The allogeneic effect on tumor growth. II. Suppression of both ascitic and solid MOPC 315 plasmacytoma by the graft-vs-host reaction, with pathologic correlation.

The growth of an ascitic murine plasmacytoma, MOPC 315, can be retarded in CAF1 hybrid host mice by the i.p. injection of donor lymphoid cells. The graft-vs-host reaction can be established by a variety of donor cells, including parental BALB/c and A/J and congenic inbred B10.D2 which share the major histocompatibility locus with BALB/c(H-2d). Optimal results are consistently obtained when parental BALB/c spleen cells are injected before tumor inoculation, and a second dose of donor spleen cells injected 1 week later. This aloogeneic effect on tumor growth is manifested by delayed appearance of the tumor and prolonged host survival. Pathologic studies on the ascites tumor indicated that the allogeneic effect suppresses the initial appearance and early growth of the plasmacytoma. However, once established, MOPC 315 grows rapidly and fatally in both control mice and recipients of donor lymphoid cells. Further, a subcutaneous implant of MOPC 315 is suppressed by an allogeneic effect established either i.v. with BALB/c spleen cells before tumor inoculation or by BALB/c spleen cells administered subcutaneously at the time of MOPC 315 implant. Thirty percent of mice treated by i.v. or subcutaneous donor lymphoid cells were tumor free at 150 days after tumor inoculation.     

Tumor-specific immunity induced by somatic hybrids: III. Persistence of adoptively transferred immunity specific for TEPC-15 plasmacytoma in normal BALB/c mice

Immunity against TEPC-15 tumor cells was induced in BALB/c mice by injecting semi-allogeneic hybrid cells derived from fusion of TEPC-15 tumor cells with LM(TK^?) cells of the C3H origin. Adoptive transfer of spleen cells from the immune mice into normal BALB/ c recipients rendered them free from tumors following tumor challenge; the recipients were most significantly protected from the tumor when tumor cells were injected 7–14 days after the adoptive transfer of immune cells. Such immunity following adoptive transfer appeared to persist in the recipients for at least 60 days. Moreover, the tumor-specific immunity was consecutively transferable (more than nine passages) into normal BALB/c recipients by serially passing spleen cells from the recipients every 14 days, without further stimulation with the hybrid cells or inactivated TEPC-15 tumor cells. Such consecutive transfer of the immune spleen cells induced splenomegaly in the recipients: a two- to five-fold increase over normal spleen cell recipients. The ability of spleen cells to transfer immunity, but not splenomegaly, was abrogated by treatment with mitomycin C. These results suggest that proliferation of donor cells is necessary to transfer immunity, and that splenomegaly alone does not manifest such immunity in the recipients.     

Anti-idiotypic mechanisms involved in suppression of a mouse B cell lymphoma, BCL1

Immunization of BALB/c mice with idiotypic IgM rescued by hybridization from the syngeneic BCL1 lymphoma protects specifically against challenge with tumor cells, with 83% surviving greater than 100 days compared with controls (38 +/- 10 days). Spleens from long-term survivors (greater than 6 mo) with no macroscopically visible tumor, when examined with anti-idiotypic antibody, showed a range of apparently dormant tumor with BCL1 cells present at 2 to 50% of total. A spectrum of protection against tumor resulted from immunization, and tumor emerging in the period 53 to 173 days postpassage was investigated for expression of idiotype. It was found that cells from individual mice expressed variable amounts of idiotypic IgM at the cell surface, although it was always detectable in the intracellular compartment. Unlike typical BCL1 cells, tumor cells developing in immune spleens often secreted little idiotypic IgM either in vitro or in vivo. This modulation of expression and secretion of idiotype was detected even in the apparent absence of serum anti-idiotypic antibody. On passage of spleen cells from the long-term survivors into naive animals, BCL1 tumor developed and killed the recipients in a way indistinguishable from routine tumor passage. These tumor cells, however, both expressed and secreted IgM of the same idiotype as the original tumor. It appears therefore that tumor development in immunized mice is suppressed by a process that includes modulation but not selection of the tumor cell idiotypic determinants. Analysis of possible mechanisms of suppression revealed the presence of cytotoxic anti-idiotypic antibody at variable levels in sera of immunized mice, and splenic T cells that proliferated specifically in response to idiotypic IgM. Only low levels of cytotoxic T cells were found. Passive transfer studies demonstrated a major role for antibody in protection against tumor, with no significant enhancement by immune lymphocytes.     

不同方式构建A20鼠B细胞淋巴瘤动物模型

目的探索多种方式构建A20鼠B细胞淋巴瘤动物模型及不同方式造模成瘤的特征。方法鼠源性B细胞淋巴瘤细胞株A20经皮下、尾静脉、脾脏和腹腔接种于同源BALB/c小鼠或先接种裸鼠成瘤后组织块移植BALB/c小鼠,观察动物成瘤时间、成瘤率、成瘤部位;取肿瘤组织和动物脏器行石蜡包埋、病理切片、HE染色观察其组织学特点。结果BALB/c鼠皮下注2×10^6组、2×10^7组和裸鼠瘤组织移植BALB/c小鼠组成瘤率皆为100%,成瘤时间分别为（15.29±3.2）d（、7.0±0.82）d和（6.29±0.49）d。BALB/c小鼠尾静脉注射2×106组、2×107组、脾脏注射组、腹腔注射组成瘤率分别为71.4%、100%、71.4%、14.3%,成瘤时间分别为（76.8±12.0）d、（26.1±7.99）d、（32.6±5.99）d和27 d。尾静脉成瘤部位播及肝脏、脾脏、胰腺、肾脏、食道、胃、肠、肠系膜、脑、淋巴结、骨、子宫、肌肉等多脏器和组织。BALB/c鼠A20成瘤组织学类似人弥漫大B细胞淋巴瘤。结论成功构建A20皮下移植瘤模型、血行播散性模型,为利用有免疫功能动物进行B淋巴瘤相关研究提供了实验平台。     

