Role of IL-2, IL-4 and IL-6 in the growth and differentiation of tumor-specific CD4+ T helper and CD8+ T cytotoxic cells

Interleukin-2 (IL-2) Interacts With IL-2 Receptor Beta (IL-2Rβ): Its Potential to Enhance the Proliferation of CD4+ T Lymphocytes in Flounder (Paralichthys olivaceus)

Interleukin-2 (IL-2) is an important immunomodulatory cytokine that primarily promotes the activation, proliferation, and differentiation of CD4+ T helper subsets and CD4+ T regulatory cells. In our previous studies, IL-2 and IL-2 receptor beta (IL-2Rβ) genes of flounder (Paralichthys olivaceus) were cloned, and IL-2Rβ molecules expressed on both B and T lymphocytes were identified. In the present study, the interaction of flounder IL-2 (fIL-2) with the IL-2 receptor beta (fIL-2Rβ) was investigated. The proportion of CD4+ T lymphocytes and IL-2Rβ+ cells were detected both in vivo and in vitro. Firstly, the binding of recombinant flounder IL-2 protein (rfIL-2) and rfIL-2Rβ was verified by pull-down assay and enzyme-linked immunosorbent assay. Indirect immunofluorescence assay showed that rfIL-2 enhanced the proliferation of CD4+ and IL-2Rβ+ cells in the gill and spleen. Furthermore, CD4-1+, CD4-2+ T lymphocytes and IL-2Rβ+ cells were significantly upregulated in cultured peripheral blood lymphocytes (PBLs) with addition of rfIL-2, as shown by Flow cytometry. The related genes were examined by Q-PCR in cultured PBLs with added rfIL-2. The results showed that the IL-2-IL-2R interaction induced upregulated expression of T lymphocyte surface makers, Th1-related cytokines or transcription factors, and critical genes of the IL-2 signaling pathway. In addition, these IL-2-elicited biological functions and immune responses were downregulated by blocked with anti-rfIL-2Rβ and anti-rfIL-2 Abs, showing that IL-2Rβ plays an indispensable role in IL-2 elicited biological function. Our results demonstrated that the interaction between IL-2 and IL-2Rβ showed its potential to enhance the proliferation of CD4+ T lymphocytes in flounder. As found in mammals, a Th1-mediated mechanism regulated by this interaction exists in teleost.

TLR9 acts as a sensor for tumor-released DNA to modulate anti-tumor immunity after chemotherapy

The tumor microenvironment exists in a state of dynamic equilibrium, in which a balance of agonist and antagonist signals govern the anti-tumor immune responses. Previous studies have shown that chemotherapy could shift this balance in favor of agonistic signals for the anti-tumor immune responses mounted by CD8+ cytotoxic T lymphocytes (CTL), providing sufficiently high antigen density within the tumor. We undertook the current study to characterize the anti-tumor immune response following chemotherapy and its underlying mechanisms. We show that this 'adjuvant effect' of chemotherapy is, at least partially, mediated by the release of tumor DNA and acts through the Toll-like receptor 9 (TLR9) pathway. We found that tumor-released DNA causes accumulation, antigen uptake, and maturation of dendritic cells (DCs) in the tumor in a TLR9-dependent manner. These DCs subsequently migrate into the draining lymph nodes and prime tumor-specific CTLs. Our study provides novel insights to the molecular and cellular mechanisms by which chemotherapy converts the tumor microenvironment into a site permissive for the activation of a potent tumor-specific adaptive immune response.

