Low doses of IL-4 injected perilymphatically in tumor-bearing mice inhibit the growth of poorly and apparently nonimmunogenic tumors and induce a tumor-specific immune memory

The ability of rIL-4 to trigger host reactivity against both a chemically induced fibrosarcoma (CE-2) and a spontaneous adenocarcinoma (TS/A) of BALB/c mice was studied. Daily local s.c. administration around tumor draining lymph nodes of 10 injections of progressive amounts (0.00001 to 1000 pg/day) of rIL-4 induced appreciable inhibition of the growth of both tumors after a dose-response survival curve peaking at 0.1 pg/day. Inasmuch as rIL-4 has no direct antitumor activity, as shown by in vitro tests, host immune reactivity plays a fundamental role in this lymphokine activated tumor inhibition (LATI). LATI, in fact, is abolished when recipient mice are sublethally irradiated or treated with cyclosporin A, or when the reactivity of CD4+ lymphocytes is suppressed, whereas it is not affected by anti-asialo GM1 antibody. The morphologic data show that rIL-4 LATI rests on the recruitment of several cell reaction mechanisms, among which those that are nonspecific seem to predominate. rIL-4 LATI also leads to a state of long lasting and specific immune memory: the growth of a second contralateral tumor challenge is significantly impaired after LATI. This immune memory takes place after LATI of both the poorly immunogenic CE-2 fibrosarcoma and the TS/A adenocarcinoma, previously classed as nonimmunogenic on the basis of immunization-protection tests. In the latter case, adoptive transfer experiments show that Thy-1+ lymphocytes and, in particular, the CD4 cell-depleted T lymphocyte subpopulation, are responsible for the immune memory. Finally, the ability of rIL-4 to trigger LATI is greater than that of the most effective doses of rIL-2, rIL-1 beta, and IFN-gamma, whereas its association with rIL-1 beta induces a more effective immune memory.     

Lymphokine-activated tumor inhibition in vivo. I. The local administration of interleukin 2 triggers nonreactive lymphocytes from tumor-bearing mice to inhibit tumor growth

CE-2 is a chemically induced tumor of low immunogenicity in syngeneic BALB/c mice. Nylon wool columns eluting lymphocytes from the spleen of mice bearing clinically evident (5-mm mean diameter) CE-2 tumors (CE-2 TB lymphocytes) do not react with CE-2 cells in vitro, nor are they able to affect their growth in vivo in a Winn-type neutralization assay at 5:1 lymphocyte:tumor cell ratio. However, they become able to inhibit CE-2 tumor growth when 20 U of interleukin 2 (IL 2) in 0.4 ml are injected daily for 10 days at the challenge site. In contrast, mice injected with CE-2 cells and IL 2 only display tumor takes and growth that are not significantly different from those in controls challenged with CE-2 cells alone. This lymphokine-activated tumor inhibition (LATI) is not a peculiarity of the CE-2 tumor-host combination, because different tumors can be inhibited in this way and various TB lymphocytes can initiate it. In these experiments, IL 2-rich 25,000 to 30,000 m.w. fractions were obtained routinely from the culture supernatants of a clone of EL-4 thymoma stimulated with phorbol myristic acetate. Equally active IL 2-rich preparations were obtained from rat spleen cells stimulated with concanavalin A, or from MLA 144 gibbon lymphosarcoma spontaneously releasing IL 2. Treatment of CE-2 TB lymphocytes with various antibody and C, with 2000 rad gamma-irradiation, or fractionation on Percoll density gradients suggested that radioresistant functions of Thy-1.2+, Lyt-1.2+, Lyt-2.2- and of asialo GM1+ cells are independently involved in LATI induction. These lymphocytes inhibit tumor growth by recruiting the radiosensitive effector mechanisms of the recipient mice required for ultimate tumor destruction. CE-2 tumor inhibition by LATI leaves a specific delayed-type hypersensitivity and an immunologic memory, resulting in rejection of a second lethal CE-2 challenge in a significant number of mice.     

