Jak3 selectively regulates Bax and Bcl-2 expression to promote T-cell development

Jak3-deficient mice display vastly reduced numbers of lymphoid cells. Thymocytes and peripheral T cells from Jak3-deficient mice have a high apoptotic index, suggesting that Jak3 provides survival signals. Here we report that Jak3 regulates T lymphopoiesis at least in part through its selective regulation of Bax and Bcl-2. Jak3-deficient thymocytes express elevated levels of Bax and reduced levels of Bcl-2 relative to those in wild-type littermates. Notably, up-regulation of Bax in Jak3-deficient T cells is physiologically relevant, as Jak3 Bax double-null mice have marked increases in thymocyte and peripheral T-cell numbers. Rescue of T lymphopoiesis by Bax loss was selective, as mice deficient in Jak3 plus p53 or in Jak3 plus Fas remained lymphopenic. However, Bax loss failed to restore proper ratios of peripheral CD4/CD8 T cells, which are abnormally high in Jak3-null mice. Transplantation into Jak3-deficient mice of Jak3-null bone marrow transduced with a Bcl-2-expressing retrovirus also improved peripheral T-cell numbers and restored the ratio of peripheral CD4/CD8 T cells to wild-type levels. The data support the concepts that Jak kinases regulate cell survival through their selective and cell context-dependent regulation of pro- and antiapoptotic Bcl-2 family proteins and that Bax and Bcl-2 play distinct roles in T-cell development.

Promotion of S-phase entry and cell growth under serum starvation by SAG/ROC2/Rbx2/Hrt2, an E3 ubiquitin ligase component: association with inhibition of p27 accumulation

The sensitive-to-apoptosis gene (SAG) was initially identified as a redox-inducible, apoptosis-protective protein and subsequently found to be the second family member of regulator of cullins (ROC)/RING box protein (Rbx)/Hrt, which acts as a component of E3 ubiquitin ligase. We report here that SAG promoted cell growth under serum starvation. Microinjection of SAG mRNA into quiescent NIH/3T3 cells induced S-phase entry as determined by [(3)H]-thymidine incorporation. Likewise, overexpression of SAG by either adenovirus infection of immortalized human epidermal keratinocytes (Rhek-1) or DNA transfection of SY5Y human neuroblastoma cells induced cell proliferation under serum starvation. Because cyclin-dependent kinase inhibitors (CKIs), including p21, p27, and p57, are degraded through the ubiquitin pathway, we tested whether SAG-induced cell growth is associated with CKI degradation. Although there was no significant difference in the levels of p21 and p57 between the vector controls and SAG-overexpressing cells, serum starvation induced 10- to 18-fold accumulation of p27 in control Rhek-1 cells. Accumulation of p27 was remarkably inhibited (only 2 to 5-fold) in SAG-infected cells. Inhibition of p27 accumulation was also observed in stably SAG-overexpressing SY5Y cells. Significantly, SAG-associated inhibition of p27 accumulation was largely abolished by the treatment with a proteasome inhibitor. In vivo binding of SAG and Skp2, an F-box protein that promotes p27 ubiquitination, was detected, and the binding was enhanced in SAG-overexpressing cells grown under serum starvation. Thus, SAG-induced growth with serum withdrawal appears to be associated with SAG-mediated p27 degradation. Mol. Carcinog. 30:37-46, 2001.

Disruption of the ARF transcriptional activator DMP1 facilitates cell immortalization, Ras transformation, and tumorigenesis

The DMP1 transcription factor induces the ARF tumor suppressor gene in mouse fibroblasts, leading to cell cycle arrest in a p53-dependent manner. We disrupted sequences encoding the DNA-binding domain of DMP1 in mouse embryonic stem cells and derived animals lacking the functional protein. DMP1-null animals are small at birth, and males develop more slowly than their wild-type littermates. Some adult animals exhibit seizures and/or obstuctive uropathy, each of unknown cause. The growth of explanted DMP1-null mouse embryo fibroblasts (MEFs) is progressively retarded as cells are passaged in culture on defined transfer protocols; but, unlike the behavior of normal cells, p19(ARF), Mdm2, and p53 levels remain relatively low and DMP1-null MEFs do not senesce. Whereas the establishment of cell lines from MEFs is usually always accompanied by either p53 or ARF loss of function, continuously passaged DMP1-null cells readily give rise to established 3T3 and 3T9 cell lines that retain wild-type ARF and functional p53 genes. Early-passage DMP1-null cells, like MEFs from either ARF-null or p53-null mice, can be morphologically transformed by oncogenic Ha-Ras (Val-12) alone. Splenic lymphocytes harvested from both DMP1-null and ARF-null mice exhibit enhanced proliferative responses in long-term cultures when stimulated to divide with antibody to CD3 and interleukin-2. Although only 1 of 40 DMP1-null animals spontaneously developed a tumor in the first year of life, neonatal treatment with dimethylbenzanthracene or ionizing radiation induced tumors of various histologic types that were not observed in similarly treated DMP1(+/+) animals. Karyotypic analyses of MEFs and lymphomas from DMP1-null animals revealed pseudodiploid chromosome numbers, consistent with the retention of wild-type p53. Together, these data suggest that ARF function is compromised, but not eliminated, in animals lacking functional DMP1.

