An alpha 5 beta 1-like integrin receptor mediates the binding of less pathogenic Candida species to fibronectin

The present study was undertaken to investigate whether less pathogenic Candida species (C. tropicalis, C. stellatoidea, C. krusei and C. glabrata) express a fibronectin receptor (FNr) antigenically related to alpha 5 beta 1 integrin, which mediates their binding to fibronectin (FN). By flow cytometric analysis, a monoclonal antibody (MAb) directed against human alpha 5 integrin subunit (clone SAM-1) and two different antisera to FNr positively stained C. tropicalis, C. stellatoidea and C. glabrata, with the greatest expression observed for C. tropicalis. No or only marginal immunoreactivity was found on C. krusei. C. tropicalis, C. stellatoidea, C. glabrata, but not C. krusei yeasts specifically adhered to FN; higher levels of adhesion were found for C. tropicalis and C. stellatoidea with respect to C. glabrata. Less pathogenic Candida spp. bound to the Arg-Gly-Asp (RGD) containing 120-kDa fragment of FN and adhesion to intact FN was markedly inhibited by Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP), but not by Gly-Arg-Gly-Glu-Ser-Pro (GRGESP) peptides. In addition, anti-alpha 5 SAM-1 MAb and both anti-FNr antisera strongly blocked binding of less pathogenic Candida spp. to FN. Overall, these results indicate that less pathogenic Candida spp., including C. tropicalis, C. stellatoidea and C. glabrata, express a receptor antigenically related to alpha 5 beta 1 integrin which mediates their adhesion to FN.

Augmentation of carcinoembryonic antigen release from intact, viable tumor cells by a factor in human serum

BACKGROUND

Measurement of carcinoembryonic antigen (CEA) levels in human serum is frequently used to detect tumor recurrence in patients with resected primary colorectal cancers. These levels are highly variable from patient to patient, and the mechanism that determines these levels is still poorly understood.

METHODS

Using a 6-h in vitro CEA-release assay, we determined that a factor in human and fetal bovine sera significantly augments the release of CEA from the tumor cell surface into cell culture supernatants.

RESULTS

As little as 1% serum admixed with tumor cells results in CEA release up to 200% greater than that of serum-free controls. It is not inhibited by 1,10-phenanthroline or heat inactivation (of serum) but is calcium dependent. The electrophoretic mobility and membrane linkage of CEA released by serum appear to be identical to those of CEA released by bacterial phospholipase C. Because bacterial phospholipase C is known specifically to cleave the phosphoinositol (PI) glycan moiety that anchors CEA to the tumor cell surface, a mechanism of action for serum cleaving this anchor is suggested.

CONCLUSIONS

The large range of CEA levels observed in patients with colorectal cancers may be related to differential sensitivity of the CEA membrane anchor to the CEA-releasing factor in serum.

Role of extracellular adenosine triphosphate in the cytotoxic T-lymphocyte-mediated lysis of antigen presenting cells

The lysis of antigen presenting cells (APCs) by cytotoxic T lymphocytes (CTLs) may be one mechanism whereby an immune response is downregulated by Staphylococcus superantigens. Disappearance of monocytes/macrophages from staphylococcal enterotoxin A (SEA)-activated peripheral blood mononuclear cell (PBMC) cultures, but not from control PBMC cultures was seen by flow cytometry. Recently, adenosine triphosphate (ATP) has been described as an effector molecule in CTL-mediated lysis of some murine tumor target cells. We have also shown that ATP caused the lysis of human macrophages, and that treatment of cells with interferon gamma (IFN gamma) rendered macrophages significantly more sensitive to ATP than untreated cells. To show that this purine nucleotide may play a role in modulating the immune system, we generated human CTLs that were stimulated with SEA, and used them as effector cells against SEA-pulsed autologous macrophages. CTLs were found to specifically lyse SEA-pulsed macrophages, while control, unpulsed, macrophages were unaffected. The addition of hexokinase, an enzyme that hydrolyzes ATP, significantly abrogated the killing of SEA-pulsed cells during the assay. In examining the mechanism of cytotoxicity, electron microscopy showed that macrophages incubated with both ATP and CTLs underwent necrosis, rather than apoptosis. From these results, it is suggested that ATP is released from CTLs during antigen presentation, and that IFN gamma-activated macrophages, which are inherently more sensitive to this mediator, are readily lysed and therefore removed from circulation, thus downregulating an immune response.

