Simultaneous production of interleukin 2, interleukin 4 and interferon-gamma by activated human blood lymphocytes

Effect of mycophenolate mofetil (RS-61443) on cytokine production: inhibition of superantigen-induced cytokines

The effects of the immunosuppressant mycophenolate mofetil (MPAM, RS-61443) on cytokine production at the single cell level were assessed using in vitro activated human mononuclear cells. Cytokine production was studied with UV microscopy of fixed and permeabilized cells stained with cytokine specific monoclonal antibodies (mAbs). The cytokines evaluated included interleukin-1 alpha (IL-1 alpha), IL-1 beta, IL-2, IL-3, IL-4, IL-5, IL-6, IL-10 interferon gamma (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), TNF-beta, and granulocyte macrophage-colony stimulating factor (GM-CSF). MPAM exhibited a marked antiproliferative effect without cytotoxicity in all mononuclear cell cultures. Six to 24 hours after stimulation with the superantigen Staphylococcus aureus enterotoxin A (SEA), most cytokine production was unaffected by MPAM at therapeutic concentrations (10(-6) M), with the exception of GM-CSF. In contrast, by 48 h after antigen activation, MPAM significantly inhibited all studied cytokine production (p < 0.05). Cyclosporin A (CsA), used as a control at a concentration of 100 ng/ml, inhibited production of all studied cytokines, at all time points. Monokine production after lipopolysaccharide (LPS) stimulation was unaffected by MPAM. Similarly, the production of most of the cytokines studied after mitogen stimulation with phorbol ester (PMA) plus calcium ionophore (ionomycin) was not affected by MPAM, in comparison to CsA which demonstrated significant inhibition of all cytokines tested under these conditions. However, a late inhibitory effect on IL-3 production was seen by MPAM at 48 h after mitogenic stimulation. Further observations are required to explain the divergent results on cytokine production by MPAM in superantigen-activated and mitogen-activated human mononuclear cells.

Human peripheral blood basophils primed by interleukin 3 (IL-3) produce IL-4 in response to immunoglobulin E receptor stimulation

In contrast to most cytokines, interleukin 4 (IL-4) expression is restricted to T lymphocytes, with the exception of mast cell lines and mast cells, as more recently demonstrated in rodents. Little is known, however, about the capacity of human nonlymphoid cells to produce IL-4. In this study we show that mature human basophils are capable of expressing IL-4 and examine the regulation of IL-4 production in comparison with the lipid mediator leukotriene C4. IL-4 was produced upon immunoglobulin E receptor (IgER) activation of basophils cultured with IL-3, a cytokine previously shown to prime these cells for enhanced release of inflammatory mediators. In some experiments, IL-3 or IgER activation alone also induced IL-4 production close to the detection limit. The effect of IL-3 on IgER-dependent IL-4 expression was dose and time dependent: maximal IL-4 production occurred between 18 and 48 h preexposure of basophils to 3-10 ng/ml IL-3. IgER-induced IL-4 synthesis and release by basophils cultured with IL-3 was rapid and complete after 6 h. In contrast to IL-3, other cytokines (IL-5, granulocyte/macrophage colony-stimulating factor, and nerve growth factor) that also prime basophils for enhanced histamine and leukotriene C4 release did not promote IgER-induced IL-4 synthesis. Basophils appear to secrete a "TH2-like" cytokine profile since no detectable IL-2 or interferon gamma was produced upon IgER activation. Mononuclear cells (depleted of basophils), cultured in parallel, did not release IL-4 in response to IL-3 and/or IgER activation, and produced approximately ten times less IL-4 than basophils upon nonspecific activation by phorbol ester and calcium ionophore. Thus, human basophils are an important cellular source of IL-4, and may, therefore, in addition to their inflammatory effector functions, also regulate the differentiation of T helper cells and B cells, in particular in allergic diseases.