Lymphokine-activated tumor inhibition in mice. Ability of a nonapeptide of the human IL-1 beta to recruit anti-tumor reactivity in recipient mice

The ability of the VQGEESNDK synthetic peptide corresponding to fragment 163-171 of human IL-1 beta to trigger lymphokine-activated tumor inhibition (LATI) of a poorly immunogenic fibrosarcoma (CE-2) of BALB/c mice was compared to that of the whole IL-1 beta. Neither molecule inhibits in vitro proliferation of CE-2 cells. Administration at the tumor challenge site for 10 days of daily injections of 50 micrograms of peptide 163-171 induce a consistent, although limited, inhibition of tumor growth, whereas similar injections of 1 pg of IL-1 beta induced a more marked LATI. However, strong LATI was elicited when these injections were performed in mice challenged with tumor cells admixed at 1/10 cell ratio with nonreactive lymphocytes from CE-2-bearing mice. The L3T4+ lymphocyte subset is mainly responsible for this enhancement. This reaction is abolished when recipient mice are sub-lethally irradiated, treated with cyclosporin A, or when the reactivity of L3T4+ and asialo GM1+ cells is suppressed. A similarly efficient LATI is found on combining the daily peptide injections with that of 10 U of IL-2. LATI stemming from this association, too, is abolished when mice are irradiated or treated with anti-L3T4 antibody, whereas it is not affected by cyclosporin A or anti-asialo GM1 antibody. Finally, a tumor-specific immune memory is acquired by about 50% of mice after LATI induced by IL-1 beta or 163-171 peptide alone and by about 80% of mice after LATI induced by peptide and lymphocytes from tumor-bearing mice or peptide and IL-2. These findings could lead to the building of a molecularly defined system to induce efficient immune recognition of tumor cells by using a peptide that does not cause any of the several inflammation-associated changes induced by the whole IL-1 beta.     

Systemic administration of recombinant interleukin 2 stimulates in vivo lymphoid cell proliferation in tissues

Recent work in our laboratory has demonstrated that the repeated injections of high doses of recombinant interleukin 2 (IL 2) can dramatically reduce the number of established pulmonary and hepatic metastases and the growth of intradermal tumors in a variety of murine tumor models. We have thus undertaken studies to define the mechanisms underlying these in vivo effects of IL 2. Using an in vivo DNA-labeling technique in which we employed 5-[125I]iodo-2'-deoxyuridine (125IUdR), we examined the in vivo cell proliferation in the tissues of mice treated with IL 2. A proliferation index (PI) was calculated by dividing the raw counts per minute (cpm) of tissues in IL 2-treated mice by the cpm in corresponding tissues of control animals. At an IL 2 dose of 6000 U given i.p. three times a day, the highest 125IUdR incorporation was seen in the lungs, liver, spleen, kidneys, and mesenteric lymph nodes (PI = 6.9, 6.9, 5.1, 7.1, 24.6, respectively, at 5 days). The amount of lymphoid proliferation in these organs was a direct function of the dose of IL 2 administered. Other tissues including thymus, intestines, skin, and hind limb showed no significant increase in 125IUdR uptake even after host treatment with the highest doses of IL 2. Blood and brain demonstrated intermediate incorporation of the radiolabel. Preirradiation of the host largely eliminated the proliferative response to IL 2. Histologic studies of normal and irradiated mice receiving IL 2 corroborated the result of the 125IUdR findings. In normal IL 2-treated mice, large collections of activated lymphoid cells were seen, most prominently in the lungs, liver, and kidneys, whereas markedly decreased lymphoid proliferation was evident histologically in preirradiated mice. A fluorescein-labeled monoclonal antibody directed against the Thy-1.2 surface determinant was used to identify these dividing cells in frozen tissue sections as T lymphoid cells. Activated lymphocytes isolated from the lungs, liver, spleen, and mesenteric lymph nodes of IL 2-treated mice demonstrated significant lysis of a fresh murine sarcoma target in short-term 51Cr-release assays. These studies demonstrate that the systemic administration of recombinant IL 2 causes in vivo activation and proliferation of host lymphoid cells and has important implications for the adoptive immunotherapy of tumors.     

