bluuebunny/crossref_metadata_2025_split huggingface dataset:
Potent heme-degrading action of antimony and antimony-containing parasiticidal agents
Authors: Drummond GS , Kappas A 
Published: June 2004

The ability of antimony and antimony-containing parasiticidal agents to enhance the rate of heme degradation in liver and kidney was investigated. Trivalent antimony was shown to be an extremely potent inducer of heme oxygenase, the initial and rate-limiting enzyme in heme degradation, in both organs, whereas the pentavalent form was a weak inducer of this enzyme. The ability of antimony to induce heme oxygenase was dose-dependent, independent of the salt used, and not a result of a direct activation of the enzyme in vitro. Concomitant with heme oxygenase induction by antimony, microsomal heme and cytochrome P-450 contents decreased, the cyto-chrome P-450-dependent mixed function oxidase system was impaired, and δ-ami-nolevulinate synthase (ALAS), the rate-limiting enzyme of heme synthesis, underwent the sequential changes-initial inhibition followed by rebound induction-usually associated with the administration of transition elements such as cobalt.
Antimony induction of heme oxygenase however, unlike the enzyme induction elicited by cobalt, was not prevented either by cysteine administered orally or as a cysteine metal complex, or by simultaneous zinc administration. Desferoxamine also did not block heme oxygenase induction by antimony, but this chelator did prevent the rebound increase in ALAS activity associated with antimony or cobalt treatment.
Antimony-containing parasiticidal drugs were also potent inducers of heme oxygenase in liver and kidney. The heme degradative action of these drugs may be related in part to the jaundice commonly associated with the prolonged therapeutic use of these agents.
The heme-oxygenase-inducing action of antimony-containing parasiticidal drugs is a newly defined biological property of these compounds. The relation between the parasiticidal and the heme-oxygenase-inducing actions of such drugs is unknown. However, certain parasites contain hemoproteins or require heme compounds during their life cycle. It may therefore be useful to explore the possibility that the heme-degrading and the parasiticidal actions of certain metals or metal-containing therapeutic agents are in some way related.
Interaction of the legionnaires' disease bacterium (legionella pneumophila) with human phagocytes. I. L. pneumophila resists killing by polymorphonuclearleukocytes, antibody, and complement
Authors: Horwitz MA , Silverstein SC 
Published: June 2004

We have previously reported that virulent egg yolk-grown Legionella pneumophila, Philadelphia 1 strain, multiplies intracellularly in human blood monocytes. We now report on the interaction between virulent L. pneumophila and human polymorphonuclear leukocytes (PMN), antibody, and complement, in vitro, under antibiotic-free conditions.
L. pneumophila in concentrations ranging from 10(3) to 10(6) colony forming units (CFU)/ml are completely resistant to the bactericidal effects of 0-50 percent fresh normal human serum, even in the presence of high concentrations of rabbit or human anti-L. pneumophila antibody.
L. pneumophila bacteria fix the third component of complement (C3) to their surfaces, as measured by fluorescence microscopy using rhodamine- conjugated goat anti-human C3 IgG, only when the bacteria are incubated with both specific anti-L. pneumophila antibody and complement. Similarly, L. pneumophila adhere to PMN, as measured by fluorescence microscopy, only in the presence of both specific antibody and complement. Electron microscopy revealed that these opsonized bacteria are phagocytosed by the PMN.
PMN require both antibody and complement to kill L. pneumophila; even then, PMN reduced CFU of L. pneumophila by only 0.5 log under conditions in which they reduce CFU of a serum-resistant encapsulated strain of Escherichia coli by 2.5 logs. Separation of PMN-associated and nonassociated CFU of L. pneumophila revealed that the major proportion of the surviving bacteria are PMN associated. Thus, the ineffective killing of opsonized L. pneumophila is a result of a failure of PMN to kill these bacteria after they become PMN- associated. With or without antibody, PMN do not support the growth of L. pneumophila. These findings suggest that PMN, even in conjunction with the humoral immune system, do not play a decisive role in defense against the Legionnaires' disease bacterium.
Studies of the cell surface of mouse dendritic cells and other leukocytes
Authors: Nussenzweig MC , Steinman RM , Unkeless JC , Witmer MD , Gutchinov B , Cohn ZA 
Published: June 2004