IL-4 is required for defense against mycobacterial infection

Although the involvement of T helper (Th1) cells is central to protection against intracellular bacteria, including Mycobacterium tuberculosis, the involvement of Th2 cells, characterized by potent interleukin (IL)-4 secretion in mycobacterial infection is still unclear. In order to clarify the role of IL-4 in murine tuberculosis, IL-4-deficient mutant mice, IL-4 knockout (IL-4 KO) mice, were utilized. The mice were infected with H37Rv, Kurono or BCG Pasteur via an airborne infection route by placing them in the exposure chamber of a Middlebrook airborne infection apparatus. Their capacity to control mycobacterial growth, granuloma formation, cytokine secretion, and nitric oxide (NO) production were examined. These mice developed large granulomas, but not necrotic lesions in the lungs, liver or spleen (P<0.05). This was consistent with a significant increase in lung colony-forming units (CFU). Compared with levels in wild-type mice, upon stimulation with mycobacteria, splenic IL-10 levels were low and IL-6 levels were intermediate, but interferon (IFN)-gamma and IL-12 levels were significantly higher. IL-18 levels were within the normal range. The level of NO production by alveolar macrophages of the IL-4 KO mice was similar to that of the wild-type mice. Granulomatous lesion development by IL-4 KO mice was inhibited significantly by treatment with exogenous recombinant IL-4. These findings were not specific to the IL-4 KO mice used. Our data show that IL-4 may play a protective role in defense against mycobacteria, although IFN-gamma and TNF-alpha play major roles in it. Our data do not rule out an IFN-gamma-independent function of IL-4 in controlling tuberculosis.

Lack of evidence for MHC-unrestricted (atypical) recognition of mucin by mucinous pancreatic tumour-reactive T-cells

Cytotoxic T-cells generated against heterologous, mucinous pancreatic tumour cells were shown to recognize mucin in a major histocombatibility complex (MHC)-unrestricted fashion. In contrast, the present study demonstrates a typical allogeneic response of heterologous cytotoxic T-cells established against mucin-expressing pancreatic tumour cells. Heterologous cytotoxic T cells lysed targets that were used as stimulators and other targets that shared human leucocyte antigen (HLA) with the stimulator. These cytotoxic T-cells lysed mucin-expressing stimulator cells but not autologous tumour cells in spite of expressing mucin on their surface. Likewise, tumour-infiltrating CD4+ T-cells proliferated against its own tumour cell target, while such T-cells did not respond to heterologous, mucin-expressing pancreatic tumour cells. Culturing heterologous tumour-specific cytotoxic T-cells with purified pancreatic tumour cell-mucin rendered them unresponsive to their target cells. Furthermore, purified mucin did not produce a mucin-specific response in mucinous pancreatic tumour patients' primary T-cells even in the presence of antigen-presenting cells. Our study finds no evidence for MHC-unrestricted recognition of mucin by pancreatic cancer patients' T-cells.

Intracutaneous vaccination of rabbits with the E6 gene of cottontail rabbit papillomavirus provides partial protection against virus challenge

DNA vaccination of rabbit skin with the L1 gene of cottontail rabbit papillomavirus (CRPV) has previously been shown to induce prophylactic immunity against CRPV. We now describe the effects of vaccination with the CRPV E6 gene, using the same approach. The experimental vaccine pdCMV-E6 encoded both the truncated and full length forms of CRPV E6 protein. The control vaccine pCMV-beta encoded beta galactosidase. Rabbits were vaccinated with DNA-coated gold particles, using a gene gun. Each rabbit received an initial vaccination with 30 micrograms DNA and 3 weeks later a booster vaccination, also with 30 micrograms DNA. pdCMV-E6-vaccinated rabbits developed E6-specific cellular immunity as determined by proliferation assays using peripheral blood mononuclear cells from animals prior to challenge, but did not develop detectable humoral immunity to E6 proteins, as evaluated by ELISA using two different E6 antigen preparations. Control rabbits developed humoral immunity to beta galactosidase. All rabbits were challenged by infection of nine skin sites with live CRPV virus and monitored for papilloma formation. None of four control rabbits was protected at any of the challenge sites. Of six rabbits vaccinated with pdCMV-E6, two were completely protected and one was virtually completely protected (tiny papillomas at just two of nine challenge sites). These three rabbits also exhibited significant E6-specific in vitro proliferative responses. The four E6 DNA-vaccinated rabbits that were not completely protected exhibited evidence of partial protection: some challenge sites did not form papillomas; papilloma onset was delayed; papilloma burden was less. These results demonstrate that partial prophylaxis against papillomavirus-induced disease can be achieved by intracutaneous vaccination with a recombinant plasmid encoding the papillomavirus.

