Profile of serum IL-1beta and IL-10 shortly after ovariectomy and estradiol replacement in rats

Ovariectomy leads to progressive and significant increases in body weight gain and osteoporosis and is related to changes in serum and tissue cytokine profiles, such as observed in other models of overweight. We aimed to evaluate serum interleukin-1beta and interleukin-10 shortly after ovariectomy, before the establishment of overweight in rats. Female Wistar rats were submitted to ovariectomy, ovariectomy and estradiol replacement, or sham operation and compared with intact controls. Rats were killed 3, 6, 9, or 13 d after ovariectomy. Body mass and retroperitoneal fats were significant higher only 13 d after ovariectomy, and estradiol replacement to ovariectomized rats impaired both body mass and retroperitoneal fat gain. Shortly after ovariectomy (at 3 d) serum interleukin-1beta levels significantly increased in ovariectomized rats, treated or not with estradiol, while serum interleukin-10 levels increased only 9 d after ovariectomy. Our results suggest the existence of an important interplay between the immune system and ovarian function. This interplay occurs regardless of significant changes in adipose tissue compartment, as ovarian excision leads to short-term changes in the pattern of interleukin-1beta and interleukin-10 cytokine production that precede body weight gain and are not reverted by estradiol replacement.

mCD14 expression in human monocytes is downregulated by ouabain via transactivation of epithelial growth factor receptor and activation of p38 mitogen-activated protein kinase

BACKGROUND AND AIMS

The steroid ouabain is found in plasma and in many mammalian tissues, and is now considered as a hormone. In the immune system, ouabain regulates a number of lymphocyte functions, but little is known about its effects on monocyte function. Monocytes are important for adequate immune responses. The aim of this work was to analyze the effect of ouabain on mCD14 expression, a surface molecule involved in the response against Gram-negative bacteria and phagocytosis.

METHODS

Human peripheral blood mononuclear cells obtained from healthy donors were separated by density gradient centrifugation. Monocytes were separated by adherence and treated for 24 h with 100 nM ouabain. mCD14, CD1a and P-p38 expression was analyzed by flow cytometry. Inhibitors of cell-signaling pathways, i.e. SB202190, reduced glutathione, rottlerin, tyrphostin A23, genistein, chelerythrine chloride, PD98059, PP1 and Ly 294002, were used concomitantly with ouabain to observe their effect on mCD14 expression.

RESULTS

Ouabain induced a significant decrease in mCD14 expression. This feature was not related to receptor endocytosis or cell death. Furthermore, mCD14 downregulation did not reflect a shift in differentiation into dendritic cells because this hormone failed to induce CD1a expression. Amongst several inhibitors of cell-signaling pathways triggered by ouabain, only epidermal growth factor receptor (EGFR) and p38 mitogen-activated protein kinase (MAPK) inhibitors (tyrphostin A23 and SB202109) significantly reverted the effect of ouabain on mCD14 expression. Accordingly, the levels of P-p38 were increased on monocytes after ouabain treatment. However, incubation with epidermal growth factor did not alter mCD14 expression.

CONCLUSION

These findings suggest that ouabain downregulates mCD14 expression on monocytes through EGFR transactivation and p38 MAPK activation.

Negative affect as a predisposing factor for cortisol release after an acute stress--the impact of unpleasant priming

Glucocorticoids have a key role in stress responses. There are, however, substantial differences in cortisol reactivity among individuals. We investigated if affective trait and mood induction influence the reactivity to psychological stress in a group of 63 young adults, male (n=27) and female (n=36), aged ca. 21 years. On the experimental day the participants viewed either a block of pleasant or unpleasant pictures for 5 min to induce positive or negative mood, respectively. Then, they had 5 min to prepare a speech to be delivered in front of a video-camera. Saliva samples were collected to measure cortisol, and questionnaire-based affective scales were used to estimate emotional states and traits. Compared to basal levels, a cortisol response to the acute speech stressor was only seen for those who had first viewed unpleasant pictures and scored above the average on the negative affect scale. There were no sex differences. In conclusion, high negative affect associated with exposure to an unpleasant context increased sensitivity to an acute stressor, and was critical to stimulation of cortisol release by the speech stressor.

Bax expression and apoptotic cell death in Fanconi anaemia peripheral blood lymphocytes

OBJECTIVE

Deregulated apoptosis might be involved in some of the features of Fanconi anaemia (FA). The possibility that the pro-apoptotic Bax protein could be involved in an increased susceptibility to apoptosis in FA patients was investigated.

MATERIALS AND METHODS

Intracellular Bax expression, Bcl-2 expression (an anti-apoptotic protein) and cell death were analysed in 26 FA peripheral blood lymphocyte samples.

RESULTS

Most FA samples (69%) displayed increased levels of Bax and were more susceptible to both spontaneous apoptosis and mitogen activation-induced cell death. Two subgroups were identified: one presented elevated levels of Bax (n = 18), whereas the other (n = 8), had Bax levels lower than controls. Two subgroups based on Bcl-2 expression were also identified: one with normal and another with high Bcl-2 expression. No inverse correlation was found between Bcl-2 levels and Bax expression. A clear difference in susceptibility to induced cell death could be observed between control and FA samples. The best correlation was observed between high levels of Bax and mitogen-induced apoptosis of cells; these displayed characteristics of necrosis secondary to apoptosis, suggesting that the intrinsic apoptotic pathway was being activated.

CONCLUSION

Despite increased susceptibility to cell death induction, there was no correlation between Bax levels, chromosome breakage, haematological parameters or androgen therapy. The importance of apoptosis and Bax expression in the clinical development of FA awaits clarification.

