Cyclosporin immunosuppression of sheep: pharmacokinetics and allograft survival.

A chronically immunosuppressed sheep model was established using a regimen of cyclosporin A (CsA; 2-3mg/kg twice daily) and ketoconazole (10mg/kg twice daily). Blood CsA concentrations reached a steady-state after 17 days of treatment. The clearance of CsA decreased from a mean (95% CI) of 9.47 (6.2-12.7)ml/min/kg after a single (first) dose (3mg/kg i.v.) to 1.62 (1.38-1.86)ml/min/kg after 18 days of CsA (3mg/kg i.v. twice daily) co-administration with ketoconazole. These data indicated that the combination of CsA and ketoconazole could be used to give stable high concentrations of CsA in the sheep. Using this regimen in the sheep, the long-term survival of skin allografts was monitored as an indicator of effective immunosuppression. CsA in blood was measured daily and CsA dose adjusted to various target concentration ranges. Provided that the trough concentration of blood CsA was maintained between 1500-2500 mg/l, long-term healthy skin allografts were maintained on the sheep without significant adverse effects on haematological or biochemical parameters.

Effects of the glucolipid synthase inhibitor, P4, on functional and phenotypic parameters of murine myeloma cells.

This study describes the effects of the glucolipid synthase inhibitor P4, (DL-threo-1-phenyl-2-palmitoylamino-3-pyrrolidino-1-propanol ), on various functional and phenotypic parameters of 5T33 murine myeloma cells. Cell recovery was reduced by >85% following incubation of the cells for 3 days in the presence of 4 microM P4 (the IC50 concentration). Both cytostatic and cytotoxic inhibition was observed with tumour cell metabolic activity and clonogenic potential reduced to 42% and 14% of controls, respectively, and viability reduced to 52%. A dose-dependent increase in cells undergoing apoptosis (from 7% to 26%) was also found. P4 induced a decrease in the number of cells expressing H-2 Class I and CD44, and a large increase in cells expressing H-2 Class II and the IgG2b paraprotein. It did not affect surface expression of CD45 or CD54 (ICAM-1). Based on these alterations in tumour cell growth, adhesion molecule expression and potential immunogenicity, it is anticipated that P4 will provide a novel therapeutic approach for the treatment of multiple myeloma. In addition, given that essentially all tumours rely heavily on overexpressed or abnormal glucosphingolipids for growth, development and metastasis, glucolipid synthase inhibitors may prove to be universally effective anti-cancer agents.

The efficacy of benzimidazole drugs against Plasmodium falciparum in vitro.

The sensitivities in vitro of Plasmodium falciparum to the benzimidazoles, albendazole, thiabendazole, mebendazole, omeprazole and 2 albendazole metabolites, albendazole sulphone and albendazole sulphoxide, were investigated and compared to those of the commonly used antimalarial drugs chloroquine and quinine. Quinine and chloroquine were the most potent drugs tested (EC50 values of 8 x 10(-9)-6 x 10(-8) mol/L and 5-7 x 10(-9) mol/L, respectively). Thiabendazole, mebendazole, albendazole sulphone and albendazole sulphoxide reached maximum growth inhibitions of 13-36% at the highest concentration tested (1 x 10(-4) mol/L). Albendazole (EC50 range: not achieved-2 x 10(-6) mol/L) and omeprazole (EC50 range: 2-4 x 10(-5) mol/L) were the most effective benzimidazoles. The activity of albendazole was pH dependent, as was that of chloroquine, and variable. Albendazole has its primary mode of action on trophozoites, suggesting that the drug may target parasite tubulin polymerization. Omeprazole, although also primarily effective against trophozoites, had additional activity against schizonts and ring forms, suggesting a distinct or additional parasitic target. Given the variable activity of albendazole and its rapid metabolism in vivo into compounds with even less antimalarial activity, it appears unlikely that this benzimidazole will be useful in the treatment of malaria. The rapid activity and different stage-specific profile of the more soluble benzimidazole omeprazole warrants further investigation.

Cyclosporine a immunosuppression in sheep with response enhancement by concomitant ketoconazole.

