Molecular biology of interleukin 4 and interleukin 5 genes and biology of their products that stimulate B cells, T cells and hemopoietic cells

Cytokines and Ig switching: evolutionary divergence between mice and humans

Cytokines exert control over many aspects of immunoglobulin regulation, including isotype switching. But is the same mechanism used in subclass regulation in mice and humans? Robin Callard and Malcolm Turner think not, and here caution against the wholesale application of murine studies to humans.

Eosinophil cytotoxicity enhancing factor: purification, characterization and immunocytochemical localization on the monocyte surface

The monokine eosinophil cytotoxicity enhancing factor (ECEF) increases antibody-dependent cytotoxicity of eosinophils towards helminth larvae. A monokine biochemically indistinguishable from ECEF increases the release of leukotriene C4 and other arachidonic acid metabolites by eosinophils. We have developed monoclonal antibodies (mAb) to these monokines by immunizing mice with ECEF made by the U-937 histiocytic lymphoma cell line. mAb 81.10.C9 (IgG2b) and 9A6G (IgG1) inhibit the effect of the monokine on release of AA products. Both mAb bind ECEF, which appears after affinity chromatography purification as a major 13-14-kDa and a minor 62-kDa component (13-14 kDa and 52 kDa after reduction) in silver-stained gels. An additional component of 30 kDa is detectable after radioiodination of the immunopurified material. The specificity of both mAb was studied in several ways. In immunoprecipitation, both recognize the 13-14-kDa and the 30-kDa components, while the 62-(52)-kDa protein is not significantly precipitated. Both mAb react in enzyme-linked immunosorbent assay with products secreted by peripheral blood mononuclear cells and monocytes, as well as with those secreted by phorbol 12-myristate 13-acetate and lipopolysaccharide-stimulated U-937 cells and with the immunopurified proteins. These were separated in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, electroeluted and assayed for ECEF activity. Activity was associated with the 13-14-kDa and the 30-kDa fractions, as seen by increased eosinophil antibody-dependent adherence to schistosomula and cytotoxicity. Granulocyte-monocyte-colony-stimulating factor and interleukin 1, but not tumor necrosis factor, could be detected in crude U-937 supernatants. However, active immunopurified ECEF has no activity in assays for granulocyte-monocyte-colony-stimulating factor, interleukin 1 or tumor necrosis factor. Immunocytochemical localization of ECEF employing the mAb shows strong surface staining of viable monocytes and U-937 cells, suggesting that ECEF is associated to the cell surface. These properties distinguish ECEF from other monokines previously reported to activate eosinophils.

Evolutionary aspects, structure, and expression of the rat interleukin 4 gene

The rat interleukin 4 (IL 4) gene has been isolated from a genomic lambda phage library by cross-hybridization to the mouse IL 4 cDNA. Like the mouse and human counterparts, it exists as a single copy gene in the genome and consists of four exons. The overall structure of the IL 4 locus seems highly conserved. This is indicated by the low degree of restriction fragment length polymorphism in a number of laboratory and wild mice and by the conservation of the intron size between human, rat, and mouse IL 4 genes. Furthermore, evolutionary conserved elements are the promoter region, the position of cysteine residues and sequence motifs in the 3' untranslated regions that are believed to be involved in destabilization of the mRNA. In contrast, the predicted amino acid sequence of the rat IL 4 gene shows low homology (57%) with the mouse homologue. The divergence between mouse and rat IL 4 genes is even more pronounced in the carboxy-terminal region (47% homology in the last 68 amino acids). The ratio between replacement and silent mutations in the IL 4 genes of different species suggests a complex pattern of selective forces acting on the IL 4 gene, which includes both selection against and for amino acid substitutions in individual positions. The functional identity with IL 4 has been confirmed by expression of the gene and the demonstration of the ability to induce MHC class II antigen expression on spleen cells.

A comparative study on the effects of rIL-4, rIL-2, rIFN-gamma, and rTNF-alpha on specific T-cell non-responsiveness to mycobacterial antigens in lepromatous leprosy patients in vitro

We have studied lepromatous leprosy (LL) as a human model disease for T-cell non-responsiveness to specific mycobacterial antigens and studied the effect of rIL-4, rIL-2, rIFN-gamma and rTNF-alpha thereon. T-cell non-responsiveness to Mycobacterium bovis bacillus Calmette-Guerin (BCG) or purified protein derivative of M. tuberculosis (PPD) antigens could be overcome in 5 out of 8 non-responder patients by rIL-2 and in 2 out of 8 by rIL-4. The ability of rIL-4 to overcome BCG/PPD non-responsiveness was strongly dose-dependent. When rIL-2 and rIL-4 were added simultaneously, they seemed to synergize in their effect. T-cell non-responsiveness to M. leprae could be overcome only in 2 out of 18 non-responders by rIL-2 but not by rIL-4 alone. The ability of rIL-2 to overcome T-cell non-responsiveness to M. leprae antigens became particularly marked when the recombinant 65-kDa heat shock antigen of M. leprae was used instead of whole bacilli. Exogenously added rIL-4, and to a lesser extent rIL-2, strongly enhanced existing T-cell responses to BCG or M. leprae in the majority (8 out of 11) of responders. These findings may have implications for the in vivo manipulation of the immune response by recombinant lymphokines and vaccines.