Interleukin-12-mediated tumoricidal activity of patient lymphocytes in an autologous in vitro ovarian cancer assay system

This study was designed to examine if interleukin-12 (IL-12) can induce cytolytic function of lymphocytes from ovarian cancer patients against either an ovarian cancer cell line or their own autologous tumor cells. Lymphocytes were obtained from the peripheral blood or ascites of ovarian cancer patients and activated with IL-12 alone or concomitantly with interleukin 2 (IL-2) for 2 to 3 days. Activation of lymphocytes and assessment of tumoricidal function by a chromium release assay were performed directly in a standard control medium (RPMI 1640 containing 2 mM glutamine, 100 micrograms/ml streptomycin, 100 units penicillin, 5% heat-inactivated human AB serum, and 5 mM 4-(2-hydroxyethyl)-1-piperazinesulfonic acid) and in 50% ascitic fluid (50% by volume filter-sterilized ascites with 50% of the above-mentioned control medium). Target cells were added directly into the medium in which the lymphocytes were activated in order to more closely mimic in vivo conditions. Lymphocytes, activated by IL-12 in 50% ascitic fluid, were able to lyse autologous tumor cells in 3 of 6 assays and were able to lyse SKOV3 cells (an ovarian cancer cell line) in 5 of 7 assays. The results were not significantly different in the control medium. When both IL-2 and IL-12 were used to activate lymphocytes in 50% ascitic fluid, significant cytotoxicity was generated in 6 of 6 autologous assays and in all 7 patient assays using SKOV3 as a target (P < 0.05). Synergy between the two cytokines was seen in all 13 patient assays in ascitic medium compared to only 5 of 13 assays in control medium. Additionally, when lymphocytes were stimulated with both IL-2 and IL-12, significantly greater cytotoxicity was seen in the ascitic fluid medium compared to the control medium in 13 of 14 assays (P < 0.05). No significant tumoricidal activity was seen by lymphocytes maintained in either medium without the addition of IL-2 or IL-12. Ascitic fluid consistently potentiates the synergy between IL-2 and IL-12 in generating cytotoxicity against ovarian cancer cells but does not increase cytotoxicity induced by IL-12 alone. IL-12 by itself activates tumoricidal activity of lymphocytes in ascitic fluid; however, the addition of IL-2 increases the degree and consistency of this effect. These data support the possibility that IL-12 may warrant further investigation as a potential therapeutic agent in the treatment of advanced ovarian cancer.

Inhibition of extracellular ATP-mediated lysis of human macrophages by calmodulin antagonists

Lysis of human culture-derived macrophages by extracellular ATP has recently been described, and treatment of macrophages with interferon-gamma rendered those cells significantly more sensitive to lysis. In addition, cell death occurred more rapidly in interferon (IFN)-treated cells than in untreated macrophages. In an attempt to identify the mechanism by which extracellular ATP affects macrophages, as well as to explore the differences between interferon-gamma-treated and untreated macrophages, selected metabolic inhibitors were included in the lytic assays. Of the compounds tested, three antagonists of calmodulin-linked pathways (trifluoperazine, KN-62, and calmidazolium) blocked the ATP-mediated lysis of both interferon-gamma-treated and colony-stimulating factor-treated macrophages in a dose-dependent manner. Early signals of the ATP ligation of the P2Z purinoceptors of human macrophages included increases in cytosolic [Ca2+] and depolarization of the plasma membrane. However, the inclusion of calmodulin antagonists in these assays did not abrogate either effect. These results suggest that the mechanism which mediates the efflux of 51Cr-labeled proteins from ATP-lysed macrophages is distinct from calcium mobilization and membrane depolarization, and may involve the generation of secondary pores/channels in the plasma membrane via a calmodulin-linked pathway.