1. The pharmacokinetics of a single dose of Cyclosporine A (CsA) administered to sheep by intravenous (i.v.) route were examined. 2. Concomitant administration of ketoconazole was found to increase the area under the blood CsA concentration-time curve (AUC) and was effective when administered by the oral or intraperitoneal route. 3. The effects of CsA and ketoconazole on the immune system of sheep were also assessed. 4. A single dose of CsA 5 mg/kg resulted in abrogation of in vitro lymphocyte function manifest at 24 h after injection of CsA. Normal responsiveness recovered in 48-72 h. Numbers of T lymphocytes in peripheral blood were elevated transiently at 48 h although no other significant alteration in lymphocyte subsets was observed with this treatment. 5. Concomitant ketoconazole administration enhanced the CsA-induced suppression of in vitro lymphocyte responses. Blood levels of CsA (AUC values to 24 h) were significantly elevated with concomitant ketoconazole administration and depression of lymphocyte responses to mitogens were also significantly enhanced. An increase in the proportion of T4 positive cells in the blood was observed at 48 h and at 7 days after administration of CsA with ketoconazole. 6. These findings indicate that CsA effectively abrogates immunocompetence in the sheep and this immunosuppressive effect is enhanced by concomitant administration of ketoconazole.

In vitro stage-specific sensitivity of Plasmodium falciparum to quinine and artemisinin drugs.

The inhibitory effects of quinine, chloroquine and 4 qinghaosu drugs, artemisinin, artemether, artesunate and dihydroartemisinin, on 4 culture-adapted isolates and 2 standard clones of Plasmodium falciparum were determined in vitro. All isolates were sensitive to the widely used antimalarial drugs quinine (EC50 range 3 x 10(-8)-1 x 10(-7) mol/L) and chloroquine (EC50 range 1 x 10(-9)-7 x 10(-9) mol/L), irrespective of the geographical origin or treatment history of the patients from which they were taken. In general, the qinghaosu drugs were more potent than the conventional antimalarials, having EC50 values of 3 x 10(-11)-3 x 10(-8) mol/L. Stage-specific data indicated that quinine has a primary mode of action on mature parasite forms, achieving 80-100% growth inhibition within 2-4 h of drug exposure. The stage-specific activity of the 3 qinghaosu drugs artemisinin, artemether and dihydroartemisinin differed from that of quinine, and each derivative displayed a unique stage-specific profile. Artemisinin was rapidly effective against both rings and schizonts, achieving 100% growth inhibition within 6-8 h. The inhibitory effects of artemether were less rapid, requiring 10 h to achieve 70-80% ring stage growth inhibition. Dihydroartemisinin was highly effective against all parasite stages in most cases achieving 100% growth inhibition within 2-4 h of exposure. The results confirm that the qinghaosu drugs are potent antimalarials, and suggest different stage-specific profiles compared to conventional antimalarial drugs.

Assessment of the therapeutic potential of cytokines, cytotoxic drugs and effector cell populations for the treatment of multiple myeloma using the 5T33 murine myeloma model.

The therapeutic potential of six cytokines, eight cytotoxic drugs and two effector cell populations for the treatment of multiple myeloma was assessed in vitro using the 5T33 murine myeloma model. The efficacy of combination IFN-alpha and melphalan therapy was also evaluated in vitro and in vivo. Of the cytokines tested in vitro using the MTT assay, only IFN-alpha demonstrated significant inhibition of myeloma cell growth at non-toxic concentrations (ED50 = 1508.3 +/- 181.3 U/mL and 2617.9 +/- 334.0 U/mL for murine IFN-alpha [mIFN-alpha] and human IFN-alpha hybrid B/D [hIFN-alpha B/D], respectively). The ED50 for the eight cytotoxic drugs tested ranged from 2.3 x 10(-9) to 4.3 x 10(-13) mol/L and all were within the therapeutic range for humans. Combination hIFN-alpha B/D and melphalan were found to be additive in their inhibitory effects on myeloma cell growth in vitro and this finding was confirmed in vivo in C57BL/KaLwRij mice bearing disseminated 5T33 myeloma. Control animals demonstrated a median survival duration of 25.3 days whereas hIFN-alpha B/D or melphalan treatment alone increased survival to 30.5 and 33.3 days, respectively (P < 0.001). Combination IFN-alpha/melphalan therapy increased median survival duration to 38.5 days (P < 0.001) which was also significantly greater than that obtained with single agent therapy (P < 0.01). The murine myeloma cells were found to be resistant to NK cell lysis but susceptible to lysis by LAK cells (49.3 +/- 6.3% lysis at an effector to target ratio of 100:1).(ABSTRACT TRUNCATED AT 250 WORDS)

Patho- and immunobiology of malignant mesothelioma: characterisation of tumour infiltrating leucocytes and cytokine production in a murine model.

