Interleukin-4 Secreting Cells Research Articles

Uric Acid; a Possible Mediator of the Adjuvant Effect of Alum in Mice Immunized with Ovalbumin

One proposed mechanism by which alum enhances an immune response is by its ability to induce an inflammatory response that results in the release of uric acid from necrotic cells. Uric acid is thought to be a mediator in enhancing the immune response. The aim of this study was to investigate the immunopotentiating effect of uric acid. Groups of BALB/c mice were injected intraperitoneally with ovalbumin, ovalbumin + alum, ovalbumin + uric acid, uric acid, alum, or allopurinol. Two other groups were pretreated with allopurinol and were given ovalbumin + alum, or ovalbumin + uric acid 24 hours later. An additional two groups served as controls. On days 4, 7 and 10 post-injection, the numbers of Interleukin 4(IL-4) and Interferon-γ (IFN-γ) secreting spleen cells were determined by the ELISPOT assay. Serum uric acid levels were determined using an autoanalyser and nitric oxide using the Greiss reagent. The groups that received alum + ovalbumin or uric acid + ovalbumin had the highest numbers of IL-4 and INF-γ secreting cells as compared to all the groups. Allopurinol administration one day prior to alum + ovalbumin or uric acid + ovalbumin resulted in a decrease in the number of IL-4 and INF-γ secreting cells when compared to alum+ ovalbumin or uric acid + ovalbumin allopurinol - untreated groups. Groups that received alum, alum + ovalbumin, uric acid, and uric acid + ovalbumin had high serum uric acid levels as compared to all the groups. All groups that received alum had the highest levels of nitric oxide when compared to the groups that were not given alum. In conclusion, it appears that uric acid might be a mediator in the adjuvant effect of alum.

Immune responses of pigs after experimental infection with a European strain of Porcine reproductive and respiratory syndrome virus

The purpose of this experiment was to study the immune response of pigs during an experimental infection with a European strain of Porcine reproductive and respiratory syndrome virus (PRRSV). Five pigs were challenged intranasally with PRRSV strain VP21 and another five were kept as controls. Clinical course and humoral and cell-mediated responses were monitored for 70 days post-infection (p.i.). Infected pigs developed mild signs at 24 h p.i. Viraemia was detectable by nested RT-PCR until day 14 p.i. Earliest seroconversions (ELISA) were seen by day 7 p.i. (three of five animals) and, by day 14, all inoculated pigs had seroconverted (ELISA and immunoperoxidase monolayer assay). Virus-neutralizing antibodies were undetectable until day 56 p.i. and, by day 70 p.i., two inoculated pigs still were negative. Flow-cytometry assays using peripheral blood mononuclear cells (PBMC) showed an upshift in CD8(+) cells (day 7 p.i.) and a downshift of CD21(+) cells (days 7 and 28 p.i.). Regarding cell-mediated responses, development of PRRSV-specific gamma interferon-secreting cells (IFN-gamma-SC) and interleukin 4-secreting cells (IL4-SC) in PBMC was examined by ELISPOT assay. IFN-gamma-SC were not detected significantly until day 14 p.i., whereas, for IL4-SC, no differences between groups were seen. Concurrently with the onset of viraemia and the development of clinical signs, serum haptoglobin levels and interleukin 10 (IL10) in PRRSV-stimulated PBMC-culture supernatants increased significantly. These differences disappeared later on. For IL2, IL4, IL8 or transforming growth factor beta, no differences were seen among groups. These results are compatible with a model in which the immune response does not fully control the outcome of the infection.

