae of the intestinal helminth Nippostrongylus brasiliensis are surrounded by skin-infiltrating cells and are prevented from migrating out of infected skin during the second but not the first infection. B cell– or IgE receptor FcεRI–deficient mice showed impaired larval trapping in the skin. Selective ablation of basophils, but not mast cells, abolished the larval trapping, leading to increased worm burden in the lung and hence severe lung injury. Skin-infiltrating basophils produced IL-4 that in turn promoted the generation of M2-type macrophages, leading to the larval trapping in the skin through arginase-1 production. Basophils had no apparent contribution to worm expulsion from the intestine. This study thus reveals a novel mode of acquired antihelminth immunity, in which IgE-armed basophils mediate skin trapping of larvae, thereby limiting lung injury caused by larval migration.

Inflammatory monocytes recruited to allergic skin acquire an anti-inflammatory M2 phenotype via basophil-derived interleukin-4

Monocytes and macrophages are important effectors and regulators of inflammation, and both can be divided into distinct subsets based on their phenotypes. The developmental and functional relationship between individual subsets of monocytes and those of macrophages has not been fully elucidated, although Ly6C(+)CCR2(+) inflammatory and Ly6C(-)CCR2(-) resident monocytes are generally thought to differentiate into M1 (classically activated) and M2 (alternatively activated) macrophages, respectively. Here we show that inflammatory monocytes recruited to allergic skin acquired an M2-like phenotype in response to basophil-derived interleukin-4 (IL-4) and exerted an anti-inflammatory function. CCR2-deficient mice unexpectedly displayed an exacerbation rather than alleviation of allergic inflammation, in spite of impaired recruitment of inflammatory monocytes to skin lesions. Adoptive transfer of inflammatory monocytes from wild-type but not IL-4 receptor-deficient mice dampened the exacerbated inflammation in CCR2-deficient mice. Thus, inflammatory monocytes can be converted from being proinflammatory to anti-inflammatory under the influence of basophils in allergic reactions.

Recent developments in basophil research: do basophils initiate and perpetuate type 2 T-helper cell responses?

Basophils account for only 0.1-1% of all peripheral blood leukocytes. They were considered to be a redundant cell type for a long time. However, several findings show a non-redundant role for basophils in type 2 T-helper cell (Th2) immune responses in helminth infections, allergy and autoimmunity. Both immunoglobulin-E-dependent and -independent pathways have been described to contribute to basophil activation. In addition, several recent studies reported that basophils can function as antigen-presenting cells and are important in the initiation of Th2 immune responses. However, there are also conflicting studies that do not corroborate the importance of basophils in Th2 immune responses. This review discusses the role of basophils in Th2 immune responses in view of these recent findings.

Generation and characterization of mouse basophils from bone marrow and purification of basophils from spleen

Basophils are rare circulating granulocytes that originate from progenitor cells in the bone marrow and have been considered important effector cells in IgE-mediated allergic inflammation. Basophils constitute <1% of blood leukocytes and are usually absent or present only in small numbers in tissues. They may, however, be recruited to inflammatory sites when an antigen is present and contribute immediately to hypersensitivity reactions. Basophils can therefore serve as primary effector cells in allergic disorders. Despite a large pool of experimental evidence that has led to the discovery of these functional attributes of basophils, many questions regarding their contribution to these immune responses remain unanswered. This is due, in part, to the lack of methods for generation and purification of basophils and the lack of animal models appropriate for their functional analysis. Recent studies, however, have revealed a role for basophils as antigen-presenting cells that preferentially induce Th2 cells in response to complexes of antigen plus antigen-specific IgE, to protease allergens, or to helminth parasites in vitro and in vivo through the production of "early IL-4" and the presentation to CD4(+) T cells of complexes of peptide plus MHC class II molecules. These findings have uncovered previously unknown functional characteristics of basophils. Knowledge of these and other functional properties of basophils may translate into the design of novel therapeutic strategies for Th2-IgE-mediated diseases, such as bronchial asthma. In this unit, protocols that will enable the study of mouse basophils are described.