Proliferative kinetics of large and small intraepithelial lymphocytes in the small intestine of the mouse.

The proliferative kinetics of the intraepithelial lymphocytes (IL) of the mouse intestine have been evaluated. By inducing mitotic arrest it was found that large IL - constituting about 50% of the IL - showed a mitotic rate of 2.3. Autoradiographic results obtained after two different schedules of 3H-thymidine injections showed that 30% of the large IL were in DNA synthesis, and that the large IL were renewed at a rate comparable to that of blast cells from Peyer's patches, mesenteric lymph nodes and thoracic duct lymph. The small IL were renewed very rapidly compared to small lymphocytes of peripheral lymphoid tissues, although small lymphocytes with lifespans of several weeks were also present in the epithelial sheet. By the use of intestinal perfusion, in vivo, it was estimated that the loss of lymphocytes from intestinal villi into the lumen of the gut was negligible, and it is concluded that the most probable kinetic model for the majority of IL is: B and T lymphoblasts invade the epithelium and undergo mitosis. B lymphoblasts give rise predominantly to plasma cells, and T lymphoblasts give rise to small lymphocytes - probably long-lived - which reenter the circulation.     

Immunological determinants of ventilatory changes induced in mice by dermal sensitization and respiratory challenge with toluene diisocyanate

The objective of the study was to characterize better the immunologic mechanisms underlying a previously developed animal model of chemical-induced asthma. BALB/c and severe combined immunodeficiency disease (SCID) mice received toluene diisocyanate (TDI) or vehicle on each ear on day 1 and/or day 7. On day 10, they were intranasally challenged with TDI or vehicle. Ventilatory function was monitored by whole body plethysmography for 40 min after challenge. Reactivity to methacholine was measured 23 h later: enhanced pause and actual resistance measurements. Pulmonary inflammation was assessed 1, 6, and 24 h after challenge by bronchoalveolar lavage (BAL). Tumor necrosis factor-alpha and macrophage inflammatory protein (MIP)-2 levels were measured in BAL. Immunological parameters included total IgE, IgG1, and IgG2a in serum, lymphocyte populations in auricular and cervical lymph nodes, and IL-4 and IFN-gamma levels in supernatants of lymph node cells, cultured with or without concanavalin A. Ventilatory changes suggestive of airway obstruction and increased methacholine reactivity were observed in all TDI-sensitized and TDI intranasally instilled mice, except in SCID mice. A neutrophil influx, accompanied by an increase in MIP-2 levels, was found in BAL of all responding groups 6 and 24 h after intranasal challenge. In BALB/c mice an increased level of CD19+ B cells was found in the auricular lymph nodes. IL-4 and IFN-gamma levels were increased in supernatants of concanavalin A-stimulated auricular lymph node cells from BALB/c mice completely treated with TDI. These results indicate that our model is dependent on the presence of lymphocytes, but it is not characterized by a preferential stimulation of Th1 or Th2 lymphocytes.     

Studies of nonmigrating long-lived lymphocytes in rats. V. Presence and reactions to antigens after neonatal thymectomy

Neonatally thymectomized and sham-operated rats were given courses of hind foot pad injections of tritiated thymidine after immune stimuli, and the popliteal lymph nodes were examined for the presence of persistently labeled lymphocytes 32 days later. A larger proportion of labeled small lymphocytes was found in the nodes of thymectomized rats than in the nodes of sham-operated rats, indicating that a significant portion of the long-lived nonmigrating cells are B cells. In sham-operated rats given a course of tritiated thymidine after an immune stimulus with a Salmonella flagellin, labeled blasts appeared 3 days after secondary challenges with both the same or a serologically distinct flagellin. In neonatally thymectomized rats, a blastogenic response occurred after challenge with the same flagellin but not after challenge with the non-specific flagellin. Thus, in normal rats there are also long-lived nonmigrating T cells in primed lymph nodes, and these are the cells responsible for the nonspecific blasto-genesis seen in earlier experiments.     