Production of granulopoiesis-stimulating and -inhibiting activities by T cells associated with malignant cells in lymphomas

The possible role of T lymphocytes in the formation of granulomatous reactions seen in certain malignant lymphoid tumours was investigated by measuring the granulopoietic colony-stimulating activity (CSA) and granulopoietic-inhibiting activity (IA) produced by stimulated T-lymphocytes isolated from peripheral blood, spleen and lymph nodes of patients and normal subjects. Lymph-node T-cells from patients with benign lymphoid hyperplasia, B-cell non-Hodgkin's lymphoma (B-NHL), and non-granulomatous Hodgkin's disease (HD) showed no CSA, but the cells produced IA of 40 +/- 23%, 40 +/- 24% and 50.5 +/- 22.5% respectively. The corresponding cells from patients with HD accompanied by granulomatous reactions produced CSA of 6.85 +/- 6.5 u/microliters and IA of 23.5 +/- 21%. The presence of a granulomatous reaction in malignant lymphoma was correlated with the stimulation of granulopoiesis in vitro by T lymphocytes associated with malignant cells. A correlation was demonstrated between neutrophilic and eosinophilic colonies obtained in vitro under the influence of CSA-producing T cells isolated from malignant lymphomas and the neutrophils and eosinophils present in the granuloma. These results showed that tumour-infiltrating T cells play a role in the presence of granulomatous reactions seen in lymphomas. Peripheral-blood T cells from healthy subjects, and from patients with B-NHL, or with HD unaccompanied by granulocytic reactions produced CSAs of, respectively, 5 +/- 0.5 u/microliter, 4.8 +/- 2.2 u/microliters and 5.3 +/- 0.4 u/microliters, and IAs of 45 +/- 18%. 50 +/- 5.5% and 50.5 +/- 7% respectively. The corresponding values for HD patients with granulocytic reactions were CSA. 17 +/- 15.5 u/microliters, and IA, 9.5 +/- 9%. No correlation was demonstrated between neutrophilic colonies obtained in vitro under the influence of HD blood T cells and neutrophils present in blood. Only one correlation was found: between the percentage of eosinophilic colonies and the number of blood eosinophils. HD blood T cells did not seem to explain completely granulocytic reactions seen in blood.

Interleukin 4 receptors on normal human B lymphocytes: characterization and regulation

Human interleukin 4 (IL 4) up-regulates the expression of CD23 on both resting and "in vivo" activated B cells but induces proliferation and/or differentiation only on "in vitro" activated B lymphocytes. Resting B cells express 360 high-affinity IL 4 receptors (R) per cell (Kd = 25-75 pM). Activation of resting B cells with anti-IgM antibody or Staphylococcus aureus Cowan I (SAC) results in a two-to-threefold increase of IL 4R number without alteration of IL 4R affinity for IL 4. Flow cytometric analysis of biotinylated IL 4 binding shows that IL 4R expression is up-regulated on virtually all anti-IgM-stimulated B cells, but only on a subpopulation of larger cells among SAC-activated B lymphocytes. Culturing cells for 40 h with optimal concentrations of IL 4 does not significantly affect IL 4R levels on resting and anti-IgM-preactivated B lymphocytes but triples IL 4R levels on SAC-preactivated B cells. Removal of IL 4 from cell cultures results in a two-to-fourfold increase of IL 4R levels 2 h later, suggesting an increase in IL 4R turnover. Resting and activated B cells degrade 125I-labeled IL 4 at 37 degrees C. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of IL 4 binding molecules on resting, "in vivo" activated and anti-IgM-activated B cells reveals the same three species of 130, 80-75, 70-65 kDa. Thus, IL 4 displays its different biological activities on resting and activated B cells through IL 4R of the same affinity, gross biochemical structure and ability to mediate IL 4 degradation.

Human interleukin 4 receptor confers biological responsiveness and defines a novel receptor superfamily

IL-4, a pleiotropic cytokine produced by T lymphocytes, plays an important role in immune responsiveness by regulating proliferation and differentiation of a variety of lymphoid and myeloid cells via binding to high affinity receptors. In this report we describe the isolation and functional expression of a human IL-4-R cDNA. When transfected into COS-7 cells, the cDNA encodes a 140-kD cell-surface protein. After transfection into a murine T cell line, the cDNA encodes a protein that binds human IL-4 with high affinity and can confer responsiveness to human IL-4. The predicted extracellular domain of the IL-4-R exhibits significant amino acid sequence homology with the beta subunit of the IL-2-R (p75), and the receptors for IL-6, erythropoietin, and prolactin. These receptors comprise a novel superfamily with extracellular domains characterized by four conserved cysteine residues and a double tryptophan-serine (WSXWS) motif located proximal to the transmembrane region.