C3d Enhances Immune Responses Using Low Doses of DNA Expressing the HIV-1 Envelope from Codon-Optimized Gene Sequences

DNA vaccinations effectively induce both humoral and cellular immune responses to immunogens from diverse infectious agents. However, DNA vaccines expressing the HIV-1 envelope glycoprotein (Env) are poorly immunogenic when expressed from wild-type (wt) DNA sequences. Two recent approaches used to enhance the immunogenicity of Env expressed from a DNA vaccine are the fusion of the molecular adjuvant, C3d, to a soluble form of Env and the use of codon-optimized (co) env gene inserts. Independently, each approach enhances antibody titer and cellular responses against Env expressed from gene inserts. The goal of this study was to examine if both codon-optimization of env gene inserts and C3d conjugation to Env could function in a synergistic manner to enhance immunogenicity. Mice (BALB/c) were inoculated with decreasing doses (2.0 microg, 0.2 microg or 0.02 microg) of co DNA expressing Env alone or fused to three copies of murine C3d (mC3d3) gene. Mice vaccinated with the highest dose (2.0 microg) of DNA had high anti-Env specific antibody titers regardless of the addition of mC3d3. At lower doses (0.2 microg and 0.02 microg) of DNA, mice vaccinated with Env-mC3d3 had enhanced immune responses compared to mice vaccinated with DNA expressing Env only. In addition, mice vaccinated with Env-mC3d3 at the highest doses of DNA had enhanced interleukin-4 secreting cells, while mice vaccinated with the lowest dose of DNA had enhanced interferon-gamma secreting cells. Therefore, both codon-optimization of env sequences and C3d conjugation to Env appear to enhance anti-Env antibodies in an independent and additive manner.

A possible association between the presence of interleukin-4–secreting cells and a reduction in the risk of acute graft-versus-host disease

We monitored cytokine-secreting cells using an enzyme-linked immunospot (ELISPOT) assay in a prospective study to assess the cytokine network after transplantation. Peripheral blood mononuclear cells were collected from 23 patients who received allogeneic stem cell transplantation, from before the preconditioning regimen to 56 days after transplantation. The number of interleukin-4 (IL-4), interferon-gamma (IFN-gamma), and tumor necrosis factor-alpha (TNF-alpha)-secreting cells were measured by ELISPOT assay. For IL-4 and IFN-gamma, in vitro stimulation with phorbol 12-myristate 13-acetate and phytohemagglutinin was performed. The frequency of IL-4-secreting cells was significantly higher in five patients receiving peripheral blood stem cell transplantation (PBSCT) than that in 18 patients who received bone marrow transplantation (BMT). Based on IFN-gamma and TNF-alpha release, there was a trend toward a decrease in the number of cytokine-secreting cells in PBSCT compared with BMT. Furthermore, patients who did not develop acute graft-vs-host disease (GVHD, n=5) showed a significantly higher number of IL-4-secreting cells compared with those who developed acute GVHD (n=18). Both IFN-gamma-secreting cells and TNF-alpha-secreting cells showed a trend to increase in number in patients with acute GVHD. In patients who received reduced-intensity stem cell transplantation (n=7) compared with conventional stem cell transplantation (n=16), there was a large number of cytokine-secreting cells detected by IL-4 and IFN-gamma release. These results are consistent with the hypothesis that IL-4-producing cells inhibit the development of acute GVHD. In addition, the increased percentage of IL-4-secreting cells may be responsible for the unexpected low incidence of acute GVHD in PBSCT, despite the presence of large numbers of mature T cells in the donor infusion.

Interleukin-4 induced by measles virus and measles-derived peptides as measured by IL-4 receptor-blocking ELISA