Newly appreciated roles for basophils in allergy and protective immunity

Basophils are evolutionarily conserved in many animal species, in spite of the fact that they account for <1% of peripheral blood leukocyte. This suggests that basophils have an indispensable and nonredundant role in vivo, even though they show some phenotypic similarity with tissue-resident mast cells. However, their functional significance remained uncertain long after Paul Ehrlich discovered them as blood-circulating cells with basophilic granules more than 130 years ago. The study of basophils has been far behind that of mast cells, owing to the rarity of basophils and the paucity of tools for their detection and functional analysis. Recent development of novel analytical tools, including basophil-depleting antibodies and genetically engineered mice deficient only in basophils, has greatly advanced basophil research and illuminated previously unrecognized roles of basophils. We now appreciate that basophils and mast cells play distinct roles in immune responses. Basophils have crucial roles in the development of acute and chronic allergic responses, the protective immunity against ecto- and endoparasites, and the regulation of acquired immunity, including the augmentation of humoral memory responses and the initiation of Th2 responses. Thus, basophils are no longer the neglected minority and are key players in the immune system.

Type 2 innate immune responses and the natural helper cell

The T helper type 2 (Th2) immune response, characterized by the production of interleukin-4 (IL-4), IL-5 and IL-13, is a critical immune response against helminths invading cutaneous or mucosal sites. It also plays a critical role in the pathophysiology of allergic diseases such as asthma and allergic diarrhoea. The Th2 cytokines are induced soon after helminth infection, even before a pathogen-specific adaptive immune response is established. Recent studies have shed light on such innate Th2 cytokine production by formerly uncharacterized innate immune cells such as natural helper cells capable of producing Th2 cytokines in response to IL-25 and IL-33 independently of adaptive immune responses. These cells produce large amounts of Th2 cytokines, most notably IL-5 and IL-13, leading to eosinophilia and goblet cell hyperplasia. We discuss here the mechanisms of innate production of Th2 cytokines in host immune responses against helminth infection as well as allergic immune responses and the similarities and differences between recently identified Th2-cytokine producing cells.

Basophils support the survival of plasma cells in mice

We have previously shown that basophils support humoral memory immune responses by increasing B cell proliferation and Ig production as well as inducing a Th2 and B helper phenotype in T cells. Based on the high frequency of basophils in spleen and bone marrow, in this study we investigated whether basophils also support plasma cell survival and Ig production. In the absence of basophils, plasma cells of naive or immunized mice rapidly undergo apoptosis in vitro and produce only low amounts of Igs. In contrast, in the presence of basophils and even more in the presence of activated basophils, the survival of plasma cells is markedly increased and continuous production of Igs enabled. This effect is partially dependent on IL-4 and IL-6 released from basophils. Similar results were obtained when total bone marrow cells or bone marrow cells depleted of basophils were cultured in the presence or absence of substances activating basophils. When basophils were depleted in vivo 6 mo after immunization with an Ag, specific Ig production in subsequent bone marrow cultures was significantly reduced. In addition, depletion of basophils for 18 d in naive mice significantly reduced the number of plasma cells in the spleen. These data indicate that basophils are important for survival of plasma cells in vitro and in vivo.

Natural helper cells: a new player in the innate immune response against helminth infection

The Th2-type immune response, characterized by the production of IL-4, IL-5, and IL-13, is a critical immune response against helminths invading cutaneous or mucosal sites. Th2 cytokines are induced soon after helminth infection, even before a pathogen-specific adaptive immune response is established. Although the expulsion and clearance of helminths usually requires pathogen-specific Th2-mediated immunity, early induction of Th2 cytokines during the innate immune phase is important for host protection from helminth invasion. Recent studies have shed light on such Th2 cytokine production by formerly uncharacterized innate immune cells such as a newly identified natural helper cell. We discuss here the mechanisms of innate production of Th2 cytokines in host immune responses against helminth infection.