Interleukin 1, interleukin 6 and transforming growth factor-beta production by human gingival mononuclear cells following stimulation with Porphyromonas gingivalis and Fusobacterium nucleatum

Gingival mononuclear cell production of interleukin 1 (IL-1), interleukin 6 (IL-6) and transforming growth factor-beta (TGF-beta) after stimulation with the putative periodontopathic bacteria, Porphyromonas gingivalis and Fusobacterium nucleatum was investigated. Using an ELISA method, gingival mononuclear cells extracted from 18 adult periodontitis subjects were found to be producing IL-1. However, IL-1 activity could only be detected in 5 out of these 18 cases when tested using a thymocyte proliferation bio-assay, suggesting the presence of IL-1 inhibitors. Depletion of monocytes from peripheral blood cultures resulted in a significant decrease in IL-1 activity following P. gingivalis stimulation while there was no effect in the level of IL-1 activity following stimulation with F. nucleatum. This suggests that P. gingivalis and F. nucleatum stimulate different cell types to produce IL-1. Like IL-1, IL-6 production by gingival mononuclear cells was significantly greater than that produced by the control peripheral blood mononuclear cells. Following P. gingivalis and F. nucleatum stimulation, higher levels of IL-6 could be detected; however, both organisms stimulated similar levels. Intracytoplasmic immunofluorescence staining demonstrated a lower percent TGF-beta+ cells in bacterial stimulated peripheral blood mononuclear cell cultures compared with cells in medium alone. In the gingival mononuclear cell cultures, the percentage TGF-beta+ cells peaked at day 1 in F. nucleatum-stimulated, whereas in P. gingivalis-stimulated cultures the peak TGF-beta+ cells occurred at day 3, again suggesting stimulation of different cell subsets. These results illustrate that different periodontopathic bacteria may stimulate different cell types to produce cytokines which may have synergistic or antagonistic effects.

Detection of intracellular cytokines by flow cytometry

During the last years it has become increasingly clear that production of most cytokines is not confined to one cell type. Thus, a method to detect cytokines at the single cell level would be a helpful tool to study the contribution of different cells to cytokine production in heterogeneous cell populations. Recently, Sander et al. (1991) demonstrated that it is possible to detect intracellular cytokines by fixation with paraformaldehyde, permeabilization with saponin and subsequent indirect immunofluorescent staining using fluorescence microscopy. Here, we describe a modified method to increase the specific intracellular staining which enables us to detect IFN-gamma, IL-2 and IL-4 producing cells by single laser flow cytometry. The carboxylic ionophore monensin was used to interrupt intracellular transport processes leading to an accumulation of the cytokine in the Golgi complex. This resulting increase of the signal/noise ratio permitted us to detect weakly fluorescent cells such as IL-4 producing cells. While IL-4 was detected in approximately 1-3% of peripheral mononuclear cells from healthy donors, up to 30% of the cells produced IFN-gamma and nearly 50% IL-2 after phorbol ester and ionomycin stimulation. Microscopic and flow cytometric analysis showed a highly significant correlation. Using three-color flow cytometry it was possible to measure intracellular cytokines and cell surface markers simultaneously. Subpopulations of human T cells (e.g., CD4+ CD45R0-) producing a restricted cytokine pattern could be identified by cell surface staining and were characterized by their cytokine production. Consequently, there was no further need for cell sorting to determine cytokine producing subsets in heterogeneous cell populations. We have tested human T cell clones for intracellular cytokine production and found a high concordance to ELISA analysis of the supernatants. We conclude that detection of intracellular cytokines by flow cytometry is a rapid, easy and semiquantitative assay which may be used to study individual cells in heterogeneous populations as well as to screen homogeneous cells for their cytokine pattern. This method is particularly relevant in view of the accumulating evidence of the functional role that subsets of (T) cells may play in various diseases depending on the pattern of cytokines they produce.

T helper type 2-like cells and therapeutic effects of interferon-gamma in combined immunodeficiency with hypereosinophilia (Omenn's syndrome)

