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.

The extent of the human germline T-cell receptor V beta gene segment repertoire

An assessment of the size of the human TCRBV gene segment repertoire based on the identification of TCRBV gene segments in genomic DNA was undertaken. PCR amplification from cloned and uncloned genomic DNA sources, nucleotide sequencing, Southern blot hybridization, and cosmid cloning were used to identify TCRBV gene segments in multiple unrelated individuals. The key advantages to this approach were: 1) TCRBV gene segments which are expressed only at very low levels in cDNA libraries were still detectable, and 2) it was possible to discriminate between alleles at the same locus vs products of different loci. A total of 63 unique TCRBV gene segments were identified and sequenced. Six of these TCRBV gene segments had not been previously described. Thirty-four cosmid clones containing 51 of the 63 identified TCRBV gene segments were isolated and screened for the presence of additional novel TCRBV subfamily members. These results, obtained by a variety of complementary approaches, indicate that the human TCRBV germline repertoire encodes at least 63 TCRBV gene segments of which 52 are functional. The availability of the majority of these TCRBV gene segments on cosmid clones should facilitate further investigation of germline TCRBV gene segment polymorphism and putative disease associations.

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.

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.

Immunomodulation in vivo by the Mycoplasma arthritidis superantigen, MAM

Mycoplasma arthritidis produces a potent superantigen (MAM) that activates specific murine and human T lymphocytes to proliferate and secrete lymphokines. We show here that MAM also influences both T- and B-cell functions in vivo. Lymphocytes from mice injected with MAM exhibit a suppression of proliferative responses to MAM in vitro but only a partial suppression of responses to other mitogens. This T-cell anergy not only decreased contact sensitivity to dinitrofluorobenzene but also prolonged survival of skin transplants. In contrast, B-cell reactivity is increased following in vivo injection of MAM, as evidenced by enhanced antibody responses to sheep red blood cells and ovalbumin. Also, there is a marked decrease in the ability of splenocytes from MAM-injected mice to produce interleukin-2 (IL-2) but a marked increase in their ability to produce IL-4 and IL-6. The combined results suggest that MAM induces a lymphokine profile that favors activation of B-cell functions, with a resulting potential for triggering of autoimmune disease.

Coinduction of granulocyte-macrophage colony-stimulating factor release and lymphokine-activated killer cell susceptibility in monocytes by interleukin-2 via interleukin-2 receptor beta

Human monocytes express interleukin-2 receptor beta (IL-2R beta) constitutively; however, the function of these receptors has not been fully delineated. We discovered that IL-2R beta directs two biologic activities in human monocytes, the release of granulocyte-macrophage colony-stimulating factor (GM-CSF) and increased susceptibility to lysis by lymphokine-activated killer cells (LAK) cells. Human monocytes were purified from peripheral blood mononuclear cells by plastic adherence and anti-CD2 plus complement lysis. By a 5-hour 51Cr-release assay, monocytes cultured in IL-2 were found to gain increasing susceptibility to LAK cells with time and this effect was dose dependent. Maximal susceptibility was obtained with a 4-day culture in 1,000 U/mL of IL-2. Monocytes were also found to release GM-CSF in response to IL-2 using a CSF-dependent cell line, Mo7e. Because IL-2-induced GM-CSF release coincides with LAK lysis of IL-2-cultured monocytes, we treated monocytes with anti-GM-CSF and anti-IL-2R beta to determine whether GM-CSF release and LAK susceptibility were dependent or independent events. We found that both phenomena were inhibited by either antibody. Therefore, we conclude that IL-2-induced release of GM-CSF is mediated by IL-2R beta, which then acts to modulate the susceptibility of monocytes to lysis by LAK cells.