Helianthus tuberosus agglutinin directly induces neutrophil migration, which can be modulated/inhibited by resident mast cells

We investigated the effect of Helianthus tuberosus agglutinin (HTA) on neutrophil migration in vivo and in vitro. The role of resident cells in this effect was analyzed. Peritonitis was induced by injecting stimuli into rat (150–200 g) peritoneal cavities, and in vitro neutrophil chemotaxis was performed using a Boyden microchamber. HTA (80, 200, or 500 µg/mL per cavity) induced significant in vivo neutrophil migration (p < 0.05); in vitro assays showed that this lectin also induced neutrophil chemotaxis, an effect inhibited by the incubation of lectin associated with α-D(+)-mannose, its specific binding sugar. Depletion of the resident-cell population by peritoneal lavage did not alter HTA-induced neutrophil migration (200 µg/mL per cavity). The opposite strategy, increasing peritoneal macrophages by intraperitoneally injecting rats with thioglycollate, did not enhance the neutrophil migration produced by HTA (200 µg/mL per cavity). In addition, injection of supernatant from HTA-stimulated macrophage culture (300 µg/mL) into rat peritoneal cavities did not induce neutrophil migration. However, reduction of the peritoneal mast-cell population potentiated the neutrophil migration (p < 0.05) induced by HTA (200 µg/mL per cavity). Lectin from H. tuberosus has a direct neutrophil chemotatic effect that is modulated by mast cells.Key words: lectins, inflammation, Helianthus tuberosus, neutrophil migration.

Environmental factors favoring the allergen-specific Th2 response in allergic subjects

Allergen-reactive type 2 helper T cells (Th2) play a triggering role in the activation and/or recruitment of IgE antibody-producing B cells, mast cells, and eosinophils, i.e., the cellular triad involved in the allergic inflammation. Interleukin (IL)-4 production at the time of antigen presentation to the Th cell is critical for the development of Th2 cells. Other cytokines, such as IL-1 and IL-10, and hormones, such as calcitriol and progesterone, also play a positive role. In contrast, cytokines such as interferon (IFN)-alpha, IFN-gamma, IL-12, and transforming growth factor (TGF)-beta, and relaxin play a negative regulatory role on the development of Th2 cells. However, the mechanisms underlying the preferential activation by environmental allergens of Th2 cells in atopic individuals still remain obscure. Some gene products selectively expressed in Th2 cells or selectively controlling the expression of IL-4 have recently been described. Moreover, cytokines and other gene products that dampen the production of IL-4, as well as the development and/or the function of Th2 cells, have been identified. These findings allow us to suggest that the upregulation of genes controlling IL-4 expression and/or abnormalities of regulatory mechanisms of Th2 development and/or function may be responsible for Th2 responses against common environmental allergens in atopic subjects.

Interaction of Bordetella pertussis with mast cells, modulation of cytokine secretion by pertussis toxin

Together with macrophages and dendritic cells, mast cells have recently been shown to interact with certain pathogenic bacteria and present microbial antigens to the immune system. We show here that Bordetella pertussis can adhere to and be phagocytosed by mast cells. In addition, mast cells are able to process and present B. pertussis antigens to T lymphocytes. Furthermore, exposure of mast cells to B. pertussis induced the release of the proinflammatory cytokines tumour necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6). The release of IL-6 was strongly reduced by pertussis toxin expressed by B. pertussis. The production of IL-10, but not that of IL-4, by mast cells was also inhibited by pertussis toxin. Depletion of mast cells in vivo resulted in significant reduction of early TNF-alpha production in bronchoalveolar lavage (BAL) fluids of B. pertussis-infected mice. These data suggest that mast cells may play a role in the induction of immune responses against B. pertussis through the release of cytokines, especially TNF-alpha.

Naive human T cells can be a source of IL-4 during primary immune responses

IL-4 plays a key role in driving the differentiation of CD4+ Th precursors into Th2 cells, both in mice and in humans. The source of IL-4 during primary immune responses is, however, still debated. When IL-4 consumption in in vitro T cell cultures was blocked with a MoAb to the IL-4 receptor alpha-chain (IL-4Ralpha), it became evident that freshly isolated naive (CD45RO-) CD4+ T cells from adults or cord blood produce IL-4 upon activation with anti-CD3 and CD80. IL-4 production by naive T cells is strictly IL-2-dependent. Endogenous IL-4 activity in naive CD4+ T cell cultures modulates the production of interferon-gamma (IFN-gamma) on the one hand and IL-5 and IL-13 on the other hand in opposite directions, and it is partly responsible for the low IFN-gamma production by cord blood T cells. Comparison of the ratio of IL-4/IFN-gamma in supernatants of T cell cultures reveals a skewing towards IL-4 production by cord blood T cells, while naive T cells from (non-atopic) adults predominantly produce IFN-gamma. We conclude that CD4+ naive T cells can produce IL-4 without the need for Th2 differentiation, and therefore that they can be the initial source of IL-4 required at the time of priming for T cell differentiation into Th2 cells.

