Interleukin-2 Receptor Expression Research Articles

Determination of the interleukin-2 receptor β chain by peripheral blood mononuclear cells in patients with primary biliary cirrhosis

Interleukin-2 receptor (IL-2R) β chain expression was assessed in peripheral blood mononuclear cells (PBMCs) by flow cytometry using an IL-2R β chain-specific mouse monoclonal antibody in 23 patients with primary biliary cirrhosis (PBC) and 20 normal controls. The percentages of IL-2R β chain positive cells in PBMCs were significantly decreased in PBC patients compared with those of normal controls ( P < 0.01). IL-2R β chain expression showed no difference between patients with asymptomatic and symptomatic PBC, or among the stages of a histological grading by Scheuer's classification. The IL-2R β chain was mainly expressed by CD 16 positive cells (natural killer cells) in PBC patients as well as in normal controls. To study the biological significance of the diminishment of the IL-2R β chain in PBC patients, natural killer (NK) activity and Iymphokine activated killer (LAK) activity was determined simultaneously in 12 PBC patients. A significant correlation was observed between the percentage of IL-2R β chain positive cells and NK activity ( r = 0.778, P < 0.01) or LAK activity ( r = 0.736, P < 0.01). These findings suggest that the decreased expression of IL-2R β chain is linked to diminished NK activity and LAK activity in PBC patients.

SUPPRESSION OF DIALYSIS PATIENTS' LYMPHOCYTE IL-2R EXPRESSION BY GLUCOCORTICOIDS AND CYCLOSPORINE

Previous studies have shown interindividual heterogeneity in the suppressive effects of glucocorticoids and cyclosporine (CsA) on the proliferation responses of dialysis patients' peripheral blood mononuclear cells (PBMC). In addition, methylprednisolone (MP) was shown to be significantly more suppressive than prednisolone (P), and PBMC from patients on peritoneal dialysis (PD) were found to be more sensitive to both glucocorticoids than those from patients on haemodialysis (HD). In order to begin to explore the cellular mechanism(s) underlying these observations, the differential suppressive effects of these drugs on lymphocyte interleukin 2 receptor (IL-2R) expression by mitogen-stimulated PBMC from 23 PD and 30 HD were determined.The mean±SD concentrations (ng/ml) of steroid causing 50% inhibition (IC50) of cell proliferation was significantly lower for PD than HD PBMC with both P (94±93 vs 148±105,P<0.05) and MP (21±25 vs 35±31,P<0.05). MP was significantly (P<0.001) more suppressive than P of IL-2R expression in both PD and HD. PD IL-2R expression was significantly (P<0.05) more suppressed by CsA alone and by 400 ng/ml CsA+10−7MP than was HD IL-2R expression. CsA+10−7M MP was significantly (P<0.001) more suppressive of IL-2R expression than the other drugs, alone or in combination, in both groups of patients.In conclusion, these results support the notion that at least one mechanism underlying the significantly greater efficacy of MP compared to P in suppressing PBMC proliferation is its significantly greater suppression of lymphocyte IL-2R expression, either alone or in combination with CsA. Thus, use of MP following allograft transplantation may result in more effective immunosuppression for many recipients.

Retinoid Regulation of Interleukin-2 Receptors on Human T-Cells

The ability of retinoids to regulate interleukin-2 receptor (IL-2R) levels on human T-cells may play a fundamental role in the immunomodulating effects of these compounds. As a cell line model for studying this phenomenon, we tested the effects of retinoic acid (RA) on the expression of IL-2Rα and IL-2Rβ in Hut78 cells, a mature T-cell line derived from a Sezary T-cell leukemia. Our results demonstrated 4- to 20-fold increases in the surface expression and mRNA levels of both of these receptor components at RA concentrations starting at 10−10Mwith maximal induction at 1 μMRA. RA-induced upregulation of IL-2Rβ was found to be transcriptionally mediated in a protein-synthesis-independent fashion; however, activation of the IL-2Rβ promoter could not be demonstrated in transient transfection experiments utilizing reporter gene constructs containing all currently known regulatory elements of the IL-2Rβ promoter. Enhancement of IL-2Rα/β by RA was accompanied by upregulation of the expression of CD38, CD69, CD45RO, and HLA-DR, surface molecules known to be associated with T-cell activation. Parallel effects were induced by RA on T-blasts generated from primary human lymphocytes suggesting the physiologic relevance of the Hut78 cell line model. Taken together, our findings demonstrate the ability of RA to upregulate IL-2R expression and enhance the activation state of Hut78 cells. The dramatic enhancing ability of RA on IL-2Rβ expression does not appear to be mediated through interaction with currently defined regions of the IL-2Rβ promoter.