The role of adoptively transferred CD8 T cells and host cells in the control of the growth of the EG7 thymoma: factors that determine the relative effectiveness and homing properties of Tc1 and Tc2 effectors

We had previously examined the factors that regulate the response of OVA-specific TCR-transgenic CD8 T cells to the B16 OVA melanoma, growing as lung metastases. We examine here whether the same parameters operate for EG7, growing intradermally. Tc1 or Tc2 CD8 effector cells from OT-1 mice were injected either mixed with the tumor or i.v. at day 0 or 7. Tc2 were one-fifth to one-tenth as effective as Tc1 when injected with the tumor, in controlling tumor growth, but were only 1/20 to 1/100 injected i.v. Tc1 injected i.v. entered the draining lymph nodes faster than Tc2 and caused a faster accumulation of host cells. Both caused an abrupt termination of host cell entry into lymph nodes and spleen after tumor elimination, but this occurred earlier for Tc1 than for Tc2. Host responses were ineffective in the absence of adoptive transfer but were essential after transfer. Perforin expression in the donor cells plays no role in adoptively transferred Tc1 or Tc2 control of the tumor, and neither IL-4 nor IL5 is needed for Tc1 or Tc2 function. Tc1 cells from mice lacking IFN-gamma, however, control tumor growth less well, whereas Tc2 effectors lacking IFN-gamma are unaffected. Tc1 from IFN-gamma-deficient mice attract fewer host cells to the draining lymph node, whereas Tc1 cells from perforin-deficient donors are unimpaired. We conclude that host cell recruitment is a crucial element in adoptive immunotherapy. The differences between the EG7 and the previous B16 melanoma model are discussed.     

Activation by anti-CD3 of tumor-draining lymph node cells for specific adoptive immunotherapy.

Lymph nodes draining progressive tumors contain tumor-sensitized but not functional preeffector T lymphocytes. These cells can acquire antitumor reactivity after stimulation with tumor cells and interleukin-2 (IL-2). We demonstrated here that, in the absence of tumor cells, preeffector cells could be stimulated and expanded by sequential culture with anti-CD3 monoclonal antibody and IL-2. The adoptive transfer of such activated cells mediated immunologically specific reductions of established pulmonary metastases. The therapeutic effects could be enhanced by the administration of IL-2. This activation represents a secondary immune response because effector cells could be generated only from tumor-draining but not from normal or adjuvant-stimulated lymph nodes. Furthermore, treatment of advanced metastases with these cells resulted in prolongation of survival and cure of the disease. Thus, anti-CD3 may serve as a universal reagent for activating tumor-sensitized T lymphocytes for cancer therapy.     

Antigen-specific, interleukin 2-propagated T lymphocytes confer resistance to a murine malarial parasite, Plasmodium chabaudi adami

To explore cell-mediated immune mechanisms in host defense against malaria, we utilized a murine model system in which antibody-independent mechanisms of immunity are known to play a major role. Splenic T lymphocytes obtained from Plasmodium chabaudi adami-immune mice were maintained in vitro by using IL 2-containing medium and frequent antigenic stimulation. These IL 2-propagated T lymphocytes were characterized for their antigen reactivity, surface phenotype, and ability to confer protection to P. chabaudi adami in reconstituted mice. IL 2-dependent T lymphocytes maintained their capacity to proliferate in vitro to solubilized parasite preparations of homologous but not heterologous antigens. Antigen-specific proliferation was H-2 restricted, requiring antigen-presenting cells of the correct haplotype. More importantly, these propagated T lymphocytes were effective in adoptively transferring protection to both athymic nude mice and sublethally irradiated recipients. The protective response was dose dependent and antigen specific, because recipients resisted challenge infection with P. chabaudi adami but not with the heterologous parasite Plasmodium yoelii 17X. Pretreatment of the IL 2-propagated cells with anti-Thy-1.2 and complement abrogated their ability to transfer protection. Collectively, these results suggest that T lymphocytes obtained from P. chabaudi adami-immune mice, propagated and expanded in vitro, retain antigen specificity and passive protective activity in vivo.     