Glucocorticoid Suppresses Autocrine Survival of Mast Cells by Inhibiting IL-4 Production and ICAM-1 Expression

When mast cells are activated through their high affinity IgE receptors (FcεRI), release of chemical mediators is followed by secretion of multiple cytokines. In this work, we report that IL-3-dependent mast cell line MC9 undergoes apoptosis when IL-3 is withdrawn. However, cross-linking of FcεRI prevents apoptosis of MC9 by an autocrine mechanism, producing IL-3, IL-4, and GM-CSF. Although stimulated MC9 synthesizes mRNAs and proteins of these cytokines, secretion of endogenous IL-3 and GM-CSF is not enough for cell survival, whereas IL-4 itself does not have survival effect on MC9, but it induces cell aggregation by expressing LFA-1 and makes it reactive to endogenous growth factors. Addition of dexamethazone (DXM) to MC9 results in significant down-regulation of IL-4 mRNA in activated MC9. However, mRNA levels of IL-3 and GM-CSF are not changed by DXM. DXM also directly down-regulates the expression of ICAM-1 that is the high affinity ligand of LFA-1, by which the self-aggregation of MC9 is inhibited. Thus, glucocorticoids suppress autocrine survival of mast cells by inhibiting IL-4 production and ICAM-1 expression.

Expansion of IL-3-responsive IL-4-producing non-B non-T cells correlates with anemia and IL-3 production in mice infected with blood-stage Plasmodium chabaudi malaria

A prominent switch of CD4+ T cells from Th1 to Th2 type response occurs in mice infected with the non-lethal malaria parasite Plasmodium chabaudi chabaudi AS around the time of peak parasitemia. This is reflected by a decrease in IFN-gamma- and an increase in IL-4-producing cells. The peak occurs approximately 9-10 days after infection and is accompanied by anemia. The mechanism behind the switch in Th cell response is poorly understood. We here report on the production of IL-4 from a non-T cell source during P. chabaudi infection in BALB/c mice. Flow cytometric analysis of spleen and peripheral blood leukocytes (PBL) showed a dramatic increase in the percentage of non-B non-T (NBNT) cells 9-23 days after P. chabaudi infection with peak values by day 15 (approximately 30 % of splenocytes and approximately 55 % of PBL being NBNT cells). The expansion of NBNT cells correlated closely with the appearance of a cell type secreting IL-4 and IL-6 following stimulation with IL-3 and/or cross-linking of FcgammaR. Compared to cells from uninfected animals, NBNT cells from P. chabaudi-infected mice were shown to be hyper-responsive to IL-3. The levels of the hematopoietic cytokine IL-3 were elevated in supernatants from unstimulated spleen cell cultures as well as in serum at the same time points at which NBNT cell-derived IL-4 and IL-6 were detected from spleen cultures and PBL. Thus, IL-3-responsive IL-4-producing NBNT cells may provide cytokines supporting the switch from Th1 to a Th2 response which is important for the final clearance of the parasite in P. chabaudi malaria.