The surface of dendritic cells (DC) has been analyzed by means of monoclonal antibodies (Ab) and lactoperoxidase (LPO)-mediated radioiodination. Antigens and other exteriorily disposed polypeptides of purified spleen DC were compared with those of tissue macrophages (Mφ), monocytes, and other bone marrow-derived elements.
Quantitative binding studies and autoradiography with (125)I-Ab established that DC expressed high levels of I-A and H-2D, 2 × 10(5) and 1 × 10(5) Ab binding sites per cell, respectively. DC from conventional, germ-free, and specific pathogen-free mice were all rich in Ia. Expression of Ia on B cells was 5-10 percent of that on DC and increased fivefold during lipopolysaccharide mitogenesis. More than 70-90 percent of purified Mφ and monocytes from specific pathogen-free mice were Ia negative, but increased levels of Ia were noted on cells from mice reared under conventional conditions. Thus large amounts of Ia on DC is a constitutive trait, whereas the expression of Ia by other cell types may be governed by the environmental and immunological status of the host.
The 2.4G2 Fc receptor Ag was not detected on DC. Peritoneal and spleen Mφ had 10(5) 2.4G2 binding sites/cell, whereas monocytes and lymphocytes were less reactive (1 × 10(4)-3 × 10(4) binding sites/cell).
Four other Mφ-related antigens were evaluated. Each had a distinctive tissue distribution and none bound exclusively to Mφ and monocytes. Neither 1.21J (Mac-1) nor F4/80 reacted with DC. Immunoprecipitation studies of externally ((125)I) and biosynthetically ([(35)S]methionine)dabeled cells confirmed the binding data.
Sensitive binding assays with (125)I-Ab confirmed previous observations that DC lack Ig and Thy-1. Lyt-1 was also not found on DC, but 5-12 percent of the cells in purified DC preparations expressed both Lyt-2 and Ia. All DC expressed the leukocyte common antigens at levels similar to other leukocytes.
The spectrum of surface polypeptides labeled by LPO-mediated iodination was different on Mφ, DC, and lymphocytes. Polypeptides migrating at molecular weights of 155,000, 85,000, and 62,000 appeared to be restricted to DC.
These observations establish that the cell surface of DC differs considerably from other leukocytes, including the blood monocyte, and suggest that the DC is part of a unique Ia-rich leukocyte differentiation pathway.
Activated human monocytes inhibit the intracellular multiplication of legionnaires' disease bacteria
Authors: Horwitz MA , Silverstein SC 
Published: June 2004

We have examined the interaction between virulent egg yolk-grown L. pneumophila, Philadelphia 1 strain, and in vitro-activated human monocytes, under antibiotic-free conditions. Freshly explanted human monocytes activated by incubation with concanavalin A (Con A) and human lymphocytes inhibited the intracellular multiplication of L. pneumophila. Both Con A and lymphocytes were required for activation. Con A was consistently maximally effective at greater than or equal to 4 μg/ml.
Monocytes activated by incubation with cell-free filtered supernatant from Con A-sensitized mononuclear cell cultures also inhibited the intracellular multiplication of L. pneumophil a. The most potent supernatant was obtained from mononuclear cell cultures incubated with greater than or equal to 15 μg/ml Con A for 48 h. The degree of monocyte inhibition of L. pneumophila multiplication was proportional to the length of time monocytes were preincubated with supernatant (48 {greater than} 24 {greater than} 12 h) and to the concentration of supernatant added (40 percent {greater than} 20 percent {greater than} 10 percent {greater than} 5 percent). Monocytes treated with supernatant daily were more inhibitory than monocytes treated initially only. With time in culture, monocytes progressively lost a limited degree of spontaneous inhibitory capacity and also lost their capacity to respond to supernatant with inhibition of L. pneumophila multiplication.
Supernatant-activated monocytes inhibited L. pneumophila multiplication in two ways. They phagocytosed fewer bacteria, and they slowed the rate of intracellular multiplication of bacteria that were internalized. As was the case with nonactivated monocytes, antibody had no effect on the rate of intracellular multiplication in supernatant-activated monocytes.
Neither supernatant-activated nor nonactivated monocytes killed L. pneumophila in the absence of antibody. Both killed a limited proportion of these bacteria in the presence of antibody and complement.
We have previously reported that anti-L, pneumophila antibody and complement neither promote effective killing of L. pneumophila by human polymorphonuclear leukocytes and monocytes nor inhibit the rate of L. pneumophila multiplication in monocytes. These findings and our present report that activated monocytes do inhibit L. pneumophila multiplication indicate that cell-mediated immunity plays a major role in host defense against Legionnaires' disease.
Interstitial mononuclear cell populations in renal graft rejection. Identification by monoclonal antibodies in tissue sections
Authors: Platt JL , LeBien TW , Michael AF 
Published: June 2004