Malignant mesothelioma (MM) is an aggressive, uniformly fatal serosal tumour, usually associated with asbestos exposure, for which there currently is no effective treatment. In order to gain insight into the mechanism(s) whereby MM might escape immune surveillance, a murine model for MM was used (a) to characterise the tumour-infiltrating lymphocytes (TIL) and macrophages (TIM) phenotypically, (b) to examine systemic immune recognition of MM, and (c) to examine the possible influence of tumour-derived cytokines on systemic and local pathobiological manifestations of MM. A profound down-regulation of lymphocyte surface markers, known to be involved in T cell activation, was found in TIL. Likewise, although TIM were present in large numbers, their expression of MHC class II antigen and integrins was weak or absent, suggestive of altered functional activity. Significant amounts of cytokines, in particular transforming growth factor beta, interleukin-6 (IL-6), IL-1 and tumour necrosis factor were produced during the course of MM tumour development-directly by the MM cells and/or indirectly in response to tumour growth. These factors may contribute both to derangement of antitumour effector mechanisms and to the clinical and pathological manifestations of the disease.

Radiopharmaceutical therapy of 5T33 murine myeloma by sequential treatment with samarium-153 ethylenediaminetetramethylene phosphonate, melphalan, and bone marrow transplantation.

BACKGROUND: Total-body irradiation, followed by hematopoietic system rescue by bone marrow transplantation (BMT), has been found to improve the response of patients with multiple myeloma to treatment with melphalan. The problems of nonhematopoietic toxicity from whole-body irradiation might be circumvented by using a bone-seeking radiopharmaceutical, such as samarium-153 ethylenediaminetetramethylene phosphonate (153Sm-EDTMP), to ablate the bone marrow. PURPOSE: A mouse model system for multiple myeloma was used to evaluate the potential therapeutic efficacy of sequential therapy with 153Sm-EDTMP, melphalan, and BMT. METHODS: Female C57BL/KaLwRij mice were inoculated with 8 x 10(5) 5T33 murine myeloma cells. Treatment protocols were begun 3 or 10 days later, when the myeloma was either confined to bone marrow or disseminated in liver, spleen, and lymph nodes, simulating human multiple myeloma. 153Sm, a potent beta particle-emitting radioisotope of short half-life (46.7 hours), was linked to the bone-seeking chelate EDTMP. Animals in the first treatment group were each given 22.5 MBq 153Sm-EDTMP via the jugular vein (day 3 or 10), followed by 18.5 mg/kg melphalan (maximum tolerated dose) given intraperitoneally 5 days later (day 8 or 15) and syngeneic BMT another 2 days later (day 10 or 17). Survival in groups of six to 10 animals for each time series was compared with that in mice left untreated (control cohort), in mice treated with 153Sm-EDTMP alone (day 3 or 10), or in mice treated with melphalan alone (day 8 or 15). The hematopoietic systems of animals in the latter two treatment groups recovered full function, obviating the necessity of BMT. The end point was onset of paraparesis, at which time the animals were immediately killed by carbon dioxide asphyxiation. RESULTS: Median survival in untreated control animals was 23 days in those with localized disease and 24 days in those with disseminated myeloma. Treatment with 153Sm-EDTMP alone improved survival to a median of 29 days when commenced on day 3 and 30 days when begun on day 10. Melphalan treatment alone improved the median survival to 31 days for animals with localized myeloma and 34 days in animals with disseminated disease. Additional improvement in survival to a median of 42 days was achieved in animals treated 3 days after tumor inoculation with sequential 153Sm-EDTMP, melphalan, and BMT; median survival was 40 days using this regimen in animals with disseminated myeloma. CONCLUSIONS: Animals in all three treatment protocols survived longer than those left untreated after inoculation with myeloma cells (P < .001). Sequential treatment with 153Sm-EDTMP, melphalan, and BMT was significantly more effective than single-agent treatment (P < .01). No evidence of radiotoxicity was detected in nonhematopoietic organs. IMPLICATIONS: The survival advantage conferred by our sequential treatment protocol suggests its potential clinical usefulness in the treatment of multiple myeloma and other hematologic malignancies in humans.

