Whole blood interleukin-2 release test to detect and characterize rare circulating gluten-specific T cell responses in coeliac disease

Whole blood cytokine release assays (CRA) assessing cellular immunity to gluten could simplify the diagnosis and monitoring of coeliac disease (CD). We aimed to determine the effectiveness of electrochemiluminescence CRA to detect responses to immunodominant gliadin peptides. HLA-DQ2·5⁺ CD adults (cohort 1, n = 6; cohort 2, n = 12) and unaffected controls (cohort 3, n = 9) were enrolled. Cohort 1 had 3-day gluten challenge (GC). Blood was collected at baseline, and for cohort 1 also at 3 h, 6 h and 6 days after commencing 3-day GC. Gliadin peptide-stimulated proliferation, interferon (IFN)-γ enzyme-linked immunospot (ELISPOT) and 14- and 3-plex electrochemiluminescence CRA were performed. Poisson distribution analysis was used to estimate responding cell frequencies. In cohort 1, interleukin (IL)-2 dominated the gliadin peptide-stimulated cytokine release profile in whole blood. GC caused systemic IL-2 release acutely and increased gliadin peptide-stimulated IFN-γ ELISPOT and whole blood CRA responses. Whole blood CRA after GC was dominated by IL-2, but also included IFN-γ, C-X-C motif chemokine ligand 10/IFN-γ-induced protein 10 (CXCL10/IP-10), CXCL9/monokine induced by IFN-γ (MIG), IL-10, chemokine (C-C motif) ligand 3/macrophage inflammatory protein 1-alpha (CCL3/MIP-1α), TNF-α and IL-8/CXCL8. In cohorts 2 and 3, gliadin peptide-stimulated whole blood IL-2 release was 100% specific and 92% sensitive for CD patients on a gluten-free diet; the estimated frequency of cells in CD blood secreting IL-2 to α-gliadin peptide was 0·5 to 11 per ml. Whole blood IL-2 release successfully mapped human leucocyte antigen (HLA)-DQ2·5-restricted epitopes in an α-gliadin peptide library using CD blood before and after GC. Whole blood IL-2 release assay using electrochemiluminescence is a sensitive test for rare gliadin-specific T cells in CD, and could aid in monitoring and diagnosis. Larger studies and validation with tetramer-based assays are warranted.

Serum cytokines elevated during gluten-mediated cytokine release in coeliac disease

Cytokines have been extensively studied in coeliac disease, but cytokine release related to exposure to gluten and associated symptoms has only recently been described. Prominent, early elevations in serum interleukin (IL)-2 after gluten support a central role for T cell activation in the clinical reactions to gluten in coeliac disease. The aim of this study was to establish a quantitative hierarchy of serum cytokines and their relation to symptoms in patients with coeliac disease during gluten-mediated cytokine release reactions. Sera were analyzed from coeliac disease patients on a gluten free-diet (n = 25) and from a parallel cohort of healthy volunteers (n = 25) who underwent an unmasked gluten challenge. Sera were collected at baseline and 2, 4 and 6 h after consuming 10 g vital wheat gluten flour; 187 cytokines were assessed. Confirmatory analyses were performed by high-sensitivity electrochemiluminescence immunoassay. Cytokine elevations were correlated with symptoms. Cytokine release following gluten challenge in coeliac disease patients included significant elevations of IL-2, chemokine (C-C motif) ligand 20 (CCL20), IL-6, chemokine (C-X-C motif) ligand (CXCL)9, CXCL8, interferon (IFN)-γ, IL-10, IL-22, IL-17A, tumour necrosis factor (TNF)-α, CCL2 and amphiregulin. IL-2 and IL-17A were earliest to rise. Peak levels of cytokines were generally at 4 h. IL-2 increased most (median 57-fold), then CCL20 (median 10-fold). Cytokine changes were strongly correlated with one another, and the most severely symptomatic patients had the highest elevations. Early elevations of IL-2, IL-17A, IL-22 and IFN-γ after gluten in patients with coeliac disease implicates rapidly activated T cells as their probable source. Cytokine release after gluten could aid in monitoring experimental treatments and support diagnosis.