The interstitial mononuclear cell populations of 22 renal grafts with interstitial rejection (IR), 6 grafts with interstitial nephritis without rejection (IN), and 5 kidneys without infiltration (3 donor kidneys, 2 grafts) were identified and quantitated by monoclonal antibodies recognizing T cells (TA-1, OKT3), helper inducer cells (OKT4), cytotoxic/suppressor cells (OKT8), B cells (BA-1), and monocytes and null cells (OKM1). Double-layer fluorochrome enhancement using F(ab')(2) reagents and nuclear counter staining with ethidium bromide enabled quantitation of the number of positive mononuclear cells, interstitial cells, and total cells on each of 30-55 microscopic fields per tissue section. T cells were the most abundant infiltrating cell in tissues with IR (35 +/- 9.8 percent), significantly higher than that seen in IN (21 +/- 16 percent) or in kidneys without infiltration (5.0 +/- 3.9 percent). The percentage of T cells identified by TA-1 or OKT3 was approximately equivalent to the summation of OKT4 plus OKT8. Although no differences were observed in the percentage of OKT4 cells, the percentage of OKT8 was significantly higher in IR (26 +/- 7.7 percent, P {less than} 10(-4)) than in IN (9.3 +/- 6.2 percent) or in kidneys with normal interstitium (3.0 +/- 2.4 percent). The ratio of OKT8/OKT4-positive T cells in 22 graft tissues with IR (3.2 +/- 1.4) was greater (P {less than} 0.0007) than 6 graft tissues with IN without rejection (0.82 +/- 0.39) and the 5 kidney tissues without interstitial infiltration (0.75 +/- 0.25). There was no significant difference between the groups in the relatively low percentage of interstitial cells identified as B cells reacting with BA-1 or containing S(IgD,M). The percentage of interstitial cells recognized by OKM1 was similar in rejection and interstitial nephritis, with both being greater than controls (P {less than} 0.02). The relative numbers of blood mononuclear cells identified by the monoclonal antibodies was generally not predictive of the proportions present in kidney tissue, although OKT4-positive blood cells were less numerous and OKMI+ blood cells were more numerous than in controls (P {less than} 0.002).
Quantitative analysis of identifiable interstitial cells in graft rejection reveals that most infiltrating cells are T cells, the greater proportion of which are recognized by OKT8. OKT8-positive cells may play an important role in mediating renal graft rejection.
Serial depletion and regeneration of the murine hematopoietic system. Implications for hematopoietic organization and the study of cellular aging
Authors: Ross EAM , Anderson N , Micklem HS 
Published: June 2004