We characterized the defects of CD4+ cells in a 17-month-old girl suffering from combined immunodeficiency with hypereosinophilia (Omenn's syndrome). Because the vast majority of peripheral blood CD4+ cells expressed the CD45R0 isoform, we purified circulating CD4+ CD45R0+ cells from the patient and healthy individuals in order to compare their production of cytokines. The patient's CD4+ CD45R0+ cells spontaneously produced high levels of interleukin-5 (IL-5) in vitro (1600 pg/ml after 24 h of culture) and this was associated with the presence of IL-5 in serum (323 pg/ml). After stimulation with phorbol 12-myristate 13-acetate (PMA) and calcium ionophore A23187, they produced higher levels of IL-4 (306 vs. 55 +/- 4 pg/ml) and IL-5 (2900 vs. 213 +/- 72 pg/ml) and lower levels of IL-2 (17 vs. 63 +/- 17 IU/ml) and interferon-gamma (IFN-gamma) (16 vs. 299 +/- 70 IU/ml) than controls CD4+ CD45R0+ cells. This T helper type 2 (Th2) pattern was confirmed by the detection using reverse polymerase chain reaction of IL-4, IL-5 and IL-10 mRNA within peripheral blood mononuclear cells. During a therapeutic trial with human IFN-gamma (40 micrograms/day) which ameliorated the clinical status of the patient, we observed a down-regulation of the in vivo expression of IL-5 and IL-10, a normalization of the eosinophil count and an improvement of the T cell response to phytohemagglutinin. This observation indicates for the first time that Th2-like cells might be involved in certain forms of congenital immunodeficiency and that IFN-gamma might down-regulate their activities in vivo.

Mechanisms of airways inflammation which may be amenable to prophylaxis

The presence of mucosal inflammation in the lower airways of atopic asthmatics and to a milder degree of atopic nonasthmatics suffering from rhinitis points to atopy and allergen exposure as risk factors for lower airways disease. The study of mechanisms which regulate the degree of inflammation should enable the understanding of why some individuals suffer from rhinitis alone whereas others go on to develop bronchial disease. This information should enable the development of prophylactic strategies to prevent atopy from expressing itself in the lower airways.

Endotoxin and Staphylococcus aureus enterotoxin A induce different patterns of cytokines

The effects of Staphylococcus aureus enterotoxin A (SEA) and lipopolysaccharide (LPS) in cytokine production were assessed at the single cell level in cells obtained from healthy blood donors. Cytokine production was studied with UV-microscopy of fixed and permeabilized cells stained with cytokine specific monoclonal antibodies. The cytokines evaluated included tumour necrosis factor (TNF)-alpha, interleukin (IL)-1 alpha, IL-1 beta, IL-6, IL-8, IL-10, IL-2, IL-4, interferon (IFN)-gamma and TNF-beta. LPS exhibited marked production of IL-1 alpha, IL-1 beta, TNF-alpha, IL-6 and IL-8. After LPS stimulation IL-1 alpha, IL-1 beta, TNF-alpha and IL-8 were the dominating products, all peaking at or before 4 hours after cell stimulation. In addition, IL-10 production was evident after 12 hours of cell stimulation. The T-lymphocyte-derived cytokines TNF-beta, IL-2, IFN-gamma and IL-4 were never detected in the cultures. All cytokine production, except IL-8, was downregulated at 96 hours. In contrast, peak production of IL-1 alpha, IL-1 beta and IL-8, which were the dominant products, occurred after 12 hours in the SEA-stimulated cultures. Further, a significant T-lymphocyte production of TNF-beta, TNF-alpha, IFN-gamma and IL-2 was found with peak production 12-48 hours after initiation. Only low amounts of IL-6 were evident. The two types of cytokine pattern and kinetics found may correspond to the different clinical conditions after invasive Gram-negative Escherichia coli vs Gram-positive Staphylococcus aureus infections in humans, with a much more rapid onset of disease after E. coli infections.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of interleukin-4 production in human mononuclear cells

Interleukin (IL)-4 is a cytokine with a broad range of effects on immune cells, however, little is known regarding the regulation of its production in freshly isolated human peripheral blood mononuclear cells (PBMC). Here we report the production of IL-4 in such cells following stimulation with monoclonal antibodies (mAb) directed against different cell surface antigens. We show that triggering via CD2 is more efficient for IL-4 production than triggering via the CD3 complex. The addition of a CD28 mAb enhances IL-4 production approximately threefold. Cell depletion experiments show that among CD2 plus CD28-stimulated PBMC the production of IL-4 is restricted to the CD8-CD45RA-T cell subpopulation. mAb interfering with the binding of IL-2 to its receptor can inhibit the production of IL-4 in CD2 plus CD28-stimulated PBMC. As IL-2 induces cell proliferation and production of interferon-gamma, but not production of IL-4, it follows that IL-2 is necessary but not sufficient for IL-4 production.

