Non-metastatic Ewing's sarcoma: twenty years of experience suggests that surgery is a prime factor for successful multimodality therapy

Eighty-five patients (37 female, 48 male; median age 14 years) with non-metastatic Ewing's sarcoma received definitive treatment at the University of Texas M.D. Anderson Cancer Center between 1969 and 1988. Multidisciplinary therapy was administered as follows: combination chemotherapy (CC) and local radiotherapy (XRT): 65 patients; CC, XRT and surgery, 19 patients; and XRT and surgery, 1 patient. This permitted a 10-20 year follow-up for 75% of our patients. The overall survival at 5 and 10-20 years was 46.1%, and 37.2%, respectively. At 5 years, 80.5% of live patients had control of local disease. The influence of sex, age, ethnicity, primary site, size, lactic dehydrogenase (LDH) level, presence or absence of systemic symptoms, and XRT dose (<60 Gy and </=60 Gy) was analyzed and was not found to be of prognostic significance in survival. The presence of a soft tissue mass at diagnosis was found to be a significant unfavorable prognostic variable. Nine of 11 patient who underwent resection after CC and/or XRT had residual tumor in the surgical specimen. Patients who received surgery as part of the planned treatment of their primary tumor had significantly better local control and disease-free survival than those who did not undergo resection. Complications in long-term survivors are described.

GABA(B) receptors function as a heteromeric assembly of the subunits GABA(B)R1 and GABA(B)R2

The principal inhibitory neurotransmitter GABA (gamma-aminobutyric acid) exerts its effects through two ligand-gated channels, GABA(A) and GABA(C) receptors, and a third receptor, GABA(B) , which acts through G proteins to regulate potassium and calcium channels. Cells heterologously expressing the cloned DNA encoding the GABA(B)R1 protein exhibit high-affinity antagonist-binding sites, but they produce little of the functional activity expected from studies of endogenous GABA(B) receptors in the brain. Here we describe a new member of the GABA(B) polypeptide family, GABA(B)R2, that shows sequence homology to GABA(B)R1. Neither GABA(B)R1 nor GABA(B)R2, when expressed individually, activates GIRK-type potassium channels; however, the combination of GABA(B)R1 and GABA(B)R2 confers robust stimulation of channel activity. Both genes are co-expressed in individual neurons, and both proteins co-localize in transfected cells. Moreover, immunoprecipitation experiments indicate that the two polypeptides associate with each other, probably as heterodimers. Several G-protein-coupled receptors (GPCRs) exist as high-molecular-weight species, consistent with the formation of dimers by these receptors, but the relevance of these species for the functioning of GPCRs has not been established. We have now shown that co-expression of two GPCR structures, GABA(B)R1 and GABA(B)R2, belonging to the same subfamily is essential for signal transduction by GABA(B) receptors.

HIV peptide conjugated to heat-killed bacteria promotes antiviral responses in immunodeficient mice

Enhancement of immunity in the setting of HIV infection is difficult owing to loss of functional CD4+ T cells. The MHC class II-deficient mouse (II-/-) environment simulates that of the immunocompromised HIV-infected individual, since these mice have low CD4+ T cell numbers, defective CD4-dependent responses, and are susceptible to opportunistic infection. This strain was used to test whether heat-killed Brucella abortus (BA), covalently conjugated to the V3 peptide of HIV-1 (MN), could elicit anti-HIV responses. V3-BA, but not the T-dependent antigen V3-KLH, induced high levels of IL-12, IFN-gamma, and IL-10 mRNA in both wild-type (WT) and II-/- mice within 24 hr of injection. V3-BA-treated, but not V3-KLH-treated, II-/- mice developed serum IgG and IgA anti-V3 antibodies, with IgG2b and IgG3 as the predominant isotype. Viral neutralization studies, using a syncytium inhibition assay, demonstrated that the antibodies generated by V3-BA in II-/- mice were capable of neutralizing HIV. These experiments demonstrate that a heat-inactivated bacterium such as BA, when used as a carrier, can generate a cytokine environment that results in the production of neutralizing antiviral antibodies in an immunodeficient host. Such strategies could be important in the development of immunotherapies and vaccines for HIV-1 patients.