Interaction of interleukin-5 with its receptors on murine leukemic BCL1 cells and its implication in biological activity

Interaction of interleukin (IL)-5 with its receptors on murine leukemic cell line, BCL1 cells was examined. 125I-labeled recombinant murine IL-5(rmIL-5) bound specifically to high-affinity receptors on BCL1 cells. rmIL-5, which was about 2500-fold more active than recombinant human IL-5(rhIL-5) in IgM-inducing activity on BCL1 cells, also showed about 5000-fold higher affinity to receptors. These results suggest that the bioactivity of IL-5 correlates with its receptor-binding activity. When disulfide bond formation was blocked, rmIL-5 dissociated into a monomer and lost its biological activity. This monomeric form of rmIL-5 also lost its ability to bind to cells, suggesting that dimer formation is essential for the biological activity of IL-5.

Expression cloning of a cDNA encoding the murine interleukin 4 receptor based on ligand binding

Interleukin 4 (IL-4) is a potent mediator of growth and differentiation for various lymphoid and myeloid cells. To isolate a cDNA encoding the murine IL-4 receptor, we have developed an expression cloning method that uses biotinylated ligand as a probe and that may be generally applicable to cloning of receptor genes. COS-7 cells transiently transfected with the cloned full-length cDNA bind murine IL-4 specifically with a Kd = 165 pM. Crosslinking of 125I-labeled IL-4 to COS-7 cells transfected with the cDNA reveals binding to proteins of 120-140 kDa. IL-4-responsive cells also express IL-4-binding proteins of 120-140 kDa but show additional bands at 60-70 kDa; the relationship of the smaller proteins to the larger ones is unclear. The nucleotide sequence indicates that the full-length cDNA encodes 810 amino acids including the signal sequence. While no consensus sequence for protein kinases is present in the cytoplasmic domain, a sequence comparison with the erythropoietin receptor, the IL-6 receptor, and the beta chain of the IL-2 receptor reveals a significant homology in the extracellular domain, indicating that the IL-4 receptor is a member of a cytokine receptor family.

A long-range restriction map of the interleukin-4 and interleukin-5 linkage group on chromosome 5

The genes for two of the hematopoietic growth factors, interleukin-4 and interleukin-5, are located on a small segment of chromosome 5 (q23-31), which is frequently deleted in myeloid disorders. Using pulsed-field gel electrophoresis, we demonstrate physical linkage of these two genes and present a long-range restriction map of the locus. The two genes are closely linked (maximum separation, 310 kb) and appear to be separated by an HTF island. We were unable to physically link these genes to two other closely related hematopoietic growth factor genes, interleukin-3 and granulocyte/macrophage colony-stimulating factor, which also map to this region of the genome. The clustering of these and other growth-related genes suggests that a higher order of genetic organization exists in this region of the chromosome.

Recombinant interleukin 4 suppresses the production of interferon gamma by human mononuclear cells

rIL-4 inhibits the production of IFN-gamma by PBMC stimulated with mitogens or allogeneic cells. The suppression is observed at the protein and at the mRNA level; it is dose and time dependent, and it is abolished by a neutralizing mAb to IL-4. It is suggested that the balance between the production of IL-4 and IFN-gamma may be significantly influenced by the chronological order of activation of their respective gene.

Purification and characterization of recombinant human interleukin 4. Biological activities, receptor binding and the generation of monoclonal antibodies

A synthetic gene coding for human interleukin 4 (IL-4) was cloned and expressed in Saccharomyces cerevisiae (baker's yeast) as a C-terminal fusion protein with the yeast prepro alpha-mating factor sequence, resulting in secretion of mature IL-4 into the culture medium (0.6-0.8 micrograms/ml). A protocol was developed for purification of this protein. Crude cell-free conditioned medium was passed over a concanavalin A-Sepharose affinity column; bound proteins were eluted and further purified by S-Sepharose Fast Flow cation exchange and C18 reverse-phase h.p.l.c. Highly purified IL-4 was obtained by this method (0.3-0.4 mg per litre of culture) with a recovery of 51%. Thermospray liquid chromatography-mass spectrometry showed the C-terminal N-glycosylation site to be largely unmodified, and also showed that the N-terminus of the purified recombinant IL-4 (rIL-4) was authentic. Thiol titration revealed no free cysteine residues, implying that there are three disulphide groups, the positions of which remain to be determined. We have characterized the biological activities of the purified rIL-4. This material is active in B-cell co-stimulator assays, T-cell proliferation assays and in the induction of cell-surface expression of CD23 (the low-affinity receptor for IgE) on tonsillar B-cells. Half-maximal biological activity of the rIL-4 was achieved at a concentration of 120 pM. We have radioiodinated rIL-4 without loss of biological activity and performed equilibrium binding studies on Raji cells, a human B-cell line. The 125I-rIL-4 bound specifically to a single class of binding studies on Raji cells, a human B-cell line. The 125I-rIL-4 bound specifically to a single class of binding site with high affinity (Kd = 100 pM) and revealed 1100 receptors per cell. Receptor-ligand cross-linking studies demonstrated a single cell-surface receptor with an apparent molecular mass of 124 kDa. Two monoclonal antibodies have been raised to the human rIL-4, one of which blocks both the biological activity of rIL-4 and binding to its receptor.