Regulation of cellular immune response against autologous human melanoma. II. Mechanism of induction and specificity of suppression

The cytotoxic immune response in the peripheral blood lymphocytes (PBL) against an autologous malignant melanoma cell line, PJ-M, was found to be down-regulated in in vitro co-culture (IVC) selectively by unfractionated resident lymph node lymphocytes (derived from a lymph node infiltrated with the PJ-M melanoma cells) and T4+ as well as T8+ fractions of the resident lymph node-derived lymphocytes. In this study, the mechanism involved in, and the specificities of, cytotoxic immune response in this autologous system were examined at population and clonal levels. Resident lymph node lymphocytes were isolated from both involved and uninvolved lymph nodes from the same patient. Resident lymphocytes from both sources regulated the generation of cytotoxic immune response when both types of resident lymph node lymphocytes were further sensitized against the PJ-M cells in IVC and were expanded in interleukin 2 (IL 2). An IL 2-dependent homogeneous lymphocyte line (I-10:1) bearing the phenotype of a helper T cell (T4+) and a T4+ clone (I-10.3) of the I-10:1 line, established by limiting dilution culture, also down-regulated the generation of cytotoxic immune effector cells in the PBL in IVC against the PJ-M targets. The IL 2-dependent T4+ inducer line I-10:1 generated a functionally differentiated T8+ suppressor population(s) that, in turn, could abrogate cytotoxic response in fresh PBL in IVC against PJ-M cells. The inducer line I-10:1 and its subclone I-10.3 suppressed the generation of cytotoxic effector cells in the PBL in IVC selectively against the autologous PJ-M cells. Generation of cytotoxic allo-response in IVC was unaffected by the inducer lines. These results provide further evidence for the involvement of the regulatory network in cytotoxic immune response in an autologous human tumor system, and suggest a potential explanation for cytotoxic unresponsiveness against autologous melanoma cells.     

Systemic IL-1 and adjuvant treatment of an experimental tumor

In this investigation, systemic administration of interleukin-1 (IL-1) and local adjuvant therapy were shown to modify immunological parameters associated with the lymphatics draining the site of experimental tumor inoculation. These immunological parameters were shown to be modified early (within 7 days) following tumor inoculation and within the time period of IL-1 administration. IL-1 induced a marked increase in the number of lymphocytes within the brachial and axillary lymph nodes associated with the tumor inoculation site. This increase was characterized by an overall augmentation in the number of CD8⁺ and CD4⁺ lymphocytes.In vitro, these lymph node cells showed enhanced proliferation in response to interleukin-2 (IL-2) when compared to non-IL-1 treated animals, and were capable of mounting a potentially greater cytotoxic response for both NK sensitive and NK resistant tumor targets. Without IL-1 administration, temporal and sequential lymph node cellular changes were observed, but were diminished and delayed when compared to the IL-1 treated animals. By adoptive transfer of tumor resistance, lymph node cells from IL-1 treated animals were demonstrated to be tumor-protectivein vivo. These results demonstrate that systemic IL-1 induces regional changes in the lymphatics of mice undergoing primary tumor challenge with adjuvant therapy and that these changes result in tumor protection for the host.     