Human gastric carcinoma transduced with the IL-2 gene: increased sensitivity to immune effector cells in vitro and in vivo.

We transduced a human gastric carcinoma cell line, HR, with the interleukin 2 (IL-2) gene. Stable HR transfectants secreted nanogram quantities of biologically active IL-2 and had significantly increased expression of IL-2 mRNA relative to that in parental cells. Expression of intracellular IL-2 protein was not quantitatively different in the parental and IL-2 gene-transduced cells, although the former did not secrete IL-2. Surface expression of IL-2 receptors was comparable in the parental and transduced cells at the mRNA or protein levels. Nevertheless, in vitro proliferation of IL-2 gene-transduced HR cells was significantly more rapid than that of parental cells. Both parental and IL-2 gene-transduced HR cells were equally sensitive to lysis by IL-2-activated natural killer (A-NK) cells, as measured in 4 hr 51Cr-release assasys or to apoptosis induced by NK or A-NK cells, assessed in 1 hr 3H-TdR-release assays. In 24 hr MTT assays, however, the IL-2 gene-transduced cells were significantly more sensitive to these effector cells than were parental cells. Upon intrasplenic injection of 5 x 10(6) parental or transduced HR cells into nude mice, liver metastases developed. Metastases of parental HR cells killed the animals in 24 days. In contrast, metastases of the IL-2 gene-transduced HR cells became necrotic by day 14 and were found to be surrounded by murine NK cells and macrophages. Survival of nude mice injected with IL-2 gene-transduced HR cells was significantly prolonged (>50 days) relative to that of mice injected with parental HR. Thus, IL-2 gene-transduced HR cells produced sufficient amounts of functional IL-2 in vivo to be able to recruit to the tumor site and support functions of endogenous cytotoxic immune effector cells, which were responsible for regression of hepatic metastases and significant improvement of survival in these mice.

Glutamine requirement of proliferating T lymphocytes

Glutamine is required for lymphocyte proliferation but the site of glutamine action is not yet known. In this study, the effect of glutamine on key events that occur during lymphocyte activation [interleukin-2 (IL-2) production, IL-2 use, IL-2 receptor expression, transferrin receptor expression] was investigated. Rat or mouse spleen lymphocytes were cultured in the presence of the T-cell mitogen concanavalin A (Con A) and various concentrations of glutamine. There was a trend (not significant) for the ratio of CD4 +:CD8 + spleen lymphocytes to increase (from 1.9 to 2.6) as the concentration of glutamine in culture medium increased from 0 to 2 mmol/L. As the concentration of glutamine increased, there was an increase in the proportion of cells expressing the IL-2 receptor (from 30 to 45%) and the transferrin receptor (from 34% to 55%). As the concentration of glutamine increased there was a 2.7-fold increase in the concentration of IL-2 in the culture medium. The IL-2 concentration was decreased when an IL-2 receptor-blocking antibody was included in the culture medium; the IL-2 concentrations measured were taken to indicate the initial Con A-stimulated production of IL-2. In these conditions, the IL-2 concentration in the medium increased 39-fold as the glutamine concentration increased. The use of IL-2 by an IL-2-dependent cell line was dependent on the glutamine concentration in the culture medium. Thus, all four components of lymphocyte activation investigated (IL-2 production, IL-2 use, IL-2 receptor expression, transferrin receptor expression) were dependent on the concentration of glutamine present in the culture medium. Thus, glutamine might provide an early signal in the lymphocyte activation process.

Blastogenic responses, interleukin-2 production and interleukin-2 receptor expression on CD4+ and CD8+ lymphocytes in rhesus monkeys experimentally inoculated with Loa loa.