Interleukin-4 (IL-4) is a signature cytokine for T-helper 2 (Th2) type immune responses in humans. However, data on antigen-specific secretion of IL-4 is limited due to difficulties detecting IL-4. We evaluated an IL-4 receptor-blocking assay for the detection of secreted IL-4 in peripheral blood mononuclear cells (PBMC) stimulated in vitro with measles virus (MV) and MV-derived nucleoprotein (N) and phosphoprotein (P) peptides. We recruited 20 healthy subjects, previously immunized with two doses of measles–mumps–rubella-II (MMR-II) vaccine. We evaluated the cellular and humoral immune status of these study subjects by an in vitro lymphoproliferation assay and an enzyme-linked immunosorbent assay (ELISA), respectively. We analyzed the MV-induced and N and P peptide-induced IL-4 levels in PBMC culture supernatants. Using the IL-4 receptor blocking assay, 50% of the subjects were positive for secreted IL-4 in response to MV stimulation, and 5% and 23.1% of study subjects were positive for secreted IL-4 in response to MV-derived N and P peptides, respectively. In contrast, we did not find any positive secreted IL-4 response to MV using conventional ELISA without IL-4 receptor-blocking antibody in our optimization study. Further, we found very low frequencies of IL-4 secreting cells using an alternate ELISpot technique, accounting for only a 5% positive response to MV and no response to P peptide. We propose that the IL-4 receptor-blocking assay is an easy-to-adapt technique for screening antigen-specific immune responses in large-scale population-based studies.

A human dual-color enzyme-linked immunospot assay for simultaneous detection of interleukin 2- and interleukin 4-secreting cells

The enzyme-linked immunospot (ELISPOT) assay is an efficient technique for the enumeration of single cells secreting antibodies and cytokines. For simultaneous differentiation of individual cells producing interleukin-2 (IL-2) and interleukin-4 (IL-4) at a single cell level in human peripheral blood mononuclear cells (PBMCs), a human dual-color ELISPOT assay has been optimized. In the present system, the red spots corresponding to IL-2-secreting cells (T helper type 1, Th1, cells) were developed with horseradish peroxidase and the amino ethyl carbazole (AEC)/H 2O 2. The blue spots corresponding to IL-4-secreting cells (T helper type 2, Th2, cells) were developed with an alkaline phosphatase and the Vector blue. The usefulness of the assay method was tested. With this system, we could detect the IL-2- and IL-4-secreting cells simultaneously in human PBMCs of a juvenile rheumatoid arthritis (JRA) patient. This procedure provides useful information on clinical immune disorders.

The T-helper 1/T-helper 2 balance in peripheral blood of women with hyperemesis gravidarum

Objective: The purpose of this study was to evaluate the T-helper 1/T-helper 2 balance and its relation with pregnancy-related hormones in hyperemesis gravidarum. Study Design: The T-helper 1/T-helper 2 ratio and plasma progesterone and estrogen levels were examined in the peripheral blood of 22 women with hyperemesis gravidarum and normal pregnancies. The proportion of CD4-positive cells that expressed intracellular cytokines (interferon gamma and interleukin-4) were analyzed by blood flow cytometry. The ratio of interferon gamma–secreting cells to interleukin-4–secreting cells was taken as the T-helper 1/T-helper 2 ratio. Results: In hyperemesis gravidarum, the proportions of interleukin-4–secreting cells increased, and the T-helper 1/T-helper 2 ratio averaged 8.4 ± 0.9, which was significantly lower than in normal pregnancy (11.6 ± 1.1, P <.05). The changes in the T-helper 1/T-helper 2 ratio in hyperemesis gravidarum were accompanied by the elevation of progesterone and estrogen levels. Conclusion: A further shift of the T-helper 1/T-helper 2 balance to the T-helper 2 dominance in hyperemesis gravidarum may be related to the increase of progesterone and estrogen levels. (Am J Obstet Gynecol 2002;187:1631-5.)

Decreased production of interleukin-2 (IL-2), IL-2 secreting cells and CD4+ cells in medication-free patients with schizophrenia

There are a number of indications that schizophrenia is associated with changes in the immune system. Although functional studies have mostly demonstrated decreased in vitro production of IL-2 by peripheral blood mononuclear cells (PBMCs) stimulated with mitogen, the reason is unclear. The aim of the study was to explore the relationship between IL-2 production and CD4+ cells which mainly secret IL-2 in non-Caucasian patients with schizophrenia. Blood CD4+ cells and mitogen-stimulated IL-2 secreting cells identified by an immunohistochemical study with the alkaline phosphatase/anti-alkaline phosphatase (APAAP) technique, and in vitro IL-2 production with radioimmunometric assay (RIA) were measured in 30 schizophrenic patients and 30 normal control subjects matched for sex, age and race. The results showed that blood CD4+ cells and mitogen-induced IL-2 secreting cells and IL-2 production were significantly lower in schizophrenic subjects than in the normal controls. There was significantly positive correlation between CD4+ cells and IL-2 production in normal controls but not in patients. These findings suggest that immune disturbance may be present in schizophrenic patients. The lower in vitro IL-2 production is probably related to the decreased number of T-cells that secret IL-2, as well as to the intrinsic disorder of the patients' T cells.