Dynorphin uses a non-opioid mechanism to potentiate N-methyl-D-aspartate currents in single rat periaqueductal gray neurons

The interaction of the endogenous K-opioid, dynorphin, with N-methyl-D-aspartate (NMDA) receptors was studied in single periaqueductal gray (PAG) cells using the whole cell patch recording technique. We have found that dynorphin A (1-17) rapidly and reversibly potentiates NMDA-activated currents in a subpopulation of PAG cells. The potentiation cannot be blocked by the non-specific opioid antagonist, naloxone, nor can it be reversed by the specific kappa-opioid antagonist, nor-BNI. In addition, the non-opioid fragment of dynorphin, dynorphin A (2-17), is effective in potentiating NMDA currents, while the specific kappa-opioid, U50,488, cannot mimic the action of dynorphin A (1-17). The non-opioid dynorphin action and the rapid onset and recovery of the potentiation are consistent with the idea that dynorphin interacts directly with NMDA receptors in PAG cells.

Dynorphin block of N-methyl-D-aspartate channels increases with the peptide length

We examined the non-opioid actions of various forms of dynorphin A (DynA) on N-methyl-D-aspartate (NMDA) receptor channels in isolated rat trigeminal neurons using the whole-cell patch recording technique. All the dynorphins tested blocked NMDA-activated currents. The blocking actions were voltage-independent. The IC50 was 0.26 microM for DynA(1-32), 6.6 microM for DynA(1-17) 7.4 microM for DynA(1-13), 42.0 microM for DynA(1-10). DynA(1-8) had no detectable blocking action on NMDA responses. Thus, the IC50s of dynorphins for NMDA receptors increased 160-fold as the length of the peptides decreased from 32 to 10 amino acids. Amidation of dynorphins dramatically reduced their IC50s and eliminated the large difference in the IC50s of various lengths of dynorphins. The reduction in the IC50s of dynorphin amides could not be explained by the resistance of the peptides to enzymatic degradation. Our observations suggest that peptide processing affects dynorphin blocking actions on NMDA responses. The positively charged residues, lengths of the peptides and amidation may contribute to their affinities for NMDA receptors.

Cross-modulation of glycine-activated Cl- channels by protein kinase C and cAMP-dependent protein kinase in the rat

1. The cross-modulation of glycine responses by cyclic-AMP-dependent protein kinase (PKA) and protein kinase C (PKC) was determined in acutely dissociated trigeminal neurons. 2. Whole-cell glycine-evoked Cl- current (IGly) was recorded using the patch clamp technique. Protein kinases and their inhibitors were intracellularly perfused into the cells. 3. Both PKA and PKC when applied separately potentiated IGly. 4. When PKA and PKC were sequentially applied, PKC could not increase the IGly any further after the glycine responses were enhanced by PKA. 5. In 42% of our cells, IGly increased spontaneously. Endogenous PKA was found to mediate the increase. PKC had no effects on IGly in these cells. 6. The effect of PKA on IGly was studied in PKC-pretreated cells. PKA failed to potentiate IGly in these cells, suggesting that the PKA action also depends on the activity of PKC inside the cells. 7. These results suggest that the PKC action on IGly is conditional upon the modulation of the currents by PKA and vice versa. This cross-regulation of ligand-gated channel activity by protein kinases may play a role in neuronal integration and synaptic plasticity.

Cloning and characterization of the human galanin GALR2 receptor

We present the molecular cloning and characterization of the human galanin receptor, hGALR2. hGALR2 shares 85%, 39%, and 57% amino acid identities to rGALR2, hGALR1, and hGALR3, respectively. hGALR2, along with rGALR2, can be distinguished from the other cloned galanin receptors by a tolerance for both N-terminal extension and C-terminal deletion of galanin, as well as by a primary signaling mechanism involving phosphatidyl inositol hydrolysis and calcium mobilization. By RT-PCR, GALR2 mRNA was abundant in human hippocampus, hypothalamus, heart, kidney, liver, and small intestine. A weak GALR2 mRNA signal was detected in human retina, and no signal was detected in cerebral cortex, lung, spleen, stomach, or pituitary.