Effect of lymphokines on 35sulfate uptake by the glomerular basement membrane

We have previously shown that lymphocytes from idiopathic minimal-lesion nephrotic patients produce a lymphokine (supernatant factor) that increases the 35sulfate uptake in the glomerular basement membrane (GBM). The purpose of this report was to further characterize the supernatant factor by studying the effects of interleukins (IL) 2-4, 6, and 8, granulocyte-macrophage colony stimulating factor, and tumor necrosis factor on the 35sulfate incorporation by rat glomeruli in vitro. A significant increase in GBM 35sulfate uptake was only seen when the glomeruli were cultured with the addition of IL-8 as compared with control cultures: 10.8 +/- (SEM) 1.7 and 7.9 +/- 1.4 cpm/micrograms GBM protein, respectively (p < 0.005). IL-8 reproduces the effect of the reported supernatant factor on the GBM 35sulfate uptake. Because IL-8 was detected in the supernatant of peripheral mononuclear cell cultures from idiopathic minimal-lesion nephrotic syndrome patients in relapse and because the increased GBM 35sulfate incorporation induced by the supernatant factor has been abolished by the addition to the culture media of anti-IL-8 neutralizing antibodies, we postulate that IL-8 is the previously described supernatant factor.

Expression of interleukin-2 receptor gamma on human monocytes: characterization of lineage specific post-translational modifications

Functional interleukin-2 receptors (IL-2R) on lymphocytes contain both IL-2R beta and gamma chains. Whereas constitutive expression of IL-2R beta has been found on monocytes, the expression of IL-2R gamma on these phagocytes has not been examined. We performed reverse-transcription-polymerase chain reaction with Southern blot analysis on RNA derived from purified human monocytes and discovered that they constitutively produce IL-2R gamma mRNA. Western immunoblotting revealed 58- and 64-kDa forms of IL-2R gamma on YT-1 and human monocytes, whereas 58-, 64-, and 69-kDa bands were detected using peripheral blood mononuclear cells and non-adherent lymphocytes. These different forms resulted from variable N-linked glycosylation since culture of the cells in tunicamycin resulted in detection of a single 39-kDa band which corresponds to the molecular weight predicted from the deduced amino acid sequence. By co-immunoprecipitation, the IL-2R beta subunit associates with only the 64-kDa IL-2R gamma protein band in monocytes.

Monocytes overcome lymphocyte dysfunction in injured adults with elevated Candida antigen titers

OBJECTIVE

Severely injured adults with elevated Candida antigen titers have increased mortality from sepsis, in part because of known neutrophil (PMN) dysfunction. Since PMN function is modulated by monocytes and lymphocytes, this study was undertaken to determine the ability of monocytes and lymphocytes isolated from injured adults with elevated Candida antigen titers to activate the anticandidal function of normal PMNs.

METHODS

Lymphocytes with or without monocytes, isolated from 18 injured adults with elevated titers, were cultured in the presence or absence of heat-killed Candida albicans for 48 hours. Culture supernatants were harvested, diluted 1:40, 1:160, and 1:640, and tested for the ability to stimulate the anticandidal function of normal PMNs using an 3H-glucose incorporation assay. Monocytes and lymphocytes isolated from nine volunteers were studied for comparison.

RESULTS

Supernatants of lymphocytes from healthy volunteers that were cultured with heat-killed C. albicans significantly augmented normal PMN anticandidal function. Supernatants of lymphocytes from injured adults with elevated titers that were cultured with heat-killed C. albicans did not significantly augment normal PMN anticandidal function. Supernatants of monocytes or lymphocytes from both groups of patients were able to upregulate PMN anticandidal function.

CONCLUSIONS

Lymphocytes from injured adults with elevated Candida antigen titers are defective in their ability to stimulate PMN anticandidal function. Monocytes from these patients can respond to Candida exposure and overcome the lymphocyte functional defect seen in injured patients with elevated titers.