The absence of lymphoid suppressor cells in tumor-involved lymph nodes of patients with head and neck cancer

Patients with head and neck cancer often have decreased local or regional immunocompetence. Lymphocytes obtained from tumor-involved or -uninvolved lymph nodes (LNL) of these patients showed low or undetectable levels of antitumor cytotoxicity and low proliferative responses in vitro to interleukin 2 (IL2) or mitogens in comparison to peripheral blood lymphocytes (PBL). Lymphokine-activated killer (LAK) cell activity of LNL was lower (P less than 0.05) than that of autologous PBL. Fresh LNL were neither enriched in cells with the CD8+ CD11b+ "suppressor" phenotype nor did they suppress proliferative or cytotoxic responses of autologous PBL in mixing experiments. LNL did not inhibit LAK cell generation from autologous PBL in the presence of IL2. Also, no evidence for the inhibition of autotumor-restricted responses by IL2-activated LNL was obtained. Spontaneous or in vitro-induced production of IL1 beta. TNF alpha, and IFN-tau was low or undetectable in LNL from tumor-involved and -uninvolved lymph nodes in comparison to that in normal or autologous PBL. Mitogen-induced IL2 production was normal in LNL. The depressed ability to produce certain cytokines may be in part responsible for a state of unresponsiveness present in lymph nodes obtained from patients with head and neck cancer. No evidence for the presence of lymphoid suppressor cell in LNL of these patients was obtained.     

Graft-versus-host response,measured by splenomegaly assay,by populations of allosensitized mouse lymphocytes

The graft-vs-host (G-v-H) reactivity of sensitized or nonsensitized mouse lymphoid cell populations was measured using a splenomegaly assay. Sensitized populations were obtained either from the local lymph nodes of alloimmunized animals or from the spleens of heavily irradiated mice previously infused iv with allogeneic lymphocytes (educated cells). Immunization of animals resulted in increased G-v-H responses of the cells in their local lymph nodes. This effect was more pronounced when the immunizing cells differed only at non-H-2 transplantation antigens than when H-2-disparate strain combinations were tested. There was no evidence of a changed doseresponse profile of lymphocytes obtained from immunized mice. The G-v-H reactivity of educated cell populations was complex. The slopes of the dose-response lines obtained for lymph node cells or thymic cells educated in an H-2-disparate strain were generally lower than those obtained for nonsensitized cells. This difference was particularly evident when testing educated thymocytes. By studying the G-v-H indices obtained in A/Sn × C57B1 hybrids after inoculation of nonsensitized C57B1 lymph node cells or specifically educated C57BL lymph node cells, it was observed that the latter cells were approximately 30 times more reactive when small cell inocula were compared. On the contrary, education of lymphocytes in H-2-compatible allogeneic hosts did not result in any increment of their G-v-H reactivity. The results indicate that different methods of sensitizing lymphocyte populations against alloantigens may lead to activation of different subclasses of T-cells which differ in their mode of antigen reactivity.     

Skewed Th1/Th2 immune response to Sarcoptes scabiei

Scabies is a contagious skin disease of humans and many other species of mammals. Previous studies suggested that the balance between the Th1 and Th2 immune responses may influence the outcome of a scabies infestation in a sensitized host. Therefore, in this study, we examined the T-helper cell cytokine profiles of splenocytes and lymph node cells in BALB/c mice that were immunized with scabies extract (primary response), infested with scabies mites (primary response), or immunized and then infested (secondary response). Lymphocyte cytokine expression was analyzed by flow cytometry after staining for intracellular cytokines. Immunization with scabies extract induced production of interferon-gamma (IFNgamma) (Th1 response) by both spleen and lymph node cells. Mice that were infested with scabies increased production of interleukin-4 by lymph node cells and of IFNgamma by splenocytes. Mice that were first immunized and then infested with mites increased production of IFNgamma by both spleen and lymph node cells. However, this increased level of IFNgamma was only about half of that induced by immunization alone. These results suggest that live scabies mites produced something that inhibited IFNgamma production in the lymph nodes of scabies-immunized mice. Our data also indicate that lymphocytes in the spleen and lymph nodes can present different cytokine response profiles.     

