Intraocular in vivo imaging of activated T-lymphocytes expressing green-fluorescent protein after stimulation with endotoxin.

BACKGROUND: Intravital microscopy allows imaging of specific cell populations in vivo. The value of this technique is well established, but would be enhanced if one could distinguish functional states of cells in vivo. Interleukin-2 (IL-2) is expressed upon stimulation of T-cells and is a commonly used marker for T-cell activation. This study tests the use of enhanced green fluorescent protein (GFP) as a reporter gene for interleukin-2 (IL-2) expression in vivo. METHODS: Characterization of mice that have the GFP gene under the control of IL-2 regulatory sequences has previously been published. Uveitis was induced by injection of E. coli endotoxin into the vitreous of these IL-2/GFPki transgenic mice. Four hours later, 3 microg of recombinant mouse IL-2 was injected into the anterior chambers of one group of mice. In vivo imaging of infiltrating cells in the iris stroma was performed with fluorescence microscopy at 6, 24, 48, and 72 h after endotoxin injection. The absolute number of fluorescent cells per mm2 was evaluated. RESULTS: Eyes with endotoxin-induced uveitis had cells that expressed GFP and were identifiable by intravital microscopy. The fluorescent cells were exclusively seen in the subset of cells that had infiltrated the iris stroma or arrested along the vascular endothelium. The number of GFP-positive infiltrating cells in the iris increased from undetectable at baseline to 0.5 cells/mm2 at 6 h and 1.3 cells/mm2 at 72 h. The animals that received endotoxin as well as IL-2 tended to have more GFP-positive cells at the 48-h and 72-h time points, but these differences were not statistically significant CONCLUSIONS: GFP is commonly used as a reporter gene for in vitro expression assays. The results presented here document that transgenic mice with GFP under the control of IL-2 regulatory elements can be used with intravital microscopy for in vivo expression assays that allow detection of activated T-cells at multiple time points within the same animal. This provides a novel method for temporal and spatial studies on the state of cell activation in inflammatory responses.

A positive regulatory role for Cbl family proteins in tumor necrosis factor-related activation-induced cytokine (trance) and CD40L-mediated Akt activation.

Tumor necrosis factor (TNF)-related activation-induced cytokine (TRANCE) is a TNF family member essential for osteoclast differentiation, and it induces the activation and survival of osteoclasts and mature dendritic cells. We recently demonstrated that TRANCE activates Akt via a mechanism involving TRANCE receptor (TRANCE-R)/RANK, TRAF6, and c-Src. Here, we show that TRANCE-R and CD40 recruit TRAF6, Cbl family-scaffolding proteins, and the phospholipid kinase phosphatidylinositol 3-kinase in a ligand-dependent manner. The recruitment of Cbl-b and c-Cbl to TRANCE-R is dependent upon the activity of Src-family kinases. TRANCE and CD40L-mediated Akt activation is defective in Cbl-b -/- dendritic cells, and CD40L-mediated Akt activation is defective in c-Cbl -/- B cells. These findings implicate Cbl family proteins as not only negative regulators of signaling but as positive modulators of TNF receptor superfamily signaling as well.

Cytokine response gene 8 (CR8) regulates the cell cycle G1-S phase transition and promotes cellular survival.

Cellular proliferation and survival are modulated by the expression of specific genes. Cytokine response gene 8 (CR8), which was originally cloned as an IL-2-induced gene in human T lymphocytes, encodes a basic helix--loop--helix (bHLH) transcription factor. The CR8 gene product is highly conserved among human, mouse and rat, and contains sequence motifs that distinguish it from other bHLH families. The CR8 gene is ubiquitously expressed, and CR8 gene expression is induced by both growth-promoting as well as growth-inhibitory stimuli. As bHLH proteins have been found to regulate both the G1-S phase cell cycle transition, as well as cellular survival, the effects of CR8 on these processes were investigated. Ectopic CR8 expression in asynchronous U2OS cell cultures reduces the percentage of cells in the cell cycle S phase, and also slows the entry of G1-synchronized cells into S phase. The prolonged G1 interval correlates with impaired elevation of cyclin E protein and prolonged p21 protein expression in G1. CR8 expression also protects U2OS cells from serum-withdrawal induced apoptosis. These results indicate that CR8 is an important modulator of both the G1-S phase cell cycle transition, and cellular survival.

Acquisition of CD80 (B7-1) by T cells.