Expression of interleukin-2 receptor gamma chain on human neutrophils

The interleukin-2 (IL-2) receptor gamma is an indispensable functional component of IL-2, IL-4, and IL-7 receptors, and thus, is denoted the common gamma chain, gamma c. The present study was undertaken to determine whether human polymorphonuclear neutrophils (PMNs) expressed gamma c chain. Reverse transcription-polymerase chain reaction and Northern blot analysis showed that fresh human PMN constitutively expressed a remarkable level of gamma c mRNA, which is of the size and intensity of that from the peripheral blood mononuclear cells (PBMCs). Granulocyte macrophage-colony stimulating factor, IL-2, and IL-8, which are known to activate PMN functions, failed to regulate the gamma c gene expression. Western blot analysis with a rabbit anti-gamma c polyclonal antibody identified 64-, 58-, and 50-kD gamma c bands in lysates from PMN, but only 64- and 58-kD bands from PBMCs. After the PMNs and PBMCs were treated with tunicamycin to prevent N-linked glycosylation, Western blot analysis detected a single 39-kD band, which is equal to the calculated molecular weight from the cloned cDNA. Thus, our results indicate that PMNs constitutively express high levels of gamma c and the three forms detected are caused by different glycosylation of a protein translated from a single mRNA species.

Candida albicans expresses a fibronectin receptor antigenically related to alpha 5 beta 1 integrin

Cell adhesion molecules, by regulating host-micro-organism interaction, play a major role in the pathogenesis of infectious diseases. The present study was undertaken to investigate the expression of the fibronectin (FN) receptor prototype, alpha 5 beta 1 integrin, on Candida albicans and its involvement in the adhesion to FN. By immunofluorescence and fluorescence activated cell sorter (FACS) analysis, several monoclonal antibodies (mAbs) directed against human alpha 5 or beta 1 integrin subunits, or two different antisera to FN receptor positively stained C. albicans yeast and germ tube phases, this immunoreactivity increasing upon germ tube transition. Twenty-five to thirty per cent of [3H]glucose-labelled Candida yeasts specifically adhered to FN and this adhesion was increased upon germ tube transition. C. albicans yeast and germ tube forms bound to an RGD-containing 120 kDa tryptic fragment of FN and adhesion to FN was markedly inhibited by GRGDSP, but not GRGESP peptides. Moreover, binding of both C. albicans phases to FN was strongly inhibited by anti-alpha 5 SAM-1 mAb, or both anti-fibronectin receptor (FNr) antisera. Overall these results indicate that C. albicans yeast and germ tube phases express a receptor antigenically related to alpha 5 beta 1 integrin which mediates their adhesion to FN. The alpha 5 beta 1 integrin-like receptor expression on C. albicans could be relevant for fungus-host interaction and in the dissemination process of Candida infection.

Phospholipase C-gamma 1 is present on the surface of human colorectal cancer cells

Using murine monoclonal antibodies, we have detected the novel signal transducing enzyme, phospholipase C-gamma 1, on the surface of cultured human colorectal cancer cells. We have also demonstrated the presence of this enzyme on the surface of fresh human tumor cells derived from primary and metastatic colorectal tumors. This enzyme has previously been described to be associated only with the inner face of the plasma membrane and the cell cytosol. The finding of an enzyme critical to the signal transduction pathway may have important implications for additional functions of this protein.

Candida antigen titer is a marker of neutrophil dysfunction after severe injury

Trauma patients with positive Candida antigen titers have high mortality rates. Death is the result of sepsis and multi-organ system failure. Considerations of host immunity to Candida led us to concurrently study the function of neutrophils (PMNs) from severely injured adults with positive titers (n = 20), patients with negative titers matched for age, sex, and injury (n = 20), and volunteers (n = 20). Anticandidal PMN function was determined using a 3H-glucose incorporation assay. RESULTS are expressed as mean percentage of growth inhibition +/- SEM.

RESULTS

PMN, from all groups inhibited Candida growth, although PMNs from titer-positive patients demonstrated less growth inhibition. In vitro cytokines granulocyte macrophage-colony stimulating factor [(GM-CSF), interferon-gamma (IFN-gamma), and interleukin 8 (IL-8)] improved function of PMNs from each group and corrected the impaired anticandidal function of PMNs from titer-positive patients, with GM-CSF being most effective.

CONCLUSIONS

Seriously injured patients with positive Candida antigen titers have PMNs with impaired anticandidal function, which can be restored by cytokines. These findings begin to explain why seriously injured patients with positive Candida antigen titers have increased mortality and to offer hope of therapeutic intervention.