Phospholipase Cgamma2 is essential in the functions of B cell and several Fc receptors

Many receptors activate phospholipase Cgamma1 or -gamma2. To assess the role of PLCgamma2, we derived enzyme-deficient mice. The mice are viable but have decreased mature B cells, a block in pro-B cell differentiation, and B1 B cell deficiency. IgM receptor-induced Ca2+ flux and proliferation to B cell mitogens are absent. IgM, IgG2a, and IgG3 levels are reduced, and T cell-independent antibody production is absent. The similarity to Btk- or Blnk-deficient mice demonstrates that PLCgamma2 is downstream in Btk/Blnk signaling. FcRgamma signaling is also defective, resulting in a loss of collagen-induced platelet aggregation, mast cell FcepsilonR function, and NK cell FcgammaRIII and 2B4 function. The results define a signal transduction pathway broadly utilized by immunoglobulin superfamily receptors.

Light treatment enhances photoreceptor survival in dystrophic retinas of Royal College of Surgeons rats

PURPOSE

To determine whether treatment with bright light elicits a protective response that enhances photoreceptor survival in Royal College of Surgeons (RCS) rats with inherited retinal degeneration.

METHODS

RCS rats were illuminated for 10 to 12 hours with 130 foot-candles (fc) of white or green light. Untreated littermates that were kept under low cyclic light levels were used as control subjects. Photoreceptor survival was determined by quantitative analysis of photoreceptor nuclei and ultrastructural assessment of cellular organization. Basic fibroblast growth factor (bFGF) and ciliary neurotrophic factor (CNTF) gene expression were determined at the mRNA and protein levels.

RESULTS

Treatments of RCS rats with a single dose of bright light on postnatal day 23 (P23) greatly enhanced photoreceptor survival. Ultrasturctural analysis revealed intact inner segments in light-treated retinas, whereas in untreated retinas only remnants of inner segments were observed. By P42, numerous viable nuclei were counted in the posterior retina of light-treated rats, whereas most of the remaining nuclei in untreated RCS rat retinas were highly pyknotic. At 2.5 days after treatment with a single dose of bright light, bFGF gene expression was significantly higher than in untreated RCS rat retinas. By P42, bFGF protein levels were still significantly higher in the treated retinas.

CONCLUSIONS

Exogenous bFGF has been shown to promote photoreceptor survival in the RCS rat retina. Thus, the increased bFGF expression that was measured in the light-treated RCS rat retinas may be a protective response to light stress, which supports the observed rescue of photoreceptors in light-treated RCS rat retinas.

Activation of caspase-3 in the retina of transgenic rats with the rhodopsin mutation s334ter during photoreceptor degeneration

The role of caspase-3 in photoreceptor degeneration was examined in a line of transgenic rats that carry a rhodopsin mutation S334ter. Photoreceptor degeneration in these animals is rapid. It is detected as early as postnatal day (PD) 8, and by PD 20, only one of the original 12 rows of nuclei remain in the outer nuclear layer. At PD 11 and 12, the number of photoreceptors dying per day reaches a peak of approximately 30% of the total photoreceptors in the retina. Coincident with this rapid degeneration is an increase in caspase-3-like activity as assessed by the cleavage of a fluorescent substrate N-acetyl-Asp-Glu-Val-Asp-aminomethylcoumarin and an increase in activated caspase-3 as determined by Western blot analysis for its 12 kDa subunit. Intraocular injection of an irreversible caspase-3 inhibitor N-benzyloxycarbonal-Asp(OMe)-Glu(OMe)-Val-Asp(Ome)-fluoromethyk etone partially protected photoreceptors from degeneration. These findings indicate that a caspase-3-dependent mechanism is operative in photoreceptor death in the transgenic rats under investigation.