Retinol release by activated rat hepatic lipocytes: regulation by Kupffer cell-conditioned medium and PDGF

In normal liver, lipocytes are the principal reservoir for retinoids, which are stored as retinyl esters. In liver injury, lipocytes activate into myofibroblast-like cells, which lack retinoid. We examined mechanisms of retinoid loss using a culture model in which lipocyte activation is provoked by exposure to Kupffer cell-conditioned medium (KCM) (S.L. Friedman and M. J. P. Arthur, J. Clin. Invest. 84: 1780-1785, 1989). In lipocytes exposed to KCM, there was approximately 11-fold more retinol in medium than in untreated cells, without release of retinyl esters. Both bile salt-dependent and -independent retinyl ester hydrolase was entirely intracellular, suggesting that the increase in retinol was due to intracellular hydrolysis; activity of bile salt-independent hydrolase was increased in KCM-treated lipocytes. Release of retinol was serum dependent and inhibited 40% by antibodies to platelet-derived growth factor (PDGF). The addition of 10 nM PDGF to serum-free KCM also induced retinol release. Lipocyte expression of mRNAs for cellular retinol-binding protein, retinoic acid receptor (RAR)-alpha, and RAR-beta was unchanged after exposure to KCM. In summary, activation of cultured lipocytes by KCM is accompanied by serum- and PDGF-dependent release of retinol; a similar mechanism may underlie retinoid loss by activated lipocytes in vivo.

Organization of human T-cell receptor beta-chain genes: clusters of V beta genes are present on chromosomes 7 and 9

To ascertain the extent and organization of the germ-line human T-cell receptor (TCR) beta-chain gene repertoire, beta-chain variable region (V beta) genes were mapped by pulsed-field gel electrophoresis, cosmid cloning, and in situ hybridization. Probes derived from the 24 known V beta families were mapped to a total of six Sfi I fragments in DNA samples from multiple individuals representing all possible haplotypes of TCR V- and C (constant)-region insertion/deletion-related polymorphisms. Four of the Sfi I fragments were linked to one another to develop an extended map of the TCR beta-chain gene complex previously localized to chromosome 7q35. The remaining two Sfi I fragments, containing 6 V beta genes, could not be linked to the TCR beta-chain gene complex. Using human-hamster somatic cell hybrids and in situ hybridization, these orphon genes were localized to chromosome 9p. Nucleotide sequences of the orphon V beta genes, derived from cosmid clones, were 93-97% identical to V beta genes in the TCR beta-chain gene complex. Open reading frames in three of the orphon V beta genes were intact as were the recombination signal sequences. As expected, based on their orphon status, none of the V beta genes of chromosome 9 was detected in transcripts containing C beta. These results indicate that the functional germ-line V beta repertoire in humans is substantially (10%) smaller than previously estimated.

Activation of tumor necrosis factor-alpha production from human neutrophils by IL-2 via IL-2-R beta

In addition to T cells, NK cells, B cells, and monocytes, we provide new evidence that human polymorphonuclear neutrophils (PMN) can be functionally activated by IL-2 via binding to IL-2R beta expressed on the cell surface. Brief exposure of normal PMN to human rIL-2 enhanced both transcriptional and translational expression of TNF-alpha. The release of TNF-alpha protein by IL-2-treated PMN was inhibitable by a specific mAb against human IL-2-R beta. The response to IL-2 was dose and time dependent with the increase in TNF-alpha mRNA detected maximally 3 h after IL-2 exposure, followed by a continuous maintenance of high mRNA levels up to 18 h. The TNF-alpha mRNA was significantly increased above the medium control level, with as little as 10 U/ml of IL-2. 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, IL-8, and Candida albicans. Using actinomycin D, it was found that new and continuous synthesis of a labile TNF-alpha mRNA was responsible for the observed high levels of transcripts. Of significance was the observation that cycloheximide could selectively modulate TNF-alpha mRNA transcription in neutrophils, depending on the cytokine used. Cycloheximide did not affect or alter TNF-alpha mRNA induction in IL-2-treated neutrophils but abrogated it in granulocyte-macrophage-CSF-treated neutrophils and superinduced transcription in C. albicans-treated neutrophils. Thus various control elements must be involved in the transcription of the TNF-alpha genes that are responsive to different cytokines and activating factors. The induction of TNF-alpha and functional activation of neutrophils by IL-2 is therefore an important immunomodulatory property of IL-2 that has not heretofore been recognized.