Modification of the Sendai virus-specific antibody and CD8+ T-cell responses in mice homozygous for disruption of the interleukin-4 gene

Homozygous disruption (-/-) of the interleukin-4 (IL-4) gene did not obviously modify the severity of Sendai virus infection in the highly susceptible 129/J mouse strain. The virus was cleared from the respiratory tract, and potent cytotoxic T lymphocyte (CTL) effectors were present in the cell population recovered by bronchoalveolar lavage. However, the prevalence of virus-specific CTL precursors (p) was consistently diminished in the spleen and regional lymph nodes of the IL-4 -/- mice at day 7 after infection. Also, virus-specific serum immunoglobulin G1 (IgG1) levels were greatly reduced and few IgG1-producing cells were detected in the lymphoid tissue. The effect on IgG1 class switching was to be expected, but the decrease in CTLp numbers has not been observed previously for a virus-specific immune response.

Characterization of factors regulating successful immunotherapy using a tumor-specific cytotoxic T lymphocyte clone: role of interleukin-2, cycling pattern of lytic activity and adhesion molecules

Adoptive immunotherapy against cancer has met with varying degrees of success, the reasons for which remain unclear. The present study characterizes factors that regulate successful immunotherapy of mice bearing a syngeneic T-cell lymphoma, designated LSA, using a tumor-specific cytotoxic T lymphocyte (CTL) clone, PE-9. Adoptive transfer of PE-9 cells afforded significant protection in normal but not in nude mice against LSA tumor. However, the PE-9 cells could protect the nude mice when injected along with normal CD4+ T cells. Administration of IL-2 along with PE-9 cells failed to enhance tumor immunotherapy. IL-2 therapy was toxic inasmuch as injection of the CTL clone PE-9 + IL-2, but not PE-9 or IL-2 alone, for 5 days into irradiated mice caused vascular leak syndrome (VLS). PE-9 cells cultured with high doses of rIL-2 in vitro also caused TCR-independent and MHC-unrestricted lysis of SV40-transformed endothelial cells. Furthermore, PE-9 cells cultured in vitro for 24-96 hr with IL-2 exhibited cycling pattern of tumor-specific cytotoxicity with maximum cytotoxicity demonstrable at 48 hr and virtually no cytolytic activity at 96 hr of culture or thereafter. The loss of cytotoxicity correlated with down-regulation of several adhesion molecule expressions on PE-9 cells, particularly the alpha beta-TCR, as well as the mRNA for TNF-alpha, IFN-gamma and perforin, although the levels of granzyme A were not altered. Interestingly, the outcome of immunotherapy by PE-9 cells depended on the cycling pattern of cytotoxicity. Our data suggest that successful immunotherapy against cancer using a CTL clone depends on several factors, such as the cycling pattern of lytic activity, density of adhesion molecules, levels of cytokines expressed and the ability of IL-2 and CTL to trigger VLS.

Generation of effector cytotoxic T cells from cytotoxic T cell precursors: role of soluble factors

Cytotoxic T lymphocytes (CTL) have long been recognized as playing a major role in the immune response to alloantigens and viral antigens as well as tumor antigens. The progress of the last decade in the identification and characterization of soluble factors involved in the regulation of the immune response has greatly improved our knowledge of the mechanisms of CTL activation and regulation. This review will summarize the data available in the literature regarding different lymphokines and their specific activity on CTL. In addition it will point out a few of the elements of the systems that hamper its full understanding and it will suggest possible directions for future research.