Efficacy and safety of colesevelam in combination with pioglitazone in patients with type 2 diabetes mellitus

Colesevelam improves glycemic control in patients with type 2 diabetes when added to existing metformin-, sulfonylurea-, or insulin-based regimens. We evaluated colesevelam's effects in subjects on stable pioglitazone-based therapy. This 24-week multicenter, double-blind, randomized, placebo-controlled study enrolled adults with type 2 diabetes who had suboptimal glycemic control [HbA1c ≥ 58 mmol/mol (7.5%) and ≤ 80 mmol/mol (9.5%)] on pioglitazone (30 or 45 mg) with or without 1-2 other oral antidiabetes medications. Subjects were randomized to colesevelam 3.8 g/day (n = 280) or placebo (n = 282) added to existing pioglitazone-based therapy. Primary efficacy variable was mean change in HbA1c from baseline to Week 24. Secondary variables included safety and tolerability, fasting plasma glucose changes, glycemic responses, and lipid profile. Tertiary variables included lipid particle profile changes by nuclear magnetic resonance. Colesevelam decreased HbA1c [least-squares mean treatment difference, - 3.5 mmol/mol (- 0.32%); p < 0.001] and fasting plasma glucose (- 14.7 mg/dl; p<0.001) vs. placebo at Week 24. More subjects receiving colesevelam vs. placebo achieved HbA1c reduction ≥ 7.7 mmol/mol (0.7%) (40% vs. 25%; p<0.001) or HbA1c < 53 mmol/mol (7.0%) (21% vs. 13%; p = 0.012). Colesevelam also decreased total cholesterol (mean treatment difference, - 6.5%), LDL-cholesterol (- 16.4%), non-HDL-cholesterol (- 9.8%), apolipoprotein B (- 8.8%), and total LDL particle concentration, and increased apolipoprotein A1 (+3.4%) and triglycerides (median treatment difference, + 11.3%) vs. placebo (all p < 0.001). There were no serious drug-related adverse events, and the majority of adverse events were mild or moderate. In subjects with type 2 diabetes inadequately controlled with pioglitazone-based therapy, add-on colesevelam therapy improved glycemic control and lipid parameters and was well tolerated. ClinicalTrials.gov identifier: NCT00789750.

A 26-week, placebo- and pioglitazone-controlled monotherapy study of rivoglitazone in subjects with type 2 diabetes mellitus

AIMS

To evaluate the efficacy and safety of rivoglitazone, a peroxisome proliferator-activated receptor γ agonist in the thiazolidinedione class, in subjects with suboptimally controlled type 2 diabetes mellitus (T2DM).

METHODS

Subjects aged ≥18 years with T2DM and haemoglobin A1c (HbA1c) >7.0% and ≤8.5%, who were treatment naïve or receiving a non-thiazolidinedione antidiabetes monotherapy, entered a 2-week washout and single-blind placebo run-in period and were then randomized 2 : 4 : 11 : 11 to double-blind treatment with placebo, rivoglitazone 1.0 mg/day, rivoglitazone 1.5 mg/day, or pioglitazone 45 mg/day, for 26 weeks.

RESULTS

A total of 1912 subjects received placebo (n = 137), rivoglitazone 1.0 mg (n = 274), rivoglitazone 1.5 mg (n = 750) or pioglitazone (n = 751). Rivoglitazone 1.5 mg was statistically superior (p = 0.0339) and rivoglitazone 1.0 mg was non-inferior (p = 0.0339) to pioglitazone in reducing HbA1c from baseline (changes of -0.7%, -0.4% and -0.6%, respectively). Rivoglitazone also significantly reduced fasting plasma glucose from baseline (p < 0.0001). Rivoglitazone significantly improved estimates of insulin sensitivity, high-density lipoprotein cholesterol levels, and other metabolic and inflammatory biomarkers. Rivoglitazone was generally well tolerated at both doses, with treatment-emergent adverse event (TEAE) rates similar to pioglitazone. The most common drug-related TEAEs were peripheral oedema (active, 5.2-6.2%; placebo 0.7%), increased weight (active, 1.6-3.1%; placebo, 0%) and pitting oedema (active, 1.3-2.2%; placebo, 0%).

CONCLUSIONS

In subjects with suboptimally controlled T2DM, rivoglitazone 1.5 mg was associated with statistically superior glycaemic control to pioglitazone 45 mg, while rivoglitazone 1.0 mg was non-inferior; the safety profiles of the two drugs appeared similar.