Identification of interleukin 4 receptor-associated proteins and expression of both high- and low-affinity binding on human lymphoid cells

Interleukin 4 (IL4) produced by activated T cells expresses its biological effects on T and B lymphocytes by binding to specific membrane receptors. Cross-linking of human recombinant 125I-IL4 to peripheral blood mononuclear cells identifies a trimolecular complex consisting of a 65/70-kDa doublet and a 110-kDa protein. Scatchard analysis reveals about 300 IL4 binding sites/cell on resting cells with an equilibrium binding constant (Kd) of approximately 100 pM. Stimulation by anti-CD3 antibodies causes an up-regulation of IL4 receptors by a factor of 2 to 3 without any change in binding affinity. In addition to this high-affinity binding site a second class of a previously unidentified, low-affinity receptor (Kd approximately 30 nM, approximately 9000 sites/cell) is expressed on resting lymphocytes. The number of low-affinity binding sites for IL 4 also increases twofold upon cell activation. Exogenous IL 4 enhances the expression of its receptor on resting lymphocytes and this effect is further increased by anti-CD3 activation. Binding of IL4 to its receptor is specific, being only inhibited by IL 4 and not by IL2. By contrast, the gibbon leukemia cell line MLA 144 expresses only high-affinity receptors for IL4. Cross-linking studies reveal a 45/50-kDa IL 4 receptor-associated doublet in addition to the three proteins identified in human peripheral blood mononuclear cells. The functional significance of the different proteins composing the receptor for IL4 is discussed.

Hyperresponsibility to exogeneous interleukin 4 in atopic dermatitis

Many humoral and cellular immunological abnormalities have been reported in atopic dermatitis (AD). Since interleukin 4 (IL-4) enhances IgE production and IgE-Fc receptor expression by B cells as well as [3H]-TdR incorporation by T cells, we hypothesized that IL-4 may play an important role in the regulation of the immune response in AD. We examined [3H]-TdR incorporation by peripheral blood lymphocytes from AD patients or from non-AD controls in the presence or absence of IL-4 or interleukin 2 (IL-2). We found that IL-4/IL-2 responsiveness was significantly higher in AD than controls, although the IgE levels did not seem to be correlated with IL-4/IL-2 responsiveness. It is possible that most humoral and cellular immunological abnormalities of AD may be due to this hyperresponsibility to IL-4.

T-cell activation signals and human T-cell leukemia virus type I-encoded p40x protein activate the mouse granulocyte-macrophage colony-stimulating factor gene through a common DNA element

Activation of T cells by an antigen, a mitogen, or a combination of a phorbol ester (12-O-tetradecanoylphorbol-13-acetate [TPA]) and a calcium ionophore (A23187) leads to induction of a set of lymphokine genes. Treatment of human T-cell leukemia line Jurkat by a mitogen or p40x, a transactivator protein encoded by human T-cell leukemia virus type I, activates many transfected lymphokine genes in a transient transfection assay. To study the mechanism of lymphokine gene induction, we examined the effects of mitogen stimulation and p40x on the gene for the mouse granulocyte-macrophage colony-stimulating factor (GM-CSF) in Jurkat cells. Deletion and mutation analyses showed that the 5'-flanking region of the gene for the GM-CSF is composed of two types of regulatory elements. One sequence, located at positions -95 to -73, determines response to stimulation by either TPA-A23187 or p40x. This region contains conserved lymphokine element 2, which appears in the gene for interleukin 3 (IL-3) and is followed by a GC-rich stretch. This GC-rich stretch alone specifies inducible response to p40x but not to TPA-A23187. Another sequence, located at positions -113 to -96 upstream of a TATA-like sequence, mediates inducible response to p40x but not to TPA-A23187. This sequence includes conserved lymphokine element 1, which appears in several lymphokine-cytokine genes, such as those for IL-3, G-CSF, and IL-2. We previously showed that the simian virus 40 early region promoter was also induced by a mitogen or p40x in Jurkat cells. Deletion analysis showed that the minimum region require for stimulation by both signals are identical. These results, which indicate that p40(x) stimulates transcription of the gene for the GM-CSF or the simian virus 40 early region promoter through the same DNA element or an overlapping DNA element required for induction by a mitogen, lend further support to the notion that p40(x) can exert its function by activating a component(s) of the T-cell signal transduction pathway which is activated by an antigen or a mitogen.