To better understand cellular responses in loiasis infection, in vitro blastogenesis of peripheral blood mononuclear cells (PBMC) to filarial antigen was assessed in 12 Loa loa-inoculated rhesus monkeys over a two-year period. Cellular reactivity to antigen was observed between 10-35 weeks postinoculation (WPI), but had declined by week 50. The roles of interleukin-2 (IL-2) and IL-2 receptor (IL-2R) expression of CD4+ and CD8+ T cells in regulating the response to antigen were examined during the initial (57 WPI) and late (92 WPI) time points of the observed diminished reactivity to antigen. The levels of IL-2 in antigen cultures at both time points were not significantly different from those in unstimulated cultures. Also, exogenous IL-2 partially reversed the PBMC response to antigen. The percentages of CD4+ and CD8+ T cells expressing IL-2R in antigen cultures at 57 WPI were not different from those of control animals. Likewise at 92 WPI, the percentage of CD4+ T cells expressing IL-2R in antigen cultures, were not increased above those of control animals. In contrast, the percentage of CD8+ T cells expressing IL-2R in antigen cultures were significantly increased above those of control animals (P < 0.0001), coinciding with an increase in CD8+ T cells numbers in these cultures. The data show that factors besides IL-2; and probably an imbalance in the percentages of CD4+ and CD8+ T cells bearing IL-2R in antigen cultures, may contribute to the diminished reactivity to antigen in L. loa-inoculated rhesus monkeys.

Effect of 5-fluorouracil on interleukin-1 and interleukin-2 receptor expression.

We have studied the effect of anticancer drug 5-fluorouracil on the expression of human Interleukin-1 and Interleukin-2 receptor. In this report, we show that 5-Fluorouracil increases the Interleukin-1 expression upto 2.66 folds without significantly affecting the levels of surface expression of p55 IL-2 receptor on human Peripheral blood mononuclear cells, CD4 and CD8 T cells. On contrary, the drug decreases the levels of Interferon-gamma secretion by upto 42%. In earlier studies we have shown that 5-fluorouracil increases the IL-2 expression both at mRNA and protein levels. Taken together, 5-fluorouracil differentially affects the expression of Interleukin-1, Interferon-gamma and Interleukin-2 receptor.

Early infiltration of arterial intima by activated dendritic γ/δ T-cells in ligated human arteries: An ultrastructural and immunocytochemical study

To clarify the role of immune mechanisms in the vascular response to injury in humans, the sequence, subset and activation status of lymphocytes infiltrating acutely ischemic arteries were studied. Thirty-five branches of mesenteric arteries removed from 8 men during surgery—22 of which were ligated for 0.5–4 hours—were examined ultrastructurally and immunocytochemically. The ligated arteries showed early intimal infiltration by activated T-cells, the predominant subset of which was dendritic, γ/δ T-cell receptor (TCR)-bearing and phenotyped CD3+, CD4-, and CD8-. Their activated status is shown by strong HLA-DR positivity, expression of interleukin-2 receptors, increased expression of lymphocyte function antigen-1, and frequent lymphocyte-macrophage interactions. Intimal macrophage infiltration consisted of single cells in the earlier biopsy specimens and clusters of cells in the later ones. These findings suggest that an early immune mechanism initiated by activated γ/δ dendritic T-cells, and amplified later by macrophages, may play a pivotal role in the inflammatory response after acute arterial injury.

Uterine natural killer cells do not require interleukin-2 for their differentiation or maturation.

Natural Killer lymphocytes (NK cells) from the pregnant uterus and from other tissues in pregnant and nonpregnant mammals can be stimulated by interleukin-2 (IL-2) during culture to become Lymphokine Activated Killer (LAK) cells. The susceptibility of cultured trophoblast cells to lysis by LAK cells raises the enigma of why uterine (u) NK cells that are characterized by morphology and by surface phenotyping as "activated," and thus potentially damaging to the placenta, become localized to implantation sites during normal rodent gestation. uNK cells migrating from explant cultures of the metrial gland were assessed for expression (mRNA and protein) of each chain of the IL-2 receptor (IL-2R). Implantation sites from transgenic mice lacking a functional IL-2 gene were examined histologically for the differentiation of mature, granulated uNK cells. Early post-implantation, mRNA from migrating uNK cells contains transcripts for all three chains of the IL-2R. Only IL-2Rgamma was expressed at day 12 of gestation; expression of this gene was also lost by day 16. Loss of IL-2R transcription did not result in loss of protein expression; however, it did coincide with loss of uNK cell viability in vivo. Apparently normal differentiation of uNK cells occurred in IL-2(-/-) mice and in doubly mutant IL-2(-/-).beta2m(-/-) mice. Thus, despite uNK cell expression of the full IL-2R at day 8 of gestation, IL-2 is not required for the maturation of uNK cells to their fully granulated form or for normal placental development.

Use of the methylxanthine derivative A802715 in transplantation immunology: I. Strong in vitro inhibitory effects on CD28-costimulated T cell activities.