Independent Regulation of ABCB1 and ABCC Activities in Thymocytes and Bone Marrow Mononuclear Cells during Aging

Aging modifies a number of functional and phenotypic parameters of cells from the immune system. In this study, the activities of two members of the superfamily of ATP-binding cassette (ABC) transport proteins, ABCB1 and ABCC (measured by rhodamine 123 efflux and Fluo-3 efflux respectively), were compared in murine bone marrow cells and thymocytes of young (3-4 weeks old), adult (2-3 months old) and old (18 months old) mice. ABCB1 activity was shown to be age regulated in murine bone marrow mononuclear cells and thymocytes. In the bone marrow, the increased amount of cells with ABCB1 activity observed in old mice was restricted to the c-kit(-)Sca-1(+) and c-kit(+)Sca-1(+) subpopulations. Only a small percentage of c-kit(+) cells in the thymus had ABCB1 activity, and this subpopulation increased with age. In the thymus, old age augmented this activity in the CD4(-) CD8(-) double-negative cells and in the CD4(+) and CD8(+) single-positive populations. The activity of another ABC transporter, the ABCC-related activity, was also modified by age in the bone marrow. However, the age-related increase was observed in the subpopulations were ABCB1 was not modified, namely the non-progenitor population (c-kit(-)Sca-1(-)cells) and c-kit(+)Sca-1(-) cells. Nearly, all thymocytes expressed the ABCC1 molecule in an active form and aging did not affect this pattern. This study demonstrates an independent upregulation of ABCB1 and ABCC activities during the aging process. The increases were observed in different subsets of cells but followed a developmentally regulated pattern. The functions played by these transporters and alterations in aging are discussed.

Pomolic acid-induced apoptosis in cells from patients with chronic myeloid leukemia exhibiting different drug resistance profile

Pomolic acid (PA) is a pentacyclic triterpene which has been previously described as active in inhibiting the growth of K562 cell line-originated from chronic myeloid leukemia (CML) in blast crisis-and its vincristine-resistant derivative K562-Lucena1. In this work, cells from CML patients were treated with PA and the apoptotic index was compared with the multidrug resistance (MDR) profile and clinical status of the patients. Our findings show that PA 12.5 microg/ml at 24 h (p = 0.000), at 48 h (p = 0.012) and at 72 h (p = 0.005) has a potent apoptotic index in CML cells as compared to mononuclear cells from healthy donors. PA was capable to induce apoptosis in cells from CML patients exhibiting functional MDR phenotype but not in P-glycoprotein expression. In addition, PA was effective in chronic as well as in blast phase of CML. Moreover, similar apoptotic index induced by PA was observed in low, intermediate and high-risk Sokal score as well as in samples from the group of patients with clinical resistance to interferon and/or imatinib and non-treated patients. These results suggest that PA may be an effective agent for the treatment of CML.

On the molecular mechanisms for the highly procoagulant pattern of C6 glioma cells

BACKGROUND

That there is a correlation between cancer and procoagulant states is well-known. C6 glioma cell line was originally induced in random-bred Wistar-Furth rats and is morphologically similar to glioblastoma multiforme, the most common aggressive glioma resistant to therapeutic interventions.

OBJECTIVES

In this study we analyzed the molecular mechanisms responsible for the highly procoagulant properties of C6 glioma cells.

METHODS

The presence of tissue factor (TF) and phosphatidylserine (PS) in C6 cells was investigated by flow-cytometric and functional analyses. The assembly of extrinsic tenase, intrinsic tenase and prothrombinase complexes on these cells was studied using enzymatic assays employing plasma or purified proteins.

RESULTS

TF was identified by flow-cytometric and functional [factor (F) Xa formation in the presence of cells and FVIIa] assays. Alternatively, conversion of FX into FXa was also observed in the presence of C6 cells, FIXa and FVIIIa. This effect was both cell- and FVIIIa-dependent, being consistent with formation of the intrinsic tenase complex. C6 cells were also able to activate prothrombin in the presence of FXa and FVa, thus supporting formation of the prothrombinase complex. This ability was similar to positive controls performed with PS-containing vesicles. Accordingly, exposure of PS on C6 cells was demonstrated by flow cytometry employing specific anti-PS antibodies. In addition, annexin V, which blocks PS binding sites, inhibited FX and prothrombin conversion by their respective C6-assembled activating complexes.

CONCLUSION

C6 glioma cells support all procoagulant reactions leading to robust thrombin formation. This ability results from concomitant TF exposure and from the presence of the anionic lipid PS at the outer leaflet of cell membrane. Therefore, this animal cell line may be used to explore new aspects concerning the role of blood coagulation proteins in tumor biology, especially those affecting the central nervous system.

Methylene blue is more toxic to erythroleukemic cells than to normal peripheral blood mononuclear cells: a possible use in chemotherapy

Methylene blue (MB) is a phenothiazine with radio and photosensitizing properties and anti-tumoral activity. Our group has shown that MB was capable of inhibiting the in vitro growth of erythroleukemic cells with multidrug resistance (MDR). However, there are no studies comparing the cytotoxicity of this molecule for normal and tumoral cells. In this work, the cytotoxicity of MB was measured by MTT method in erythroleukemic and melanoma lineages, comparing it with that of normal cells:lymphocytes and melanocytes. MB was more cytotoxic for tumoral cells; however, there was no difference between erytroleukemic cells with or without MDR phenotype. Lymphocytes and erythroleukemic cells were much more sensitive to the effects of MB than melanoma cells and melanocytes. The proliferation of phytohemagglutinin-activated lymphocytes was inhibited when 3H-thymidine incorporation to DNA was measured. We tried to analyze whether the cells were dying, via apoptosis or necrosis, using Anexin-V and propidium iodide. Despite higher levels of Anexin-V, it was not possible to distinguish necrosis from apoptosis, as the fluorescence of MB is in the same channel as propidium iodide. The production of hydrogen peroxide was measured by cytometry using dihydrorhodamine 123 (DHR). Despite the erythroleukemic cells and lymphocytes being capable of producing free radicals, there was no relation between the production and the sensitivity of various cells to MB. Our results suggest that MB should be used as a chemotherapeutic agent, because of its preferential cytotoxic effects over tumor cells, considering the fact that MDR cells are also sensitive, and due to its radio and photosensitizing activities.

Oral mucosa alterations induced by cyclosporin in mice: morphological features

BACKGROUND AND OBJECTIVE

The mechanisms involved in the pathogenesis of cyclosporin A-induced gingival hyperplasia are not well understood. The present work aimed at developing a mouse model with the characteristics of the human process, i.e. time of appearance, dose dependency and the capacity of developing in a variety of genetic backgrounds. This model would present the advantages of using a very well known animal species, small and easy to handle, with a number of experimental reagents (antibodies, etc.) already available against its products.

METHODS

Three different strains of mice were used: CBA, F1(C57Bl x DBA), Balb/c. Groups of mice received different concentrations of cyclosporin A (CSA) (10 mg/kg, 25 mg/kg and 40 mg/kg body weight) intraperitoneally five times a week. Anatomical and histological alterations were recorded at various time intervals.