Effect of interferon-alpha 2a on malignant mesothelioma.

Malignant mesothelioma (MM) is a tumor that is resistant to conventional therapy. Interferon-alpha (IFN-alpha) has been used in the treatment of some human tumors, and we have previously demonstrated an in vitro anti-proliferative effect of IFN against MM cell lines. Therefore, the effect of recombinant human IFN-alpha (IFN-alpha 2a) (Roferon-A, Hoffmann-La Roche) on previously untreated patients with MM has been studied. Twenty-five patients (24 male and 1 female), with a mean age of 59 +/- 9.9 years, were treated for 3 months with IFN-alpha 2a. The starting dose was 3 x 10(6) IU daily increasing to a maximum of 18 x 10(6) IU daily or as tolerated. All patients had measurable tumor on thoracic CT prior to commencement. CT scans were performed at 6 and 12 weeks to determine tumor response. Twenty patients completed 3 months of treatment. Five patients were withdrawn because of disease progression. Side effects were predictable and dose related. Dose reductions were necessary in 12 patients for grade 2 toxicity. One patient had a complete response (CR), 2 patients had partial responses (PR) (response rate = 12%), 13 (52%) patients remained stable, 1 of whom exhibited a delayed PR, and 9 (36%) had progressive disease. These data suggest that IFN-alpha 2a is well tolerated in patients with MM and is active against MM in a proportion of patients.

An analysis of the relationship between gamma delta T cell receptor V gene usage and non-major histocompatibility complex-restricted cytotoxicity.

gamma delta T cells are capable of mediating non-major histocompatibility complex (MHC) restricted lysis of a variety of tumour cell lines. The mechanism of this lysis and its significance in tumour immunity are not clear. We have used a panel of five malignant mesothelioma (MM) cell lines, as well as standard tumour targets K562 and Daudi, to investigate some of the factors which could be involved in non-MHC restricted cytotoxicity mediated by gamma delta T cells. Individual MM cell lines, representing a panel of lines derived from a single cell type, varied in their susceptibility to lysis by gamma delta T cell clones. Individual gamma delta T cell clones also showed unique cytotoxic profiles, and differed in their cytotoxic potential. T cell receptor (TCR) V gamma gene usage correlated with the ability of clones to lyse Daudi or K562; clones lysing Daudi expressing V gamma 9 and clones lysing K562 expressing V gamma I subgroup genes. No strict correlation between V gamma and V delta gene usage and MM reactivity was, however, demonstrable. There was also no correlation between gamma delta T cell lysis of MM cell lines and the capacity of gamma delta T cells to produce interferon-gamma, tumour necrosis factor-alpha, interleukin-2 or interleukin-4, nor with their expression of CD8.

Establishment of a murine model of malignant mesothelioma.

Malignant mesothelioma (MM) is an aggressive tumour of the serosal cavities which is associated with previous asbestos exposure and is generally found to be resistant to conventional forms of therapy. Adequate scientific and clinical assessment of this disease has been severely limited by the relatively low incidence of mesothelioma and the lack of representative cell lines and animal models. The purpose of this study was to develop an asbestos-induced murine model of MM both as an in vivo-passaged malignancy and as in vitro-established cell lines. Such a model system would be invaluable for use in the study of various cellular, molecular and genetic aspects of the disease, and for the pre-clinical evaluation of potential therapeutic agents. BALB/c and CBA mice were injected intraperitoneally with crocidolite asbestos. Seven to 25 months after exposure, 35% of the mice developed mesothelioma (5 BALB/c, 9 CBA), as determined by standard cytological and histological parameters. From these primary tumours, 12 continuously growing cell lines (5 BALB/c, 7 CBA) were established in culture. All have been confirmed as mesothelioma by cytological and ultrastructural (electron microscopy) analyses. These lines have been in culture for 7 to 24 months and have achieved passages above 32 (range 32 to 106). As in the human disease, the murine mesothelioma lines vary in their morphology and growth rates (doubling times ranging from 14 to 30 hr). All cell lines produced tumours when injected into syngeneic mice.