Relation between adenosine and T-helper 1/T-helper 2 imbalance in women with preeclampsia

OBJECTIVE: To evaluate the relationship between changes in plasma adenosine concentration and imbalances in the T-helper 1/T-helper 2 ratio in peripheral blood of women with preeclampsia. METHODS: Plasma adenosine concentrations and the T-helper 1/T-helper 2 ratio were examined in the peripheral blood of 16 preeclamptic and normal pregnant women. The proportion of specific T-cell marker CD4-positive cells expressing intracellular cytokines, interferon-γ derived from T-helper 1 and interleukin-4 derived from T-helper 2 cells, were analyzed by flow cytometry. The ratio of interferon-γ secreting cells to interleukin-4 secreting cells was taken as the T-helper 1/T-helper 2 ratio in vivo. The effect of the adenosine-receptor blocker 8-sulfophenyltheophylline was also measured in vitro. RESULTS: Mean plasma adenosine concentration in preeclampsia was significantly higher than that in normal pregnancy (0.68 ± 0.07 μmol/L versus 0.39 ± 0.06 μmol/L, P < .05). The proportions of interferon-γ secreting cells increased and interleukin-4 secreting cells decreased significantly in preeclampsia, and the T-helper 1/T-helper 2 ratio in preeclampsia was significantly higher than in normal pregnancy (18.1 ± 2.6 versus 9.9 ± 1.5, P < .05). The increase of the proportion of interferon-γ secreting cells after adenosine receptor blockade in preeclampsia significantly exceeded that of normal pregnancy. The T-helper 1/T-helper 2 ratio in preeclampsia was significantly greater than that in normal pregnancy (36% versus 17%, P < .05). CONCLUSION: Increased plasma adenosine may be involved in the regulation of imbalances in the T-helper 1/T-helper 2 ratio in women with preeclampsia.

Expansion of helper T-cell recognition in mice immunized with a synthetic peptide corresponding to the C-terminal thyrotropin receptor-specific insert

We previously reported that immunization with a synthetic peptide of human thyrotropin receptor (TSH-R) expanded humoral autoimmunity to TSH-R (Sugawa H, Ueda Y, Ueda M, Kosugi S, Ichiyama S, Mori T. Immunization with the ‘immunogenic Peptide’ of TSH receptor induces oligoclonal antibodies with various biological activities. Peptide 1998;19:1303–7.). In the present study, we examined this phenomenon at the T-cell level. Balb/c mice were immunized with a synthetic peptide corresponding to the C-terminal-specific insert of human TSH-R. Spleen cells were collected and subjected to antigen-specific ELISPOT assay. The number of interleukin 4-secreting cells specific to P354–367 increased within 3 weeks. Cells responding to the other peptides increased 7 weeks after immunization. This phenomenon was not observed in mice immunized with bovine serum albumin alone. During immunization, numbers of interferon-γ-secreting lymphocytes were not changed significantly. These results indicated that immunization with C-terminal TSH-R-specific insert peptide causes fluctuation in the type 2 helper T-cell population but not type 1 Th cells against the TSH-R, and the recognition repertoire of type 2 helper T cell was expanded by the peptide.

Flow cytometric analysis of in vitro proinflammatory cytokine secretion in peripheral blood from multiple sclerosis patients.