RESULTS

All strains of mice presented gingival hyperplasia after 8 weeks of CSA treatment. A dose-dependency was observed with regard to the time of first appearance of alterations. Increased redness was seen in all animals at the sixth week, independent of the dosage used. Histologic examination exhibited increased vascularization, epithelial and connective tissue thickening, edema and a mononuclear infiltrate.

CONCLUSIONS

It was possible to develop CSA-induced gingival hyperplasia in mice with the characteristics described in humans and other species. The use of this animal model may help in the elucidation of the process involved in CSA-induced gingival overgrowth.

p53 gene analysis in childhood B non-Hodgkin's lymphoma

CONTEXT

Mutations or deletions in the tumor-suppressor gene p53 are among the commonest genetic changes found in human neoplasms including breast, lung and bowel cancers. In hematological malignancies, p53 is most often mutated in Burkitt's lymphoma, with p53 mutations present in 30 to 40% of tumor samples and in 70% of cell lines.

OBJECTIVE

To analyze the p53 gene alterations in child patients with B non-Hodgkin's lymphoma.

DESIGN

Descriptive study.

SETTING

Tertiary oncology care center.

PARTICIPANTS

The study investigated 12 patients with childhood B non-Hodgkin's lymphoma (Burkitt's lymphoma). Screening for p53 mutations was done by polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) analysis of exon 5 to 8/9 of the gene.

RESULTS

Abnormal polymerase chain reaction-single strand conformational polymorphism migration pattern was observed in 4 patients (33.3%), one on exon 6 and three on exon 7. Positive cases included 2 patients who died from disease.

CONCLUSION

These preliminary results suggest that p53 mutations are quite frequent in children with Burkitt's lymphoma and may play a role in lymphoma genesis or disease progression.

Reduced glutathione protect cells from ouabain toxicity

It is widely accepted that a prolonged ouabain blockade of the Na(+),K(+)-ATPase makes cells detach from each other and from the substrate, leading to their death and that cellular resistance to ouabain is due to the presence of isoforms of Na(+),K(+)-ATPase with low affinity to this glycoside. In the present work the effect of reduced glutathione in the response of two types of renal cells to ouabain: MDCK, a ouabain-sensitive cell line and Ma104, a ouabain-resistant one, was studied. Glutathione protected MDCK cells from ouabain toxicity and inhibition of glutathione synthesis by L-buthionine-S,R-sulfoximine sensitized Ma104 cells to ouabain. As glutathione is involved with multidrug resistance (MDR) in cells expressing the multidrug resistance-related protein MRP1 and as Ma104 cells have a MDR phenotype, it was investigated whether Ma104 cells express this protein. The expression of the MRP1-mRNA in Ma104 cells was detected by reverse transcriptase-polymerase chain reaction and ribonuclease protection assay, and the protein was detected by Western blotting and immunofluorescence. Treatment of Ma104 cells with ouabain increased MRP1-mRNA expression and altered the localization of MRP1 in these cells. Our results suggest that some cells may have mechanisms to protect themselves from ouabain toxicity and that MRP1 may have a role in controlling the toxic effects of ouabain.

Multidrug resistance in tumour cells: characterization of the multidrug resistant cell line K562-Lucena 1

Multidrug resistance to chemotherapy is a major obstacle in the treatment of cancer patients. The best characterised mechanism responsible for multidrug resistance involves the expression of the MDR-1 gene product, P-glycoprotein. However, the resistance process is multifactorial. Studies of multidrug resistance mechanisms have relied on the analysis of cancer cell lines that have been selected and present cross-reactivity to a broad range of anticancer agents. This work characterises a multidrug resistant cell line, originally selected for resistance to the Vinca alkaloid vincristine and derived from the human erythroleukaemia cell K562. This cell line, named Lucena 1, overexpresses P-glycoprotein and have its resistance reversed by the chemosensitisers verapamil, trifluoperazine and cyclosporins A, D and G. Furthermore, we demonstrated that methylene blue was capable of partially reversing the resistance in this cell line. On the contrary, the use of 5-fluorouracil increased the resistance of Lucena 1. In addition to chemotherapics, Lucena 1 cells were resistant to ultraviolet A radiation and hydrogen peroxide and failed to mobilise intracellular calcium when thapsigargin was used. Changes in the cytoskeleton of this cell line were also observed.

Comparison between anthracyclines and rhodamine-123 accumulation in chronic lymphoid leukemia: effect of cyclosporin A and verapamil

Multidrug resistance in leukemic cells is associated with decreased drug accumulation. A resistant cell line and cells from 11 patients with chronic lymphoid leukemia B were used for the evaluation of intracellular accumulation of daunorubicin (DNR), idarubicin (IDA), epirubicin (EPI) and rhodamine-123 (Rh-123). Cyclosporin A (CSA) and verapamil were used to test their modulatory effects on anthracyclines and the fluorescent dye. In leukemic samples there was a tendency for a lower accumulation index in samples tested with Rh-123 as compared to anthracyclines. IDA was a poorer substrate to P-glycoprotein (Pgp) than two of its analogues, e.g. DNR and EPI. A good correlation (80%) was found between Rh-123 accumulation and Pgp expression by phosphatase-anti-alkaline phosphatase. A strict correlation (100%) was found between modulation by CSA of Rh-123 accumulation and immunoreactivity to Pgp. Two discordant results were seen suggesting that other mechanisms of resistance could be present. The Rh-123 accumulation test seems to give a better indication than anthracyclines, however, it is not selective and may allow the detection of other drug-transport pumps.

Methylene blue reverts multidrug resistance: sensitivity of multidrug resistant cells to this dye and its photodynamic action

Photodynamic action has been advocated as an alternative treatment of tumors but the most common used dyes, hematoporphyrin derivatives, are substrate for P-glycoprotein. This study investigated the MDR-reverting properties of methylene blue (MB) and compared the sensitivity to its photodynamic action (PDA) in five cell lines that either express or do not express the MDR phenotype. MB was able to revert the MDR phenotype and there was no difference in sensitivity to MB-PDA between MDR and non-MDR cells, suggesting that MB has the advantage of being used simultaneously as a MDR reverser and a photodynamic agent.