Activation of tumor necrosis factor-alpha production from human neutrophils by IL-2 via IL-2-R beta

In addition to T cells, NK cells, B cells, and monocytes, we provide new evidence that human polymorphonuclear neutrophils (PMN) can be functionally activated by IL-2 via binding to IL-2R beta expressed on the cell surface. Brief exposure of normal PMN to human rIL-2 enhanced both transcriptional and translational expression of TNF-alpha. The release of TNF-alpha protein by IL-2-treated PMN was inhibitable by a specific mAb against human IL-2-R beta. The response to IL-2 was dose and time dependent with the increase in TNF-alpha mRNA detected maximally 3 h after IL-2 exposure, followed by a continuous maintenance of high mRNA levels up to 18 h. The TNF-alpha mRNA was significantly increased above the medium control level, with as little as 10 U/ml of IL-2. 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, IL-8, and Candida albicans. Using actinomycin D, it was found that new and continuous synthesis of a labile TNF-alpha mRNA was responsible for the observed high levels of transcripts. Of significance was the observation that cycloheximide could selectively modulate TNF-alpha mRNA transcription in neutrophils, depending on the cytokine used. Cycloheximide did not affect or alter TNF-alpha mRNA induction in IL-2-treated neutrophils but abrogated it in granulocyte-macrophage-CSF-treated neutrophils and superinduced transcription in C. albicans-treated neutrophils. Thus various control elements must be involved in the transcription of the TNF-alpha genes that are responsive to different cytokines and activating factors. The induction of TNF-alpha and functional activation of neutrophils by IL-2 is therefore an important immunomodulatory property of IL-2 that has not heretofore been recognized.

Effects of L-type calcium channel antagonists on the serotonin-depleting actions of MDMA in rats

The calcium channel antagonists verapamil nifedipine and flunarizine all increased the threshold for convulsions induced by N-methyl-D-aspartate in rats. By contrast, only flunarizine blocked the long-term serotonin-depleting effects of 3,4-methylenedioxymethamphetamine. Flunarizine was also the only drug that antagonized methamphetamine-induced stereotypy. These findings suggest that calcium influx through L-type channels does not participate in the neurotoxic mechanism of MDMA, and that the neuroprotective actions of flunarizine are probably related to its anti-dopaminergic activity.

Function associated with IL-2 receptor-beta on human neutrophils. Mechanism of activation of antifungal activity against Candida albicans by IL-2

Polymorphonuclear neutrophils (PMN) are essential components of the host defense system against a wide variety of pathogens. We report here the novel finding that freshly isolated human PMN constitutively express detectable surface levels of IL-2R beta, but not IL-2R alpha, as analyzed by flow cytometry. Northern blot analysis confirmed the constitutive expression of mRNA for IL-2R beta in PMN. Scatchard analysis using 125I-labeled IL-2 demonstrated the presence of approximately 600 intermediate binding IL-2R per PMN, with a dissociation constant of 1.1 x 10(-9) M, similar to that of IL-2 binding to YT-1 tumor cells that specifically express IL-2R beta. More importantly, PMN were able to respond functionally to IL-2 by enhanced growth-inhibitory activity against an opportunistic fungal pathogen, Candida albicans. IL-2 activation of antifungal activity was dose-dependent, with some functional activation detected at 1 U/ml of rIL-2 and maximal activation at 1000 U/ml. The action of IL-2 was rapid, with maximal PMN activation after 30-min incubation with IL-2. The IL-2 enhancement of antifungal activity could be blocked by a specific antibody against IL-2R beta, but not by anti-IL-2R alpha. Analysis of the mechanism of IL-2 activation of PMN indicated that oxidative metabolism, as measured by superoxide anion production, was not involved. Instead, PMN release of lactoferrin appeared to be responsible for the heightened activity against C. albicans in IL-2-treated PMN. Not only was lactoferrin detected in the supernatants of IL-2-treated PMN, but also the antifungal activity of PMN activated by IL-2 could be blocked in the presence of antilactoferrin. These results, taken together, indicate that normal PMN are capable of functionally responding to IL-2 via expression of the IL-2R beta chain.