The mouse hematopoietic system was subjected to repeated depletion and regeneration either by serial transfer of bone marrow cells through lethally irradiated recipients or by repeated treatment with the cycle-active drug hydroxyurea (HU).
The capacity of surviving stem cells to proliferate and self-renew was assayed at intervals by two methods: (a) the spleen colony method; and (b) competitive repopulation of irradiated recipients using chromosome markers, with normal bone marrow cells as an internal control.
The progressive decline in stem cell function that occurred during serial transfer of bone marrow and that had already begun after a single transfer was not seen during HU treatment; up to 25 pairs of HU injections given over more than 1 yr had no discernible effect on the number of stem cells present 3 wk after the final injection or on their capacity to self-renew.
Within 2 d after exposure to HU, the average self-renewal capacity of surviving stem cells was enhanced. This implies that the drug selectively eliminates poorly self-renewing stem cells and hence that these enter cycle more readily than stem cells with a high self-replicative potential. However, the fact of being in cycle at the time of injection did not of itself affect self-renewal.
The results show that serial transfer of bone marrow is not a valid method for studying clonal aging phenomena because it does not fulfill the assumptions on which such studies are based. No evidence was obtained for any intrinsic limitation in the capacity of bone marrow populations for repeated regeneration after HU-induced depletion. However, this does not necessarily imply that individual hematopoietic clones are capable of indefinite expansion because hematopoiesis may (as suggested by the relative resistance of highly self-replicative stem cells to mitogenic signals) proceed on the basis of clonal succession.
Down-regulation of mannosyl receptor-mediated endocytosis and antigen F4/80 in bacillus calmette-guerin-activated mouse macrophages. Role of T lymphocytes and lymphokines
Authors: Ezekowitz AB , Gordon S 
Published: June 2004

Bacillus Calmette-Guerin (BCG) infection alters the surface and endocytic properties of mouse peritoneal macrophages (PM) compared with thioglycollate- elicited (TPM) or resident PM (RPM). Expression of Ia antigen (Ag) is enhanced up to fourfold, but plasma membrane receptors that mediate binding and uptake of mannosyl/fucosyl-terminated glycoconjugates (MFR), Fc receptors, and the macrophage (mφ)-specific Ag F4/80 are reduced by 50-80 percent. Levels of Mac-1 remain relatively stable. These changes are accompanied by enhanced secretion of O(2)(-), after further stimulation with phorbyl myristate acetate, and of plasminogen activator. Both these products are released by TPM, but not RPM. The characteristic surface phenotype of BCG-PM can also be induced by injection of C. parvum, another mφ- activating agent, but not by thioglycollate broth, lipopolysaccharide, or proteose peptone. Purified protein derivative (PPD) and N-acetylmuramyl-L- alanyl-D-isoglutamine. 2H(2)0 are soluble agents with partial activity.
Alteration of mφ markers by BCG infection depends on T lymphocyte function, although studies with nude mice indicate that other pathways may also serve to modify the surface of the mφ. Mφ from uninfected animals displayed all markers of activation after adoptive transfer of specifically-sensitised lymphocytes with PPD, intraperitoneally, or after co- cultivation. Treatment of primed lymphocytes with anti-Thy-1 antibody and complement ablated this effect. Lymphokines obtaned by Ag or mitogen stimulation induced similar changes in TPM and RPM. Mannose-specific endocytosis decayed rapidly, time 1/2 approximately equal to 16 h and stabilized at approximately 25 percent of control values. Single-cell analysis showed that residual MFR activity was uniform in the target population. Loss of Ag F4/80 after activation by lymphocyte and PPD was less marked than after infection (35 percent vs 80 percent), unlike MFR activity, which declined to a similar extent. Induction of mφ Ia by lymphokine reached a peak after 2-3 d and was lost within 2 d of its removal. Recovery of MFR and F4/80 was incomplete under these conditions.
These studies establish that activated mφ known to display enhanced antimicrobial/anticellular activity express markedly different surface properties distinct from elicited or resident cells. The role of antigen- stimulated T cell products in regulating mφ function is confirmed, and down-regulation of mannosyl-receptor-mediated endocytosis provides a sensitive, quantitative, and cell-specific new marker to study their properties and mechanism of action. Extensive, but selective remodeling of mφ plasma membrane structure could play an important role in controlling recognition and effector mechanisms of the activated mφ.
Helper T cells for cytotoxic T lymphocytes need not be I region restricted
Authors: Raulet DH , Bevan MJ 
Published: June 2004