Restoration of lytic function in a human natural killer cell line by gene transfection

NK cells can recognize and lyse target cells without restriction by the MHC. The molecular interaction responsible for NK cell recognition is poorly understood. It has been frequently suggested that the loss of beta 2 integrin in immune competent cells may lead to dysfunction due to inadequate cell-cell interaction. We examined the role of lymphocyte functional adhesion molecule-1 in the function of a human natural killer leukemia cell line, YT-1. A mutant YT-1(-) cell subclone showed an absence of killing activity against a B lymphoma cell line, compared with that against a CD11a/CD18 positive parental cell line, YT-1(+) cells. We found that this loss of cytotoxicity was correlated with lack of surface expression of CD11a/CD18 molecules due to the mutation of the CD18 gene. Using gene transfer experiments, we provide strong evidence demonstrating that CD18 transfection to this mutant NK cell line, YT-1(-), restored the surface expression of CD11a/CD18, and this restoration was accompanied by reexpression of cytotoxic function.

IL-8 production by peripheral blood mononuclear cells in nephrotic patients

We studied the interleukin 8 (IL-8) gene expression by peripheral blood mononuclear cells (PBMC) and the IL-8 serum concentration in patients with idiopathic minimal lesion nephrotic syndrome (IMLNS) and other glomerulopathies. PBMC from eight of the nine (IMLNS) patients in relapse demonstrated the presence of IL-8 mRNA. All three IMLNS patients in remission (P = 0.0026 when compared to patients in relapse) and the two patients with nephrotic syndrome with other glomerulopathies failed to elicit an IL-8 mRNA response. Eleven of the 12 IMLNS patients in relapse showed IL-8 serum concentration above the level of detection. Only one of the seven patients in remission had detectable serum levels of IL-8 (P = 0.0033 when compared to levels from IMLNS patients in relapse). IL-8 serum levels were not detectable in three patients with nephrotic syndrome and other glomerulopathies. Supernatants of PBMC cultures from IMLNS patients in relapse increased the 35sulfate uptake by rat GBM. This effect was abolished by the addition of anti-IL-8 neutralizing antibody to the culture media and reproduced by the addition to the media of IL-8 in concentrations found in the serum of IMLNS patients in relapse. Finally, the effect of IL-8 on the 35sulfate turnover of the glomerular basement membrane (GBM) sulfated compounds was evaluated in vitro. A significant decrease in the percentage of residual 35sulfate incorporated in the GBM (41 +/- 5, mean +/- SEM) was observed in cultures treated with IL-8 as compared to those that were not treated with IL-8 (58 +/- 8, P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of interleukin-2 receptor alpha (IL-2R alpha) mRNA and protein in advanced epithelial ovarian cancer

Advanced epithelial ovarian cancer has recently been identified by us to be associated with elevated serum and ascitic levels of the soluble Interleukin-2 receptor alpha (sIL-2R alpha). To determine the cellular source of sIL-2R alpha, the expression of IL-2R alpha was assessed at the mRNA and protein level in peripheral blood mononuclear cells (PBMC), in ovarian cancer ascitic cell infiltrates and in primary and metastatic epithelial ovarian cancer lesions by immunochemistry, by flow cytometric analysis and by in situ hybridization (ISH). Normal PBMC and the PBMC from ovarian cancer patients had a low or undetectable level of IL-2R alpha mRNA and of IL-2R alpha cell-surface protein expression. Flow cytometric analysis of the heterogeneous ascitic infiltrates revealed few cells positively expressing cell-surface IL-2R alpha. By immunocytochemistry, 1-2% of leukocytes in the ascitic infiltrates were IL-2R alpha+. Cytologically these IL-2R alpha+ cells were lymphocytes. Frozen sections of primary and metastatic ovarian cancer lesions showed sparse lymphocytic infiltration and very small numbers of these tumour infiltrating lymphocytes (TIL) were IL-2R alpha+. In situ hybridization demonstrated that although less than 2% of leukocytes in the ascitic infiltrate had detectable levels of IL-2R alpha mRNA, there was a wide range in the level of mRNA expression in these positive cells. The cells expressing IL-2R alpha mRNA had the cytologic characteristics of lymphocytes. Similarly, in the frozen sections of the solid tumours, there was a range in the level of IL-2R alpha mRNA expression in the few TIL that expressed IL-2R alpha. Importantly, ovarian cancer cells and mesothelial cells did not express IL-2R alpha mRNA or IL-2R alpha protein. Our observations lead us to conclude that lymphocytes are the main, if not the only, source of sIL-2R alpha in ovarian cancer patients. Although cells expressing IL-2R alpha were relatively few in number, as the source of the high levels of sIL-2R alpha, they may contribute to the immunosuppression of ascitic lymphocytes in advanced epithelial ovarian cancer.