Function associated with IL-2 receptor-beta on human neutrophils. Mechanism of activation of antifungal activity against Candida albicans by IL-2

Polymorphonuclear neutrophils (PMN) are essential components of the host defense system against a wide variety of pathogens. We report here the novel finding that freshly isolated human PMN constitutively express detectable surface levels of IL-2R beta, but not IL-2R alpha, as analyzed by flow cytometry. Northern blot analysis confirmed the constitutive expression of mRNA for IL-2R beta in PMN. Scatchard analysis using 125I-labeled IL-2 demonstrated the presence of approximately 600 intermediate binding IL-2R per PMN, with a dissociation constant of 1.1 x 10(-9) M, similar to that of IL-2 binding to YT-1 tumor cells that specifically express IL-2R beta. More importantly, PMN were able to respond functionally to IL-2 by enhanced growth-inhibitory activity against an opportunistic fungal pathogen, Candida albicans. IL-2 activation of antifungal activity was dose-dependent, with some functional activation detected at 1 U/ml of rIL-2 and maximal activation at 1000 U/ml. The action of IL-2 was rapid, with maximal PMN activation after 30-min incubation with IL-2. The IL-2 enhancement of antifungal activity could be blocked by a specific antibody against IL-2R beta, but not by anti-IL-2R alpha. Analysis of the mechanism of IL-2 activation of PMN indicated that oxidative metabolism, as measured by superoxide anion production, was not involved. Instead, PMN release of lactoferrin appeared to be responsible for the heightened activity against C. albicans in IL-2-treated PMN. Not only was lactoferrin detected in the supernatants of IL-2-treated PMN, but also the antifungal activity of PMN activated by IL-2 could be blocked in the presence of antilactoferrin. These results, taken together, indicate that normal PMN are capable of functionally responding to IL-2 via expression of the IL-2R beta chain.

Impaired polymorphonuclear leukocyte anticandidal function in injured adults with elevated Candida antigen titers

Per protocol, adults with an Injury Severity Score of 18 or greater underwent Candida antigen titer measurements weekly. If titers were 1:4 or greater, neutrophil function against Candida albicans was determined with use of a tritiated glucose incorporation assay, and polymorphonuclear leukocytes obtained from healthy blood donors were studied concurrently for comparison. Polymorphonuclear leukocytes from healthy blood donors and injured patients with elevated titers were able to inhibit C albicans growth in a dose-dependent fashion. Polymorphonuclear leukocytes from injured patients with elevated titers had a significantly depressed ability to inhibit Calbicans growth compared with those from healthy blood donors at all effector cell-to-target cell ratios tested. Cytokine-treated polymorphonuclear leukocytes from healthy blood donors and injured patients with elevated Candida antigen titers demonstrated significantly improved anticandidal activity at all ratios of polymorphonuclear leukocytes-to-Candida. Granulocyte macrophage-colony stimulating factor was the most potent cytokine at reconstituting polymorphonuclear leukocyte function, followed by interferon gamma and interleukin 8. In conclusion, an elevated Candida antigen titer in injured adults is associated with impaired polymorphonuclear leukocyte antifungal activity. This depressed activity can be reconstituted by the addition of cytokine.

Resolution of dihydroxyeicosanoates and of dihydroxyeicosatrienoates by chiral phase chromatography

A chromatographic method is described for the direct enantiomeric characterization of 5,6-, 8,9-, 11,12-, and 14,15-vic-dihydroxyeicosatrienoic acids (DHETs), metabolites of the cytochrome P-450 arachidonate epoxygenase pathway, and of their corresponding saturated vic-dihydroxyeicosanoic acids. Following esterification, the individual methyl or pentafluorobenzyl esters are resolved by chiral-phase chromatography utilizing a Chiralcel OC or OD column. This methodology will find analytical and preparative applications since it is simple and efficient and preserves, intact, the diol functionality.