Lipopolysaccharide induces human interleukin-1 receptor antagonist and interleukin-1 production in the same cell

A new member of the interleukin-1 (IL-1) family has recently been described. Human IL-1 receptor antagonist (IL-1ra) is structurally related to IL-1 alpha and IL-1 beta but binds to IL-1 receptors on various target cells without demonstrable agonist activity. Understanding the mechanisms of regulation of IL-1ra production may clarify the biology of this unique cytokine as well as elucidate its possible role as a natural anti-inflammatory protein. The effects of lipopolysaccharide (LPS) on IL-1 alpha, IL-1 beta and IL-1ra production was studied at a single-cell level by use of cytokine-specific antibodies and indirect immunofluorescence technique. The peak synthesis of IL-1ra and IL-1 alpha/beta occurred in peripheral blood monocytes obtained from healthy blood donors within 4 and 6 h of cell stimulation, respectively. By double-staining procedure all IL-1ra-positive cells were also IL-1 alpha and/or beta positive. Thus, endotoxin induced simultaneous synthesis of the IL-1 gene family in the same cells. Only monocytes contributed to the production of IL-1 alpha, beta and IL-1ra during the 96 h of cell culture. The maximum number of IL-1ra-producing monocytes was 48 +/- 16% as compared to peak production of IL-1 alpha and beta which occurred in 75 +/- 9% and 80 +/- 12% (p < 0.001), respectively, of all peripheral blood monocytes. The incidence of IL-1 alpha- and beta-containing cells was not only significantly higher but also occurred for a longer time period, 72 h as compared to 24 h for IL-1ra localized in the Golgi organelle. However, IL-1ra-containing cells with a diffuse cytoplasmic appearance were also evident (20%-30%) at a later stage, 12 to 72 h after stimulation. Blocking IL-1 surface receptors by addition of exogenous recombinant IL-1 beta before stimulation could not inhibit the diffuse cytosolic localization. This indicates that the "late" staining pattern did not reflect IL-1ra being secreted and internalized after binding to extracellular receptors. Thus, perhaps IL-1ra modulates IL-1 effector mechanisms by receptor interactions both inside and outside the cell.

Qualitative Shift of Lymphokine Production in Response to Stimulation, as a Consequence of Preactivation In Vivo or In Vitro

Lymphokine production, analysed at the single cell level, was compared in resting and primed T-cell populations. Cells were preactivated in vitro by repeated mitogen stimulations, or isolated as large, low density cells naturally activated in vivo, from normal spleens of unimmunized animals. A similar qualitative shift in the pattern of lymphokines synthesized after restimulation was found as a result of in vivo and in vitro preactivation of cells. Repeated stimulations in vitro resulted in a qualitative shift in the lymphokines produced in response to activation, from a dominance of IL-2 during the first and second culture, to a dominance of IL-4 and IL-5 in the later stimulations. In vivo activation lead to a similar separation of lymphokine production as primarily IL-2 was made by small resting cells, while large cells preferentially produced IL-4 and IL-5. IFN-gamma was produced by both small and large cells. Preactivation in vitro lead to a more rapid appearance of lymphokines during restimulation. In contrast, the in vivo naturally activated cells responded with a slow onset of lymphokine production when stimulated in vitro.

Interleukin (IL)-4 production by human T cells: differential regulation of IL-4 vs. IL-2 production

We have examined the regulation of interleukin (IL)-4 production by human peripheral blood T cells. Production of IL-4 was shown to be regulated differently from IL-2 and interferon(IFN)-gamma production. Stimulation of peripheral blood lymphocytes with anti-CD3, anti-CD2, anti-CD28, Phorbol 12-myristate 13-acetate (PMA) or IL-2 as a single stimulant did not induce IL-4 production. However, combinations of anti-CD2 with either anti-CD28 or IL-2 resulted in IL-4 production, peaking at days 3-4. Stimulation with anti-CD3 instead of anti-CD2 gave similar results, but was less potent. After days 3-4, IL-4 levels decreased, most likely due to consumption of IL-4. PMA profoundly affected cytokine production, it enhanced IL-2 production by at least tenfold, whereas, in the same cell population, IL-4 production was almost completely inhibited. This was observed at the protein as well as at the mRNA level. In contrast, agents that increase intracellular cAMP levels inhibited IL-2 production but left IL-4 production unaffected. IFN-gamma production behaved similar to IL-2 production but the effects were less outspoken.