Comparison of thymocyte development in normal and invariant chain-deficient mice provides evidence that maturation-related changes in TCR and co-receptor levels play a critical role in cell fate

Cells of invariant chain-deficient mice show a substantial decrease in cell surface MHC class II protein expression, as well as a change in the occupancy of the expressed class II molecules. Taking advantage of recent advances in phenotypic identification of transitional populations of developing thymocytes, the effects of these changes in MHC class II on positive and negative selection were reanalyzed. A marked (approximately 6-fold) reduction in CD4 single-positive mature cells was seen in H-2b mutant mice, yet there was little change in the number of CD4hiCD8intTCRint cells, a population containing the cells from which mature CD4+ cells derive. In normal mice expressing I-E and MMTV-encoded vSAG, V beta-specific negative selection occurred at a later point in the maturation pathway for cells showing greater expression of CD8 than CD4. In invariant chain-deficient mice, vSAG-mediated negative selection was diminished in general and what deletion still occurred was seen in more mature populations as compared to wild-type mice. Taken together, the decrease in MHC class II expression in invariant chain mutant mice and these alterations in the timing of thymocyte deletion provide strong support for an avidity model of negative selection. Perhaps more importantly, they emphasize the importance of the increasing TCR expression, the changing co-receptor levels and the movement from one antigen-presenting cell to another that accompany T cell maturation in determining the fate of developing thymocytes.

Ca(2+)-dependent exocytosis in the somata of dorsal root ganglion neurons

Using capacitance measurements and the single-cell immunoblot assay to study secretion in dorsal root ganglion neurons, we found that the somata underwent robust exocytosis upon depolarization and released substance P, in response to KCl stimulation. The parallel changes between capacitance responses and intracellular Ca2+ concentration ([Ca2+]i) at different membrane potentials and the inhibition of exocytosis by Ca2+ chelators suggest that soma release is Ca(2+)-dependent. We also assessed the level of Ca2+ required for exocytosis by raising the average [Ca2+]i with the Ca2+ ionophore, ionomycin. Capacitance changes were triggered by cytosolic Ca2+ > 0.6 microM; the [Ca2+]i at the release sites during depolarizations was estimated to be 3-10 microM. These Ca2+ levels are similar to those obtained from neuroendocrine cells, but are at least 10 times lower than those required for transmitter release from nerve terminals.

[Clinical manifestations and effects of IVGG in patients with Kawasaki disease]

From Jan 1984 till Dec 1992, 293 patients--180 males and 113 females (M:F = 1.5:1)--with Kawasaki disease visited the Pediatric Department of Kaohsiung Medical College Hospital. The mean age from the total cases were 28.5 months (2 months-10 years). Fever was the most common clinical symptom, followed by dry cracked lips (93.5%), pharyngeal injection (92.8%) and conjunctivitis (90.5%). Only 62.6% of the total cases had cervical lymph node swelling of which the prevalence was higher than the previous report of the National Taiwan University Hospital in 1985. Two hundred and ninety-three cases were divided randomly into 3 groups according to the different treatment regimens. The first group of 199 cases whose coronary artery change occurred in 85 cases (42.7%), were treated with aspirin alone. The second group of 80 cases were treated with aspirin and IVGG 400 mg/kg/day for 5 consecutive days. The prevalence of coronary artery abnormalities was 22.5% (18/80). The third group of 14 cases were treated with aspirin and single high dose IVGG (2 gm/kg) for 10-12 hours. Coronary artery abnormalities occurred in 3 cases (21.4%). IVGG, initiated within 10 days of the onset of fever, in conjunction with aspirin decreased the prevalence of coronary artery dilatation and aneurysms significantly in comparison with treatment by the aspirin alone (p < 0.05). However, there was no difference in the prevalence of coronary aneurysm between the groups of single high dose and multiple doses, though the single high dose of IVGG can improve the clinical symptoms quickly and shorten the duration of hospitalization.