Induction of IL-8 gene expression in human polymorphonuclear neutrophils by recombinant IL-2

Induction of IL-8 gene expression was investigated in IL-2-stimulated circulating peripheral blood polymorphonuclear neutrophils (PMN). Brief exposure of normal PMN to human rIL-2 enhanced both transcriptional and translational expression of IL-8. The IL-8 mRNA was first detectable by 3 h, followed by a continuous maintenance of high mRNA levels up to 18 h. Maximal transcription was obtained with 1000 U/ml of IL-2, which achieved the level observed with known neutrophil-activating factors such as granulocyte macrophage-CSF and Candida albicans. The protein synthesis inhibitor, cycloheximide, had no detectable effect on levels of IL-8 mRNA expression in PMN incubated in medium alone; however, cycloheximide could selectively modulate IL-8 mRNA transcription in PMN, depending on the cytokine used. Cycloheximide did not affect or alter IL-8 mRNA induction in IL-2-treated PMN but abrogated it in granulocyte macrophage-CSF-treated PMN and super-induced the level of IL-8 mRNA in C. albicans-treated PMN. Of significance was the observation that IL-2 has no direct chemotactic effect on PMN, whereas the cell-free supernatants from IL-2-stimulated PMN show potent chemotaxis for freshly isolated PMN, which can be specifically blocked by anti-IL-8 Abs. These findings suggested that the induction of IL-8 gene expression in PMN by IL-2 may be involved in the recruitment of PMN into tissues during local IL-2 therapy in human cancer and in part contribute to tumor rejection.

Induction of IL-8 gene expression in human polymorphonuclear neutrophils by recombinant IL-2

Induction of IL-8 gene expression was investigated in IL-2-stimulated circulating peripheral blood polymorphonuclear neutrophils (PMN). Brief exposure of normal PMN to human rIL-2 enhanced both transcriptional and translational expression of IL-8. The IL-8 mRNA was first detectable by 3 h, followed by a continuous maintenance of high mRNA levels up to 18 h. Maximal transcription was obtained with 1000 U/ml of IL-2, which achieved the level observed with known neutrophil-activating factors such as granulocyte macrophage-CSF and Candida albicans. The protein synthesis inhibitor, cycloheximide, had no detectable effect on levels of IL-8 mRNA expression in PMN incubated in medium alone; however, cycloheximide could selectively modulate IL-8 mRNA transcription in PMN, depending on the cytokine used. Cycloheximide did not affect or alter IL-8 mRNA induction in IL-2-treated PMN but abrogated it in granulocyte macrophage-CSF-treated PMN and super-induced the level of IL-8 mRNA in C. albicans-treated PMN. Of significance was the observation that IL-2 has no direct chemotactic effect on PMN, whereas the cell-free supernatants from IL-2-stimulated PMN show potent chemotaxis for freshly isolated PMN, which can be specifically blocked by anti-IL-8 Abs. These findings suggested that the induction of IL-8 gene expression in PMN by IL-2 may be involved in the recruitment of PMN into tissues during local IL-2 therapy in human cancer and in part contribute to tumor rejection.