Bee venom phospholipase A2-specific T cell clones from human allergic and non-allergic individuals: cytokine patterns change in response to the antigen concentration

Protein antigens with both allergenic and immunoprotective properties represent appropriate molecules to study IgE and IgG regulation. We have established a panel of T cell clones specific to bee venom phospholipase A2 (PLA) from human individuals allergic, hyposensitized or immune (protected) to bee sting. All clones obtained were CD3+, CD4+ and expressed alpha, beta T cell receptor. Depending on the T cell clone, maximal stimulation required 1 to 100 micrograms/ml of PLA, and the addition of interleukin (IL)-2 and/or IL-4 increased their antigen-dependent proliferation. Following antigen stimulation, the clones produced IL-4, interferon-gamma (IFN-gamma) and granulocyte-macrophage colony-stimulating factor. Most clones also produced tumor necrosis factor alpha (TNF-alpha) and tumor necrosis factor beta (TNF-beta), and some produced IL-5 and/or IL-2. Both absolute and relative amounts of secreted cytokines depended on the antigen concentration. At low antigen doses, IL-4 was produced but little or not IFN-gamma, whereas at higher PLA concentrations significant amounts of both IL-4 and IFN-gamma were obtained. Thus, these PLA-specific T cell clones could be classified according to the changes in the ratio of IL-4/IFN-gamma production in response to increasing antigen concentrations. Clones derived from allergic and hyposensitized individuals required higher critical amounts of antigen for IFN-gamma induction, and expressed increasing IL-4/IFN-gamma ratios with increasing concentrations of PLA. Modulation of cytokine patterns by the dose of the antigen may be a driving force for IgE or IgG formation resulting in allergy or immunoprotection.

In vivo cocaine administration influences lymphokine production and humoral immune response

The effect of in vivo cocaine administration on in vitro mitogen-induced lymphokine production was examined. Splenocyte cultures from BALB/c mice treated with an acute (1 mg/kg) or daily cocaine administration (1 mg/kg/day for 7 consecutive days) were less responsive to induction of IFN-gamma, IL-2 and IL-4 production by mitogen stimuli. We also evaluated the humoral immune response to both a T-dependent (HEL) and a T-independent antigen (rHBcAg). It was found that cocaine inhibits T-dependent antibody production only. This inhibition was greatest when cocaine was given during immunization. The results suggest that T-cell-mediated responses may be more affected by cocaine use/abuse.

Activation events during thymic selection

During their differentiation in the mouse thymus, CD4+8- cells undergo several of the sequential changes observed upon normal activation of mature, peripheral CD4+ lymphocytes. Expression of CD69, an early activation marker, is first observed on a minority of cells at the T cell receptor (TCR)lo/med double-positive stage, is maximal (50-90%) on heat-stable antigen (HSA)hi TCRhi double-positive, HSAhi TCRmed CD4+8lo, and HSAhi TCRhi CD4+8- cells, and is downmodulated at the mature HSAlo CD4+8- stage. In contrast, CD44, a late activation marker, is selectively expressed at the HSAlo stage. The set of lymphokines that CD4+8- thymocytes can produce upon stimulation also characteristically expands from mainly interleukin 2 (IL-2) at the HSAhi stage, to IL-2 and very large amounts of IL-4, IL-5, IL-10, and interferon gamma (IFN-gamma) at the HSAlo stage. 1 in 30 HSAlo CD4+8- adult thymocytes secrete IL-4 upon stimulation through their TCR. This frequency is 25% of the frequency of IL-2 producers, about 100-fold above that of peripheral (mainly resting) CD4+ T cells. With time after their generation in organ culture, CD4+8- thymocytes lose their capacity to secrete IL-4, IL-5, and IFN-gamma, but not IL-2. Similarly, the frequency of IL-4, but not of IL-2, producers progressively decreases after emigration to the periphery as judged by direct comparison between thymic and splenic CD4+ cells in newborns, or by following the fate of intrathymically labeled CD4+8- cells in adults after their migration to the spleen. This sequence suggests that thymic selection results from an activation process rather than a simple rescue from death at the double-positive stage, and shows that the functional changes induced after intrathymic activation, although transient, are still evident after export to the periphery.