Alpha2-adrenergic agonists selectively activate extracellular signal-regulated kinases in Müller cells in vivo

PURPOSE

Alpha2-adrenergic agonists have specific and selective effects on the retina to induce expression of basic fibroblast growth factor and to protect photoreceptors. This work explores the signaling pathway that mediates these effects.

METHODS

Alpha2-adrenergic agonists xylazine and clonidine were administered systemically to male adult Sprague-Dawley rats. The activation state of extracellular signal-regulated kinases (ERKs) in the retina was assessed by immunoblot analysis, using antibodies that specifically recognize the dually phosphorylated forms of p44/p42 ERKs. Localization of phosphorylated ERKs was determined by immunocytochemistry.

RESULTS

Intramuscular injection of 6 mg/kg xylazine induced an increase in ERK phosphorylation in the retina within 30 minutes that lasted 3 hours. Xylazine induced ERK phosphorylation at 1 mg/kg and reached a maximum at 10 mg/kg. Injection of clonidine also induced ERK phosphorylation in the retina. Yohimbine, a specific alpha2-adrenergic antagonist, completely prevented the induction of ERK phosphorylation. Immunocytochemical studies showed that the increase in ERK phosphorylation occurred mainly in Müller cells. In the brain, xylazine injection resulted in a decrease in ERK phosphorylation.

CONCLUSIONS

Our results indicate that systemically administered alpha2-adrenergic agonists selectively activate ERKs in retinal Müller cells. The induced activation of ERKs in Müller cells is probably one of the early events that result in photoreceptor protection. These results also indicate that Müller cells are unique in response to alpha2-adrenergic agonists and imply a role for Müller cells in alpha2-adrenergic agonist-induced photoreceptor protection.

Continuous exposure to bright light upregulates bFGF and CNTF expression in the rat retina

PURPOSE

To examine mRNA expression of neurotrophic factors in the retina after exposure to bright light.

METHODS

Male adult Sprague-Dawley rats were exposed to light of 115-130 ft-c. Retinas were collected after 1, 2, 4 or 7 days of exposure. Northern blot analysis was performed to determine mRNA levels for the following factors and their receptors: basic fibroblast growth factor (bFGF), ciliary neurotrophic factor (CNTF), acidic fibroblast growth factor (aFGF), brain-derived neurotrophic factor (BDNF), insulin-like growth factor 1 (IGF-1) and glial fibrillary acidic protein (GFAP). Expression of bFGF, CNTF and GFAP was localized by in situ hybridization.

RESULTS

Exposure to light of 115-130 ft-c resulted in a substantial increase in bFGF and CNTF expression that persisted during the entire 7-day period of exposure. The peak expression of bFGF was almost 9-fold at day 2. The increase in CNTF mRNA reached a maximum of 6-fold at day 4. A small increase (50%) in IGF-1 mRNA was also seen at day 4. Among the receptors, an elevation of 3-fold in FGF receptor 1 (FGFR-1) was observed at day 2. There was also a small increase (70%) in IGF-1 receptor (IGF-1R) at day 2. In addition, the expression of GFAP showed a rapid elevation of about 8-fold by day 1 and 9-fold by day 2, and 18-fold by day 4. There was, however, no significant alteration in the expression of aFGF and BDNF. In situ hybridizations showed that the elevation of bFGF, CNTF and GFAP occurred across the entire retina with especially prominent increases over specific layers for each gene.

CONCLUSIONS

Continuous exposure to bright light upregulates bFGF, CNTF, FGFR-1 and GFAP expression in the rat retina. The pattern of induced expression closely resembles that induced by mechanical injury, implying a common underlying mechanism.

[Mechanism of preventing the recurrence of bladder carcinoma by intravesical instillation of BCG plus IL-2]

OBJECTIVE

To study the mechanism of preventing the recurrence of bladder carcinoma by intravesical instillation of BCG plus IL-2.

METHOD

Intravesical instillation of BCG or BCG plus IL-2 were carried out in the bladder transitional cell carcinoma patients undergoing surgical operation (16, 19 cases respectively).

RESULT

They were followed up for 14-22 months. The recurrence rates were 31.25% and 21.05% respectively. At 6 weeks after the instillation of IL-2 plus BCG, the peripheral blood NKCF activity was increased significantly and there was a significant positive correlation between the activities of NKCF and IL-2.