Analysis of cytokine profile in human colonic mucosal Fc epsilonRI-positive cells by single cell PCR: inhibition of IL-3 expression in steroid-treated IBD patients

Mast cells can serve as a possible important source of cytokine production in inflamed tissue which can be regulated by stimuli different from those activating other immune system cells. To study the expression of specific genes in mast cells derived from small human colonic mucosal endoscopic biopsies, we first modified a previously reported procedure to achieve a significantly enriched mast cell fraction. Then, by using single-cell RT-PCR analysis the expression of the IgE Fc receptor (Fc epsilonRI) and c-kit mRNA was determined. It was observed that the Fc epsilonRI-positive cells also expressed c-kit. This observation provided further evidence that Fc epsilonRI-positive cells are indeed mast cells. Analysis of biopsies from 12 patients (four control and eight patients with inflammatory bowel disease (IBD)) was carried out, revealing that all of the Fc epsilonRI-positive cells expressed IL-3, while the expression of IL-4 was detected only in some of these positive cells. TNF alpha was not detected in these cells. Therefore, it would seem that most intestinal mast cells produce IL-3. Since it has been reported that IL-3 synthesis was down-regulated in steroid-treated cells, the expression pattern of IL-3 in intestinal mast cells derived from steroid-treated IBD patients was then determined. IL-3 mRNA was detected in only two out of 24 Fc epsilonRI-positive cells derived from these steroid-treated patients. These results lend strong support to the idea that the down-regulation of IL-3 in mast cells derived from steroid-treated IBD patients occurs in vivo and could be an important mechanism for immunomodulation in IBD.

Postburn constitutional changes in T-cell reactivity occur in CD8+ rather than in CD4+ cells

BACKGROUND

Impairment of T-helper cell function and polarization toward T-helper 2-type cytokine synthesis have been postulated to represent a major cause for posttraumatic immunodeficiency. With a recently developed technology for intracellular cytokine measurement, a new diagnostic tool has become available to discriminate, within hours, a shift of functionality in T-cell subsets via their individual cytokine profiles. Thus, it was the objective of this study to obtain further insight into the constitutional, phenotype-dependent changes of T-helper 1 (TH1) and T-helper 2 (TH2), respectively, signature lymphokine synthesis under traumatic stress.

METHODS

Peripheral blood mononuclear cells from 10 patients with major burn injury on day 1, 3, 5, and 7 after injury and from 15 healthy individuals were separated and incubated (5 hours) for cytokine production induced with the accessory cell-independent stimulus of ionomycin and phorbol 12-myristate 13-acetate. After fixation and permeabilization, cell samples were immunofluorescently stained for cell surface antigens (CD4 and CD8) as well as for intracellular interferon (IFN)-gamma and interleukin (IL)-4 synthesis. Results were correlated with corresponding enzyme-linked immunosorbent assay measurements of the culture supernatants.

RESULTS

Phenotypic assessment of peripheral blood mononuclear cells showed a continuously diminished percentage of CD8+ cells during the immediate posttraumatic course compared with controls, whereas the number of CD4+ cells was found to be within the range of the control group. The production of IL-4, the index cytokine of TH2 cells, was excessively up-regulated (from 437.8 +/- 137.0 pg/mL on day 1 to 1,333.6 +/- 532.7 pg/mL on day 7 burns vs. 82.3 +/- 15.8 pg/mL controls), whereas the release of IFN-gamma, the index cytokine of TH1 cells, however, was only slightly increased. The predominant cellular source of IL-4 after burn trauma has been shown to be the CD8+ cell with a nearly fivefold elevated production on day 5 (7.2 +/- 2.6%) versus 1.5 +/- 0.4% in controls. Although CD8+ cells are also capable of enhancing their IFN-gamma synthesis under stress by about 60%, the CD4+ IFN-gamma release remained largely unchanged.

CONCLUSION

Our data corroborate that major burn trauma will induce a significant shift of cytokine response toward the TH2 direction and demonstrate that the CD8+ rather than the CD4+ phenotype is the crucial cell for the polarization toward a TH2-driven immune response.

Abnormal production of T helper 2 cytokines interleukin-4 and interleukin-5 by T cells from newborns with atopic parents

T cell clones were generated from umbelical cord blood lymphocytes (UCBL) of nine newborns with atopic or nonatopic parents and their cytokine secretion profile was assessed. Both phytohemagglutinin-induced and Dermatophagoides pteronyssinus-specific T cell clones from newborns with atopic parents exhibited an enhanced ability to produce the Th2 cytokines interleukin (IL)-4 and IL-5, compared to T cell clones from newborns with nonatopic parents. In contrast, the ability to produce interferon-gamma by UCBL from the two groups of newborns was not different. Of the five children who could be followed up to 3 years after birth, four with atopic parents developed clinical and/or biological atopic manifestations, whereas one without atopic parents did not. Thus, the pronounced production of IL-4 and IL-5 by UCBL not only appears to be related to the atopic status of parents, but also associates with the subsequent development of atopy in childhood.