Autoantibodies against arterial antigens: characterization by ELISA and immunoblot analysis in the spontaneously hypertensive rat

The presence of autoantibodies directed against arterial antigens in serum samples from spontaneously hypertensive rats and related controls that included Wistar-Kyoto and Sprague-dawley rats were assayed by enzyme-linked immunosorbent assay and immunoblotting technique. Circulating immunoglobulin G antibodies reactive against arterial antigen, as measured by enzyme-linked immunosorbent assay, could be detected in serum samples of 26 of 30 spontaneously hypertensive rats (87%) and 8 of 30 (27%) Wistar kyoto rats. These antibodies (Abs) were not detectable either by enzyme-linked immunosorbent assay or immunoblotting in sera from Sprague-dawley rats. The arterial antigen-reactive antibody was antigen specific, because the binding reactivity was absorbed by arterial antigen but not by fibroblasts or peripheral blood mononuclear cells. Immunoglobulin G arterial antigen-reactive antibody was significantly higher in adult spontaneously hypertensive rats with established hypertension, compared with young prehypertensive rats or normotensive wistar kyoto rats. Immunoblotting of spontaneously hypertensive rats sera revealed reactivity of arterial antigen-reactive antibody against arterial antigen ranging in size from 20 to 97 kDa. Sera from Wistar kyoto rats recognized arterial antigen ranging in size from 40 to 90 kDa. A significant correlation (p < 0.004) was found between adult spontaneously hypertensive rats with established hypertension and the presence of arterial antigen-reactive antibody reactivity against arterial antigen of 20, 69 and 97 kDa. Antibody directed against a 20 kDa arterial antigen was detected in both young prehypertensive rats and adult rats with established hypertension but not in Wistar kyoto or Sprague-dawley rats. Antibodies directed against both 69 and 97 kDa arterial antigens were detected only in spontaneously hypertensive rats sera. These data show that the pattern of arterial antigen-reactive antibody reactivity in sera of hypertensive rats in heterogeneous, and suggest that arterial antigen-reactive antibody directed against few arterial antigens may be involved in the pathogenesis of hypertension in the spontaneously hypertensive rat.

The mechanism of action for the block of NMDA receptor channels by the opioid peptide dynorphin

Dynorphin is one of the endogenous opioids that modulates the excitability of nociceptive (pain-sensing) neurons. We have shown recently that dynorphin blocks NMDA-activated currents directly without the participation of kappa-opioid receptors. In order to understand the mechanism underlying this novel action of dynorphin, we examined, in detail, the interactions between dynorphin and NMDA receptors in isolated trigeminal neurons. Dynorphin reversibly blocks NMDA-activated current (INMDA). The onset and recovery of the block were determined with concentration jump experiments. The association rate (k+) of dynorphin(1-17) is 4.9 x 10(6) sec-1 M-1 and the dissociation rate (k-) is 7.5 sec-1. The apparent dissociation constant (KD) of dynorphin, calculated from these rate constants, is 1.6 microM. Dynorphin does not change the EC50 of NMDA, nor the potentiating action of glycine. The binding site for dynorphin is distinct from that of Zn2+ or H+. Upon treatment with the disulfide reducing agent dithiothreitol (DTT), NMDA receptors become less susceptible to dynorphin block. The affinity of dynorphin for the modified NMDA receptors is reduced by 2.7-fold. In analyses of single NMDA channels in cell-free patches, we found that dynorphin shortens the mean open time, decreases the probability of opening of NMDA channels, but has no effect on the single channel conductance. These results suggest that dynorphin interacts with a site conformationally linked with the redox site(s) on the NMDA receptor, thus altering the gating properties of the channel.