Interleukin 4 strongly augments or inhibits DNA synthesis and differentiation of B-type chronic lymphocytic leukemia cells depending on the co-stimulatory activation and progression signals

This study describes the opposing effects that interleukin (IL) 4 exerts on the B cell stimulatory factor (BSF-MP6) and IL 2-dependent proliferation and differentiation of cells of one selected B-type chronic lymphocytic leukemia cell clone (I83), which depend on the nature of the activation inducer. In I83 cells activated by a 1-h pulse of 12-O-tetradecanoylphorbol 13-acetate, the BSF-MP6-dependent DNA synthesis was strongly enhanced by 50-100 U/ml of recombinant IL 4. Recombinant IL 2 stimulation was necessary only when a suboptimal dose of BSF-MP6 was used. The differentiation was also markedly enhanced by IL 4 as measured by quantitation of IgM secretion both at the population (enzyme-linked immunosorbent assay analyses of the supernatant) and single-cell level (enzyme-linked immunospot technique), by morphological examination of the maturation stage and flow cytometric analysis of differentiation-associated surface antigens (CD11c, FMC7, PCA-1 and CD38). No Ig isotype switch was found. In contrast, DNA synthesis and differentiation of I83 cells, activated by Staphylococcus aureus Cowan strain I (SAC) and co-stimulated with BSF-MP6 plus IL 2, were strongly inhibited by IL 4, both when it was added simultaneously with SAC or after 2 days of SAC exposure. Analysis of the cell-cycle progression of SAC and BSF-MP6 plus IL 2 and IL 4-stimulated cells by acridine orange staining and fluorescence-activated cell sorter (FACS) analysis demonstrated an arrest of a minor cell population in G0 and a block of the transition of G1 cells to S phase. Neither the enhancing nor the inhibitory effect of IL 4 on the proliferation and differentiation of I83 cells was an indirect effect via IL 4-induced activation of contaminating T cells, monocytes or natural killer cells, as shown by experiments where these cell types were depleted by FACS sorting. Furthermore the expression of CD23 and CD25 was not inhibited by IL 4. The results thus demonstrate contrasting biological effects of IL 4 on clonal leukemic B cells depending on the nature of the activation and progression stimuli. This adds to the emerging picture of a very complex cytokine and cell-to-cell contact-mediated regulation of the activation and subsequent growth and/or differentiation of human B cells.

CD23: a multi-functional receptor/lymphokine?

With the demonstration of identity between CD23 and the low affinity IgE Fc receptor (Fc epsilon RII), two previously separate avenues of immunological research have converged into one. Particularly in its guise as 'Blast-2' antigen, evidence has been mounting to implicate CD23 as an important molecule in B-cell growth regulation. It might seem pertinent, however, to question a role for an apparently isotype-specific immunoglobulin (Ig) receptor in general B-cell processes. In this article, John Gordon and colleagues attempt to reconcile the two, currently diverse, schools of thought regarding the primary function of CD23 and to provide a structural model that accounts for the biological pleiotropy observed.

Enhanced production of interleukin-6 in mice with type II collagen-induced arthritis

We established an interleukin-6 (IL-6)-dependent cell line from murine plasmacytoma MOPC-104E cells. This cell line (designated PIL-6) was found to respond to murine and to human IL-6, but not to any other cytokines. We used this cell line to investigate the involvement of IL-6 production in type II collagen-induced arthritis in DBA/1 mice. Only marginal IL-6 activity was detected in sera from DBA/1 mice inoculated with Freund's complete adjuvant (FCA) alone, with an unrelated protein (bovine serum albumin) plus FCA, or with type II collagen plus Freund's incomplete adjuvant. However, enhanced IL-6 activity was observed in DBA/1 mice that had been injected with type II collagen plus FCA to induce arthritis. The elevated level of serum IL-6 activity was associated with high levels of IL-6 produced when lymph node cells from arthritic mice were stimulated in vitro with type II collagen. We also found that the L3T4+ T cell subset is responsible for the enhanced production of IL-6 in arthritic mice. The results are discussed in the context of potential roles of IL-6 in the induction and/or expression of chronic, progressive arthritis.