1,3-Bis(2-chloroethyl)-1-nitrosourea (BCNU)/interleukin-2 chemoimmunotherapy of murine L1210 leukemia

We have developed a chemoimmunotherapy regimen for the treatment of L1210-cell-induced ascites tumors in mice using a combination of sub-toxic doses of interleukin-2 (IL-2) and 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). BCNU is administered intraperitoneally 4 days after tumor implantation and followed 2 days later by single doses of human recombinant IL-2 for 3 consecutive days. An optimum survival of 84% was achieved using 1500 U IL-2. Reduced survival was observed when lower or higher IL-2 dosages were used. No therapy resulted when heat-inactivated IL-2 was used or when IL-2 was used without chemotherapy. Surviving animals were resistant to L1210 leukemia but not P815 mastocytoma tumor challenge suggesting the combined BCNU/IL-2 therapy stimulated tumor-specific immunity.

Human allogeneic melanoma-reactive T-helper lymphocyte clones: functional analysis of lymphocyte-melanoma interactions

Lymphocyte clones were isolated from CD4+ peripheral-blood lymphocytes (PBL) of melanoma (Me) patient 9923 (HLA-DR7, DQw2, w6), co-cultured for 30 days with autologous accessory cells, allogeneic Me (Me 1811) (HLA-DR7, DQw1, w2), IL-1 beta (2 U/ml) and IL-2 (15 IU/ml). The 55 clones tested displayed a CD3+, CD4+, CD8-, T-cell receptor (TCR) alpha/beta+, gamma/delta- phenotype. Twenty clones were assayed for proliferation in the presence of Me 1811 and B-lymphoblastoid cell line (LCL) 1811, both expressing HLA-class-I and -II (DR7 and DQw2 shared with patient 9923), intercellular adhesion molecule-1 (ICAM-1) and lymphocyte-function-associated antigen-3 (LFA-3) molecules. Eight clones were found to be reactive to Me 1811 but not to LCL 1811. Specificity analysis of these 8 clones revealed that each of them proliferated only to Me 1811, not to other 14 Me and 12 different LCL, suggesting recognition of melanoma-associated antigen (MAA) expressed on the stimulating Me. One clone (103) was analyzed in more detail. A wider specificity analysis showed that it reacted to Me 1811 but not to 10 other Me expressing or not HLA-DR7, 5 normal melanocyte cultures (2 of them typing HLA-DR7-positive when exposed to interferon-gamma--IFN-gamma), 4 tumors other than Me and 20 different LCL. Clones did not show proliferation in the presence of autologous Me cells. Clone proliferation in response to Me 1811 was significantly inhibited by monoclonal antibodies (MAbs) directed to CD3, TCR alpha/beta, TCR beta chain V12, CD4 and HLA-DR. Moreover, following stimulation with Me 1811, clone 103 showed increased surface expression of CD25 (IL-2 receptor) and CD71 (transferrin receptor) and produced significant amounts of IL-2 and IFN-gamma. The supernatant taken from co-culture of clone 103 with Me 1811 augmented the cytotoxicity of PBL 9923 and other allogeneic PBL against K562 and Me 1811. Thus, the lymphocyte clone 103 is a CD4+ Th clone which uses its CD3/TCR alpha/beta complex to recognize an MAA in conjunction with HLA-DR7. Availability of this type of reagent may prove useful to identify and characterize MAA recognized by T lymphocytes.