Effect of the psychoactive metabolite of marijuana, delta 9-tetrahydrocannabinol (THC), on the synthesis of tumor necrosis factor by human large granular lymphocytes

The natural killer cell (NK)/3polymorphonuclear neutrophil axis has recently been identified to be important in early defense against the opportunistic fungi, Candida albicans. Repression of this system is therefore likely to contribute to susceptibility to opportunistic infections. delta 9-Tetrahydrocannabinol (THC), an active constituent of marijuana, has been reported to be immunosuppressive at concentrations that exceed attainable plasma levels. In this report, we examine the possibility that human large granular lymphocytes (LGL) can be immunosuppressed by exposure to THC at physiologically relevant concentrations and probed two functions associated with LGL, i.e., cytokine production and tumoricidal activity. We find that these low levels of THC inhibit tumor necrosis factor-alpha (TNF) induction from LGL by C. albicans and are dependent upon THC dose (0.005-5.0 micrograms/ml) and length of exposure (0.05-3.0 hr). Northern blot analysis indicates that the downregulation of TNF production from LGL by THC resides at the mRNA level. Moreover, exposure of LGL to physiological THC concentrations (0.01-2.0 micrograms/ml) diminishes their cytolytic activity against K562 tumor cells.

Lysis of neuroblastoma cell lines by human natural killer cells activated by interleukin-2 and interleukin-12

Neuroblastoma is the most common extracranial, solid tumor in children. Despite intensive chemotherapy and bone marrow transplantation, the 5-year projected survival rate is 20% to 25%. In vitro studies have shown enhanced natural killer cell (NK) lysis of tumor cells after exposure of NK cells to interleukin-2 (IL-2). In vivo studies have demonstrated similar immunologic effects but have also revealed severe toxicities associated with the use of IL-2. IL-12 is a newly described cytokine that has several properties, including the ability to act synergistically with IL-2 in generating lymphokine-activated killer cells (LAK) against known tumor targets. We investigated the role of IL-12 in the generation of peripheral blood mononuclear cell (PBMC) lysis of neuroblastoma cell lines. PBMC were activated with IL-12 alone and in combination with IL-2. Whereas IL-12 alone produced only modest enhancement of NK cell cytotoxicity, the combination of IL-2 and IL-12 was most effective in activating NK cell lysis of neuroblastoma cell lines. Further, we showed that large granular lymphocytes were the effector cells involved in target cell lysis. Finally, the CD18 molecule was shown to be critical in the lysis of neuroblastoma cells by activated PBMC.

Interleukin-2 prevention of apoptosis in human neutrophils

Evidence is presented that interleukin (IL)-2 maintains viability of human polymorphonuclear cells (PMN) in culture by preventing these cells from undergoing programmed cell death (PCD) and induces the synthesis of new RNA and protein. Our laboratory has recently discovered that human PMN constitutively express IL-2 beta receptor and more importantly, PMN are able to respond functionally to IL-2 by enhanced growth inhibitory activity against an opportunistic fungal pathogen, Candida albicans. We now report that IL-2 was able to interfere with the PCD process and reduce the number of apoptotic PMN to < 40% in 72-h culture. Freshly isolated PMN usually underwent a time-dependent aging process and > 80% of PMN cultured in medium alone for 72 h showed morphologic features of PCD as depicted by hematoxylin and eosin staining as well as by electron microscopy. During the PCD process, untreated PMN not only exhibited condensed nuclear structure and decrease in cell size, but also displayed DNA fragmentation. DNA fragmentation in PMN was prevented by IL-2. Prevention of PCD by IL-2 was associated with an increase in new RNA and protein synthesis in PMN, which may reflect cytokine induction, such as tumor necrosis factor, as we have recently shown. Thus, our data expands our current understanding of PMN in that they may be an active component of the immune system, with a longer life-span when activated than expected.

Elevated Candida antigen titers are associated with neutrophil dysfunction after injury

This study was undertaken to determine if impaired neutrophil (polymorphonuclear leukocytes [PMNL]) function is associated with an elevated Candida antigen titer after injury. PMNL from eight severely injured adults with Candida antigen titers of > or = 1:4 (titer positive) were evaluated for the ability to inhibit growth of Candida albicans in vitro by using a [3H]glucose incorporation assay. PMNL from eight severely injured adults with titers of < 1:4 (titer negative) and from eight healthy volunteers were studied for comparison. PMNL from the titer-positive patients had suppressed ability to inhibit C. albicans growth compared with PMNL from titer-negative patients and healthy volunteers. In vitro, PMNL function against C. albicans could be augmented significantly by cytokines. Granulocyte macrophage-colony-stimulating factor was most potent at augmenting function, followed by interleukin-8 and gamma interferon. Injured patients with elevated candida antigen titers have impaired PMNL function against C. albicans, and this function can be restored by cytokines.