CONCLUSION

The intravesical instillation of IL-2 plus BCG is clearly superior to only BCG in preventing recurrence of bladder carcinoma. There may be immuno-enhancement and immuno-synergism.

Prostaglandin E2 induces vascular endothelial growth factor and basic fibroblast growth factor mRNA expression in cultured rat Müller cells

PURPOSE

To investigate the induction of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) gene expression by prostaglandin E2 (PGE2) in cultured rat Müller cells and to study the mechanism of the induction.

METHODS

Müller cells were obtained from neonatal Sprague-Dawley rat retinas and cultured in essential modified Eagle's medium supplemented with 10% fetal calf serum for up to four passages. Cells were treated with PGE2, protein kinase A (PKA) inhibitors H-89 or SQ 22536, protein kinase C (PKC) inhibitors calphostin C or GF 109203X, PKC activator phorbol 12-myristate 13-acetate (PMA), or the PKA activator forskolin. Northern blot analysis was performed to determine the levels of VEGF and bFGF mRNA.

RESULTS

PGE2 induced VEGF and bFGF mRNA expression in a dose- and time-dependent manner. VEGF and bFGF mRNA reached peaks of 2- and 3.5-fold at 10 microM PGE2. No further increases were observed at 100 microM PGE2. When treated with 10 microM PGE2, the increases in VEGF and bFGF mRNA reached maximum by 2 hours, then slowly declined toward the control level within 24 hours of PGE2 treatment. The inductions of VEGF and bFGF mRNA expression by PGE2 were blocked by the specific PKA inhibitors H-89 (30 microM) or SQ 22536 (500 microM, 1000 microM). Forskolin (10 microM), a cyclic adenosine monophosphate activator, also stimulated VEGF and bFGF mRNA expression. However, the effects of forskolin and PGE2 on VEGF gene expression were not additive, whereas forskolin enhanced the effect of PGE2 on bFGF mRNA expression. The specific PKC inhibitors, GF 109203X (2 microM) and calphostin C (1 microM), did not inhibit PGE2-induced VEGF gene expression, whereas PGE2-induced bFGF expression was blocked by the PKC inhibitor GF 109203X. In addition, downregulation of PKC by PMA (0.8 microM) treatment did not block the induction of VEGF gene expression, whereas it did inhibit the induction of bFGF mRNA expression.

CONCLUSIONS

These results indicate that PGE2 stimulates VEGF and bFGF mRNA expression in cultured rat Müller cells. The induction of VEGF seems to occur through activation of the PKA pathway, whereas that of bFGF occurs through PKA and PKC activation. These findings raise the possibility that endogenous PGE2 stimulates VEGF and bFGF mRNA expression in Müller cells in vivo under conditions in which PGE2 production is increased, such as in injury.

Preconditioning with bright light evokes a protective response against light damage in the rat retina

Constant exposure to bright light induces photoreceptor degeneration and at the same time upregulates the expression of several neurotrophic factors in the retina. At issue is whether the induced neurotrophic factors protect photoreceptors. We used a preconditioning paradigm to show that animals preconditioned with bright light became resistant to subsequent light damage. The preconditioning consisted of a 12-48 hr preexposure, followed by a 48 hr "rest phase" of normal cyclic lighting. The greatest protection was achieved by a 12 hr preexposure. Preconditioning induces a prolonged increase in two endogenous neurotrophic factors: basic fibroblast growth factor (bFGF) and ciliary neurotrophic factor (CNTF). It also stimulates the phosphorylation of extracellular signal-regulated protein kinases (Erks) in both photoreceptors and Müller cells. These findings indicate that exposure to bright light initiates two opposing processes: a fast degenerative process that kills photoreceptors and a relatively slower process that leads to the protection of photoreceptors. The extent of light damage, therefore, depends on the interaction of the two processes. These results also suggest a role of endogenous bFGF and CNTF in photoreceptor protection and the importance of Erk activation in photoreceptor survival.