Human interleukin 4 down-regulates the surface expression of CD5 on normal and leukemic B cells

CD5 is a pan-T cell antigen which is expressed on a minor subset of normal B lymphocytes and on most chronic lymphocytic leukemia B cells (B-CLL). In this study, it is demonstrated that interleukin (IL) 4 down-regulates the surface expression of CD5 on tonsil B cells and B-CLL cells, but not on T cells. IL 4 inhibits both the spontaneous and the phorbol myristate acetate (PMA)-induced hyperexpression of CD5 on tonsil B cells. In contrast, IL 4 only suppresses the PMA-induced hyperexpression of CD5 on B-CLL, whereas the spontaneous CD5 expression is essentially unaffected. The IL 4 concentrations required to down-regulate CD5 are the same as those required to up-regulate CD23. The IL 4-mediated down-regulation of CD5 is an intrinsic property of this IL, since an anti-IL 4-neutralizing antiserum blocks this effect. Interferon (IFN)-gamma, which inhibits the IL 4 induced CD23 expression, does not block the IL 4-induced down-regulation of CD5. Recombinant IL 1 alpha, IL 2, IL 3, IL 5, IL 6, tumor necrosis factor (TNF)-alpha, IFN-gamma and granulocyte macrophage colony-stimulating factor neither inhibit nor stimulate CD5 expression on B cells, therefore suggesting that the capacity to down-regulate CD5 expression on B cells is specific to IL 4.

Ubiquitous and lymphocyte-specific factors are involved in the induction of the mouse interleukin 2 gene in T lymphocytes

The immediate upstream region of the mouse interleukin 2 (Il-2) gene harbors a strong transcriptional enhancer. This enhancer contains most, if not all of the sequence elements necessary for the T cell specific induction of the Il-2 gene by the phorbol ester TPA and the plant lectin Concanavalin A. DNase I footprinting studies with fractionated extracts obtained from induced and uninduced E14 T cells revealed numerous recognition sites for potential trans-acting factors. Five of these sites are also recognized by the TPA-activated HeLa cell factors AP-1 and AP-3. Other sites including two TATA-boxes, two purine-rich sequence motifs and two copies of the GGGPuTTTCAA motif are recognized by lymphocyte specific factors. The latter motif is highly conserved between several lymphokine genes and is therefore designated as a T cell element (TCE). In E14 T cells, pentamers of the distal TCEd confer an activity similar to that of the entire Il-2 enhancer, whereas in B and HeLa cells, the TCEd-pentamer is inactive as is the Il-2 enhancer. These data indicate the involvement of the TCEd and its recognition factor(s) in the cell type specific induction of the Il-2 gene during T cell activation.

Helper strategy in tumor immunology: expansion of helper lymphocytes and utilization of helper lymphokines for experimental and clinical immunotherapy

Two main kinds of immune strategy are possible against neoplasia. The first potentiates a selected effector arm. In vitro culture with exogenous interleukin-2 (IL-2) increases the activity of natural killer cells and leads to the expansion of T cytotoxic lymphocytes. Systemic reinfusion of both of these cells with high doses of IL-2 mediates the regression of a variety of murine and human tumors. In an alternative strategy, a few regulatory lymphocytes turn on immune reactivity by triggering a cascade of interconnected effector functions. The efficacy of this strategy rests on the repertoire of effector mechanisms moved to action. An effective immunoregulatory maneuver is the addition of helper determinants on the surface of tumor cells. Its power can be further increased by the pre-induction of helper T lymphocytes specific to the helper determinants. This approach can be achieved in mice by coupling muramyl dipeptides to tumor cells, along with eliciting T lymphocytes specifically reactive to Bacillus Calmette-Guerin. Noncytotoxic T helper lymphocytes produce factors which recruit nonspecific (macrophages) as well as specific (cytolytic T lymphocytes) anti-tumor attacking cells. In this way protection can be afforded against primary tumors and metastases, as well as leukemia cells. As the activity of helper lymphocytes rests mostly on lymphokine release, the use of molecularly defined lymphokines mimicking T-helper functions has also been attempted. In a few experimental models, the association of low doses of IL-2 with non-reactive lymphocytes from tumor-bearing mice promotes an effective anti-tumor reaction in the host. Moreover, the combination of distinct lymphokines can also build a molecularly defined helper system able to activate in sequence non-specific and specific anti-tumor reactions in vivo. Trials intended to evaluate the clinical impact of these helper approaches in the management of human tumors are being started or are already under way.

T-cell activation signals and human T-cell leukemia virus type I-encoded p40x protein activate the mouse granulocyte-macrophage colony-stimulating factor gene through a common DNA element