Activation of T cells usually requires two signals. Signal 1 is mediated via a peptide-MHC on the APC; signal 2 is mediated via a costimulatory molecule on the APC surface. We demonstrate here that naive CD4(+) T cells actually acquire the costimulatory molecule CD80 (B7-1) from syngeneic APCs after activation. This phenomenon was demonstrated showing acquisition of CD80 by T cells from CD80/CD86 (B7-2) knockout mice, and by treating T cells with cyclohexamide to further rule out endogenous expression of CD80 by T cells. Moreover, no CD80 mRNA could be detected in T cells that had acquired CD80. The amount of acquisition of CD80 by T cells was shown to be directly related to both the strength of signal 1 and the amount of CD80 on the APC. Specificity of this acquisition was also shown by the lack of acquisition by T cells from CD28 knockout mice (implicating CD28 in this process), the lack of acquisition of CD40 (another molecule on the APC surface) by T cells, and confocal microscopy studies. We demonstrate for the first time that 1) naive T cells, following acquisition of CD80 from APCs, were themselves shown to be capable of acting as APCs; and 2) memory T cells that have acquired CD80 from APCs undergo apoptosis in the presence of increased levels of signal 1. Thus we demonstrate both immunostimulatory and immunoregulatory functions as a result of CD80 acquisition by different T cell populations.

Cbl-b regulates the CD28 dependence of T-cell activation.

Whereas co-stimulation of the T-cell antigen receptor (TCR) and CD28 triggers T-cell activation, stimulation of the TCR alone may result in an anergic state or T-cell deletion, both possible mechanisms of tolerance induction. Here we show that T cells that are deficient in the adaptor molecule Cbl-b (ref. 3) do not require CD28 engagement for interleukin-2 production, and that the Cbl-b-null mutation (Cbl-b(-/-)) fully restores T-cell-dependent antibody responses in CD28-/- mice. The main TCR signalling pathways, such as tyrosine kinases Zap-70 and Lck, Ras/mitogen-activated kinases, phospholipase Cgamma-1 and Ca2+ mobilization, were not affected in Cbl-b(-/-) T cells. In contrast, the activation of Vav, a guanine nucleotide exchange factor for Rac1/Rho/CDC42, was significantly enhanced. Our findings indicate that Cbl-b may influence the CD28 dependence of T-cell activation by selectively suppressing TCR-mediated Vav activation. Mice deficient in Cbl-b are highly susceptible to experimental autoimmune encephalomyelitis, suggesting that the dysregulation of signalling pathways modulated by Cbl-b may also contribute to human autoimmune diseases such as multiple sclerosis.

Altered thymic positive selection and intracellular signals in Cbl-deficient mice.

Cbl is the product of the protooncogene c-cbl and is involved in T cell antigen receptor (TCR)-mediated signaling. To understand the role of Cbl for immune system development and function, we generated a Cbl-deficient mouse strain. In Cbl-deficient mice, positive selection of the thymocytes expressing major histocompatibility complex class II-restricted transgenic TCR was significantly enhanced. Two factors may have contributed to the altered thymic selection. First, Cbl deficiency markedly up-regulated the activity of ZAP-70 and mitogen-activated protein kinases. The mitogen-activated protein kinase pathway was shown previously to be involved in thymic positive selection. Second, Cbl-deficient thymocytes expressed CD3 and CD4 molecules at higher levels, which consequently may increase the avidity of TCR/major histocompatibility complex/coreceptor interaction. Thus, Cbl plays a novel role in modulating TCR-mediated multiple signaling pathways and fine-tunes the signaling threshold for thymic selection.

Mice with a fluorescent marker for interleukin 2 gene activation.

Production of interleukin (IL)-2 by T lymphocytes is one of the earliest events during immune response. A mutant mouse strain was generated by replacing the IL-2 gene with a cDNA encoding green fluorescent protein (GFP). In this model, GFP fluorescence is readily detectable upon T cell activation and is mostly coexpressed with IL-2 at the single cell level. Thus, individual activated T cells can express the IL-2 gene biallelically. Upon stimulation through the T cell antigen receptor, CD4+ cells separate into distinct GFP+ and GFP- populations, both of which are capable of differentiating into either Th1 or Th2 effectors. These mice allow noninvasive detection of IL-2 production by single cells and analysis of the subsequent differentiative fate of these cells as an immune response develops.

Mechanisms of cellular cytotoxicity mediated by a recombinant antibody-IL2 fusion protein against human melanoma cells.