A model of multiple myeloma: culture of 5T33 murine myeloma cells and evaluation of tumorigenicity in the C57BL/KaLwRij mouse.

The 5T33 multiple myeloma is one of a series of transplantable murine myelomas arising spontaneously in C57BL/KaLwRij mice. This study describes the establishment and characterisation of the 5T33 murine myeloma in vitro as a cultured cell line in terms of its morphology, growth rate, expression of paraprotein (IgG2b) and tumorigenicity in syngeneic animals. The 5T33 cell line has been in continuous culture for over 10 months and has achieved more than passage 34. In culture, 5T33 myeloma grows as single cells or in small clusters of loosely adherent cells on an adherent stromal cell layer. Maximum doubling time is approximately 25 h, and over 90% of the cells express cytoplasmic IgG2b paraprotein. The cultured 5T33 myeloma cells are highly tumorigenic in C57BL/KaLwRij mice with as few as 500 cells inducing paralysis and death as early as day 36 post-tumour inoculation. Kinetics of tumour development and detection of IgG2b paraprotein are dose dependent. Two weeks following intravenous inoculation of 5 x 10(5) cultured 5T33 myeloma cells, tumour cells were readily identified in the bone marrow. By 3 weeks post-tumour inoculation, 5T33 myeloma cells were found in various tissues throughout the animal. Studies are now underway to determine the sensitivity of this cell line to various therapeutic modalities.

HLA antigen expression and malignant mesothelioma.

The expression of HLA antigens by a tumor may determine its progression and metastatic potential by influencing the immune response to that tumor. The upregulation of HLA antigen expression on some cell types by interferons (IFNs) may contribute to their antitumor activity. Malignant mesothelioma (MM) is a tumor that has a poor prognosis and is unaffected by conventional therapy, although immunotherapy has not been adequately assessed. In this study, we have examined the constitutive and IFN-inducible expression of class I and class II HLA antigens on MM cell lines using indirect immunofluorescence and Northern blotting. All MM cell lines constitutively expressed class I, but not class II, surface antigen, and all three class I loci (HLA-A, HLA-B, and HLA-C) were expressed. The MM cell lines were heterogeneous in their response to the IFNs. Treatment with IFN-alpha marginally increased class I surface expression, but not class II. Class I mRNA was, however, clearly increased in all cell lines after IFN-alpha treatment, suggesting that class I surface antigen was already maximally expressed. IFN-gamma increased class I mRNA expression in all but one cell line and induced DR expression on three of the cell lines. DQ-beta, but not DQ-alpha, mRNA was inducible in the same three cell lines, but DQ surface antigen was never demonstrable.(ABSTRACT TRUNCATED AT 250 WORDS)

Interaction between dactinomycin and tumor necrosis factor in mesothelioma. Cachexia without oncolysis.

There is no effective therapy for human malignant mesothelioma, and its susceptibility to recombinant cytokines has not been studied extensively. Recombinant human tumor necrosis factor alpha (rHuTNF alpha) was evaluated for its in vitro and in vivo antitumor activity using a human malignant mesothelioma cell line [DeH128(m)], both in culture and heterotransplanted in nude mice. In vitro, rHuTNF alone had no direct antimesothelioma activity assessed using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide assay, but in combination with the transcription inhibitor, dactinomycin (AD), mesothelioma cell metabolic activity was inhibited (80% of control). The effects of this combination of agents were studied on DeH128(m) cells heterotransplanted as subcutaneous tumors in nude mice. In vivo there was no significant inhibition of tumor growth by combined rHuTNF alpha and AD therapy, but the combination produced marked cachexia in doses at which each component (rHuTNF alone or AD alone) was well tolerated. The authors conclude that the well-described in vitro interaction between AD and rHuTNF also operates in vivo to produce cachexia and that the combination of these two agents is likely to have a low therapeutic index in malignant mesothelioma.

Capacity of tumor necrosis factor to augment lymphocyte-mediated tumor cell lysis of malignant mesothelioma.