Differences in sensitivity to UVC, UVB and UVA radiation of a multidrug-resistant cell line overexpressing P-glycoprotein

Multidrug resistance (MDR) is the phenomenon in which cultured tumor cells, selected for resistance to one chemotherapeutic agent, simultaneously acquire resistance to several apparently unrelated drugs. The MDR phenotype is multifactorial. The best-studied mechanism involves the expression of a membrane protein that acts as an energy-dependent efflux pump, known as P-glycoprotein (Pgp), capable of extruding toxic materials from the cell. In this work, resistance to UVA radiation, but not to UVC nor UVB, was observed in an MDR leukemia cell line. This cell line overexpresses Pgp. To study the role of Pgp in the resistance to UVA radiation, two MDR modulators or reversing agents (verapamil and cyclosporin A) capable of blocking Pgp activity were used. Cell viability was assessed and the techniques of flow cytometry and fluorescence microscopy were employed to measure the extrusion of rhodamine 123 by the efflux pump. The results show that MDR modulators did not modify the resistance to UVA radiation. Furthermore, although cell viability was not significantly altered, Pgp function was impaired after UVA treatment, suggesting that this glycoprotein may be a physical target for oxidative damage, and that other factors may be responsible for the UVA resistance. In agreement with this, it was found that the resistant cell line presented a higher catalase activity than the parental (non-MDR) cell line.

The in vivo effect of the administration of resistance-modulating agents on rhodamine 123 distribution in mice thymus and lymph nodes

P-glycoprotein (Pgp) has been widely associated with the multidrug resistance phenotype. Nevertheless, this protein has been detected in many normal tissues and cells, including liver, kidney, endothelial cells that constitute the hematological barrier of the brain and testes, and cells from the immune system. Many in vitro models have been used to study drugs that modulate Pgp activity and the multidrug resistance phenomenon. In the present work, we investigate the in vivo effects of resistance-modulating agents on lymphoid organs. Rhodamine 123 (Rho123), a well-known Pgp substrate, was administered to mice, and the fluorescence level in thymus and lymph node cells measured. The fluorescence level on these organs showed a dose-dependent response. Cyclosporin A (CSA), Verapamil (VP) and Trifluoperazine (TFP), three resistance-modulating agents, were administered to mice 1 h prior to 1 mg/kg Rho123 administration. Surprisingly, VP (10 mg/kg) and TFP (750 microg/kg) did not modulate Rho123 retention by thymus and lymph node cells. CSA (50 mg/kg) was the only drug that increased the fluorescence level in both organs. These results point out to the need of a wider study on the in vivo effects of resistance-modulating agents in different organs and systems.

Cyclosporin A and trifluoperazine, two resistance-modulating agents, increase ivermectin neurotoxicity in mice

The P-glycoprotein expressed in the blood-brain barrier has been associated with the restricted access of many compounds to the central nervous system. Mice lacking the mdr1a P-glycoprotein gene show an accumulation of various drugs in brain tissues. P-glycoprotein is also correlated with the phenomenon of multidrug resistance in tumour cells. To investigate the effects of drugs that modulate multidrug resistance in the selective permeability of the blood-brain barrier, mice were treated with cyclosporin A or trifluoperazine plus ivermectin, a P-glycoprotein substrate, that has a limited access to the central nervous system. When mice received an injection of cyclosporin A (50 mg/kg, intraperitoneally) or trifluoperazine (750 microg/kg, intraperitoneally) one hour prior to the administration of ivermectin (10-15 mg/kg, intraperitoneally) there was an increase in the acute toxicity of ivermectin. HPLC analysis of brain tissues indicated that the ivermectin brain concentration was 2.5 times higher when mice were previously treated with cyclosporin A (50 mg/kg). These results suggest that attention should be given to the side effects of drugs that interact with P-glycoprotein and are commonly used clinically and also to the possibility of creating a pharmacological gap in the blood-brain barrier that allows the access of chemotherapeutic drugs to brain tumours.

Expression of functionally P-glycoprotein in MA104 kidney cells

Rhesus monkey kidney MA104 cells are a polarized epithelium with some unusual characteristics, including a resistance to ouabain, although their Na(+)-K(+)-ATPase has normal affinity with this drug. This work suggests that MA104 cells have high expression of functionally P-glycoprotein in their membranes. This was established using four complementary methods to investigate the expression and function of P-glycoprotein in these cells. MA104 cells were strongly resistant to vincristine, which could be reversed by three known P-glycoprotein modulators: verapamil, cyclosporin A and trifluoperazine. In addition, MA104 cells accumulate little rhodamine 123, and the incubation with verapamil increased this accumulation. The mdr1-mRNA was detected by reverse transcription-polymerase chain reaction and a subcloned 283-bp product was identified. Its nucleotide sequence was compared with the related region of human mdr1, showing a high identity (96%) between the two sequences. The expression of P-glycoprotein in the cell membrane was observed by Western blot and immunofluorescence. The results taken together suggest that MA104 cells intrinsically have a high expression of functionally P-glycoprotein in their membranes.

Phenotypic analysis of PBMCs from uterine cervix cancer patients with high natural killer activity

Phenotypic analysis of peripheral blood mononuclear cells from uterine cervix cancer patients, with increased natural killer cell activity, treated with radiation therapy was carried out. An increase in the percentage of CD56+ cells was observed in 5 out of 7 patients. When the expression of CD69, a phenotypic marker of cellular activation, was analyzed in 6 patients, an increase was observed in 4 of them. No direct correlation between cytolytic activity and the levels of CD56+ or CD69+ cells were observed. After 72 hr, an increased expression of CD56 was observed in 3 patients and a similar picture was seen at the same time following activation with IL-2 or IFN.

Natural killer cell activity in Hodgkin's disease patients undergoing radiation therapy or chemotherapy and radiation therapy

Natural killer (NK) cell activity in peripheral blood mononuclear cells (PBMCs) from patients with Hodgkin's disease was studied using 4 h 51Cr release assay and K562 cells as sensitive targets. PBMCs were obtained from 15 previously untreated patients at different stages of their disease. PBMCs were also obtained from 46 patients treated by radiation therapy or combined chemotherapy and radiation therapy. Twenty healthy age-matched volunteer donors were used as controls to the treated patients. For these normal donors the mean cytotoxicity was 24.8 +/- 5.67% at a 100:1 effector-target cell ratio; and 43.7 +/- 12.1% for the treated cancer patients. Fifteen healthy age-matched volunteer donors were used as controls to the untreated patients. The mean cytotoxicity for these normal donors was 20.8 +/- 3.61% at a 100:1 effector-target cell ratio; and 37.6 +/- 6.65% for the previously untreated cancer patients. The mean cytotoxicity for all 35 normal donors was 23.1 +/- 5.22% at a 100:1 effector-target cell ratio. Most treated patients (93.5%) had a complete response to therapy and a significant difference was found between the mean cytotoxicity of the whole group (46 treated patients), compared with controls (P < 0.001). A significant difference (P < 0.05) was also observed when the same 11 patients were studied before and after treatment.