Initial steps in lymph node metastasis formation in an experimental system: possible involvement of recognition by macrophage C-type lectins

 We used histological observations and experiments with fluorescent cell tracers to investigate the roles of tissue macrophages in recognition through a galactose/N-acetylgalactosamine-specific C-type lectin (mMGL) in lymph node metastasis formation by mouse ovarian tumor OV2944-HM-1 (HM-1) cells. Lymph node metastasis from subcutaneous sites was shown to be initiated by the entry of tumor cells into the subcapsular sinus of lymph nodes where mMGL-positive cells were mainly located. To investigate whether mMGL-positive cells contributed to host resistance against lymph node metastasis, we repeatedly treated mice bearing transplanted tumors with an mMGL-blocking monoclonal antibody that was known to inhibit mMGL binding to its ligands. The number of HM-1 cells recovered from lymph nodes 2 weeks after subcutaneous injections was significantly greater when the mice were treated with the blocking anti-mMGL antibody. These results suggested that mMGL-positive macrophages contributed to the host's defense against lymph node metastasis. Received: 30 July 1999 / Accepted: 1 November 1999     

Alloantigen-activated lymphocytes from mice bearing a spontaneous "nonimmunogenic" adenocarcinoma inhibit its growth in vivo by recruiting host immunoreactivity

Nylon wool columns eluting lymphocytes from the spleen of mice bearing a clinically evident spontaneous, nonimmunogenic adenocarcinoma of recent origin (TS/A) do not display cytotoxic response, release of lymphokines, and proliferation in vitro against TS/A cells, nor do they inhibit TS/A tumor growth in a Winn-type neutralization assay in vivo. After 5-day co-culture with allogeneic spleen cells from mice differing at multiple minor histocompatibility antigens only, these lymphocytes are still noncytolytic against TS/A cells, whereas they release interferon-gamma, mediate delayed-type hypersensitivity (DTH) reactions, and inhibit TS/A tumor growth in the Winn assay. In the Winn test, alloactivated lymphocytes from TS/A tumor-bearing mice are more effective than those from normal mice on a per cell basis. The induction of this TS/A tumor inhibition ability depends on the presence in the cultures of Thy-1+ lymphocytes. The presence of Lyt-2+ lymphocytes is also important, whereas that of asialo GM1+ is not. The TS/A inhibition in vivo by alloactivated lymphocytes mostly depends on Thy-1+, Lyt-2- and asialo GM- lymphocytes, even though a few Thy- cells are also very efficient tumor inhibitors. The alloactivated lymphocytes inhibit TS/A tumor growth by recruiting the radiosensitive effector mechanisms of the recipient mice required for ultimate tumor rejection. TS/A tumor rejection leaves a specific DTH and an immunologic memory resulting in rejection of a second lethal TS/A challenge in a significant number of mice.     

Further characterization of a clinically relevant model of melanoma metastasis and an effective vaccine

A major problem in evaluating the effectiveness of tumor cell vaccination and other biological therapies is the variability of experimental models. In this study we have further developed and characterized a model for metastatic melanoma that approximates the major clinical stages of metastatic dissemination: stage I-growth of the primary (local) tumor, stage II-dissemination to regional lymph nodes, and stage III-metastasis to distant organs (lungs). C57BL/6 mice were challenged subcutaneously with B16 F10 murine melanoma cells in the midtail, and within 3 weeks 100% of the mice had local tumors growing in their tails. By 5–7 weeks after challenge, most of the mice had developed metastases to the inguinal lymph nodes and subsequently had metastatic colonies in the lungs and in the bone marrow. Preimmunization of mice with a formalinized extracellular antigen vaccine, derived from B16F10 melanoma cells, provided partial inhibition of the growth of the primary melanoma tumors, as well as reducing the number of metastases to the regional (inguinal) lymph nodes and lungs along with concomitantly increasing survival time. This model for melanoma metastasis provides a reasonable and reproducible test system for the study of anti-melanoma immunity and the different cellular and humoral mechanisms involved.This work was supported in part by National Institutes of Health grants R37 CA45148 and R30 CA13943     