Long-term Safety and Tolerability of Colesevelam HCl in Subjects with Type 2 Diabetes

The bile acid sequestrant, colesevelam hydrochloride, is approved for glycemic control in adults with type 2 diabetes. In three double-masked, placebo-controlled studies, colesevelam hydrochloride 3.75 g/day demonstrated its glycemic-lowering properties when added to existing metformin-, insulin-, or sulfonylurea-based therapy in adults with inadequately controlled type 2 diabetes. This was a 52-week open-label extension study conducted at 63 sites in the United States and one site in Mexico to further evaluate the safety and tolerability of colesevelam hydrochloride in subjects with type 2 diabetes. All subjects who completed the three double-masked, placebo-controlled studies were eligible to enroll in this open-label extension. In total, 509 subjects enrolled and received open-label colesevelam hydrochloride 3.75 g/day for 52 weeks. Safety and tolerability of colesevelam hydrochloride was evaluated by the incidence and severity of adverse events. In total, 360 subjects (70.7%) completed the extension. Of the safety population, 361 subjects (70.9%) experienced an adverse event, most (88.1%) being mild or moderate in severity. Fifty-six adverse events (11.0%) were drug-related; the most frequent drug-related adverse events were constipation and dyspepsia. Thirty-five subjects (6.9%) discontinued due to an adverse event. Fifty-four subjects (10.6%) experienced a serious adverse event; only one was considered drug-related (diverticulitis). Seventeen subjects (3.3%) experienced hypoglycemia; most episodes were mild or moderate in severity. Glycemic improvements with colesevelam hydrochloride were seen without change in weight over 52 weeks (0.2 kg mean reduction from baseline). Colesevelam hydrochloride was safe and well-tolerated as long-term therapy for patients with type 2 diabetes.

A multicenter, randomized, controlled trial to evaluate the safety profile, tolerability, and efficacy of rofecoxib in advanced elderly patients with osteoarthritis

This 6-week study was conducted to test the efficacy, safety, and tolerability of rofecoxib (a selective COX-2 inhibitor) compared to nabumetone (a non-selective NSAID) and placebo in osteoarthritis (OA) patients aged 80 and older. Three hundred forty-one patients, mean age 83 years, were randomized. Allocations were made in an approximately 1:2:1:2 ratio (placebo: 12.5 mg rofecoxib: 25 mg rofecoxib: 1500 mg nabumetone). Least square mean changes from baseline in the primary efficacy endpoint, Patient Global Assessment of Disease Status, were as follows (with negative numbers indicating improvement): -14.85 mm for placebo; -25.34 mm for 12.5 mg rofecoxib; -25.40 mm for 25 mg of rofecoxib; and -25.95 mm for nabumetone (p<0.001 for all active treatments vs placebo.) Results from secondary endpoints, including the 3 WOMAC sub-scales (pain, stiffness, and disability) and the Investigator Global Assessment of Disease Status, were consistent with those for the primary endpoint. No significant between-group differences were observed in the proportions of patients who discontinued treatment due to either clinical or laboratory adverse experiences. Renal safety (edema and hypertension adverse experiences) was similar for rofecoxib and nabumetone. No gastroduodenal ulcers occurred; however, the demonstration of gastrointestinal risk with rofecoxib or nabumetone was beyond the scope of this trial. We conclude that in patients 80 years and older, rofecoxib, 12.5 mg and 25 mg once daily, demonstrated clinical efficacy for the treatment for OA as did 1500 mg of nabumetone. Rofecoxib and nabumetone were generally well tolerated in this elderly population.

Identification of tyrosine phosphorylation sites in the CD28 cytoplasmic domain and their role in the costimulation of Jurkat T cells

The cytoplasmic domain of CD28 contains four tyrosine residues. Because signal transduction by CD28 appears to involve its tyrosine phosphorylation, we determined sites of CD28 tyrosine phosphorylation using mutants of mouse CD28 that retained tyrosine at one position, with the remaining three positions mutated to phenylalanine. When expressed in Jurkat cells and stimulated by mAb, only the mutants with tyrosine at position 170 or 188 were tyrosine phosphorylated. Phosphorylation of Tyr170 recruits phosphatidylinositol 3-kinase to CD28. Tyr188 has not been associated with any specific signaling event, but we found that ligation of CD28 by the natural ligand B7.2 also induced phosphorylation of Tyr188, suggesting that this event is of physiological importance. Consistent with that possibility, mutation of Tyr188 to phenylalanine severely impaired the ability of mouse CD28 to deliver a costimulus for the expression of CD69 and the production of IL-2. The functional consequences of the mutation of Tyr188 were unique; mutation of the other three tyrosines, individually or in combination, did not impair costimulation. Therefore, of the four CD28 tyrosine residues only Tyr188 is required for signaling in Jurkat cells, suggesting that its phosphorylation is a key event in the costimulation of T cells.