Ouabain induces apoptosis on PHA-activated lymphocytes

Apoptotic cell death plays a critical role in immune system homeostasis, and c-myc protooncogene deregulated expression is a component of this programmed genomic response. Pharmacological intervention and modulation of peripheral lymphocytes apoptosis would have important implications. The present results indicate that ouabain, a specific inhibitor of Na+K(+)-ATPase, promotes an increased expression of c-myc mRNA, and induces apoptosis in PHA-stimulated lymphocytes. Furthermore, this ouabain-induced apoptosis cannot be counteracted by the addition of exogenous IL-2.

Uncoupling of Ca2+ transport ATPase in muscle and blood platelets by diacylglycerol analogues and cyclosporin A antagonism

The possibility that diacylglycerol analogues might have a wider spectrum of intracellular targets than the well-known protein kinase C was investigated with vesicles containing the Ca2+-ATPase derived from the dense tubular system in platelets and from the sarcoplasmic reticulum of skeletal muscle. The diacylglycerol analogues PMA and 1-oleoyl-2-acetyl-rac-glycerol (OAG) inhibited Ca2+ accumulation by these vesicles, an effect that was antagonized by cyclosporin A. The inhibitory activity of PMA and OAG resulted from the uncoupling of the Ca2+-ATPase, characterized by a pronounced inhibition of Ca2+ uptake accompanied by a discrete decrease in ATPase activity and by the inhibition of the enzyme's phosphorylation by Pi, leading to both a decrease in ATP synthesis and an enhancement of Ca2+ efflux. The inhibition of Ca2+ uptake by PMA was found to decrease as the Ca2+ concentration in the medium was raised from 0.1 to 10.0 microM. This was observed with muscle, but not with platelet vesicles. In contrast, the ability of cyclosporin A to antagonize the inhibition of Ca2+ uptake by PMA also increased when the Ca2+ concentration in the medium was raised from 0.1 to 10.0 microM, but this was observed with both muscle and platelet vesicles. The fact that phospholipase C activity and products from the inositol metabolism have been described as localized in regions of the sarcoplasmic reticulum where Ca2+-ATPase and Ca2+ channels are found suggests a possible physiological role for these products in the regulation of cytosolic Ca2+ levels.

Interaction of cyclosporin A and etoposide. Clinical and in vitro assessment in blast phase of chronic myeloid leukaemia

Combination chemotherapy has had a low impact on survival of blast crises in chronic myelogeneous leukaemia (CML) which may be due to drug resistance. This work attempted to correlate the clinical response and some experimental evidence for the MDR phenotype. Blast cells were positive for P-glycoprotein using APAAP assay. In vitro tests showed that etoposide was partially toxic to blast cells when used alone but had its toxicity increased by nearly sixfold when combined with cyclosporin A (CSA). The patient responded poorly to treatment with etoposide combined with mitoxantrone and high-dose ara-c. However, when etoposide was associated with CSA, this patient returned to the chronic phase reinforcing our in vitro studies. Because no serious toxicity was seen clinically, we are inclined to consider the circumvention protocol an useful strategy to treat blast crises of CML.

Ouabain effects on activated lymphocytes: augmentation of CD25 expression on TPA-stimulated cells and of CD69 on PHA-and TPA-stimulated cells

Ouabain (OUA) was capable of inhibiting peripheral blood lymphocyte (PBL) proliferation induced by phyothaemagglutinin (PHA) of phorbol ester (TPA), as measured by thymidine incorporation or cell cycle analysis. In this latter case it was possible to detect a block in the progression from G1 to S phase. This inhibition could not be reversed by interleukin (IL)-2 and was not due to an effect on CD 25 expression, as this molecule was only reduced in PHA cultures treated with OUA. Conversely, cultures activated by TPA and OUA showed an increased expression of CD25. The activation antigen CD69 was increased in both situation, suggesting that despite the absence of proliferative response the cells were being activated. The possibility that these cells were being deviated to the activation pathway leading to apoptosis is now under investigation. This study also suggested that CD25 induction may occur via different pathways, and that the selective effect of OUA for PHA-activated cells may become a useful tool for the understanding of the process.

Jatrophone and 12-O-tetradecanoyl phorbol-13-acetate antagonism of stimulation of natural killer activity and lymphocyte proliferation

We have recently reported that the diterpene jatrophone antagonizes the effects of phorbol ester in pharmacogical studies. In order to investigate further whether this action is associated with an inhibition of protein kinase C activity, we examined the effect of jatrophone on the stimulation of lymphocyte activities which are dependent on the protein kinase C pathway. Jatrophone (0.02-0.32 microM) caused concentration-dependent and equipotent inhibition of human lymphocyte proliferation induced by 5 micrograms/ml of phytohemagglutinin or by a combination of 100 ng/ml of 12-O-tetradecanoyl phorbol-13-acetate (TPA) plus 0.15 microM ionomicyn, with IC50 values (and their 95% confidence limits) of 53.4 (42.6-65.3) nM and 48.4 (39.4-59.8) nM, respectively. Jatrophone also blocked, in a concentration-dependent fashion, the murine lymphocyte proliferation stimulated by 5 micrograms/ml of concanavalin A, with an IC50 value of 63.5 (51.2-76.5) nM. The inhibition was not due to a toxic effect as the pre-incubation of lymphocytes for 48 h with 0.32 microM jatrophone did not impair the proliferation after removal of the diterpene from the culture medium. Human lymphocytes when pre-treated with 10 ng/ml TPA had a 3 times higher spontaneous natural killer activity against K562 cells and an increased expression of CD69. In addition, jatrophone inhibited both spontaneous and TPA-stimulated natural killer activity and the expression of CD69. Jatrophone concentrations that inhibited 75% of lymphocyte proliferation did not impair the intracellular increase in Ca2+ flux in lymphocytes stimulated by phytohemagglutinin. These results indicate that jatrophone is a potent inhibitor of activation of lymphocytes, probably through inhibition of the protein kinase C pathway.