Recently, methylxanthines such as pentoxifylline (PTX) were shown to be immunosuppressive in vitro. Unfortunately, when used in transplant patients, PTX was poorly active as an immunosuppressant. Here we report that the new methylxanthine derivative A802715 not only is more active than PTX, it also suppresses the cyclosporine (CsA)-resistant "signal two"-dependent pathway of T cell proliferation, making it an interesting drug to associate with CsA. "Signal one"- and "signal two"-dependent T cell activation was investigated with purified human T cells stimulated with immobilized anti-CD3 or anti-CD28 monoclonal antibody (mAb) plus phorbol myristate acetate (PMA) or with a 3T6 mouse fibroblast cell line presenting anti-CD3 mAb on transfected human Fcgamma receptors II (FcgammaRII) in the presence or absence of transfected B7-1 (CD80) molecules. A802715 was more immunosuppressive in the mixed lymphocyte reaction (MLR) than PTX. A802715 dose-dependently suppressed polyclonal signal one-dependent T cell activation induced by anti-CD3 mAb/PMA. In addition, A802715 also suppressed signal two-dependent T cell proliferation induced by anti-CD28 mAb/PMA. The expression of the interleukin-2 receptor on T cells stimulated by anti-CD3 mAb presented on 3T6/FcgammaRII cells was equally well suppressed by A802715 and PTX. In contrast, interleukin-2 receptor or CD40L (gp39) expression by T cells after stimulation with the same anti-CD3 mAb- 3T6/FcgammaRII cells, but coexpressing transfected B7-1, was only suppressed by A802715. The anticipated synergism between A802715 and CsA was confirmed in MLR assays. Moreover, generation of cytotoxic T lymphocytes during MLR with Epstein-Barr virus-transformed B cells, which strongly express B7-1 and B7-2, was also inhibited by A802715. These in vitro data indicate that the A802715 (1) is a stronger immunosuppressant for T cells than PTX, (2) suppresses T cell activation pathways that are resistant to PTX or CsA, and (3) acts synergistically with CsA.

Jun NH2-terminal kinase is constitutively activated in T cells transformed by the intracellular parasite Theileria parva.

When T cells become infected by the parasite Theileria parva, they acquire a transformed phenotype and no longer require antigen-specific stimulation or exogenous growth factors. This is accompanied by constitutive interleukin 2 (IL-2) and IL-2 receptor expression. Transformation can be reversed entirely by elimination of the parasites using the specific drug BW720c. Extracellular signal-regulated kinase and jun NH2-terminal kinase (JNK) are members of the mitogen-activated protein kinase family, which play a central role in the regulation of cellular differentiation and proliferation and also participate in the regulation of IL-2 and IL-2 receptor gene expression. T. parva was found to induce an unorthodox pattern of mitogen-activated protein kinase expression in infected T cells. JNK-1 and JNK-2 are constitutively active in a parasite-dependent manner, but have altered properties. In contrast, extracellular signal-regulated kinase-2 is not activated even though its activation pathway is functionally intact. Different components of the T cell receptor (TCR)-dependent signal transduction pathways also were examined. The TCRzeta or CD3epsilon chains were found not to be phosphorylated and T. parva-transformed T cells were resistant to inhibitors that block the early steps of T cell activation. Compounds that inhibit the progression of T cells to proliferation, however, were inhibitory. Our data provide the first example, to our knowledge, for parasite-mediated JNK activation, and our findings strongly suggest that T. parva not only lifts the requirement for antigenic stimulation but also entirely bypasses early TCR-dependent signal transduction pathways to induce continuous proliferation.

Neurotoxic consequences of central long-term administration of interleukin-2 in rats