Development of Th 1- or Th 2-dominated immune responses: what about the polarizing signals?

Type 1 helper T cells and type 2 helper T cells represent two extremely polarized forms of the effector specific immune response, based on a distinctive profile of cytokine production. Type 1- and type 2 helper T cell-dominated immune responses play a different role in both protection and immunopathology. The differentiation of effector phenotypes depends on a complex matrix of interconnecting factors resulting from the evolutionary interplay between vertebrates and microorganisms. These include the physical form of the antigen, as well as the density and affinity of the peptide ligand, the cytokines produced by "natural" immunity cells at the time of antigen presentation, costimulatory signals provided by antigen-presenting cells, and hormones released into the microenvironment. The elucidation of genetic and environmental factors that regulate type 1 or type 2 helper T cell development in response to different antigenic stimulation is the basis for new immunotherapeutic strategies in allergic and autoimmune disorders, as well as for the improvement of vaccines.

Contribution of interleukin-3 to antigen-induced Th2 cytokine production

Short-term stimulation of mouse spleen cells in vitro with interleukin (IL)-3 induces the secretion of the Th2 cytokines IL-4 and IL-6. Non-B/non-T cells were the target of this IL-3 effect. However, during long-term antigen-dependent culture, T cells are the major source of IL-4 and IL-6. The addition of IL-3 to such cultures also led to a significant increase in IL-4 and IL-6 production. This Th2 cytokine secretion was amplified by the addition of irradiated non-B/non-T cells at the initiation of culture, and was inhibited by anti-IL-4 antibodies. These findings suggest that IL-3 induces the rapid release of IL-4 and IL-6 by non-B/non-T cells, thereby creating an immune milieu conducive to the development of antigen-specific IL-4 and IL-6-secreting Th2 cells.

Interleukin-5 messenger RNA expression in peripheral blood CD4+ cells in asthma

BACKGROUND

IL-5 has been implicated in the pathogenesis of asthma through its regulatory role on eosinophil survival, proliferation, and effector function.

OBJECTIVE

The study was designed to investigate the relationships between IL-5 messenger RNA expression in circulating CD4+ cells and serum concentrations of eosinophil cationic protein (ECP), a marker of eosinophil activation, and disease activity in asthma.

METHODS

IL-5 gene expression was assessed semiquantitatively in ex vivo stimulated CD4+ cells by reverse transcription-polymerase chain reaction and serum ECP concentration measured from venous blood samples collected from patients with acute severe asthma before the commencement of systemic steroid therapy (day 1) and on day 7 and from patients with stable asthma and healthy volunteers.

RESULTS

IL-5 gene expression was significantly higher in patients with acute asthma before steroid treatment than in those with stable disease and healthy subjects (p < 0.0001). Similar results were obtained with serum ECP levels: levels in patients with acute asthma were highest (20.30 +/- 5.31 micrograms/L), followed by levels in patients with stable asthma (2.76 +/- 0.65 micrograms/L) and levels in normal control subjects (1.37 +/- 0.06 micrograms/L; p < 0.01 for all comparisons). Significant falls in both IL-5 expression and serum ECP level were seen on day 7 (p < 0.001) and coincided with a significant improvement in peak expiratory flow (p < 0.0001). Significant correlations were observed between IL-5 expression and ECP level (rho = 0.39, p < 0.01), IL-5 expression and peak expiratory flow (rho = -0.55, p < 0.0002), and peak expiratory flow and ECP level (rho = -0.32, p < 0.04).

CONCLUSION

Our data therefore support an important regulatory role of IL-5 on eosinophil function in human asthma in vivo.