Heparin reverses Rhodamine 123 extrusion by multidrug resistant cells

The effect of heparin as a reversing agent of multidrug resistance (MDR) was tested on normal mononuclear cells from 24 healthy volunteers and leukaemic cells from 12 acute myeloid leukaemia, five chronic myeloid leukaemia, five acute lymphoid leukaemia and three chronic lymphoid leukaemia patients. Two cell lines were used as controls, the human erythroleukaemia K562 and its vincristine-resistant derivative K562-Lucena 1. Heparin was not cytotoxic by itself as determined using a MTT assay and cell counts. MDR modulation was assessed by Rhodamine 123 extrusion using flow-cytometry. Modulation of the resistant cell line was produced by the classical reversing agent verapamil and also by heparin, the same being observed in normal and leukaemic cells and being independent of the type of leukaemia. Our work suggests that heparin may be considered a potential MDR modulator.

Immunological features of HTLV-I myelopathy in Rio de Janeiro, Brazil, and in vitro effects of cyclosporin A

Brazilian patients with HTLV-1 myelopathy present a significant spontaneous lymphocyte proliferation (SLP), and an increased response to IL-2 exogenous stimulation, in both peripheral blood lymphocytes and in whole blood proliferative assays, when compared to the control group. High antibody titers against HTLV-I antigens were also observed in comparison to healthy seropositive individuals. IL-6 was detected in cerebrospinal fluid (CSF) of 50% of the patients (10 out of 20) and TNF-alpha in four out of nineteen individuals. No correlation was found between the presence of levels of cytokines IL-6 and TNF-alpha and duration or severity of disease. The addition of cyclosporin A (CsA) significantly inhibited SLP suggesting that this therapeutic agent should be studied in HTLV-1 myelopathy. Brazilian patients with HTLV-I myelopathy present the same immunological abnormalities described in other endemic regions. The whole blood assay reflects the same results of separated blood cells and, due to its rapid execution may be used as an assay to follow clinical trials.

Sensitivity of vincristine-sensitive K562 and vincristine-resistant K562-Lucena 1 cells to anthracyclines and reversal of multidrug resistance

The phenomenon of multidrug resistance (MDR), that involves the efflux pump P-glycoprotein, can be reversed by a number of substances known as MDR modulators or reversing agents. In the present study we investigated the action of three anthracyclines, mitoxantrone and vincristine on short-term (72 h) cultures using 2 methods ([3H] incorporation and MTT (3-[4,5-dimethylthiasol-2-yl]-2,5-diphenyltetrazolium bromide)), on 2 cell lines: K562, a human erythroleukemia, and a vincristine-resistant subline K562-Lucena 1. Using the same culture methods plus flow cytometry analysis, the reversing potentials of cyclosporin A and verapamil were studied in both cell lines. There were differences in the sensitivity and resistance profiles of the two lines to the various drugs but daunorubicin (5 micrograms/ml) and idarubicin (0.035 micrograms/ml) were the most effective when each was used in high concentration. Cyclosporine at 200 ng/ml and verapamil at 5 micrograms/ml reversed MDR in the resistant line, and had a synergistic action with chemotherapeutic agents on the sensitive line. Again differences were demonstrable between combinations of the various drugs and reversal was only clearly shown with the method measuring cell proliferation ([3H] incorporation) but not by the method measuring metabolic activity (MTT). The efflux of rhodamine-123 mimics the functional activity of the pump and cyclosporine was a better reversing agent by this criteria. These data show that the results obtained in in vitro studies attempting to identify treatments for different types of leukemias depend to a large extent on the methods used to measure cell response.

Trifluoperazine reduces the expression of CD69 in phytohemagglutinin-activated lymphocytes

Trifluoperazine (TFP) is a phenothiazine capable of inhibiting lymphocyte proliferation as well as natural killer cells (NK) and lymphokine-activated killer cells (LAK) cytotoxic activity. CD69 is a surface molecule induced by various mechanisms of cellular activation. In the present work the modulation of CD69 expression by TFP was investigated on PHA-stimulated peripheral blood mononuclear cells and compared to that of CD25 (IL-2 receptor) expression. Determination of surface molecules was performed in an indirect immunofluorescence assay using anti-CD69 or anti-CD25 monoclonal antibodies, and analyzed by flow cytometry. The time course of the expression of these two molecules differed: CD69 expression was already declining at 48 h, whereas CD25 was still increasing at 72 h after stimulation. TFP (10 microM) reduced CD69 expression by 71.8% at 24 h, 68.4% at 48 h and 24% at 72 h following activation. In contrast, the same dose of TFP did not significantly affect CD25 expression at 24 h but showed an inhibitory effect at later times. These results suggest that different activation pathways are involved in the expression of CD25 and CD69.

[Clinical significance of multidrug resistance in acute leukemias]

A significant number of patients with acute leukaemias fail in their treatment as a result of the development of resistance to chemotherapy. Several evidences indicate that the expression of a mdr 1 gen, which codifies for P glycoprotein (PgP), contributes to this resistance in leukaemic cells. PgP functions as an energy-dependent efflux pump transporting a variety of unrelated drugs to the outside of the cells. It is possible to modulate this efflux using a number of drugs known as multidrug resistance (MDR) reversors or modulating agents. The present paper discusses some of the methods used for detecting the MDR phenotype, although the most reliable results are the ones that take into account an association of various methods. Despite the existence of disagreements regarding which method presents the greatest sensitivity or specificity the majority of authors agrees that the MDR phenotype, in isolation, affects the prognosis of leukaemias. The, coexpression of PgP with the molecule CD34 confers the worst prognosis in acute leukaemias. The authors demonstrate using cell cultures testing chemotherapeutic agents, alone or associated to modulating agents, that this line of research may allow in the future to elaborate an individualized clinical treatment. They emphasize the necessity of integration between haematologists and basic research as this may lead to a new therapeutic option for refractory patients to conventional treatment.

Deficit of T-cell recovery after allogeneic bone marrow transplantation in chronic myeloid leukemia patients

The immunological reconstitution that follows bone marrow transplantation (BMT) was studied in 40 leukaemia patients: 19 with chronic myeloid leukaemia (CML), 12 with acute myeloid leukaemia (AML) and the remaining 9 with acute lymphoblastic leukaemia (ALL). The recovery of the CML group was slower than that of the ALL and AML groups. This difference was produced by the T cell compartment, as NK cell activity and B cell numbers did not differ significantly. Factors such as conditioning treatment and graft versus host disease (GVHD) prophylaxis were analysed. Our experience suggests that all leukaemia patients should not be considered as one group when analysing their immunological reconstitution, as factors related to the original disease may affect their outcome.