The opioid peptide dynorphin directly blocks NMDA receptor channels in the rat

1. The actions of dynorphin on N-methyl-D-aspartate (NMDA) responses were examined in acutely dissociated trigeminal neurons in rat. Whole-cell and single-channel currents were recorded using the patch clamp technique. 2. Dynorphins reduced NMDA-activated currents (INMDA). The IC50 was 0.25 microM for dynorphin (1-32), 1.65 microM for dynorphin (1-17) and 1.8 microM for dynorphin (1-13). 3. The blocking action of dynorphin is voltage independent. 4. The inhibitory action of dynorphin cannot be blocked by high concentration of the non-selective opioid receptor antagonist naloxone, nor by the specific kappa-opioid receptor antagonist nor-Binaltorphimine (nor-BNI). 5. Single-channel analyses indicate that dynorphin reduces the fraction of time the channel is open without altering the channel conductance. 6. We propose that dynorphin acts directly on NMDA receptors.

Modulation of glycine affinity for NMDA receptors by extracellular Ca2+ in trigeminal neurons

Glycine and the divalent cation Ca2+ play key roles in regulating the activity of excitatory amino acid NMDA receptor channels. There is accumulating evidence that the concentration of glycine at the synaptic cleft is below a saturated level. We examined the effect of external Ca2+ on NMDA responses in various concentrations of glycine in isolated trigeminal neurons. We found that external Ca2+ potentiated NMDA responses and this potentiation occurred only when glycine sites were unsaturated. Since single-channel conductance decreases in the high external Ca2+ solution, the observation cannot be explained by an increase in Ca2+ influx through the channels. Studying the dose-response curves for glycine in different Ca2+ solutions, we found that the apparent dissociation constant (EC50) for glycine decreases with increasing external Ca2+ concentrations. Kinetics studies of glycine binding to NMDA receptors indicated that external Ca2+ causes a decrease in the off rate of the glycine binding, while having no effect on the on rate. Our analyses suggest that the apparent glycine affinity increases by about 3.7 times in Ca-containing solution. Thus, external Ca2+ contributes to the unusually high glycine affinity for NMDA receptors and may have a role in regulating the NMDA receptor channel activities during intensive or sustained neuronal stimulation.

[Evaluation of yellow IRIS/model 450 for routine urinalysis]

BACKGROUND

Urinalysis yields a great deal of information quickly and economically for detection of renal diseases. The inter-technician variation and time consuming are major problems while processing large amount of specimens. The purpose of this study is to evaluate the benefit of an automated urine analyzer, Yellow IRIS/model 450, and the feasibility of replacing the currently-used manual KOVA method.

METHODS

A total of 1,000 random urine specimens were analyzed with Yellow IRIS and KOVA method. Precision, correlation, and detection rate of abnormality were compared between these two methods.

RESULTS

The results revealed that Yellow IRIS had high precision with little between-run and within-run variation, while the obtained values were notably highly correlated with the expected values (r = 0.99). In addition, detection rate of blood cell abnormalities for the Yellow IRIS was twice better than for the manual KOVA method.

CONCLUSIONS

The high precision of the machine, the simple procedure of performing, and the quickness of obtaining data, can minimize variability caused by the manual method and save processing time for mass screening. It is feasible to replace the manual urinalysis by the automated urine analyzer Yellow IRIS. Nevertheless, to minimize the extent of manual manipulation, including pouring the urine into the pour cup, and placement of the urine strip, will assist in a wider acceptance for the Yellow IRIS/Model 450.

Some humoral factors and their interaction on acute hypoxic pulmonary pressor response

To determine the effect of humoral factors and their interaction on the development of acute hypoxic pulmonary pressor response (HPPR), we performed studies in 16 mongrel dogs. We measured plasma levels of noradrenaline (NE), angiotensin II (AII), prostaglandin F2 alpha (PGF2 alpha), 6-keto-prostaglandin F1 alpha (6KPGF1 alpha), thromboxane B2 (TXB2), leukotriene B4 (LTB4) and 5-hydroxytryptamine (5-HT) before, during and after HPPR. Multiple regression analysis showed that the changes of pulmonary arterial systolic pressure (PASP) and pulmonary arterial diastolic pressure (PADP) correlated well with those of plasma concentration of NE, PGF2 alpha and 6KPGF1 alpha, respectively (r were equal to 0.633 and 0.668, respectively, P < 0.01). The results of orthogonal experiment analysis with an injection of exogenous NE, PGF2 alpha and PGI alpha into main pulmonary artery of dogs showed that NE and the interaction of PGF2 alpha and PGI2 alpha increased PASP (P < 0.05) and PGI2 attenuated PASP (P < 0.01). The interaction of PGF2 alpha and PGI2 and of PGF2 alpha and NE increased PADP(P < 0.01) and PGI2 attenuated PADP (P < 0.01).