T cells with specificity for idiotypic determinants on human monoclonal autoantibodies in myasthenia gravis

The activation of T cells from 46 patients with myasthenia gravis and 28 healthy individuals by two human monoclonal autoantibodies was studied. B-cell clones were produced by transformation of peripheral lymphocytes from a patient using Epstein-Barr virus and subsequent cloning. Two myasthenia-specific autoantibodies, one anti-receptor-antibody and one antiidiotypic antibody, both carrying separate recurrent idiotopes, were used in this study. Single activated T cells were identified by their secretion of IL2 and IFN gamma using a cell enzyme-linked-immunosorbent technique. The idiotypic antibody activated T cells in patients but not in most of the controls at concentrations of 1 pg/ml and 10 pg/ml. High concentrations of antibody resulted in T-cell activation in both groups. A similar dose-response pattern was recorded using the antiidiotypic antibody. Incubation with the idiotypic antibody resulted in T-cell stimulation, measured as numbers of IFN gamma-secreting cells that exceeded the mean +2 SD of controls, in 78% of patients and in 7% of the healthy individuals (p less than 0.001). The antiidiotypic antibody activated T cells in 50% of patients and in 4% of the healthy individuals (p less than 0.001). T-cell activation measured as numbers of IL2-secreting cells showed a difference between patients and controls which was as significant as for IFN gamma secretion. The results demonstrate the presence of T cells with specificity for disease-specific determinants on idiotypic and antiidiotypic antibodies in myasthenia gravis.

Helper interleukins are produced by both CD4 and CD8 splenic T cells after mitogen stimulation

We have earlier described (Cardell, S. and Sander, B., Eur. J. Immunol. 1990. 20:389) mitogen-induced production of interleukin (IL)2, IL4 and IL5 mRNA by murine spleen cells, analyzed by in situ hybridization. In the present study we have investigated the potential of CD8 T cells to produce these interleukins, normally associated with the helper function of CD4 T cells. When concanavalin A (Con A)-activated spleen cells were restimulated with Con A and phorbol 12-myristate 13-acetate (PMA), higher levels of IL2, IL4 and IL5 mRNA were induced, as detected both by increased frequencies of positive cells, and by more mRNA per cell. Four-to-six-day Con A blasts were enriched for CD4+ or CD8+ T cells, and restimulated with Con A and PMA. Both CD4 and CD8 cells were found to produce all three kinds of mRNA when restimulated. The frequencies of IL2 mRNA-containing CD8 cells were half of those found for CD4 cells (3.5% as compared to 7%). On the average 1% of the CD8 cells were induced to produce IL4 and IL5 mRNA, while 9% and 3% of the activated CD4 cells contained IL4 and IL5 mRNA, respectively. CD4 and CD8 cells displayed different sensitivities to the reagents when tested alone. Con A induced the synthesis of IL4 and IL5 in CD4 cells, but not CD8 cells, independently of PMA. PMA alone induced extensive thymidine incorporation in CD8 cells, but not in CD4 cells, in the absence of detectable lymphokine mRNA. The results suggest that some CD8 cells have the capacity to give help in immune responses, by secretion of IL2, IL4 and IL5.

Human tumour-associated NK cells secrete increased amounts of interferon-gamma and interleukin-4

Numerous interactions between malignant and stromal/inflammatory cells take place within solid human tumours, which are mediated, in part, by the release of signalling proteins called cytokines. In the present study, we have compared the secretion of two important immunomodulatory cytokines, IFN-gamma and IL-4 by individual, immunophenotyped NK cells freshly isolated from either malignant tumour biopsies, or peripheral blood samples from patients with ductal invasive breast cancer. Due to the marked heterogeneity amongst cells isolated from these clinical samples, we have employed a technique called the reverse haemolytic plaque assay to identify and enumerate cytokine-secreting cells at the single cell level. Our data indicate that NK cells isolated directly from the tumour site secrete more IFN-gamma and IL-4 than NK cells from the blood of the same patients. However, a greater proportion of CD16+ cells from both sources in breast cancer patients secreted IFN-gamma than of those from the blood of healthy donors. We also show that factors secreted by the human breast cell lines, MCF-7 and MDA-231 PN9, were able to mimic the stimulatory influence of the tumour microenvironment on secretory activity of NK cells.