Mechanical injury increases bFGF and CNTF mRNA expression in the mouse retina

We characterized the survival-factor response of the normal mouse retina to mechanical injury by examining the expression of mRNAs for basic fibroblast growth factor (bFGF), ciliary neurotrophic factor (CNTF), and their receptors, FGF receptor-1 (FGFR-1) and CNTF receptor alpha (CNTFR-alpha). The retina was injured by making an incision through the choroid and retinal pigment epithelium that penetrated the subretinal space of each eye of an adult BALB/c mouse. Retinas were taken 6 hr, 12 hr, 1, 2, 4, 7, 10 and 16 days post-injury. Control animals were without injury. Northern blot analysis was performed to determine bFGF, CNTF and their receptor mRNA levels. A significant increase in bFGF and CNTF mRNAs was observed after injury, along with an increase in glial fibrillary acidic protein (GFAP) expression. More than 2-fold of upregulation of bFGF mRNA was seen as early as 6 hr after injury. This increase reached a maximum of more than 5-fold at day 2 post-injury and then declined slowly, and was still about 2.5-fold of the control level by day 16. Expression of CNTF showed a small increase of about 1.6-fold at 6 hr after injury. The upregulation reached a peak level of about 2.7-fold at day 4 after injury, then declined to control level by day 16. There was only a very small increase in FGFR-1 at 6, 12 and 24 hr after injury, and no significant increases in FGFR-1 at time points longer than 1 day post-injury. Expression of GFAP followed a time course similar to that of bFGF. We conclude that mechanical injury induces bFGF, CNTF, and GFAP expression in the mouse retina with time courses similar to the upregulation of these molecules in rat retina. Compared to the upregulation in rat retina, however, the injury-induced upregulation of bFGF and GFAP is much less in the mouse retina. In addition, there was only a very small induction of FGFR-1 expression in the mouse retina. These findings may explain, at least in part, the lack of injury-induced photoreceptor protection in the mouse retina.

Induction of basic fibroblast growth factor mRNA by basic fibroblast growth factor in Müller cells

PURPOSE

To investigate the induction of basic fibroblast growth factor (bFGF) gene expression in cultured rat Müller cells by bFGF and to study the mechanism of induction.

METHODS

Müller cells from 1- to 3-day-old Sprague-Dawley rats were isolated and cultured with Dulbecco's modified Eagle's medium with 10% fetal calf serum. Cultured cells were identified by immunocytochemistry using antibodies against vimentin, carbonic anhydrase II, and glutamine synthetase. Cells of passages 1 through 4 were treated with bFGF, the protein kinase C (PKC) inhibitor, H-7; calphostin C, or the PKC activator, PMA; and protein kinase A (PKA) inhibitor, H-89; as well as the adenylate cylase activator, forskolin; or the adenylate cyclase inhibitor, SQ22536. Northern blot analysis was performed to determine the mRNA expression of bFGF, ciliary neurotrophic factor (CNTF) and brain-derived neurotrophic factor (BDNF).

RESULTS

Addition of bFGF to culture medium induced bFGF gene expression in a dose- and time-dependent manner. Induction of bFCF mRNA started at a bFGF concentration of 0.1 ng/ml. The bFGF mRNA level was elevated by 2-fold at 1 ng/ml of bFGF, 2.8-fold at 5 ng/ml, and reached a peak of 4-fold at 10 ng/ml and 3.7-fold at 50 ng/ml. At 10 ng/ml of bFGF, induction of bFGF mRNA was observed as early as 2 hours (2-fold) after treatment. The bFGF mRNA level continued to increase to 3.7-fold by 4 hours, and reached a maximum of 4.4-fold by 8 hours. A slow decline of the bFGF mRNA level was observed after 8 hours of bFGF treatment (3.5-fold by 12 hours, and 3-fold by 24 hours). This induction of bFGF gene expression was blocked by PKC inhibitors H-7 (30 microM). The PKC activator PMA (0.1 microM) also upregulated bFGF gene expression, but the effects of bFGF and PMA were not additive. An adenylate cyclase inhibitor, SQ22536 (100 microM), did not inhibit bFGF-induced bFGF gene expression. Although forskolin (5 microM), an adenylate cyclase activator, also upregulated the level of bFGF mRNA, the effects of forskolin and bFGF were additive. In addition, no inhibitory effect on bFGF-induced expression of bFGF mRNA was found using H-89 (1 microM). Exogenous bFGF did not alter the mRNA levels of CNTF and BDNF.

CONCLUSIONS

These results indicate that bFGF induces bFGF gene expression in cultured rat Müller cells through PKC activation. The authors' findings raise the possibility that Müller cells in vivo also respond to available bFGF (for example, that released from the endogenous reservoirs in the case of injury) or to exogenous bFGF by producing more bFGF, which could in turn promote photoreceptor survival.