We investigated the antigenic requirements for restimulation of H-2- restricted cytolytic T lymphocytes (CTL) in vitro to determine whether H-2 I region-restricted helper T cells are required in these responses. In one set of experiments, we studied the in vitro response of (responder x nonresponder)F(1) female T cells to the male antigen H-Y. We chose to examine this response because it has been suggested that the defect in nonresponder strains is a failure of helper T cells to recognize H-Y in association with nonresponder I region determinants. However, we find that nonresponder male stimulator cells are as effective as F(1) male stimulator cells at inducing H-Y-specific CTL responses. This finding calls into question reports that secondary CTL responses to H-Y are dependent upon the activation of H-Y- specific helper T cells restricted to responder type I region determinants.
In a second set of experiments, we examined the requirements for restimulation of H-2-restricted T cells specific for minor-histocompatibility antigens from long-term mixed lymphocyte cultures. These cultures were established by repeatedly restimulating cultures of specific T cells with H- 2-matched stimulator cells expressing foreign minor histocompatibility antigens. We found that H-2D-restricted T ceils, including CTL, could be restimulated with cells that were matched with the responding cells at only the D region genes. This response did not appear to result from positive allogeneic effects or from antigen processing and "representation" by responder type APC that might contaminate the cultures. Thus, we find no evidence for a requirement for I region-restricted helper T cells in these CTL responses. However, helper T cells are required because we find that CTL lines derived by limit-dilution cloning from these long-term MLC are absolutely dependent upon exogenous helper factors for growth. The most simple interpretation of these results is that the helper cells are restricted to H-2 antigens other than I region antigens or to antigens that code outside of the H-2 complex.
Finally, we show that factor-dependent CTL lines must recognize their specific antigen to proliferate, even in the presence of exogenous factors. The requirement of activated CTL for antigen to proliferate provides an explanation for how specific CTL can be selectively enriched in MLC by specific antigen stimulation. Furthermore, it is at variance with reports that memory CTL or activated CTL require only interleukin 2 for restimulation.
Accessory and stimulating properties of dendritic cells and macrophages isolated from various rat tissues
Authors: Klinkert WEF , LaBadie JH , Bowers WE 
Published: June 2004

Single cell suspensions of rat lymphoid and nonlymphoid tissues were fractionated on discontinuous gradients of bovine serum albumin into high density and low density subfractions. In general, accessory activity required for responses of periodate-treated T lymphocytes was recovered only in a low density population containing a small percent of the total fractionated cells from lymph nodes, spleen, liver, skin, and peritoneal exudates. Further purification always led to an increase of both accessory activity and number of dendritic cells present in nonrosetting and nonadherent populations. After purification, a high recovery of the total accessory activity was found in fractions that contained a high percentage of dendritic cells resulting in a more than 1,000-fold enrichment in accessory activity per cell. No other fraction obtained during the purification contained significant accessory activity. In all cases, macrophage-enriched populations lacked accessory cell activity. With the exception of peritoneal exudate cell preparations, which contained an inhibitory cell, the level of accessory activity in a given population was always found to be a function of the number of dendritic cells present.
Dendritic cells from all sources were nonadherent, nonphagocytic, radio- resistant, and nonspecific esterase negative. They expressed Ia antigens and lacked Fc receptors. Both epidermal and lymph node dendritic cells contain Birbeck granules, subcellular structures previously described only for Langerhans cells.
Accessory activity requires viable dendritic cells but is unaffected by 1,000 rad of γ-irradiation. However, ultraviolet irradiation abolished the activity of accessory cells. The cells that responded to periodate were IgG-negative T cells, whereas IgG-positive B cells could not be stimulated under the same conditions. Only periodate-treated T cells and dendritic cells were needed for responses to occur; removal of virtually all macrophages from these purified preparations had no effect. Dendritic cells were also required as stimulators in mixed leukocyte cultures, whereas macrophages, even though Ia positive, were inert.