Cytokine regulation of immunoglobulin secretion by neonatal lymphocytes

In contrast to adult lymphocytes, neonatal lymphocytes secrete minimal amounts of Ig in response to stimulation with immobilized MAb to CD3. This deficiency could be overcome by the addition of supplemental IL-2, IL-4, or IL-6, resulting in the secretion of all Ig isotypes. There were no major differences in the distribution of Ig isotypes secreted in response to the cytokines alone or in combination. The Ig secreted in response to IL-4 or IL-6 was inhibited by MAb to CD25, suggesting that the effects of IL-4 and IL-6 were dependent on IL-2. Stimulation of neonatal lymphocytes with anti-CD3 was sufficient to induce expression of IL-2 receptors (CD25) on both T and B cells. IL-4 exerted direct effects on neonatal T cells by increasing IL-2 production and promoting IL-6 production by anti-CD3-stimulated neonatal lymphocytes. Antibody to IL-4 or IL-6 did not inhibit Ig secretion in response to IL-2 and antibody to IL-6 did not consistently inhibit Ig secretion in response to IL-4. Finally, in the presence of cyclosporin, anti-CD3-stimulated neonatal lymphocytes secreted Ig only with the combination of IL-2 and IL-4. These results have delineated unique, but not Ig isotype-specific, effects of cytokines in supporting Ig secretion by anti-CD3-stimulated neonatal lymphocytes. Deficient production of these cytokines is likely to contribute to the decreased capacity of neonatal lymphocytes to generate an Ig response.

In situ hybridization of interferon-gamma producing peripheral blood mononuclear cells

Individual interferon-gamma (IFN-gamma) producing cells in activated human peripheral blood mononuclear cells (PBMC) were characterized by in situ hybridization using [35S]-labelled antisense RNA probes. The proportion of positive cells expressing IFN-gamma mRNA varied according to the substances used for stimulation. IFN-gamma mRNA expressed a relatively low percentage of 1-8% PBMC after a single stimulus with mitogens or OKT-3 antibody and 20-30% of the cells were identified to synthesize IFN-gamma mRNA after stimulation with PHA + P-MA + OKT-3 antibody. The expression of IFN-gamma mRNA and production of the lymphokine was dependent on accessory cells. If accessory cells were replaced by recombinant interleukin-1 (IL-1) plus interleukin-6 (IL-6), then T-cell proliferation to phytohaemagglutinin (PHA) could be partially restored and measurable amounts of IFN-gamma were detected. The addition of interleukin-2 (IL-2) or phorbol-12-myristate-13-acetate to T cells stimulated with PHA, IL-1 and IL-6 did not restore the production of IFN-gamma to an extent comparable to that produced by T cells stimulated in the presence of accessory cells. In further studies, depletion of T-cell subsets showed that CD3+, CD4+, CD8+, CD29+ and CD45RA+ cells were involved in IFN-gamma production after mitogenic stimulation. In conclusion, our data demonstrate that IFN-gamma production is dependent on signals from accessory cells and IFN-gamma is synthesized by only a small proportion of T cells, that did not belong to a unique population, characterized by conventional cellular surface antigens.

Immunological memory in T cells

CD4 and CD8 T lymphocytes can be further subdivided using antibodies to isoforms of CD45 with restricted cellular distributions. These further subsets, detected in man, rodents and sheep, differ in surface phenotypes, rate of cycling, migration and response to recall antigens. Their lineage relationship has still not been fully established.

Detecting cytokine production at the single-cell level

Cytokines are versatile mediators of intercellular communication. Their functional diversity has aroused considerable interest and prompted the rapid development of a number of techniques for their detection and measurement. However, conventional cytokine assays measure only their bulk release by large numbers of cells and give no indication of the identity or frequency of producer cells. Here, the advantages and disadvantages of a relatively new approach to detect cytokine production by single cells are reviewed.