Functional characteristics were established for a genetically engineered fusion protein between human IL2 and mouse/human chimeric mAb 225 directed against human epidermal growth factor receptor (EGFR), aberrantly expressed on human melanoma cells. The emphasis of these studies was on the mechanism(s) of action by which the ch225-IL2 fusion protein mediated cytotoxic killing of human melanoma cells by different human immune effector cells. Ch225-IL2 fusion protein bound to human EGFR with the high affinity of the parental antibody, and was as active as the equivalent amount of rhIL2. Ch225-IL2 enhanced cellular cytotoxicity mediated by freshly separated PBMC, isolated natural killer (NK) cells and activated T cells against melanoma cell lines. NK cells, which constitutively express both Fc gamma RIII and IL2R, interacted with ch225-IL2, mainly through Fc gamma RIII, while the involvement of IL2R was secondary. However, the effect of ch225-IL2 on activated T cells was most likely mediated through IL2R. These results suggest that the genetically engineered ch225-IL2 fusion protein may become a potent immunotherapeutic agent capable of stimulating various immune effector populations to effectively kill human melanoma cells.

Therapeutic potential of chimeric and murine anti-(epidermal growth factor receptor) antibodies in a metastasis model for human melanoma.

On many tumors, high numbers of epidermal growth factor (EGF) receptors provide a target for antibody-mediated tumor therapy. We evaluate here the therapeutic potential of a mouse/human chimeric anti-(EGF receptor) antibody and compare it to the parental murine antibody in a xenograft model for metastatic melanoma. Our model is based on the human cell line M24met, which overexpresses the EGF receptor and metastasizes spontaneously in SCID mice. Both the chimeric anti-(EGF receptor) antibody (ch225) and the mouse monoclonal antibody (m225) exhibited saturable, high-affinity binding to M24met cells and were equivalent in their ability to target M24met tumors in mice. Neither anti-(EGF receptor) antibodies nor EGF modulated the growth of M24met cells in vitro. Further analysis revealed that the EGF receptor on these cells is not phosphorylated upon EGF binding, indicating an anomalous receptor on these cells. In antibody-dependent cellular cytotoxicity experiments, ch225 and m225 were potent mediators of M24met cytolysis by effector cells. Antibody-mediated cytotoxicity revealed a marked species preference, with ch225 activating human peripheral blood mononuclear cells and m225 activating mouse splenocytes and to a lesser degree mouse macrophages. Neither antibody mediated cytolysis in the presence of human complement. In SCID mice, m225 suppressed spontaneous metastasis considerably while ch225 had only a modest effect. Our data indicate that in the M24met melanoma tumor model, anti-(EGF receptor) antibodies suppress spontaneous metastasis solely by activating immune effector cells.

[Studies on efficacy and safety of panipenem/betamipron against infections in pediatrics and on its movement to cerebrospinal fluid including cases of penicillin-resistant Streptococcus pneumoniae meningitis].

The efficacy and the safety of panipenem/betamipron (PAPM/BP), a new carbapenem antibiotic against infections in pediatrics were studied. The obtain results are summarized as follows. 1. The transfer of PAPM/BP to cerebrospinal fluid (CSF) was studied in 2 cases of purulent meningitis. The PAPM/BP levels in CSF in a dose 26.1 mg/kg peaked at 3.21 micrograms/ml on sampling 30 minutes after administration, followed by decreasing gradually with the improvement in clinical symptoms and came to 0.86 micrograms/ml on the 12th day (30 minutes after administration). 2. PAPM/BP at dose levels of 50 mg/kg to 69 mg/kg a day (daily doses of 104 mg/kg, 175 mg/kg 4 times a day for 2 cases of purulent meningitis) was administered by intravenous drip infusion 3 times daily for 4 to 15 days to 2 cases of purulent meningitis (including 1 case of penicillin-resistant Streptococcus penumoniae meningitis), 3 cases of pneumonia, 2 cases of phlegmon, 2 cases of periproctal abscess and 2 cases of urinary tract infections for a total of 11 cases. As results, all the cases showed good responses including 5 excellent and 6 good responses. Bacteriological efficacies in all of the 9 eligible cases were assessed as "eradicated". 3. As for the safety, an increase in the platelet count and slight evaluation of GOT and GPT were seen in 1 case as abnormal changes in the laboratory findings, although no side-effect was observed. 4. The results above show that PAPM/BP is useful for the treatment of general infections in pediatrics and that a daily dose of about 60 mg/kg given in 3 divided doses in effective enough.(ABSTRACT TRUNCATED AT 250 WORDS)

[Pharmacokinetic and clinical studies of cefpirome in pediatric field].