Recombinant human tumor necrosis factor (rHuTNF) was evaluated both for direct anti-tumor action against human malignant mesothelioma and for its capacity to augment the generation and lytic phases of lymphocyte-mediated cytotoxicity against this tumor. rHuTNF was directly toxic by MTT assay to one of two mesothelioma cell lines evaluated, but had no effect on susceptibility to subsequent lymphocyte-mediated lysis of either line. TNF alone was incapable of generating anti-mesothelioma lymphokine-activated killer cell (LAK) activity. Furthermore, it did not augment the degree or LAK activity produced by submaximal interleukin-2 (IL-2) concentrations nor did it augment lysis of mesothelioma cells by natural killer (NK) or LAK effector cells during the 4-hr 51chromium release cytolytic reaction. The studies also suggest that mesothelioma targets are less responsive to TNF plus submaximal IL-2 concentrations than the standard LAK sensitive target Daudi, raising the possibility that intermediate LAK sensitive tumors such as mesothelioma may require separate and specific evaluation in immunomodulation studies. This in vitro study indicates that use of low-dose rHuTNF and IL-2 is unlikely to be an effective substitute for high-dose IL-2 in generation and maintenance of LAK activity in adoptive immunotherapy for mesothelioma.

Chemosensitivity and cytokine sensitivity of malignant mesothelioma.

Malignant mesothelioma arises in serosal tissues, is locally invasive, and is usually resistant to chemotherapeutic agents used clinically. To determine whether resistance to cytotoxic drugs was an inherent characteristic of mesothelioma cells, we performed in vitro chemosensitivity testing on five fully characterised human malignant mesothelioma cell lines and, for comparison, on three lines representative of clinically drug-resistant solid-tissue carcinomas using the MTT (tetrazolium bromide) assay system. Mesothelioma cell lines were intrinsically resistant to eight common antineoplastic drugs, with concentrations that produced a 50% reduction in optical density (IC50 values) for all drugs being equivalent, if not higher, for mesothelioma cell lines as compared with lung and colon carcinoma cell lines. We then investigated the direct anti-mesothelioma activity of recombinant human cytokines with their antineoplastic properties. All five mesothelioma cell lines were resistant to tumour necrosis factor, but they displayed varying degrees of sensitivity to interferons (IFNs). IFN gamma directly inhibited the growth of two of five mesothelioma lines. IFN alpha displayed little activity against four of five mesothelioma lines. The mesothelioma cells that were sensitive to IFN alpha were resistant to IFN gamma, indicating that sensitivity to IFNs is not a genetic characteristic of malignant mesothelioma cells. Significant interactions between cytokines in combination were not observed.

Establishment and characterization of five human malignant mesothelioma cell lines derived from pleural effusions.

Malignant mesothelioma (MM) is an aggressive tumour of the serosal cavities which is associated with exposure to asbestos. Studies of this tumour have been limited by a paucity of well-characterized human MM cell lines. In this study, 5 human MM cell lines were established from pleural effusions of patients with this malignancy. All 5 patients were males with known crocidolite asbestos exposure, who had received no treatment for their disease and in whom the diagnosis was confirmed by cytology, histology and electron microscopy (EM). These lines have been in culture from 11 to 25 months, and all of them for more than 18 passages. The appearance of the cells in culture was extremely varied; in 3 of the lines they were spindle-shaped with few vacuoles (JU77, LO68 and ONE58); in 1 line they had a thick, stellate shape with vacuoles (NO36) and in 1 they were very pleomorphic in both shape and size with irregular membranes and numerous vacuoles [DeH128 (M)]. Upon reaching confluence, cells in 3 of the 5 lines assumed the cobblestone-like pattern characteristic of epithelial-type cells, whereas in the other 2 (LO68 and ONE58) they remained spindle-shaped. All 5 lines demonstrated a loss of contact inhibition (i.e., piling) at confluence. Minimum doubling times varied significantly from 18 hr (JU77) to more than 30 hr [DeH128 (M)]. Cytological examination showed characteristic mesothelial/mesothelioma morphology, and epithelial membrane antigen (EMA) and cytokeratin were demonstrated in cells from all 5 lines. These cells lacked CEA and epithelial mucin. The presence of cell junctions, glycogen and numerous long, thin, branching microvilli was readily demonstrable by EM. All lines had abnormal karyotypes, with the modal chromosome number varying from 40 to 80. Variable chromosome numbers, numerous structural rearrangements and unrecognizable marker chromosomes were readily observed; however, the only consistent change seen was del 6q21 in 4 of the 5 lines. The establishment of these 5 cultured human MM cell lines now provides an opportunity for comparative study of several aspects of the biology of MM in vitro as well as screening new treatment modalities.