The conventional CD4+ T cell response to staphylococcal enterotoxin B is modified by its superantigenic activity

Because of the massive cytokine response elicited by superantigen exposure, it has been suggested that superantigens may act as adjuvants to boost conventional antigen responses. However, most previous studies have shown that in vivo exposure to superantigen suppressed subsequent T cell responses. Here we analyzed the effect of the superantigen Staphylococcal enterotoxin B (SEB) on a concurrent CD4(+) immune response to a conventional antigen, an I-Ab-restricted epitope derived from the same protein (SEB127-142). Heat-inactivated SEB, which had lost all superantigenic activity, was capable of eliciting a strong CD4(+) proliferative T cell response to SEB127-142. In contrast, native SEB was relatively nonimmunogenic, even when administered in association with complete Freund's adjuvant. High doses of native SEB coadministered with heat-inactivated SEB had no effect on the peptide response. However, low doses of native SEB were able to strongly enhance the ability of inactive SEB to prime CD4(+) T cells to SEB127-142. Thus, SEB is not always immunosuppressive, and low doses may actually enhance a concurrent immune response. Also, the contribution of Vbeta8(+)/CD4(+) T cells to peptide reactivity was not affected by the presence of low doses of native SEB, suggesting that the enhanced reactivity was not a Vbeta-specific effect of SEB, but was cytokine-mediated.

Carboxy-terminal residues of major histocompatibility complex class II-associated peptides control the presentation of the bacterial superantigen toxic shock syndrome toxin-1 to T cells

Previous studies have shown that the presentation of some bacterial superantigens by major histocompatibility complex (MHC) class II molecules is strongly influenced by class II-associated peptides. For example, presentation of the toxic shock syndrome toxin-1 (TSST-1) superantigen by antigen-processing-defective T2-I-Ab cells (which expresses I-Ab that is either empty or associated with invariant chain-derived peptides) can be strongly enhanced by some, but not other, I-Ab-binding peptides. Here we investigate the contribution of I-Ab-associated peptides in the presentation of TSST-1 to T cells. The data show that overlapping peptides expressing the same core I-Ab-restricted epitope, but with various N and C termini, can differ profoundly in their ability to promote TSST-1 presentation to T cells. Analysis of altered and truncated peptides indicates that residues at the C-terminal end of the peptide have a dramatic effect on TSST-1 presentation. This effect does not involve a cognate interaction between the peptide and the TSST-1 molecule, but appears to depend on the length of the C-terminal region. These data are consistent with crystallographic studies suggesting that TSST-1 may interact with the C-terminal residues of MHC class II-associated peptides. We also examined the capacity of naturally processed peptides to promote TSST-1 binding using a superantigen blocking assay. The data demonstrated that a naturally processed epitope is dominated by peptides that do not promote strong TSST-1 binding to I-Ab. Taken together, these data suggest that TSST-1 binding to MHC class II molecules is controlled by the C-terminal residues of the associated peptide, and that many naturally processed peptide/class II complexes do not present TSST-1 to T cells. Thus, the peptide dependence of TSST-1 binding to class II molecules may significantly reduce the capacity of TSST-1 to stimulate T cells.

Alpha 2-adrenergic agonists induce basic fibroblast growth factor expression in photoreceptors in vivo and ameliorate light damage

We observed an induction of basic fibroblast growth factor (bFGF) mRNA in the rat retina after systemic administration of the alpha 2-adrenergic agonists xylazine and clonidine. A single injection of xylazine or clonidine transiently increased bFGF mRNA. Preinjection of yohimbine, an alpha 2-adrenergic antagonist, completely inhibited this increase. Higher dosage of yohimbine inhibited the baseline expression of bFGF. Of particular interest is the finding that the induced bFGF expression occurred almost exclusively in the inner segment region of photoreceptors. No increase in bFGF mRNA was found in the brain after either xylazine or clonidine injection. Xylazine or clonidine given systemically before and during constant light exposure also reduces photoreceptor degeneration in albino rats. These results indicate that regulation of bFGF expression in photoreceptors is unique in the CNS and suggest that endogenous bFGF promotes photoreceptor survival.

[Soluble interleukin-2 receptor in patients with urinary bladder cancer]

Soluble interleukin-2 receptor (sIL-2R) levels in the serum and the effect of the sIL-2R on the natural killer cell factor (NKCF) activity were studied in 31 patients with transitional cell cancer of the urinary bladder. The results showed that serum levels of sIL-2R in the patients were significantly higher than those of controls. sIL-2R level correlated with the stage of the disease. Furthermore, sIL-2R was able to suppress NKCF activity. The results suggest that the sIL-2R may reflect the status of anti-tumor immunity.