Activation of T cells by an antigen, a mitogen, or a combination of a phorbol ester (12-O-tetradecanoylphorbol-13-acetate [TPA]) and a calcium ionophore (A23187) leads to induction of a set of lymphokine genes. Treatment of human T-cell leukemia line Jurkat by a mitogen or p40x, a transactivator protein encoded by human T-cell leukemia virus type I, activates many transfected lymphokine genes in a transient transfection assay. To study the mechanism of lymphokine gene induction, we examined the effects of mitogen stimulation and p40x on the gene for the mouse granulocyte-macrophage colony-stimulating factor (GM-CSF) in Jurkat cells. Deletion and mutation analyses showed that the 5'-flanking region of the gene for the GM-CSF is composed of two types of regulatory elements. One sequence, located at positions -95 to -73, determines response to stimulation by either TPA-A23187 or p40x. This region contains conserved lymphokine element 2, which appears in the gene for interleukin 3 (IL-3) and is followed by a GC-rich stretch. This GC-rich stretch alone specifies inducible response to p40x but not to TPA-A23187. Another sequence, located at positions -113 to -96 upstream of a TATA-like sequence, mediates inducible response to p40x but not to TPA-A23187. This sequence includes conserved lymphokine element 1, which appears in several lymphokine-cytokine genes, such as those for IL-3, G-CSF, and IL-2. We previously showed that the simian virus 40 early region promoter was also induced by a mitogen or p40x in Jurkat cells. Deletion analysis showed that the minimum region require for stimulation by both signals are identical. These results, which indicate that p40(x) stimulates transcription of the gene for the GM-CSF or the simian virus 40 early region promoter through the same DNA element or an overlapping DNA element required for induction by a mitogen, lend further support to the notion that p40(x) can exert its function by activating a component(s) of the T-cell signal transduction pathway which is activated by an antigen or a mitogen.

Restricted production of interleukin 4 by activated human T cells

Interleukin 4 (IL-4) is secreted by activated T cells and pleiotropically modulates both B- and T-lymphocyte function. In murine helper (CD4+) T-cell clones IL-4 production appears to be regulated independently of interferon gamma and interleukin 2. To determine whether production of these lymphokines is also differentially regulated in uncloned human T cells, we studied lymphokine production by normal human peripheral T cells and T-cell subsets after in vitro polyclonal activation. After maximal induction of lymphokine expression, IL-4 mRNA was detectable in less than 5% of CD4+ and 1-2% of unfractionated T cells, whereas approximately 33% and 60% of CD4+ cells expressed detectable mRNA for interferon gamma and interleukin 2, respectively. This finding correlated with dramatically lower production of IL-4 mRNA and protein than of interferon gamma and interleukin 2 by peripheral blood and tonsillar T cells. The helper-inducer (CD4+ CD45R-) T-cell subset, which significantly enhances in vitro immunoglobulin production, accounted for the preponderance of IL-4 mRNA accumulation and protein production by CD4+ T cells; nevertheless, cells with detectable IL-4 mRNA constituted less than 10% of the CD4+ CD45R- subset. Limitation of IL-4 production to a comparatively small population of normal human T cells could selectively regulate the effects of this lymphokine in T-cell-mediated immune responses; such selective regulation may be a fundamental mechanism for restricting the potentially pleiotropic effects of certain lymphokines to appropriate responder cells.

Coexpression of granulocyte-macrophage colony-stimulating factor, gamma interferon, and interleukins 3 and 4 is random in murine alloreactive T-lymphocyte clones

Lymphokine gene expression was examined in a panel of 116 short-term murine T-lymphocyte clones derived by single-cell micromanipulation from allogeneic mixed leukocyte cultures. About 30% of clonable T cells, including both CD4+ CD8- and CD4- CD8+ cells, could be expanded for assay at an average of 22 days after cloning. By RNA blot-hybridization analysis, most clones (85-96%) expressed detectable granulocyte-macrophage colony-stimulating factor, interleukin 3, and gamma interferon mRNAs, and 11% expressed interleukin 4 mRNA. Although no differences were noted between CD4+ and CD8+ clones in the combinations of lymphokines produced, CD4+ clones on average transcribed and secreted higher levels. When the frequencies of coexpression of any pair of lymphokine mRNAs were determined, all were found to correspond to the values predicted for random assortment of the individual frequencies. For example, among 13 interleukin 4-positive clones, 11 also transcribed gamma interferon, giving the frequency of double-positive clones expected for random association (9.6% versus 10.8%). Therefore, expression of the four lymphokine genes segregated independently among the clones and did not allow the division of T cells into subsets with distinct patterns of lymphokine synthesis.

Interleukin 4 promotes the growth of tumor-infiltrating lymphocytes cytotoxic for human autologous melanoma

Addition of IL-4 (1,000 U/ml) to either high or low concentrations of IL-2 augmented tumor-infiltrating lymphocytes (TIL) growth from human melanoma. Weekly restimulation with irradiated tumor cells in conjunction with IL-4 allowed enhanced growth of TIL. With low-dose IL-2 (10 U/ml) and IL-4, expanded TIL had little cytolytic activity against Daudi or allogeneic tumors. Further, IL-4 augmented the total lytic activity against autologous tumors in most cases. With high-dose IL-2 (1,000 U/ml), IL-4 addition decreased nonspecific killing activity against Daudi or allogeneic melanomas in many cases, and reciprocally augmented cytolytic activity against the autologous melanoma in many cases. This suggests the possible use of IL-4 in cancer therapy, especially in adoptive cellular immunotherapy using TIL or in conjunction with IL-2 administration.