Increased natural killer cell activity in uterine cervix cancer patients undergoing radiation therapy

Natural killer (NK) cell activity in peripheral blood mononuclear cells (PBMCs) from women with carcinoma of the uterine cervix was studied using a 4-hour 51Cr release assay and K562 cells as the sensitive target. PBMCs were obtained from 21 previously untreated patients at different stages of disease according to the International Federation of Gynecology and Obstetrics classification. PBMCs were also obtained from 36 patients treated with radiation therapy at different disease stages. Seventeen healthy age-matched volunteer women were used as controls. Mean cytotoxicity for the normal donors was 25.1 +/- 6.56% at a 100:1 effector-target cell ratio, 33.8 +/- 7.96% for the previously untreated cancer patients and 52 +/- 18.4% for the treated cancer patients. Most of the treated patients (86%) showed a complete response to radiation therapy and the mean cytotoxicity of the whole group (36 treated patients) was significantly increased compared to controls (p < 0.05). It is suggested that radiation therapy may produce cell alterations leading to an increase in NK cell activity in patients treated for uterine cervical cancer. The significance of this increase is discussed.

Inhibition of human LAK-cell activity by the anti-depressant trifluoperazine

The anti-depressive drug trifluoperazine (TFP) was studied on in vitro immune responses. TFP proved to be an inhibitor of lymphokine-activated killer (LAK) cells in its generative step, as well as in its effector phase. Natural killer (NK) activity and interleukin-2 (IL-2) or mitogen-induced lymphocyte proliferation were just as sensitive to the drug effects, whereas the division of tumor cells was more resistant. The mechanism through which TFP suppresses these lymphocytic systems remains unclear. It does not, however, affect an early stage of cellular activation as the addition of the drug as late as 24 h after the start of the culture was still inhibitory for lymphocyte mitogenesis. Neither the expression of CD25, nor that of CD56 was affected by TFP, and exogenous IL-2 was unable to overcome the suppression of proliferation. In relation to cell-mediated cytotoxicity, TFP partially interfered with the effector/target binding. However, addition of lectin to the assay did not overcome the inhibition of lysis produced by the drug. Although further work remains to be done, the effect of TFP on immune responses must be taken into consideration when treating immunosuppressed patients.

Effect of ouabain on lymphokine-activated killer cells

A large amount of evidence points towards the potential role of lymphokine activated killer (LAK) cells as tools in the treatment of chronically stressed conditions, such as cancer. The modulation of this activity by biologically active endogenous compounds of the HPA (hypothalamic-pituitary-adrenal) axis, however, is not completely understood. Ouabain, a specific inhibitor of Na(+)-K(+)-ATPase, and now recognized as an endogenous component present in human plasma, was tested on IL-2 and TPA-activated killer cells. Ouabain was able to inhibit the generation of LAK activity, as well as to suppress either PHA or TPA-induced lymphocyte proliferation. Once the cells were triggered for cytotoxicity, however, ouabain was not able to interfere with their effector phase, as it did not show any effect when present only during the assay. TPA-induced "LAK-simile" cells displayed the same sensitivity towards ouabain as LAK cells did. Although the physiological relevance of endogenous ouabain secretion remains elusive, these effects of ouabain on LAK cytotoxicity should be considered in patients undergoing this kind of immunotherapy.

Immunological recovery after bone marrow transplantation for severe aplastic anaemia: a Brazilian experience

Twenty-nine patients with severe aplastic anaemia (SAA) were submitted to bone marrow transplantation (BMT) and their immunological recovery analysed. Total lymphocyte counts, estimation of B lymphocytes, T lymphocytes and their subsets, natural-killer (NK) activity were performed. Cells with the CD8+ phenotype and NK activity were the first signs of immunological recovery, whereas the CD4+ subset recovered later in patients who suffered from acute graft versus host disease (GvHD) and infections. Acute and chronic GvHD, cirrhosis, rejection and HIV viral infection contributed to the persistence of the profound immunodeficiency status observed after BMT. Our results did not differ greatly from the others and confirmed that BMT may be performed in underdeveloped countries despite the difficulties it might pose.

Some biological properties of the human amniotic membrane interferon

Human amniotic interferon was investigated to define the species specificity of its antiviral action and to compare its anti-cellular and NK cell stimulating activities with those of other human interferons. The antiviral effect was titrated in bovine (RV-IAL) and monkey (VERO) cells. Amniotic interferon exhibited, in bovine cells, 5% of the activity seen in monkey cells, while alpha interferon displayed 200%. No effect was detected with either beta or gamma interferon in bovine cells. Daudi cells were exposed to different concentrations of various interferons and the cell numbers were determined. The anticellular effect of the amniotic interferon reached its peak on the third day of incubation. Results suggested a higher activity for alpha and gamma interferons and a lower activity for beta when compared to amniotic interferon. Using total mononuclear cells as effector cells and K 562 as target cells in a 51Cr release assay, it was demonstrated that low concentrations of amniotic interferon consistently stimulated NK cell activity in cells derived from several donors, the results indicating a higher level of activity with this interferon than with alpha and beta interferons.

Effect of canatoxin on cell cultures

Canatoxin, a toxic protein isolated from Canavalia ensiformis, was shown to inhibit DNA synthesis and to produce a cytolytic effect when added in vitro to various cells, in doses ranging from 50 to 500 nM. In this case no selectivity was found for a certain cell type, as both normal and transformed cells could be affected by the toxic protein. The cytostatic effect was irreversible upon removal of the toxic protein from the medium and could be fully attained after exposing the cells to canatoxin for only 30 min. The use of an in vitro cell culture system may allow for a better insight on the mode of action of canatoxin.