Interleukin-2 is an immunoregulatory cytokine with several recently established CNS activities. Central effects of interleukin-2 include growth promotion for neuronal and glial cells as well as modulatory influences on neurotransmission and hormone release. However, little is known about the consequences in the CNS of chronically elevated levels of interleukin-2. Alterations in the interleukin-2/interleukin-2 receptor system are not only associated with CNS trauma, inflammation and certain neuropathologies; elevated interleukin-2 concentrations are especially induced during the therapeutic use of interleukin-2 in cancer treatments. In the present study, intracerebroventricular (i.c.v.) interleukin-2 infusions (5–15 U/h) were performed in Sprague–Dawley rats for up to 14 days. Interleukin-2-treated animals showed significantly increased plasma levels of corticosterone indicating an hyperfunctioning of the hypothalamic–pituitary–adrenocortical axis that lasted over the 14 day infusion period. Moreover, the performance of interleukin-2-treated animals in the Morris swim maze task was transiently impaired. Quantitative receptor autoradiographic analyses revealed changes in the binding levels of cholinergic M 1 and M 2 as well as dopaminergic D 1 and D 2 receptors in selected brain areas in which interleukin-2 was shown to modulate neurotransmission and which are enriched with interleukin-2 receptor expression. Decreased receptor binding levels were observed in the frontoparietal cortex (M 2, D 1, D 2), hippocampal CA1 region (M 1, M 2) and the nucleus accumbens (D 2). Histological and immunohistochemical examination of the brains of interleukin-2-treated animals revealed multiple alterations. Interleukin-2 treatment resulted in an intracranial accumulation of non-neural, MHC class II-positive cells as well as T and B lymphocytes within the infused brain hemisphere. Cellular infiltrates were associated with angiogenesis and the deposition of extracellular matrix material, such as fibronectin. Adjacent brain regions that were partly invaded and dislodged by the cellular masses were characterized by reactive astrogliosis, microglial activation, endothelial upregulation of adhesion molecules, myelin damage and neuronal loss. Together the data suggest that persistently elevated central levels of interleukin-2 can interfere with several CNS functions and may lead to nervous tissue injury. These findings could be relevant to CNS pathologies characterized by abnormal interleukin-2 production and to central responses to interleukin-2 treatments.

Increased expression of interleukin-2 receptor alpha on peripheral blood mononuclear cells in HTLV-I tax/rex mRNA-positive asymptomatic carriers.

Using the double-nested reverse transcription-polymerase chain reaction, we assayed human T-cell leukemia virus type I (HTLV-I) tax/rex-encoded mRNA in the peripheral blood mononuclear cells (PBMCs) of asymptomatic carriers as an index of the expression of HTLV-I in vivo in relation to the proviral DNA level. HTLV-I tax/rex mRNA was detected in only 1 (3.3%) of 30 samples with medium or lower proviral DNA levels, but it was detected in 11 (39.3%) of 28 samples with high HTLV-I proviral DNA levels, estimated as equal to or more than the proviral DNA of 10 ng of HUT102 (i.e., HUT102 cells were used as positive controls). The mean number of interleukin-2 receptor alpha (IL-2R alpha)-positive cells as a percentage of the total number of PBMCs was higher (13.2%) in the tax/rex mRNA-positive carriers with high proviral DNA levels than in the carriers who were mRNA negative (8.4%) (p = 0.004, Wilcoxon test). These results suggest that virus activation as indicated by the presence of tax/rex mRNA in asymptomatic carriers with high proviral DNA levels is associated with an elevation of the IL-2R alpha-positive cells in vivo.

Different protein kinase C isoenzymes regulate interleukin-2 receptor expression and interleukin-2 synthesis in human lymphocytes stimulated via the T-cell antigen receptor

Different protein kinase C isoenzymes regulate interleukin-2 receptor expression and interleukin-2 synthesis in human lymphocytes stimulated via the T-cell antigen receptor

Staphylococcal enterotoxins modulate interleukin-2 receptor expression and ligand induced tyrosine phosphorylation of the Janus Kinase 3 (Jak3) and Stat proteins

Staphylococcal enterotoxins modulate interleukin-2 receptor expression and ligand induced tyrosine phosphorylation of the Janus Kinase 3 (Jak3) and Stat proteins

Different protein kinase C isoenzymes regulate interleukin-2 receptor expression and interleukin-2 synthesis in human lymphocytes stimulated via the T-cell antigen receptor

Different protein kinase C isoenzymes regulate interleukin-2 receptor expression and interleukin-2 synthesis in human lymphocytes stimulated via the T-cell antigen receptor

Staphylococcal enterotoxins modulate interleukin-2 receptor expression and ligand induced tyrosine phosphorylation of the Janus Kinase 3 (Jak3) and Stat proteins

Staphylococcal enterotoxins modulate interleukin-2 receptor expression and ligand induced tyrosine phosphorylation of the Janus Kinase 3 (Jak3) and Stat proteins

Intermediate Affinity Interleukin-2 Receptor Mediates Survival via a Phosphatidylinositol 3-Kinase-dependent Pathway