Interleukin 4 and soluble CD23 as progression factors for human B lymphocytes: analysis of their interactions with agonists of the phosphoinositide "dual pathway" of signalling

Human B lymphocytes pre-activated for 24 h with a combination of phorbol dibutyrate [P(Bu)2] and ionomycin were found to provide excellent targets for assessing the detailed action of B cell progression factors. Both recombinant interleukin 4 (IL 4) and affinity-purified 25-kDa fragment of the CD23 molecule (sol-CD23) were shown to be active in this assay. While the progression activity of IL 4 was enhanced by continued co-culture with P(Bu)2, that of sol-CD23 was found to be more strictly dependent upon such a joint application with the phorbol ester. Similar requirements were observed for triggering cell-cycle progression in the pre-activated B cells when using a stimulating CD23 antibody. Ionomycin, in contrast to P(Bu)2, did not augment either IL 4 or sol-CD23 in these assays but did enhance significantly the progression activity of an anti-CDw40 antibody. When added to B cells concomitantly with, or prior to, a high dose of phorbol ester, IL 4 unexpectedly down-regulated the subsequent mitogenic response to this agent whereas, when added 24 h later, IL 4 up-regulated such stimulations. The latter sequence of additions resulted in a particularly dramatic induction of CD23 at the B cell surface, much more so than seen when B cells were incubated with either IL 4 alone or with IL 4 and P(Bu)2 together. This up-regulation of surface CD23 was, in turn, mirrored by the appearance of large amounts of the soluble form of the molecule in such cultures. The findings are discussed with reference to possible mechanisms through which IL 4 and CD23 interact to exert their multiple actions on B cell regulatory pathways.

Interleukin 4 inhibits the proliferation but not the differentiation of activated human B cells in response to interleukin 2

The combined effect of IL-4 and IL-2 on proliferation of anti-IgM antibody or Staphylococcus aureus strain Cowan I (SAC)-preactivated B cells was investigated. It was observed that in most cases, rIL-2 used at optimal concentration induced higher levels of tritiated thymidine ([3H]TdR) uptake than rIL-4 used at optimal concentration. When rIL-4 and rIL-2 were added together, it was repeatedly found that B cell proliferation induced by rIL-2 was significantly reduced and was, in most cases, comparable with the proliferation induced by rIL-4 alone. Cell cycle studies demonstrated that rIL-4 significantly reduced the number of cells entering S and G2/M phases of the cell cycle upon rIL-2 stimulation. B cell blasts preincubated for 24 or 48 h with rIL-4 displayed a reduced proliferation in response to rIL-2. In contrast, preculture of resting B cells with rIL-4 did not impair their subsequent proliferation in response to rIL-2 plus insolubilized anti-IgM antibody. This suggests that rIL-4 can only exert its inhibitory effect once B cells have received an activation signal. The differentiative activity of rIL-2 measured on B cell blasts preactivated for 2 d with SAC was not altered by rIL-4, which suggests that rIL-4 did not exert its inhibitory activity on rIL-2-induced B cell proliferation by enhancing rIL-2-mediated differentiation. Delayed addition of a neutralizing anti-IL-4 antiserum demonstrated that a period of contact of at least 24 h between IL-4 and B cell blasts was necessary for the development of the antagonistic effect of IL-4 on IL-2-mediated growth of activated B cells. These data demonstrate that IL-4 antagonizes the B cell growth-promoting effect of IL-2 without affecting the differentiation of preactivated B cells in response to IL-2.

Activation of T cell-derived lymphokine genes in T cells and fibroblasts: effects of human T cell leukemia virus type I p40x protein and bovine papilloma virus encoded E2 protein

The effects of p40x, a product of an human T cell leukemia virus type I, on the activation of lymphokine genes were examined. The mouse GM-CSF and IL-3 genes were activated by cotransfection with a pX containing plasmid both in Jurkat and CV1 cells. Mouse GM-CSF gene was also activated by phytohaemagglutinin A (PHA)/phorbol myristate acetate (PMA) or PMA/calcium ionophore A23187 stimulation. The 5'-flanking region of the mouse GM-CSF gene which is required for activation by pX or mitogen was mapped within 226 bp upstream from the transcription initiation site. Action of pX was not restricted to T cells. pX activated exogenously added GM-CSF, IL-2, IL-3 and IL-4 genes in fibroblasts. Activation of the GM-CSF gene in fibroblasts appears to require the same regulatory region as in T cells. Similar results were obtained using bovine papilloma virus encoded E2 protein. We propose that pX or E2 protein, both in T cells and fibroblasts, activates cellular component(s) in the signal transduction pathway which results in the activation of lymphokine genes in the absence of extracellular stimuli.