Myeloid leukemia differentiation by phorbol ester and retinoic acid: a practical approach

The effects of TPA (12-0-tetradecanoylphorbol-13-acetate) and RA (retinoic acid) were investigated on the cell lines HL60 (acute promyelocytic leukemia) and K562 (erythroleukemia) and on cells from patients with several kinds of leukemia. There were 14 cases of acute lymphocytic leukemia (ALL), 2 cases of chronic lymphocytic leukemia (CLL), 23 cases of acute myeloid leukemia (M1-M7), 5 cases of chronic myelocytic leukemia in blast crisis (CML-BC) and 2 mixed leukemias. In almost all of the cases examined, after TPA exposure cells from patients with proven myeloid leukemia became adherent to the substrate, while lymphoid leukemia cells remained in suspension, allowing the differentiation of lymphoid from myeloid blasts. The only exception was in one case of CLL, which had cells that became adherent with long filamental projections. In addition, increased phagocytosis following TPA exposure permitted characterization of M7 as this was the only myeloid leukemia negative for phagocytosis. Further discrimination between the subtypes of myeloid leukemia could be based on the increased lysozyme production seen after TPA in M4 and M5. Esterase positivity allowed the discrimination of M1 cells, which were negative before and after TPA treatment. In agreement with the results of other authors, TPA and RA led to independent ways of differentiation, granulocytic-like lineage and monocytic-like cells being favored by RA and TPA, respectively. The capacity of the same cell to differentiate into more than one lineage, depending on whether RA or TPA was used, was only seen in the present study with M3 cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Lack of sensitivity to ouabain in natural killer activity

Natural killer (NK) activity against K562 target cells is not an ouabain-sensitive process. Inhibition of 40% of cytotoxicity was achieved only with an ouabain concentration much higher than that required to inhibit cell activation in other systems such as leukocyte chemotaxis and B lymphocyte plaque formation. Pretreatment of effector cells with biological agents such as phorbol-ester 12-O-tetradecanoylphorbol-13-acetate or interferon increased the cytotoxicity. This activation was not counteracted by ouabain. The effect of ouabain on NK activity was compared with a well-known ouabain-sensitive process, for example, phytohemagglutinin-induced peripheral blood lymphocyte proliferation. Ouabain completely blocked [3H]thymidine incorporation, independent of the stage of the culture when the drug was added, with exception of the last 6 h. This inhibition could be partially reversed by addition of KCl. Ouabain was equally effective when whole blood cultures were used. These results suggest that NK activity is ouabain resistant, unlike other systems of cell activation that lead or do not lead to proliferation.

Incidence of retroviruses in some Brazilian groups

The prevalence of human T lymphotropic virus type I (HTLV-I) and human immunodeficiency virus (HIV) antibodies was evaluated in Brazil among 116 aboriginal Indians living in a pre-Amazonian region, and in 44 patients with haematological malignant disorders being treated in Rio de Janeiro. Screening for the presence of antibodies to HIV was performed routinely for 17,224 blood donors at the National Cancer Institute, Rio de Janeiro, from January 1986 to May 1987. The results demonstrated that HIV infection was not endemic among Brazilian Indians, as none of them had antibodies to HIV, in contrast with the population of Rio de Janeiro, which showed a high prevalence (0.34%) of positivity among normal individuals. In a small group of patients with haematological disease only one with acute lymphoblastic leukaemia proved to be HIV-positive, the infection having been acquired through previous blood transfusion. None of the serum samples reacted with HTLV-I, including those of 17 non-Hodgkin's lymphoma patients. HTLV-I infection does not seem to be endemic in this country, but further large scale studies are necessary, especially in patients with haematological disorders, homosexual individuals and drug users.

Pregnancy and the susceptibility of Lewis rats to experimental allergic encephalomyelitis

Pregnant Lewis rats challenged with encephalitogen during the second or third week of gestation were afforded a high level of protection against experimental allergic encephalomyelitis, whilst females sensitised during the first week of pregnancy enjoyed only limited protection from clinical signs of disease. When rechallenged with encephalitogen, females which had been sensitised during pregnancy were marginally more susceptible to reinduction of clinical signs of disease than their virgin counterparts. Mothers inoculated during the first week of gestation were the only group to produce abnormal young.

The effect of sensitization of pregnant Lewis rats with encephalitogen on the subsequent susceptibility of their offspring to allergic encephalomyelitis

In a previous report (Smith & Rumjanek, 1984), it was shown that offspring of female Lewis rats which had been sensitized with encephalitogen during the second, but not the third or first, week of pregnancy, were resistant to the induction of EAE at 10 weeks of age. These observations have been extended to show that transfer of protection, from mothers to offspring, occurs during lactation. It is shown, furthermore, that sensitization leads to decreased incidence of disease in offspring, maternal clinical status simply determining the duration of protection enjoyed by offspring. The possible source of this protection is discussed.

Mononuclear cell accumulation and plasma protein extravasation (PPE) during induction, remission and re-challenge of experimental allergic encephalomyelitis in the rat

Plasma protein extravasation (PPE) and cell accumulation have been studied in the CNS of rats during experimental allergic encephalomyelitis (EAE) using radioisotopic techniques. Use of such techniques makes it possible to study objectively and conveniently the rate of cell infiltration and PPE during the disease process in relation to clinical signs and time after immunization. The following observations have been made: After the first immunization, the number of rats showing increased PPE in the CNS correlated well with the severity of EAE. Mononuclear cell infiltration into brain and spinal cord during EAE did not parallel one another; infiltration being of earlier onset and shorter duration in the spinal cord, in comparison with brain. Animals re-challenged with encephalitogenic antigen showed considerably increased cellular infiltration into the brain but failed to exhibit comparable infiltration in the spinal cord. In this case infiltration of cells is not accompanied by increased PPE, in contrast to what is seen during primary disease. Increased infiltration into the brain of re-challenged animals appears, therefore, unrelated to gross damage of vascular endothelium.

Modulation by cyclosporin-A of mononuclear cell distribution during experimental allergic encephalomyelitis

The capacity of CS-A to modify some inflammatory aspects of a cell mediated disease process, has been studied. In the present work, CS-A was shown to be effective at two levels during the development of experimental allergic encephalomyelitis (EAE) in rats. If CS-A was given at the time of the induction of the disease it inhibited lymphocyte proliferation in vivo, lymphocyte trapping into the draining lymph nodes, and delayed the subsequent infiltration of cells into the CNS and other inflammatory sites. When given around the time of disease manifestation, CS-A also reduced the rate of cell accumulation into the CNS and foot, but was without effect in modifying lymphocyte trapping in the draining nodes, despite the fact that this was still an ongoing process. Clinical signs were similarly delayed or reduced by both regimen of CS-A treatment. Treatment with CS-A did not lead, however, to long lasting unresponsiveness, since both treated groups suffered a relapse of disease at various times after treatment had been discontinued.