Characterization of T lymphocyte clones isolated from BCNU-cured LSA mice

1,3-Bis(chloroethyl)-1-nitrosourea (BCNU) has been shown to "cure" over 90% of the mice bearing the syngeneic tumor LSA, and the cured mice acquire elevated levels of tumor-specific immunity. In the present study, we report for the first time the establishment and characterization of several tumor-specific CD8+ cytotoxic T cell (CTL) clones from splenic T cells of BCNU-cured LSA mice. Many of these clones were found to be strongly cytotoxic to LSA but not to a different H-2b tumor target such as EL-4, or the natural killer (NK)-susceptible target YAC-1, NK-resistant target P815, or con A or LPS blasts from H-2b mice. Some of the clones showed a moderate level of cytotoxicity to the NK-susceptible target YAC-1. The relative roles of interleukins such as IL-2, IL-4 or IL-6 in supporting the proliferative response of some LSA-activated CTL clones were analyzed. As expected, recombinant human (rh) IL-2 alone supported the proliferative response of activated CTL clones. Addition of recombinant murine (rm) IL-4 or rhIL-6 alone to the culture failed to influence the response. Also, in combination with rhIL-2, neither rmIL-4 nor rhIL-6 appreciably augmented rhIL-2-supported proliferative response of CTL clones. These studies may provide insights for the development of effective approaches to modulate function and activity of effector T cells.

Generation of T cell clones binding F(ab')2 fragments of the idiotypic immunoglobulin in patients with monoclonal gammopathy

Lymphocytes from two patients with multiple myeloma stage I and one patient with monoclonal gammopathy of undetermined significance were found to proliferate specifically in response to low concentrations of F(ab')2 fragments of the autologous M component. T cell clones isolated from repeatedly stimulated cultures bound specifically the autologous idiotype and proliferated after addition of soluble idiotype and exogenous interleukin-2. The majority of clones were CD8+ and showed negligible staining for CD4. Idiotype-binding clones could not be isolated from cultures of lymphocytes from a healthy control stimulated under the same conditions. The study provides support for the existence of idiotype-reactive T cells in monoclonal gammopathies. Such cells might have a regulatory role on the tumor cell clone and may be important for a future therapeutic approach.

Immunomodulatory effects of nitrosoureas on the phenotype and functions of T cells in the thymus and periphery

We have recently demonstrated that nitrosoureas such as 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) and chlorozotocin (CLZ) can cure almost 100% of mice bearing LSA tumor, syngeneic to C57BL/6 mice. In contrast, similar or higher doses of streptozotocin (STZ) completely failed to cure LSA-bearing mice. Further studies revealed that the efficacy of nitrosoureas may depend on their immunomodulating properties. In the current study, therefore, we investigated the effect of these nitrosoureas on the immune system of normal mice. Treatment of C57BL/6 mice with 5 intraperitoneal injections of 20 mg/kg body weight of BCNU or CLZ caused an increase in the percentage of CD4(-)CD8- T cells and a decrease in the percentage of CD4(+)CD8+ T cells in the thymus. In addition, such treatment also caused an increase in the percentage of CD4+ T cells without significantly affecting the CD8+ T cells in the thymus. However, when total cellularity of the thymus was studied, BCNU and CLZ were found to decrease the total number of CD4(+)CD8+ T cells without significantly affecting the other subsets. In contrast, similar or higher (100 mg/kg body weight) doses of STZ had no significant effect on the total number and percentages of T cell subsets in the thymus. Also BCNU and CLZ but not STZ treatment caused a 50% decrease in the total number of CD4+ and CD8+ T cells in the spleen. When T cells in the spleens of nitrosourea-treated mice were functionally analysed, it was observed that BCNU and CLZ caused a dramatic decrease in the T cell responsiveness to ConA, anti-CD3 and phorbol myristate acetate plus calcium ionophore stimulation. In contrast, STZ treatment failed to significantly inhibit the T cell responsiveness to these activation signals. Using the accessory cell-dependent and -independent assays, BCNU and CLZ were found to suppress the functions of both T cells and macrophages. Also, addition of growth factors such as IL-1, IL-2, IL-4 and IL-6 failed to reconstitute the defective responsiveness of BCNU- and CLZ-treated T cells and macrophages. Together our data suggest that nitrosoureas have varying immunomodulating properties and this may in turn determine their efficacy in the treatment of cancer.