Generation from tumor-bearing mice of lymphocytes with in vivo therapeutic efficacy

Systemic transfer of sensitized lymphocytes can effectively mediate the regression of established tumors. However, virtually all prior experimental applications of this approach have utilized lymphocytes from animals that have been immunized to reject tumor challenge. A similar source of cells is not available in the human. With the use of a weakly immunogenic murine tumor, MCA 105, we demonstrate here that following in vitro sensitization (IVS) with viable tumor cells and interleukin 2, the nontherapeutic lymphoid cells from mice bearing a progressively growing tumor acquired antitumor reactivity capable of mediating the regression of established pulmonary metastases. Although the IVS system induced nonspecific lymphokine-activated killer-like cytotoxic activity from lymphoid cells of normal as well as tumor-bearing mice, therapeutically active cells could only be generated from cultures initiated with lymphoid cells from tumor-bearing animals, indicating that the IVS was a secondary in vitro immune response. Without other treatment, the IVS cells could mediate antitumor effects. However, low doses of exogenous interleukin 2 administration could enhance their therapeutic efficacy. By in vivo T cell subset depletion with monoclonal antibodies, the primary effector cells were identified as belonging to cytotoxic/suppressor T cell lineage expressing the Lyt-2 phenotype. In addition, these therapeutic effector cells could be further expanded in numbers in vitro with continuous stimulation by tumor cells in the presence of interleukin 2. Compared to the number of cells initiating the culture, as many as 126 times the number of cells were obtained after 9 days of IVS followed by in vitro expansion for an additional 5 days. Studies on the kinetics of the occurrence of the pre-effector lymphocytes during tumor growth revealed that they were readily obtained from draining lymph nodes of mice with a broad range of tumor burdens as well as durations of tumor growth. The ability to generate and expand, in vitro, therapeutically active lymphocytes from tumor-bearing hosts has important implications for cellular therapy of human cancers.     

Lymphocyte-induced production of prostaglandin E2 by tumor cells in vitro: Requirements for direct contact and lymphocyte viability

The production of prostaglandin E₂ by tumor cell lines in response to exposure to purified lymphocytes has prompted the suggestion that this phenomenon may represent a defense mechanism whereby tumors may subvert an immune response mounted against them. To further characterize this phenomenon, cell lines derived from carcinogen-induced bladder tumors and embryo fibroblasts in Fischer rats were incubated with purified lymphocytes from peripheral blood, spleen, thymus, and lymph nodes from Fischer rats under a variety of conditions, and the amount of prostaglandin E₂ (PGE₂) production was determined by radioimmunoassay. Increased numbers of blood or splenic lymphocytes were associated with the induction of increased levels of PGE₂ production by the tumor cells. However, no prostaglandin was produced by the tumor cells after exposure to thymus or lymph node lymphocytes. Irradiation of lymphocytes prior to exposure to the tumor cells led to lower levels of PGE₂ production by the tumors, as did sonication of the lymphocyte preparations prior to addition to the tumor monolayers. Separation of lymphocytes from direct contact with the tumor cells resulted in less PGE₂ production by the tumor cell lines; however, when these lymphocytes were later layered onto fresh tumor cell monolayers, PGE₂ production occurred. Results in the present study suggest that direct contact between intact, viable, functionally active lymphocytes and tumor cells is necessary for tumor cell prostaglandin production to occur. Moreover, PGE₂ production only appears to occur in response to exposure to particular populations of lymphocytes, and this may correlate with the number of specific effector or attacker lymphocytes that are present. This specificity of response to effector cell challenge may be important in probing the defense mechanisms tumor cells may have to lymphocyte challenge, as well as in gauging the efficacy of a particular cellular immune response as it may be regulated both by cells involved in effecting this response as well as by the targets in lymphocyte/tumor cell interactions.