Interleukin 4 and interferon gamma production in restimulated CD4+ and CD8+ cells indicates memory type responsiveness

Interleukin 4 (IL-4) and interferon gamma (IFN-gamma) production was analysed in murine spleen cells during primary and secondary mitogen stimulation in vitro. The kinetics, frequency and phenotype of single lymphokine-producing cells were studied by combining intracytoplasmatic immunofluorescence and surface staining. Both IL-4 and IFN-gamma was produced by CD4+ as well as CD8+ cells, however 75-80% of IL-4 producers were CD4+ and 90% of IFN-gamma+ cells were CD8+. In primary stimulations, concanavalin A (Con A) activation or anti-CD3 antibody together with phorbol 12-myristate 13-acetate (PMA) induced different patterns of lymphokine production. Approximately the same frequency of IFN-gamma+ cells was induced by both stimulation procedures but the kinetics was different with a peak at 30 h using Con A and at 52 h using anti-CD3 and PMA. IL-4 production peaked at 52 h, but the frequency of IL-4+ cells was 8-10 times higher after stimulation by anti-CD3 and PMA than after Con A stimulation. During restimulation of the mitogen activated cells, lymphokines were rapidly produced; both IL-4 and IFN-gamma production peaked at 8-11 h. Only a small increase in the frequency of IL-4+ cells was seen, at most two to three times. No evidence for a major shift of lymphokines produced between primary and secondary stimulations could be found. Instead, the pattern of lymphokine production induced by the primary stimulus was dominant also in secondary cultures irrespective of stimulation condition.

Differential induction of cytokine-specific mRNA in human PBL after in vitro culture with either IL2 or IL4

The present study was designed to investigate whether human equivalents of murine T helper cell subsets can be demonstrated by propagation of peripheral blood lymphocytes (PBL) with either recombinant human (rh) interleukin (IL) 2 or rhIL4 in the presence of neutralising antibodies. Cells of both cultures, termed T-IL2 or T-IL4, respectively, were challenged on day 8 using a combination of phorbol-12-myristate-13-acetate (PMA) and the Ca2(+)-ionophore A23187 (Io). Total cellular RNA was isolated at different time points after PMA/Io-stimulation and the expression of 7 distinct cytokine genes was assessed by Northern analysis. Whereas maximal accumulation of mRNA species for IL2, GM-CSF, TNF alpha and TNF beta did not reveal major differences between cells of T-IL2 and T-IL4 cultures, substantial differences emerged for the induction of IFN gamma and IL3 messages. Accumulation of IFN gamma-mRNA consistently was 2- to 13-fold higher in T-IL2 than in T-IL4 cells, depending on the time point of RNA harvest. In contrast, IL3-specific mRNA levels induced in T-IL4 cells were 2-5 times greater than those in T-IL2. If PBL cultured with IL2 for 7-8 days were subsequently shifted to IL4 and further propagated until day 14, the mRNA induction pattern seen for IFN gamma and IL3 was similar to that obtained if cells had continuously been propagated with IL2. Collectively, these results indicate a selective outgrowth of distinct responder phenotypes by IL2 or IL4 rather than a direct modulation of cytokine expression by these factors.

Human interleukin-4: an immunomodulator with potential therapeutic applications

Human interleukin-4 (IL-4) is a 20kDa cytokine produced by activated T cells and has an extensive range of stimulatory and inhibitory effects on the wide range of cells which express its receptor. It specifically promotes the immunoglobulin class switch to IgE and IgG4 and potently co-stimulates with CD40 monoclonal antibodies the long term proliferation of human B cells. It has variable effects on T cells, but predominantly has inhibitory actions on monocytes suggesting a potential therapeutic role as an anti-inflammatory agent. There is evidence for indirect anti-cancer activity of IL-4 both in animal models and in in vitro studies on human tumour infiltrating lymphocytes. In addition, IL-4 directly inhibits the in vitro proliferation of the majority of B cell neoplasms. Phase I studies of IL-4 in patients with cancer have commenced and promising observations have been made in patients with haematological malignancies receiving low, well-tolerated doses.