The M(r) 35,000 beta-adrenergic receptor mRNA-binding protein induced by agonists requires both an AUUUA pentamer and U-rich domains for RNA recognition

Delineating the molecular basis for agonist-induced destabilization of mRNA of G-protein-linked receptors that contributes to receptor down-regulation is fundamental to our understanding of long-term regulation of receptors by agonist. Previously we identified a prominent, M(r) 35,000 cytosolic RNA-binding protein that (i) binds selectively to beta 1 and beta 2-adrenergic receptor mRNAs, both of which undergo agonist-induced down-regulation; (ii) does not bind either to alpha 1b-adrenergic receptor mRNA, which does not undergo agonist-induced down-regulation, or to beta-globin mRNA; (iii) displays binding to beta 2-adrenergic receptor mRNA that is selectively competed by poly(U) RNA, but not poly(A),-(C), or -(G) RNA; and (iv) its abundance varies inversely with the level of receptor mRNA, being induced by agonists that down-regulate receptor mRNA (Port, J. D., Huang, L.-y., and Malbon (1992) J. Biol. Chem. 267, 24103-24108). We demonstrate here that the binding of beta-adrenergic receptor mRNA by this protein, termed beta-ARB protein, is sensitive to competition by AU-rich domains of the 3'-untranslated regions of c-fos, c-myc, and human granulocyte-macrophage colony-stimulating factor. Using the AU-rich 3'-untranslated regions of wild-type adenovirus IVa2 mRNA and variants with defined mutations in the AUUUApentamer, AU-rich, and U-rich domains, we were able to define sequences critical to the binding of the beta 2-receptor mRNA by the beta-ARB protein. Recognition of beta-ARB protein requires not only an AUUUA destabilization pentamer, but also a flanking U-rich domain(s). Using radiolabeled 3'-untranslated regions of short-lived mRNA, we were able to identify this same M(r) 35,000 cytosolic RNA-binding protein(s), beta-ARB protein, as selective for beta 2-adrenergic receptor mRNA.

Isolation of T-cell clones with specificity for arterial antigen from spontaneously hypertensive rats

OBJECTIVE

It has been postulated that hypertension in the spontaneously hypertensive rat (SHR) results from autoimmune damage to the SHR vasculature. The objective of this study was to isolate autoreactive T-cells specific for arterial antigens, and to characterize these cells.

DESIGN

The presence of autoreactive T-cells in the SHR has not been studied previously. Lymphocytes were isolated from spleens obtained from SHR and Wistar-Kyoto (WKY) rats aged 4, 8, 12, 16, 20, 24 and 28 weeks.

METHODS

Limiting dilution analysis was used to clone and to establish arterial antigen-reactive T-cell clones. The specificity of these clones was assessed by measuring lymphokine production and T-cell proliferation induced by arterial antigen and by irrelevant control antigens.

RESULTS

All of the SHR, regardless of age, possessed arterial antigen-specific CD4+, major histocompatability complex class II-restricted T-cells. The responses of freshly isolated spleen cells to arterial antigen were weaker than the proliferative responses of interleukin-2-expanded T-cells to arterial antigen. The T-cell clones also produced interleukin-2, interleukin-4 and interferon-gamma in response to arterial antigen. However, the presence of T-cells specific for arterial antigen is not unique to SHR, since a similar response was seen in normotensive WKY rats.

CONCLUSIONS

The results indicate the existence of T-cells specific for arterial antigen in the spleens of both SHR and WKY rats. Thus, arterial antigen-reactive T-cells cannot be the initial cause of hypertension, but the activation of such autoreactive T-cells might be important in the development of hypertension.