Asbestos fibres inhibit the in vitro activity of lymphokine-activated killer (LAK) cells from healthy individuals and patients with malignant mesothelioma.

Asbestos exposure is associated with an increased incidence of several malignancies, including malignant mesothelioma (MM). This study evaluates the relationship between asbestos exposure and the in vitro generation and function of LAK cells, an immune effector cell population with powerful lytic activity against MM cells. Both serpentine (chrysotile) and amphibole (amosite and crocidolite) forms of asbestos fibres suppress LAK cell generation, viability (by 5-11%, P less than 0.02) and cell recovery (by 13-15%, P less than 0.02). However, the LAK cells generated in the presence of the amphiboles were as effective as unexposed cells in lysing both standard tumour cell targets (K562, 56.4% lysis versus 61.5%, respectively, P greater than 0.5; NS; Daudi, 60.5% lysis versus 64.5% P greater than 0.5; NS), and MM tumour cell targets (mean of three MM cell lines 48.3% versus 46.3%, P greater than 0.5; NS), whereas the function of LAK cells generated in the presence of chrysotile was significantly reduced against three out of the five tumour cell targets tested (P less than 0.03). In the presence of asbestos fibres, LAK cell function was reduced against all five tumour cell targets (P less than 0.01), irrespective of whether the cell donors were healthy individuals or patients with MM. NK cell activity was also suppressed (P less than 0.01). The serpentine form of asbestos, chrysotile, was significantly more suppressive of both effector cell functions than either of the amphiboles (P less than 0.01). These findings suggest that asbestos exposure may suppress the function and in some instances the generation of immune effector cell mechanisms, thereby increasing the risk of disease and malignancy.

In vivo boosting of lung natural killer and lymphokine-activated killer cell activity by interleukin-2: comparison of systemic, intrapleural and inhalation routes.

Natural killer (NK) cells are thought to play a role in host defence against malignancy and infection, in immunoregulation and as precursor cells in a generation of lymphokine-activated killer (LAK) cells which can lyse NK-resistant tumour cells. As the lung is a major site for malignancy and infection and as there are large numbers of lymphoid cells including NK cells in the interstitial compartment of the lung, we evaluated the capacity of interleukin-2 (IL-2), a lymphokine capable of augmenting NK activity in vitro, to augment lung NK cell activity in vivo, using different routes of IL-2 administration. We compared both systemic (i.v. and i.p.) and local (intrapleural and inhalation) routes of IL-2 administration (50,000 U/daily for 5 days) using CBA mice, assessing NK and LAK cell activity in the spleen (systemic) and in the lung. The target cells used for these studies were the YAC-1 (NK-sensitive) and P815, NO36 and HA56 (NK-resistant, LAK-sensitive) cell lines. Splenic NK activity was increased by 1.4-1.9-fold for i.v./i.p., respectively, compared with controls with both systemic routes of administration, and lung NK activity was increased 3.2-fold and 3.8-fold (i.v./i.p, respectively, P less than 0.05), to levels which were comparable to systemic (splenic) NK activity following the same therapy. Intrapleural IL-2 administration similarly enhanced lung NK activity (3.3-fold) and splenic NK activity (1.3-fold; P less than 0.05 versus controls for both). Surprisingly, inhaled IL-2 suppressed both splenic and lung NK cell activity (84 +/- 8% and 78 +/- 10% suppression, respectively, P less than 0.05). LAK cell activity was also enhanced in the lung by 1.8-8-fold in response to i.v., i.p. and intrapleural IL-2, whereas inhaled IL-2 was ineffective in generating LAK cell activity. These results suggest that the systemic and intrapleural administration of IL-2 effectively boost pulmonary NK and LAK activity whereas inhalation of IL-2 does not. Thus, in clinical situations where boosting of local lung NK or LAK cell activity is desired, these routes of IL-2 administration may be effective.