Quantitation of herpes simplex virus type 1 DNA and latency-associated transcripts in rabbit trigeminal ganglia demonstrates a stable reservoir of viral nucleic acids during latency

In this investigation we determined the dynamics of herpes simplex virus type 1 (HSV-1) DNA and latency-associated transcripts (LAT) in the latently infected rabbit trigeminal ganglion. Rabbit eyes were infected with either the McKrae strain or the l7Syn+ strain of HSV-1. Rabbits were sacrificed between 5 and 360 days after infection and their trigeminal ganglia were analyzed for the number of HSV DNA genomes and the number of neuronal cells expressing LAT. There was no statistically significant change in the number of HSV genomes or the number of neuronal cells expressing LAT in these ganglia between 20 and 360 days after infection. For both strains, the amount of HSV DNA averaged 16.8 genomes per 100 cells, and 9.2% of the neurons expressed LAT. There were 17 to 34 HSV genomes per LAT-expressing neuronal cell. The number of LAT-expressing neurons did not change over the 360 days. Spontaneous reactivation (HSV-1 recovery in tear film) and recurrence (HSV-1-specific epithelial lesions) occurred during the period of this study; however, these events did not alter the quantity of HSV-1 DNA or the number of LAT-expressing cells. These results suggest that after the latent infection is established, the viral DNA in the ganglia does not replicate to any measurable extent over long periods of latency, since no significant change in the number of HSV genomes occurs. The results also suggest that only a very small number of latently infected neuronal cells are needed to produce infectious HSV-1 during reactivation.

Quantitative analysis of polymerase chain reaction products by dot blot

Quantitative analysis of polymerase chain reaction (PCR) products is usually accomplished by gel electrophoresis and Southern blotting. We have developed an alternative technique that allows PCR products to be directly quantitated from unfractionated samples. The PCR was used to amplify genomic (endogenous) DNA sequences (actin) and exogenous DNA (herpes simplex virus-1 (HSV-1) ribonucleotide reductase) isolated from the trigeminal ganglia of rabbits to demonstrate the dot blot method of PCR product analysis. Two primer pairs (actin and ribonucleotide reductase) were coamplified, resulting in two different PCR products. Duplicate aliquots of the PCR products were applied to separate nylon membranes and hybridized with 32P-labeled oligonucleotide probes. Each radioactive probe was specific for target (HSV-1 DNA) or control (actin DNA) products. Quantitation using a laser scanning PhosphorImager and ImageQuant software demonstrated that the dot blot method can be used to rapidly analyze a large number of PCR samples.

Major histocompatibility complex class II-associated peptides control the presentation of bacterial superantigens to T cells

Recent studies have shown that only a subset of major histocompatibility complex (MHC) class II molecules are able to present bacterial superantigens to T cells, leading to the suggestion that class-II associated peptides may influence superantigen presentation. Here, we have assessed the potential role of peptides on superantigen presentation by (a) analyzing the ability of superantigens to block peptide-specific T cell responses and (b) analyzing the ability of individual peptides to promote superantigen presentation on I-Ab-expressing T2 cells that have a quantitative defect in antigen processing. A series of peptides is described that specifically promote either toxic shock syndrome toxin (TSST) 1 or staphylococcal enterotoxin A (SEA) presentation. Whereas some peptides promoted the presentation of TSST-1 (almost 5,000-fold in the case of one peptide), other peptides promoted the presentation of SEA. These data demonstrate that MHC class II-associated peptides differentially influence the presentation of bacterial superantigens to T cells.

[Level and significance of the soluble interleukin-2 receptor expression in serum of patients with bladder cancer]

The results of a dynamic study of the soluble interleukin-2 receptor (SIL-2R) expression, interleukin-2 (IL-2) production and natural killer cell factor (NKCF) activity before and after operation in 24 bladder carcinoma patients were reported. The SIL-2R expression level in the patients was significantly higher, the IL-2 production and NKCF activity were remarkably lower than those of controls. Furthermore, the higher the stage of the tumor, the higher the level of the SIL-2R. There was a period of immune suppression after operation. The results suggest that the changes of the SIL-2R expression level, IL-2 production and NKCF activity are closely related to the prognosis of patients with bladder carcinoma.