The cytokines, interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), and interleukin-2 (IL-2) are important endogenous proinflammatory proteins and have been linked to disease activity in multiple sclerosis. In this study, we use flow cytometric methodology to compare the secretion of IFN-gamma, IL-2, and TNF-alpha from peripheral blood-derived T cells of multiple sclerosis patients to the secretion in healthy controls. The percentages of IFN-gamma, IL-2, and TNF-alpha secreting cells are not significantly different between multiple sclerosis patients and controls. However, the TNF-alpha secreting CD3 cell percentage is correlated with the IFN-gamma and IL-2 secreting CD3 cell percentages in multiple sclerosis patients. In the controls, only the TNF-alpha secreting CD3 cell percentage is correlated with IFN-gamma. These findings show that correlated secretion of cytokines occurs in multiple sclerosis and suggest that concerted intercytokine interactions may play an important role in the disease.

ELI-spot of Th-1 cytokine secreting PBMC's in multiple sclerosis: correlation with MRI lesions

The Th1-like cytokines, interleukin 2 (IL-2), interferon gamma (IFN- γ), and lymphotoxin alpha (LT- α) have been implicated in the immunopathogenesis of multiple sclerosis (MS) and experimental allergic encephalomyelitis (EAE), an animal model of immune mediated demyelination. These cytokines have been associated with opening of the blood brain barrier (BBB) in EAE and in vitro, but not in MS. We used an enzyme-linked immunospot (ELI-spot) assay to measure relative numbers of cytokine-secreting peripheral blood mononuclear cells (PBMC) from eight MS patients who were followed with serial monthly contrast-enhanced head magnetic resonance imagings (MRI) and phlebotomy. We found a significant positive correlation between changes in IL-2 secreting cells and MRI lesions over a 6-month time period. There was a weaker association between contrast-enhancing MRI lesions and IFN- γ or LT- α secreting cells. These data are the first to show a significant positive correlation between any cytokine and serial gadolinium (Gd-) MRI disease activity in MS patients. The association between IFN- γ and LT- α secretion and MRI lesions is less clear.

Spontaneous secretion of interferon γ and interleukin 4 by human intraepithelial and lamina propria gut lymphocytes

Background—Cytokines secreted by intestinal T lymphocytes probably play a critical role in regulation of the gut associated immune responses.Aims—To quantify interferon γ (IFN-γ) and interleukin 4 (IL-4) secreting cells (SC)...

Interleukin-2-mediated modulation of plasma cell tumor growth in a model of multiple myeloma.

A number of studies have demonstrated that inoculation of certain types of cancer cells engineered for expression of the interleukin-2 (IL-2) gene results in reduced tumorigenicity and/or protection from subsequent challenge with a tumorigenic dose of wild-type cells. In the current studies, we have employed murine plasma cell tumors to examine IL-2-mediated tumor rejection as a possible model for therapeutic approaches to human myeloma or plasma cell leukemia. Two murine plasma cell tumor lines, S107 and X24, were infected with a retroviral vector expressing the human IL-2 gene, and the antitumor potential of IL-2-expressing infectants was characterized in syngeneic BALB/c and BALB/c nu/nu mice. Results demonstrate that tumorigenicity of both lines correlates inversely with the amount of IL-2 produced by the tumor cells. However, there are clear differences between the two lines in terms of reduced tumorigenicity and the ability to protect against co-injected parental tumor cells that appear unrelated to IL-2 levels. More importantly, intravenous immunization of animals with irradiated, IL-2 secreting cells from either line leads to significant protection from challenge with highly metastatic parental cells. These results suggest that such an approach may warrant consideration in the treatment of human plasma cell dyscrasias.

Initial route of antigen administration alters the T-cell cytokine profile produced in response to the mouse pneumonitis biovar of Chlamydia trachomatis following genital infection.