Mutational analysis of CD28-mediated costimulation of Jun-N-terminal kinase and IL-2 production

The accessory molecule CD28 delivers a costimulus that acts in concert with TCR signals to promote T cell activation. Activation of Jun-N-terminal kinases (JNK) requires simultaneous stimulation of the TCR and CD28 and, therefore, likely plays an important role in signal integration during costimulation. We investigated the effects of mutations in the 41-amino acid cytoplasmic domain of murine CD28 on its ability to deliver costimuli for JNK activation and IL-2 production when expressed in Jurkat T cells. Our results indicate that the costimulus for JNK activation requires the membrane-proximal 24 amino acids of the CD28 cytoplasmic domain and is not mediated by the tyrosine-based recruitment of signaling molecules, including phosphatidylinositol 3-kinase. Deletion of the carboxyl-terminal 17 amino acids does not affect the ability of CD28 to augment JNK activation but impairs its ability to enhance TCR-mediated production of IL-2, demonstrating that optimal costimulation of IL-2 production requires CD28 signals in addition to the activation of JNK.

CD28 mediates transcriptional upregulation of the interleukin-2 (IL-2) promoter through a composite element containing the CD28RE and NF-IL-2B AP-1 sites

Mutagenesis studies have demonstrated the requirement for the CD28-responsive element (CD28RE) within the interleukin-2 (IL-2) promoter for transcriptional upregulation by CD28. Here, we demonstrate that CD28 responsiveness is conferred by a composite element containing both the CD28RE and the NF-IL-2B AP-1 sites (RE/AP). Mutations at either site within the RE/AP composite element abolish activity. The RE/AP composite element is a site for signal integration within the IL-2 promoter, since its activation is dependent on at least two separate signalling pathways being activated, through the T-cell receptor, CD28, and/or phorbol myristate acetate. Activation is maximal when all three signals occur simultaneously. By using a panel of CD28 cytoplasmic domain mutants, it was found that the transcriptional activation of the RE/AP composite element correlates exactly with the pattern of IL-2 secretion induced by these mutants upon stimulation. Similar to the upregulation of IL-2 secretion, the transcriptional upregulation of the RE/AP composite element by CD28 is FK506 insensitive. The pattern of activation of the RE/AP composite element is different from that observed for either an NFAT or consensus AP-1 site, implying that RE/AP represents a unique element. Using gel shift analysis, we demonstrate that stimulation by CD28 induces the association of the NF-kappaB family member c-Rel to the CD28RE within the RE/AP composite element. The transcriptional upregulation of IL-2 by CD28 appears, therefore, to be mediated through the RE/AP composite element, involving the association of c-Rel with the CD28RE.

Wortmannin, a phosphatidylinositol 3-kinase inhibitor, blocks antigen-mediated, but not CD3 monoclonal antibody-induced, activation of murine CD4+ T cells

Perturbation of several distinct T cell molecules, including the CD3/TCR complex, CD7, and CD28, activates phosphatidylinositol 3-kinase (PI3-K), but a clear consensus on the role of PI3-K in T cell activation has yet to emerge. We report here that CD3 mAb-induced IL-2 production by CD4+ T cells from DO11.10 TCR-alphabeta-transgenic mice is refractory to the potent PI3-K inhibitor, wortmannin, demonstrating that activation under these conditions is independent of PI3-K. In marked contrast, wortmannin substantially inhibits IL-2 production elicited by Ag (OVA(323-339) peptide) presented by appropriate APCs (syngeneic B7+ B cell blasts) and blocks Ag-induced differentiation of naive CD4+ DO11.10 T cells into IL-4-producing cells. Wortmannin inhibits Ag-induced conjugate formation between T cells and B7+ B cell blasts. Because T cell activation by Ag requires stable interactions with APCs, this inhibitory effect on conjugate formation may underlie the ability of wortmannin to block Ag-induced IL-2 production and differentiation.