Peripheral blood T lymphocytes require two signals to enter and progress along the cell cycle from their natural quiescent state. The first activation signal is provided by the stimulation through the T cell receptor, which induces the synthesis of cyclins and the expression of the high affinity interleukin-2 receptor. The second signal, required to enter the S phase, is generated upon binding of interleukin-2 to the high affinity alphabetagamma interleukin-2 receptor. However, resting T cells already express intermediate affinity betagamma interleukin-2 receptors. As shown here, T cell stimulation through intermediate affinity receptors is capable of inducing cell rescue from the apoptosis suffered in the absence of stimulation. Characterization of the signaling pathways utilized by betagamma interleukin-2 receptors in resting T cells, indicated that pp56(lck), but not Jak1 or Jak3, is activated upon receptor triggering. Compelling evidence is presented indicating that phosphatidylinositol 3-kinase associates with the intermediate affinity interleukin-2 receptor and is activated upon interleukin-2 addition. Bcl-xL gene was also found to be induced upon betagamma interleukin-2 receptor stimulation. Finally, pharmacological inhibition of phosphatidylinositol 3-kinase blocked both interleukin-2-mediated bcl-xL induction and cell survival. We conclude that betagamma interleukin-2 receptor mediates T-cell survival via a phosphatidylinositol 3-kinase-dependent pathway, possibly involving pp56(lck) and bcl-xL as upstream and downstream effectors, respectively.

T cell antigen receptor dependent signalling in human lymphocytes: cholera toxin inhibits interleukin-2 receptor expression but not interleukin-2 synthesis by preventing activation of a protein kinase C isotype, PKC- α

Activation and translocation of protein kinases C is a key event in the regulation of T lymphocyte activation, proliferation and function. Stimulation of human peripheral blood lymphocytes with the monoclonal antibody BMA 031 raised against the T cell antigen receptor led to a bimodal activation of protein kinases C. The immediate activation and translocation of the protein kinase C isoform PKC- α was followed by activation and translocation of the protein kinase C- β isoenzyme after 90 min of stimulation. Pretreatment of the cells with cholera toxin for 90 min completely abolished activation of protein kinase C- α. In sharp contrast, activation and translocation of protein kinase C- β was not influenced by the bacterial toxin, suggesting that activation and translocation of different protein kinase C isoenzymes are regulated by distinct mechanisms of transmembrane signalling coupled to the T cell antigen receptor/CD3 complex. The expression of high affinity IL-2 receptors was completely inhibited by cholera toxin, while IL-2 synthesis and secretion were not influenced in BMA 031-stimulated human lymphocytes. Extensive control experiments have shown that the effects of cholera toxin were not mediated by its B subunit, and were independent of elevation of intracellular cAMP concentration, suggesting that cholera toxin interfered with a signalling pathway leading to activation of protein kinase C- α, which could be responsible for the inhibition of IL-2 receptor expression. This hypothesis was substantiated by the finding that upon introduction of antibodies against protein kinase C- α, IL-2 receptor gene expression was completely suppressed. The results suggest, that protein kinase C- α might be the major protein kinase C isoenzyme of a signal transduction cascade regulating IL-2 receptor expression in stimulated human lymphocytes. © 1997 Elsevier Science B.V. All rights reserved.

Defective interleukin-2 production in children with chronic hepatitis B: role of adherent cells.

Chronic hepatitis B (CHB) virus infection is associated with functional abnormalities of cell-mediated immunity, defective interferons alpha and gamma synthesis, and interleukin-2 receptor expression. In this study, interleukin-2 (IL-2) production and the role of adherent cells was evaluated in 25 children chronically infected with hepatitis B virus. IL-2 activity was measured by bioassay in supernatants of phytohemoagglutinin-stimulated peripheral blood mononuclear cells. In a few patients, IL-2 concentration was also immunochemically determined. Coculture experiments using a mixture of adherent cells and lymphocytes from healthy children and patients with CHB were also performed. Children with CHB showed lower IL-2 production than healthy controls. In patients, IL-2 activity was 34.7 +/- 22.5 U/ml as compared to 152.6 +/- 78.5 U/ml of controls. Immunochemical quantitation of IL-2 confirmed a lower IL-2 production in patients. No correlation was found between the functional T-cell defect and the severity of liver damage, degree of viral replication, and duration of the disease. In co-culture experiments, adherent cells from HBsAg-positive patients inhibited IL-2 production following mitogen stimulation of control non-adherent cells by 67%. The inhibitory effect, mediated by patients adherent cells, was abolished by blocking with indomethacin prostaglandins, that are potent local immunomodulators released by adherent cells. Our results further support the observation that in children with CHB virus infection adherent cells play an important role in the inappropriate regulation of immune response, an effect being likely mediated by prostaglandins.