Injury-induced upregulation of bFGF and CNTF mRNAS in the rat retina

Focal mechanical injury to the retina has been shown to slow or prevent photoreceptor degeneration near the lesion site in two animal models of retinal degeneration, inherited retinal dystrophy in the Royal College of Surgeons (RCS) and light damage in albino rats. Thus, when injured, the rat retina activates a self-protective mechanism to minimize damage. To identify injury responsive factors and cells, we examined the mRNAs for the following factors and some of their receptors: basic and acidic fibroblast growth factors (bFGF, aFGF) and FGF receptor-1 (FGFR1); ciliary neurotrophic factor (CNTF) and CNTF receptor alpha (CNTFR alpha); brain-derived neurotrophic factor (BDNF) and its receptor trkB; and insulin-like growth factor-1 (IGF-1) and IGFR-1 receptor (IGF-1R). After a single mechanical lesion to the subretinal space and retina, there was a substantial increase in bFGF and CNTF expression that persisted for the entire 10 d period of study. The increase in bFGF mRNA after injury was prompt and great in amplitude, while the elevation of CNTF mRNA was relatively slower. In addition, there was a transient increase in FGFR1 mRNA. In situ hybridizations showed that the elevation of bFGF and CNTF was localized to the vicinity of the lesion. The expression of GFAP (glial fibrillary acidic protein) mRNA also increased in response to injury. These findings strongly suggest that increases in endogenous bFGF and/or CNTF play key roles in injury-induced photoreceptor rescue.

Variable influence of MHC polymorphism on the recognition of bacterial superantigens by T cells

Superantigen recognition by some T cells is strongly influenced by polymorphic residues of the MHC class II molecule, suggesting that the TCR contacts the class II molecule during superantigen engagement. However, the degree of MHC preference varies with V beta expression. For example, the recognition of staphylococcal enterotoxin B (SEB) by murine V beta 14+ T cell hybridomas is strongly influenced by MHC polymorphism, whereas the recognition of SEB by V beta 8.2+ hybridomas appears to be independent of MHC polymorphism. One possible explanation for this difference is that V beta 14+ TCR may have a lower avidity for SEB such that the stability of the TCR/SEB/MHC complex is more strongly influenced by potential TCR/MHC interactions. To investigate this possibility, we examined the MHC preference of SEB recognition by murine V beta 8.2+/CD4+ T cell hybridomas in which we altered the strength of SEB recognition. First, we compared the recognition of wild-type SEB and mutant SEB, which only weakly activates T cells. Second, we compared recognition of SEB presented by I-E and I-A molecules, which differ in their affinity for SEB. In both cases, the degree of MHC preference was significantly increased when the strength of SEB recognition was reduced. Furthermore, we used mutant MHC class II molecules to show that the degree of MHC preference was controlled by residues of the class II molecule predicted to interact with the TCR during SEB recognition. Taken together, these data support the idea that there is a TCR/MHC interaction during SEB recognition, and the influence of this interaction varies with the overall avidity of the TCR/SEB/MHC complex.

Variable influence of MHC polymorphism on the recognition of bacterial superantigens by T cells

Superantigen recognition by some T cells is strongly influenced by polymorphic residues of the MHC class II molecule, suggesting that the TCR contacts the class II molecule during superantigen engagement. However, the degree of MHC preference varies with V beta expression. For example, the recognition of staphylococcal enterotoxin B (SEB) by murine V beta 14+ T cell hybridomas is strongly influenced by MHC polymorphism, whereas the recognition of SEB by V beta 8.2+ hybridomas appears to be independent of MHC polymorphism. One possible explanation for this difference is that V beta 14+ TCR may have a lower avidity for SEB such that the stability of the TCR/SEB/MHC complex is more strongly influenced by potential TCR/MHC interactions. To investigate this possibility, we examined the MHC preference of SEB recognition by murine V beta 8.2+/CD4+ T cell hybridomas in which we altered the strength of SEB recognition. First, we compared the recognition of wild-type SEB and mutant SEB, which only weakly activates T cells. Second, we compared recognition of SEB presented by I-E and I-A molecules, which differ in their affinity for SEB. In both cases, the degree of MHC preference was significantly increased when the strength of SEB recognition was reduced. Furthermore, we used mutant MHC class II molecules to show that the degree of MHC preference was controlled by residues of the class II molecule predicted to interact with the TCR during SEB recognition. Taken together, these data support the idea that there is a TCR/MHC interaction during SEB recognition, and the influence of this interaction varies with the overall avidity of the TCR/SEB/MHC complex.