Wortmannin, a phosphatidylinositol 3-kinase inhibitor, blocks antigen-mediated, but not CD3 monoclonal antibody-induced, activation of murine CD4+ T cells

Perturbation of several distinct T cell molecules, including the CD3/TCR complex, CD7, and CD28, activates phosphatidylinositol 3-kinase (PI3-K), but a clear consensus on the role of PI3-K in T cell activation has yet to emerge. We report here that CD3 mAb-induced IL-2 production by CD4+ T cells from DO11.10 TCR-alphabeta-transgenic mice is refractory to the potent PI3-K inhibitor, wortmannin, demonstrating that activation under these conditions is independent of PI3-K. In marked contrast, wortmannin substantially inhibits IL-2 production elicited by Ag (OVA(323-339) peptide) presented by appropriate APCs (syngeneic B7+ B cell blasts) and blocks Ag-induced differentiation of naive CD4+ DO11.10 T cells into IL-4-producing cells. Wortmannin inhibits Ag-induced conjugate formation between T cells and B7+ B cell blasts. Because T cell activation by Ag requires stable interactions with APCs, this inhibitory effect on conjugate formation may underlie the ability of wortmannin to block Ag-induced IL-2 production and differentiation.

Structural requirements for CD28-mediated costimulation of IL-2 production in Jurkat T cells

Although under certain conditions an association with phosphatidylinositol 3'-kinase (PI3-K) appears to be critical for CD28 signaling, mutation of the PI3-K binding site (Tyr 170) does not alter the costimulatory ability of murine CD28 (mCD28) in Jurkat T cells. To define the structural requirements for this PI3-K-independent signaling, we expressed a series of mCD28 mutants in Jurkat. Mutation to Phe of all four cytoplasmic Tyr residues together (ALL F mutant) greatly reduced the ability of mCD28 to augment IL-2 production. Isolated re-constitution of Tyr 188, but not 170, 185, or 197, restored the ability of ALL F mCD28 to deliver a costimulus. Thus, a signal based upon Tyr 188 can deliver a costimulus for the enhancement of IL-2 production by Jurkat cells.

Structural requirements for CD28-mediated costimulation of IL-2 production in Jurkat T cells

Although under certain conditions an association with phosphatidylinositol 3'-kinase (PI3-K) appears to be critical for CD28 signaling, mutation of the PI3-K binding site (Tyr 170) does not alter the costimulatory ability of murine CD28 (mCD28) in Jurkat T cells. To define the structural requirements for this PI3-K-independent signaling, we expressed a series of mCD28 mutants in Jurkat. Mutation to Phe of all four cytoplasmic Tyr residues together (ALL F mutant) greatly reduced the ability of mCD28 to augment IL-2 production. Isolated re-constitution of Tyr 188, but not 170, 185, or 197, restored the ability of ALL F mCD28 to deliver a costimulus. Thus, a signal based upon Tyr 188 can deliver a costimulus for the enhancement of IL-2 production by Jurkat cells.

CD28 delivers costimulatory signals independently of its association with phosphatidylinositol 3-kinase

CD28, a cell-surface molecule expressed by T cells, delivers costimulatory signals during the activation of T cells by Ag. Stimulation of CD28 induces its association with phosphatidylinositol 3'-kinase (PI3-K), raising the possibility that PI3-K plays a critical role in CD28 signaling. We find, however, that wortmannin, a potent inhibitor of PI3-K, does not block CD28-mediated costimulation of Jurkat (a human T cell line) or of murine CD4+ T cells. To address further the role of PI3-K in CD28-mediated signaling, we expressed mutant murine CD28 molecules in Jurkat cells. Mutation of Tyr 170 of murine CD28 to Phe abrogates the association of murine CD28 with PI3-K but does not affect the ability of murine CD28 to augment IL-2 production by Jurkat cells in response to the combination of ionomycin and PMA. Conversely, a mutant of murine CD28 that has a Tyr at position 170 but has Phe substitutions at the remaining three cytoplasmic tyrosines retains the ability to associate with PI3-K and has an impaired ability to deliver a costimulus that augments IL-2 production. CD28, therefore, can deliver costimulatory signals independently of its interaction with PI3-K, and association with PI3-K is insufficient to mediate the full effector function of CD28. Optimal signaling by CD28 requires the integrity of one or more of the carboxyl-terminal three Tyr residues.