A Th1-type response develops following vaginal infection with the mouse pneumonitis biovar of Chlamydia trachomatis (MoPn). Since the type of response, i.e., Th1 versus Th2, can be influenced by factors present during T-cell activation, we examined the effects of different routes of MoPn administration on the cytokine profile and resistance against infection following a MoPn vaginal challenge. A dominant Th1-type cytokine profile developed in mice given live MoPn via the intranasal, oral, and vaginal routes with ratios of gamma interferon-secreting cells to interleukin 4-secreting cells greater than 10. In contrast, mice injected subcutaneously produced a Th2-type profile with a gamma interferon/interleukin 4 ratio of only 0.7. These mice also had significantly higher anti-MoPn immunoglobulin G1 serum titers, confirming a Th2-type cytokine profile. Exposure of mice to live MoPn, by any route prior to vaginal challenge, resulted in a shortened course of infection. However, the subcutaneous group resolved the vaginal infection more slowly, with 60% (6 of 10 mice) of the mice still isolation positive 12 days after challenge compared with only 20% of mice given live MoPn by other routes. Administration of UV-inactivated MoPn did not provide protection against a vaginal challenge. The decreased ability to clear infection was not associated with a shift in the cytokine profile, since intranasal and oral administration of UV-inactivated MoPn resulted in a predominant Th1-type response. Taken together, these data indicate that the initial route of MoPn administration can direct the type of response produced after a local MoPn infection and thus influence the ability of the immune response to protect against subsequent infection.

Modulation of anti‐idiotypic immune response by immunization with the autologous M‐component protein in multiple myeloma patients

Multiple myeloma is characterized by a proliferation of clonal B lymphocytes and plasma cells. The idiotypic structure of clonal immunoglobulin (Ig) expressed on the tumour B-cell surface can be regarded as a tumour-specific antigen and, as such, a potential target for anti-idiotypic T and B-cells in an immune regulation of the tumour-cell clone. Active immunization using the autologous mono-clonal Ig as a 'vaccine' was shown to induce tumour-specific immunity in murine B-cell tumours and in human B-cell lymphoma. With the aim to induce or amplify an anti-idiotypic response in multiple myeloma, five stage I-III patients were repeatedly immunized with the autologous monoclonal IgG. Induction of idiotype-specific cellular immunity was analysed in vitro by an enzyme-linked immunospot assay (interferon-gamma and interleukin-4 secreting cells). B cells secreting anti-idiotypic IgM antibodies were also analysed. An anti-idiotypic T-cell response was amplified 1.9-5-fold in three of the five patients during immunization. The number of B cells secreting anti-idiotypic antibodies also increased in these three patients. In two of the patients induction of idiotype-specific immunity was associated with a gradual decrease of blood CD19+ B cells. The induced T-cell response was eliminated during repeated immunization. Further studies are warranted to optimize the immunization schedule in order to achieve a long-lasting T-cell immunity against idiotypic determinants on the tumour clone. A role for immunity in controlling the tumour clone remains to be established.

Interleukin-2 and interleukin-4 display potent antitumour activity on rat medullary thyroid carcinoma cells.

Currently, surgical resection is the only treatment used for human medullary thyroid carcinoma (MTC). However, as metastases are commonly observed, we investigated the potential of adjuvant therapy with interleukin-2 (IL-2) and interleukin-4 (IL-4) in a rat model. The interleukins were delivered by means of xenogeneic tumour cells engineered to secrete IL-2 and IL-4. We found that when a mixture of MTC cells and IL-2 or IL-4 secreting cells were implanted in rats, the growth of the resulting tumours was inhibited as a function of the number of interleukin-secreting cells in the inoculum. Moreover, association of the two interleukins exerted a synergistic antitumour effect. These experimental results, showing thyroid C cell tumour rejection, are of major interest, as they show the potential therapeutic application for these two interleukins, which could be used, in particular, as postsurgical adjuvants.