T-cell-independent and T-cell-dependent IgE responses to the nematode Nippostrongylus brasiliensis: comparison of serum IgE and mast-cell-bound IgE

The IgE immune response was studied in female athymic, nude (Lewis rnu/rnu) and euthymic (Lewis +/+) rats infected with the nematode Nippostrongylus brasiliensis. During the course of the infection, serum IgE levels were followed using an enzyme-linked immunosorbent assay technique (ELISA), while the surface expression and occupancy of IgE receptors on peritoneal mast cells were quantified using flow cytometry after immunolabelling with anti-IgE. The results show that the up-regulation of IgE receptors, which takes place on the mast cells of both athymic and normal rats during the early phase of the immune response, is more pronounced and longer-lasting in normal rats than in athymic ones, thereby suggesting that T cells are necessary for a full response to the parasite infection. The increased IgE occupancy observed on the mast cells during the early phase of the parasite immune response was not reflected in the serum IgE levels, which remained low during the entire infection period in athymic rats. In euthymic rats, on the other hand, there was a pronounced increase in serum IgE, as well as an increase in IgE occupancy on the mast cells, all reaching a peak level after 2 weeks of infection. However, there was no significant correlation between the serum IgE concentration and IgE occupancy or the density of IgE receptors on the mast cells of the individual euthymic rats. This indicates that the quantification of IgE occupancy on the mast cells may be a better way of detecting low-level IgE responses than the measurement of serum IgE. These findings, which were obtained in female Lewis rats, when compared with our previous findings in male rats of the same strain, suggest that sex differences may exist in terms of the intensity and duration of the IgE immune response to the parasite infection.

Inhibition of GM-CSF production by recombinant human interleukin-4: negative regulator of hematopoiesis

Interleukin-4 (IL-4), also known as B-cell stimulatory factor-1 (BSF-1), was initially identified as a T-cell product that mediates anti-IgM-induced DNA synthesis in B-lymphocytes. Various aspects of this highly pleiotropic cytokine have been described, including those on hematopoietic progenitor cells. However, the role of IL-4 in the hematopoietic system has been given different interpretations. Normal human hematopoietic progenitor cells do not proliferate under control of the autocrine system and cytokines are needed for proliferation and differentiation. However, IL-4 in itself does not support proliferation of these cells and if this is the case, the effects of IL-4 on hematopoietic progenitor cells still need to be investigated from the point of view of synergism with other cytokines as well as the control of accessory cells in the production of cytokines. We describe here some properties of IL-4 in association with cytokine production, with special emphasis on granulocyte-macrophage colony-stimulating factor (GM-CSF) production.

Cytokine secretion by human mast cells

Mast cells have been traditionally viewed as effector cells of immediate-type hypersensitivity reactions. Besides this, mast cell activation and degranulation have been associated with various biologically and clinically important functions. Results of the past few years suggest that mast cells are involved in the development of late-phase reactions and influence other chronic inflammatory responses through the generation and secretion of various multipotential cytokines.

Biology of human TH1 and TH2 cells

Evidence is accumulating to suggest the existence of polarized human T-cell responses, reminiscent of TH1 and TH2 subsets described for mouse T cells. Human TH1 cells preferentially develop during infections by intracellular bacteria and trigger phagocyte-mediated host defense, whereas TH2 cells, which predominate during helminthic infestations and in response to common environmental allergens, are responsible for phagocyte-independent host response. Human TH1 and TH2 cells exhibit not only different functional properties but probably also distinct surface markers; TH2, but not TH1, clones express membrane CD30 and release the soluble form of CD30, a member of the TNF receptor superfamily. The cytokine profile of "natural immunity" evoked by different offending agents in the context of different host genetic backgrounds appears to be the most critical factor in determining the phenotype of the subsequent specific response. IL-12 and IFN-alpha and gamma produced by macrophages and NK cells favor the development of TH1 cells, whereas the early production of IL-4 by a still-unidentified cell type favors the development of TH2 cells. Clearly, polarized human TH1 and TH2 responses not only play different roles in protection, they can also promote different immunopathological reactions. Strong and persistent TH1 responses seen to be involved in organ-specific autoimmunity, contact dermatitis, and some chronic inflammatory disorders of unknown etiology. In contrast, polarized TH2 responses favor a reduced protection against the majority of infectious agents (including HIV) and, in genetically predisposed hosts, are responsible for triggering of allergic atopic disorders.