CD28 delivers costimulatory signals independently of its association with phosphatidylinositol 3-kinase

CD28, a cell-surface molecule expressed by T cells, delivers costimulatory signals during the activation of T cells by Ag. Stimulation of CD28 induces its association with phosphatidylinositol 3'-kinase (PI3-K), raising the possibility that PI3-K plays a critical role in CD28 signaling. We find, however, that wortmannin, a potent inhibitor of PI3-K, does not block CD28-mediated costimulation of Jurkat (a human T cell line) or of murine CD4+ T cells. To address further the role of PI3-K in CD28-mediated signaling, we expressed mutant murine CD28 molecules in Jurkat cells. Mutation of Tyr 170 of murine CD28 to Phe abrogates the association of murine CD28 with PI3-K but does not affect the ability of murine CD28 to augment IL-2 production by Jurkat cells in response to the combination of ionomycin and PMA. Conversely, a mutant of murine CD28 that has a Tyr at position 170 but has Phe substitutions at the remaining three cytoplasmic tyrosines retains the ability to associate with PI3-K and has an impaired ability to deliver a costimulus that augments IL-2 production. CD28, therefore, can deliver costimulatory signals independently of its interaction with PI3-K, and association with PI3-K is insufficient to mediate the full effector function of CD28. Optimal signaling by CD28 requires the integrity of one or more of the carboxyl-terminal three Tyr residues.

Stimulation of CD28 triggers an association between CD28 and phosphatidylinositol 3-kinase in Jurkat T cells

The T cell surface molecule CD28 can provide costimulatory signals that permit the full activation of T cells. Here we demonstrate that stimulation of CD28, either by B7, its natural ligand, or by the anti-CD28 monoclonal antibody 9.3, induces an association between CD28 and phosphatidylinositol 3-kinase (PI3-K) in Jurkat T cells, raising the possibility that an interaction with PI3-K contributes to CD28-mediated signaling. To examine the mechanism of the association, we synthesized tyrosine-phosphorylated oligopeptides corresponding to each of the four tyrosines in the CD28 cytoplasmic domain. When added to lysates of B7-stimulated Jurkat cells, the oligopeptide corresponding to Tyr 173 inhibits the coimmunoprecipitation of PI3-K with CD28; the other oligopeptides have no effect. Tyr 173 is contained within the sequence YMNM, a motif that is also found in the platelet-derived growth factor receptor and that, when phosphorylated, forms a high affinity binding site for the p85 subunit of PI3-K. These observations suggest that phosphorylation of Tyr 173 may mediate the interaction between CD28 and PI3-K. However, because CD28 is not known to be phosphorylated, it remains possible that CD28 interacts with PI3-K through a mechanism independent of tyrosine phosphorylation.

SH2-dependent association of phosphatidylinositol 3'-kinase 85-kDa regulatory subunit with the interleukin-2 receptor beta chain

Interleukin-2 (IL-2) signaling results in tyrosine phosphorylation of the 75-kDa IL-2 receptor (IL-2R) beta chain and the activation of phosphatidylinositol 3'-kinase (PI3-K). Herein, we demonstrate that the 85-kDa (p85) regulatory subunit of PI3-K physically associates with the tyrosine-phosphorylated IL-2R beta chain. A fusion protein containing both the amino- and the carboxyl-terminal src homology 2 domains of p85 precipitates an 80-kDa tyrosine-phosphorylated protein (pp80) from the lysates of IL-2-stimulated, but not unstimulated, human T lymphoblasts. Preclearing studies and immunoblotting with an antiserum to the IL-2R beta chain demonstrates that pp80 represents a portion of the IL-2R beta chain pool. A tyrosine-phosphorylated oligopeptide corresponding to tyrosine 392 of the IL-2R beta chain partially inhibits binding of the IL-2R beta chain by p85 fusion protein, raising the possibility that this residue plays a role in the interaction of PI3-K with the receptor.