A Regulatory Element in the Human Interleukin 2 Gene Promoter Is a Binding Site for the Zinc Finger Proteins Sp1 and EGR-1

Activation of the interleukin 2 (IL-2) gene after antigen recognition is a critical event for T cell proliferation and effector function. Prior studies have identified several transcription factors that contribute to the activity of the IL-2 promoter in stimulated T lymphocytes. Here we describe a novel regulatory element within the IL-2 promoter located immediately upstream of the nuclear factor of activated T cell (NFAT) domain. This region (termed the zinc finger protein binding region (ZIP)) serves as binding site for two differently regulated zinc finger proteins: the constitutively expressed transcription factor Sp1 and the inducible early growth response protein EGR-1. In unstimulated cells which do not secrete IL-2, only Sp1 binds to this region, while in stimulated IL-2 secreting cells the inducible EGR-1 protein recognizes this element. In Jurkat T cells, the ZIP site serves as an activator for IL-2 gene expression, and a combination of ZIP and NFAT binding sites is required for maximal IL-2 promoter activity. These results suggest a critical role of the ZIP site for IL-2 promoter activity.

Differential antigenic stimulation may influence cytokine production patterns in T cells and CD4+ subpopulations

The Th1-like cytokines, interleukin 2 (IL-2), interferon gamma (IFN-γ), and lymphotoxin alpha (LT-α) have been implicated in the immunopathogenesis of multiple sclerosis (MS) and experimental allergic encephalomyelitis (EAE), an animal model of immune mediated demyelination. These cytokines have been associated with opening of the blood brain barrier (BBB) in EAE and in vitro, but not in MS. We used an enzyme-linked immunospot (ELI-spot) assay to measure relative numbers of cytokine-secreting peripheral blood mononuclear cells (PBMC) from eight MS patients who were followed with serial monthly contrast-enhanced head magnetic resonance imagings (MRI) and phlebotomy. We found a significant positive correlation between changes in IL-2 secreting cells and MRI lesions over a 6-month time period. There was a weaker association between contrast-enhancing MRI lesions and IFN-γ or LT-α secreting cells. These data are the first to show a significant positive correlation between any cytokine and serial gadolinium (Gd-) MRI disease activity in MS patients. The association between IFN-γ and LT-α secretion and MRI lesions is less clear.

Interleukin‐2 transfected prostate cancer cells generate a local antitumor effect in vivo

In an effort to stimulate host-mediated antitumor response against prostate cancer in an animal model, highly malignant Dunning MAT-LyLu rat prostate carcinoma cells were transfected with the interleukin-2 (IL-2) cDNA, resulting in their ability to secrete large amounts of biologically active IL-2. Although parental cells form lethal tumors when injected subcutaneously into syngeneic hosts at doses of > or = 5,000, injections of IL-2 secreting cells initially formed tumors and regressed completely in each of over 200 animals at all doses tested (10(4)-8 x 10(7) cells). Mixtures of parental and IL-2 transfected cells were similarly rejected, demonstrating the non-cell autonomous nature of the response. Histological analysis of regressing tumors revealed a vigorous, predominantly lymphocytic and macrophage infiltrate at day 2 and marked tumor necrosis by day 6. Immunohistochemical staining of infiltrating lymphocytes at this latter time point demonstrated numerous T cells bearing either CD4 or CD8 surface markers, suggesting these cells as possibly mediating the tumor rejection. The ability of athymic mice to reject the IL-2 secreting tumor cells, however, suggests a non-T-cell-mediated mechanism. Although splenic natural killer (NK) activity is increased following injection of IL2 secreting tumor cells, this activity appears to be unnecessary for tumor elimination since syngeneic animals injected with asialo-GM1 antiserum to decrease NK activity also rejected IL-2 transfected cells, albeit slightly less effectively than untreated animals. Immunization of animals with subcutaneous injections of IL-2 transfected cells protected animals against a subsequent challenge of 10(4) wild-type cells 1 to 2 weeks later in 19 of 51 cases; however, immunization did not confer protection against larger doses of parental tumor. These studies indicate that high local concentrations of IL-2 stimulate the elimination of large local burdens of prostate cancer in this model system, and this elimination results in a weak, but detectable systemic immune response against wild-type prostate cancer cells.