IgE receptor-positive non-B/non-T cells dominate the production of interleukin 4 and interleukin 6 in immunized mice

The phenotype and antigenic specificity of cells secreting interleukin (IL) 4, IL-6, and interferon gamma was studied in mice during primary and secondary immune responses. T lymphocytes were the major source of interferon gamma, whereas non-B/non-T cells were the dominant source of IL-4 and IL-6 in the spleens of immunized animals. Cytokine-secreting non-B/non-T cells expressed surface receptors for IgE and/or IgG types II/III. Exposing these cells to antigen-specific IgE or IgG in vivo (or in vitro) "armed" them to release IL-4 and IL-6 upon subsequent antigenic challenge. These findings suggest that non-B/non-T cells may represent the "natural immunity" analogue of CD4+ T helper type 2 cells and participate in a positive feedback loop involved in the perpetuation of T helper type 2 cell responses.

Immunolocalization of intracellular interleukin-4 in normal human peripheral blood basophils

The question as to whether other cell types apart from helper T lymphocytes are capable of producing interleukin-4 (IL-4) has gained much interest over the last years. Recent studies indicate that human basophils also produce IL-4, although direct proof is missing so far. In this study we demonstrate the presence of IL-4 in the cytoplasm of in vitro activated human peripheral blood basophils derived from normal donors. Cytokine-producing cells were revealed at the single-cell level by intracellular immunofluorescence staining using IL-4-specific monoclonal antibodies. Basophils showed a characteristic, apparently granular staining pattern easily discerned from the eccentric dot-shaped staining pattern in activated T cells used in control experiments. Cell counts following priming with IL-3 and stimulation with polyclonal sheep anti-IgE antibody or the anaphylatoxin C5a revealed a significant increase in IL-4-positive basophils to about 19% as compared with unprimed, unstimulated control cells (6%). The amount of IL-4 in the supernatant of these cell preparations paralleled these observations with an at least five- to sevenfold increase following stimulation as compared with control cells (< 5 ng/ml). Using confocal scanning laser microscopy, the intracellular presence of IL-4 was confirmed, and the cells were identified as being basophils on terms of their characteristic multilobed nucleus. This observation was supported by double labeling studies using antibodies to IL-4 and to the high-affinity IgE receptor (Fc epsilon R1). Interestingly, stimulation of cells led to a decrease in the number of Fc epsilon R1-positive cells. The above results show direct evidence that IL-4 is produced by activated human basophils.

IgE receptors, IgE content and secretory response of mast cells in athymic rats

Athymic, nude (Lewis rnu/rnu) and normal (Lewis +/+) rats were used to study the T-cell dependence of the regulation of IgE receptors and IgE content on mast cells in vivo. We estimated the number of IgE receptors and the IgE content on peritoneal mast cells using a cytofluorometric technique. The secretory capacity of the mast cells was measured in terms of histamine release as a function of anti-IgE concentration by incubation with antibodies in vitro. Two groups of rats, aged 6 and 13 weeks, were examined. The mast cells of the rats belonging to the older age group (both normal and athymic) had a higher total protein (equivalent to dry mass or size) and mediator content (heparin, histamine and 5-hydroxytryptamine) in accordance with previous findings. Mast cells of the athymic rats of both age groups contained similar levels of IgE receptors and IgE and did not differ in these respects from those of the normal rats. Of the IgE receptors available for binding, about 80% were occupied by IgE in mast cells of normal and of athymic rats in both age groups. The anti-IgE-induced histamine release of the mast cells was, however, significantly lower in athymic rats compared to the normal controls. A change in housing from barrier-maintained to conventional conditions for 2 weeks enhanced the IgE-receptor and IgE content, as well as the releasability of histamine of the mast cells of both athymic and normal rats. The basal level of IgE occupancy of the receptors on mast cells was therefore not impaired in the athymic rats, as might be inferred from previous findings of a T-cell dependence of the IgE immune response. The results further indicate that T-lymphocyte-derived cytokines appear not to be required for either the expression of IgE receptors or for their ability to acquire IgE on mast cells, but such factors seem to enhance the release of histamine following the cross-linkage of the IgE receptor on mast cells in normal conditions.