We conducted a study on the pharmacokinetics and clinical application of cefpirome (CPR) in children. 1. A single intravenous injection of 20 mg/kg of CPR was given to a two-month-old boy, and the concentration of the drug in the blood was measured. Fifteen minutes after administration, the concentration was 53.3 micrograms/ml, and it gradually decreased thereafter, reaching a level of 5.18 micrograms/ml after 8 hours with a half-life in the plasma of 2.36 hours. 2. A single intravenous injection of 700 mg (50 mg/kg) of CPR and that of cefotaxime (CTX) were given to a girl with suppurative meningitis (3 years old, 14 kg, causative bacteria, Haemophilus influenzae), and concentrations of the drugs in plasma and cerebrospinal fluid after 1 hour were measured. On the second day of illness, the concentration of CTX in the plasma was 39.4 micrograms/ml and the concentration of desacetyl-CTX (D-CTX) was 25.2 micrograms/ml, while concentrations in the cerebrospinal fluid were 6.22 micrograms/ml (15.8%) for CTX and 3.94 micrograms/ml (15.6%) for D-CTX. On the third day of illness, concentration of CPR in the plasma was 59.3 micrograms/ml, while its concentration in the cerebrospinal fluid was 7.44 micrograms/ml (12.5%). 3. CPR was intravenously administered in daily dosages of 37.7-75.0 mg/kg in 2-3 portions for periods of 4-15 days to 2 patients with septicemia (causative bacteria, Klebsiella pneumoniae in 1 case and Escherichia coli in the other), 1 patient with bronchitis (K. pneumoniae), 9 patients with pneumonia (1 case of Staphylococcus aureus, 3 cases of H. influenzae, 2 cases of Haemophilus parainfluenzae, 1 case of K. pneumoniae + Pseudomonas cepacia, 2 cases of H. influenzae + Branhamella catarrhalis), 2 patients with cellulitis (1 case of S. aureus, 1 case, causative agent unknown), 1 patient with suppurative lymphadenitis (causative agent, unknown), 1 patient with staphylococcal scalded skin syndrome, 1 patient with renal abscess (causative agent, unknown), and 1 patient with a urinary tract infection (E. coli), for a total of 18 patients, with excellent results in 9 cases and good results in 9 cases, hence an efficacy rate of 100% was obtained. 4. As an accompanying side-effect, eruption was observed in 1 of the 18 patients, but when administration was discontinued, the symptom gradually receded, and it disappeared by the 4th day.(ABSTRACT TRUNCATED AT 400 WORDS)

Transcription of IL-2 receptor gene is stimulated by ATL-derived factor produced by HTLV-I(+) T cell lines.

In HTLV-I transformed T-cell lines established from the patients with adult T-cell leukemia (ATL), there is a constitutive activation of the normal IL-2 receptor (IL-2-R) gene. These cell lines continuously produce an ATL-derived factor (ADF), an IL-2-R inducing factor without IL-2 activity. ADF enhances the expression of the IL-2-R through the augmentation of the IL-2-R mRNA in the HTLV-I(+) T-cell line (ED) as well as the NK cell line cells (YT). In YT cells, the transcriptional initiation of the promoter of the IL-2-R gene was enhanced by ADF but not by IL-2. Production of ADF by HTLV-I(+) T-cell lines may be involved in the abnormal expression of IL-2-Rs on these cells.

Interleukin-2 receptor-inducing factor(s) in adult T cell leukemia.

The expression of the interleukin-2 receptor (IL-2-R) is regulated by transcriptional and post-transcriptional mechanisms. IL-2-R gene expression is induced by pharmacological agents including calcium ions, phorbol esters such as phorbol myristate acetate (PMA) and forskolin (FK), a direct activator of adenylate cyclase. HTLV-I(+) leukemic T cells and T cell lines from patients with adult T cell leukemia (ATL) continuously expressed IL-2-R without production of IL-2. However, there was no abnormality of the structural gene for IL-2-R in these cell lines as well as in fresh leukemic cells of ATL. We have detected that many HTLV-I(+) T4(+) T cell lines constitutively produce a non-IL-2 lymphokine named ATL-derived factor (ADF), which induced the expression of the high-affinity IL-2-R on a variety of cells including HTLV-I(+) T cells, myeloid leukemia cells and YT cells. IL-2-R-inducing agents such as ADF and FK were shown to induce elevation of the mRNA levels for IL-2-R through transcriptional enhancement of the IL-2-R gene. The possible involvement of IL-2-R-inducing cytokines in the physiological lymphocyte activation and the leukemogenesis in ATL and other T cell leukemias is discussed.