IL-10 inhibits macrophage costimulatory activity by selectively inhibiting the up-regulation of B7 expression

We have previously demonstrated that the inhibitory effects of IL-10 on ConA-induced T cell proliferation or IL-2 production by resting murine T cells were only observed when macrophages, but not when activated B cells, dendritic cells, or L cells, were used as accessory cells. To further elucidate the mechanism of action of IL-10 on the inhibition of macrophage costimulatory activity, we have used a system in which macrophages can develop into effective costimulator cells and the effect of IL-10 on this process can be studied in the absence of T cells. After fixation, resting macrophages have no costimulatory activity for soluble anti-CD3-induced T cell proliferation nor do they express the activation Ag B7/BB1. In contrast, macrophages activated by culture alone, or by culture with IFN gamma or LPS for 24 h, and then fixed, were effective accessory cells, expressed B7, and their costimulatory activity correlated with their level of cell surface B7 expression. Addition of IL-10 during the process of macrophage activation resulted in both a marked reduction in costimulatory activity and in B7 expression. IL-4 and transforming growth factor-beta that suppress many macrophage functions did not inhibit the induction of B7 expression. The inhibitory effect of IL-10 on the up-regulation of B7 was selective because the up-regulation of intercellular adhesion molecule-1 and MHC class II Ag was not affected. Direct evidence that the lack of B7 is the relevant limiting defect for IL-10-treated macrophage accessory cell function was obtained from studies in which the costimulatory capacity of IL-10-treated macrophages could be completely restored by the addition of B7 transfected, but not nontransfected, L cells to the assays.

IL-10 inhibits macrophage costimulatory activity by selectively inhibiting the up-regulation of B7 expression

We have previously demonstrated that the inhibitory effects of IL-10 on ConA-induced T cell proliferation or IL-2 production by resting murine T cells were only observed when macrophages, but not when activated B cells, dendritic cells, or L cells, were used as accessory cells. To further elucidate the mechanism of action of IL-10 on the inhibition of macrophage costimulatory activity, we have used a system in which macrophages can develop into effective costimulator cells and the effect of IL-10 on this process can be studied in the absence of T cells. After fixation, resting macrophages have no costimulatory activity for soluble anti-CD3-induced T cell proliferation nor do they express the activation Ag B7/BB1. In contrast, macrophages activated by culture alone, or by culture with IFN gamma or LPS for 24 h, and then fixed, were effective accessory cells, expressed B7, and their costimulatory activity correlated with their level of cell surface B7 expression. Addition of IL-10 during the process of macrophage activation resulted in both a marked reduction in costimulatory activity and in B7 expression. IL-4 and transforming growth factor-beta that suppress many macrophage functions did not inhibit the induction of B7 expression. The inhibitory effect of IL-10 on the up-regulation of B7 was selective because the up-regulation of intercellular adhesion molecule-1 and MHC class II Ag was not affected. Direct evidence that the lack of B7 is the relevant limiting defect for IL-10-treated macrophage accessory cell function was obtained from studies in which the costimulatory capacity of IL-10-treated macrophages could be completely restored by the addition of B7 transfected, but not nontransfected, L cells to the assays.

Defective major histocompatibility complex class II assembly, transport, peptide acquisition, and CD4+ T cell selection in mice lacking invariant chain expression

We used gene targeting techniques to produce mice lacking the invariant chain associated with major histocompatibility complex (MHC) class II molecules. Cells from these mice show a dramatic reduction in surface class II, resulting from both defective association of class II alpha and beta chains and markedly decreased post-Golgi transport. The few class II alpha/beta heterodimers reaching the cell surface behave as if empty or occupied by an easily displaced peptide, and display a distinct structure. Mutant spleen cells are defective in their ability to present intact protein antigens, but stimulate enhanced responses in the presence of peptides. These mutant mice have greatly reduced numbers of thymic and peripheral CD4+ T cells. Overall, this striking phenotype establishes that the invariant chain plays a critical role in regulating MHC class II expression and function in the intact animal.