IL-2 independent growth and cytotoxicity of herpesvirus saimiri-infected human CD8 cells and involvement of two open reading frame sequences of the virus

Herpesvirus saimiri is a primate tumor virus and induces acute T cell lymphomas and leukemias in New World monkeys and rabbits. We show in this report that infection of human peripheral white blood cells with a group C strain 484-77 results in selective expansion of CD8 lymphocytes with strong cytotoxic activity and these cells do not require interleukin-2 (IL-2) for growth. Infected cell cultures, termed herpesvirus-activated killer (HAK) cells, have been continuously maintained for several months in tissue culture and these HAK cells contain multiple copies of stable circular viral episomes. The growth and cytotoxicity of HAK cells was found independent of IL-2. Analysis of deletion mutant infected cells suggests that at least two open reading frame sequences of a bicistronic mRNA encoded by the viral genome is involved in controlling IL-2 independence. This model could facilitate studies on growth regulation of human cytotoxic T cells that are important effector cells in immune responses against infectious diseases and cancer and should help us to elucidate the mechanism of transformation by H. saimiri oncogenes.

Lymphocyte dysfunction in injured adults with elevated Candida antigen titers

BACKGROUND

Lymphocytes play an important role in the activation of polymorphonuclear neutrophil (PMN) antimicrobial functions. This study was undertaken to evaluate the ability of lymphocytes from severely injured adults with elevated Candida antigen titers to activate the anticandidal function of normal PMNs.

METHODS

Lymphocytes from 13 injured adults with elevated Candida antigen titers (titer+) were isolated and incubated with or without heat-killed C. albicans. After a 48-hour incubation, cell culture supernatants were harvested and tested for the ability to activate the anticandidal function of normal PMNs. Lymphocytes from 13 volunteers and 13 injury-matched patients with negative Candida antigen titers (titer-) were studied for comparison.

RESULTS

The patients with titer+ and titer- were well matched in terms of age, sex, Injury Severity Score, units of blood transfused, and length-breadth of antibiotic therapy. Patients with titer+ had a higher incidence of bacterial infections than did patients with titer-. Only 2 of the 13 patients with titer+ had a positive Candida culture. Lymphocytes from the volunteers and patients with titer- released large amounts of a PMN-activating factor(s) when exposed to C. albicans. Lymphocytes from the patients with titer+ were defective in their ability to release this activating factor(s) after exposure to C. albicans.

CONCLUSIONS

Although culture evidence of Candida was uncommon, injured adults with elevated Candida antigen titers have lymphocyte dysfunction and often suffer documented bacterial infections.

Lysis of human monocytic leukemia cells by extracellular adenosine triphosphate: mechanism and characterization of the adenosine triphosphate receptor

The present study shows that extracellular adenosine triphosphate (ATP) has the capacity to mediate dose-dependent lysis of the monocytic leukemia cell line THP-1. The lysis, assessed by 51Cr release, was found to be selective for ATP, because adenosine diphosphate (ADP) or other nucleotides were less effective in their ability to lyse the cells. The amount of 51Cr released was particularly enhanced by the stimulation of the cells with 1,000 U/mL of interferon gamma (IFN-gamma) for 3 days, and the sensitivity was time and dose dependent. Analysis of the mechanism of lysis indicated that the fully ionized form, ATP4-, mediated the lysis, because the addition of cation chelators or the absence of the divalent cations, Ca2+ and Mg2+, in the culture medium of a 6-hour 51Cr release assay increased the percent specific lysis. Therefore, the ATP receptors on THP-1 cells were classified as P2Z purinoceptors. Moreover, it is shown here that the Ca2+/calmodulin complex plays a role in the regulation of the lysis by extracellular ATP of THP-1 cells, because antagonists of this complex, such as trifluoperazine or KN-62, were found to inhibit the ATP-mediated cell lysis.