Transmembrane signaling by the interleukin-2 receptor: progress and conundrums

Activation of the multicomponent interleukin-2 receptor (IL-2R) complex leads to a rapid increase in tyrosine phosphorylation of a number of cellular proteins including the IL-2R beta and IL-2R gamma chains of the IL-2R and the RAF-1 serine threonine kinase. In addition, phosphatidylinositol 3-kinase (PI-3K) protein and activity can be immunoprecipitated with anti-phosphotyrosine and anti-IL-2R beta antibodies from IL-2-activated but not resting T lymphocytes. We have demonstrated that the SH2 (SRC homology 2) domains of the 85 kDa subunit of PI-3K are sufficient to mediate binding of the PI-3K complex to tyrosine phosphorylated, but not non-phosphorylated IL-2R beta, suggesting that tyrosine phosphorylation is an integral component of the activation of PI-3K by the IL-2R. Since none of the members of the IL-2R complex contains an intrinsic tyrosine kinase domain, IL-2-induced tyrosine phosphorylation must be the consequence of activation of intracellular tyrosine kinases. SRC family members including lck, lyn and fyn have been demonstrated to associate with IL-2R beta through binding of the kinase domain to the acidic domain of IL-2R beta. However, we have demonstrated that the serine rich (SD) region of the cytosolic domain of IL-2R beta is also required for association of a tyrosine kinase with the IL-2R complex and that IL-2 can induce proliferation and tyrosine phosphorylation in cell lines which lack the known SRC family kinases expressed by T lymphocytes. Thus members of other kinase families besides SRC may also be involved in mediating IL-2 signal transduction. Biochemical studies and studies of cells expressing mutant IL-2 receptors indicate that IL-2-induced tyrosine kinase activation initiates a complex signaling cascade. The cascade includes SRC family kinase members such as lck, fyn, and lyn, activation of Raf-1 and PI-3K, and ras, and increased expression of the fos, fra-1, and jun protooncogenes. In addition, ligation of the IL-2R leads to rapid increases in myc expression and more delayed increases in the expression of the cdc2 and cdk2 kinases and the cyclins through a tyrosine phosphorylation independent pathway. Whether other biochemical processes initiated by IL-2R ligation, including activation of the MAP2, p70S6 and p90RSK serine threonine kinases, activation of NF-kappa B, and increased expression of Raf-1, Pim-1, bcl-2, IL-2R alpha and IL-2R beta, are consequences of the IL-2-induced tyrosine kinase cascade remains to be determined.(ABSTRACT TRUNCATED AT 400 WORDS)

Production of human monoclonal antibody in mouse ascites

Human B-cell hybridomas were grown in nude mouse ascites. The growth of cells in ascites requires prior subcutaneous (SC) adaptation, but the amount of antibody harvested is 100-fold that produced in in vitro culture. The relative merits of in vitro versus in vivo production of human monoclonal antibodies are discussed.

Characterization of human hybridomas secreting antibody to tetanus toxoid

We have selected a thioguanine-resistant lymphoblastoid cell line (LTR228) that forms human-human hybrids with high efficiency. Fusions with peripheral B cells consistently yield one colony per 10(5) cells plated. To produce antitetanus monoclonal antibodies, we withdrew blood from persons who had recently received booster injections of tetanus toxoid. T cells were separated from peripheral mononuclear cells by 2-aminoethylisothiouronium bromide-induced rosette formation, given 1,500 rads (1 rad = 0.01 gray), and cultured in a 1:1 ratio with nonrosetting cells. After 3 days of pokeweed mitogen stimulation, heterokaryons were produced by a plate-fusion technique and cultured in Iscove's Dulbecco's minimal essential medium for 24 hr prior to hybrid selection. Colonies appeared after 10-14 days in hypoxanthine/azaserine supplemented medium. A direct binding enzyme-linked immunosorbent assay with specific tetanus toxoid inhibition identified positive wells. The hybridomas were cloned twice in soft agarose and by limiting dilution. The subcloned hybridomas double every 26 hr (vs. every 16 hr for LTR228) and produce 1-5 micrograms of specific IgG, kappa antibody per 10(6) cells per ml per 24 hr. All subclones (almost 200) continue to secrete antibody after 11 months of continuous culture. Twelve representative subclones have near tetraploid amounts of DNA. From hybridomas grown in 5-liter spinner flasks, milligram quantities of the IgG, kappa antibody were purified by staphylococcus protein A affinity chromatography. Specific antibody from hybridoma cultures protected mice injected with 1,000 times the LD50 of tetanus toxin. Our cell line and associated techniques should permit the production of therapeutically important human monoclonal antibodies.