Neoplastic cell spreading in rodent transplantable tumor models. I. Ehrlich tumor

Ehrlich ascites tumor cells were ectopically transplanted in femoral muscles of tumor-free Swiss and BALB/c mice with the same modality used for i.p. serial transplantations of the ascitic form. A solid tumor developed (100% takes as i.p. grafts) locally invading surrounding tissues and leading to death within 30-40 days (12-14 days in ascitic form). These animals were killed when showing signs of debilitation by tumor growth (1 mo.). The recipients' own thoracic and abdominal organs (lung, liver, spleen, and kidney plus peritoneal fluid) as well as the solid tumor were removed to obtain imprints and smears fixed and stained for cytology (May Grünwald Giemsa). Tumor-free mice were used as a control and i.p. transplanted mice were sacrificed on day 8. Disseminated tumor cells were seen in recipient organ imprints and peritoneal fluid smears scattered among local normal cells. Host defense cells with prevalence of neutrophils were observed infiltrating the solid tumor or adjacent to disseminated tumor cells. According to previous findings, organ imprints of i.p. transplanted mice showed disseminated tumor cells and host defense cells. Surprisingly, in liver imprints of ectopically transplanted BALB/c mice, numerous megakaryocytes were detected. This tumor and host organ imprint assay offers the possibility to monitor in vivo the phenomenon of metastatic tumor spread.     

Immunity to virus-free syngeneic tumor cell transplantation in the BALB/c mouse after immunization with homologous tumor cells infected with type C virus.

Syngeneic tumor cell lines free of endogenous type C virus or viral antigen antigen expression were derived from spontaneously occurring tumors of the BALB/cCr mouse. Two cell lines free of endogenous type C virus were examined and found to be highly tumorigenic in tumor growth kinetic studies. In vitro inoculation of these cell lines with Rauscher-murine leukemia virus (R-MuLV) resulted in their chronic infection in which 95 to 100% of the cells were scored as virus positive. These infected lines showed a highly significant increase in their immunogenicity as compared to their uninfected controls. Animals in which these virus-positive tumors regressed were then shown to be highly resistant to challenge with the uninfected tumor cell lines as well as to live R-MuLV. This observed resistance to uninfected tumor cell lines could not be induced by immunization of the mouse with uninfected tumor cells and R-MuLV simultaneously at the same injection site, nor could it be induced with lethally irradiated virus-infected tumor cells, subtumorigenic doses of uninfected cells, or inactivated R-MuLV or Gross leukemia virus (G-MuLV). Cell-mediated cytotoxicity studies revealed that spleen cells obtained from animals whose virus-infected tumors regressed were cytotoxic to homologous infected and uninfected tumor cells as well as to other uninfected tumor cell lines syngeneic to the BALB/c mouse. Correlation of in vitro cytotoxicity with in vivo immunity was provided by the Winn assay, by inoculation into susceptible mice of immune and nonimmune spleen cells premixed with uninfected tumor cells. The immune cells were highly effective in preventing this tumor cell transplantation. It was concluded that type-C virus infection of these syngeneic tumor cells resulted in their acquiring strong transplantation antigens that were in part due to the virion, but were at least in part due to alterations of antigens or haptens that are present in a less immunogenic form on the uninfected tumor cell.     

Regualtion of the immune response to tumor antigens. I. Immunosuppressor cells in tumor-bearing hosts.

A/Jax mice were rendered immune to the syngeneic and transplantable methylcholanthrene-induced Sarcoma 1509a by the surgical removal of the tumor 7 days after implantation; subsequent injection i.v. transfer of 10(7) to 10(8) washed thymus or spleen cells of tumor-bearing animals (TBA) to immune animals significantly inhibited the rejection of the tumor; this suppressive effect was entirely abolished by the treatment of these lymphocytes with anti-theta serum or anti-thymocyte serum (ATS) and complement before adoptive transfer. On the other hand, an equal number of thymus or spleen cells of normal animals or of animals bearing an unrelated tumor had no suppressive effect. Treatment of normal syngeneic animals with ATS after tumor cell inoculation or splenectomy of TBA resulted in the suppression of the tumor growth. The serum of TBA had no effect on tumor growth in immune syngeneic mice. Together these results suggest that TBA possess immunosuppressor T cells regulating negatively their immune response to the tumor.     

Graft-vs-host reactions (GVHR) across minor murine histocompatibility barriers. I. Impairment of mitogen responses and suppressor phenomena

In our laboratory, we have developed a murine model to examine GVHD across minor histocompatibility antigens. In our model, GVHD is induced by injecting B10.D2 spleen cells into irradiated BALB/c recipients. Seven to 10 days after irradiation and injection of cells, there are significant changes in cell function in the recipient spleens. In the B10.D2----BALB/c (600 rad) model, recipient spleen cells are profoundly unresponsive to Con A and LPS stimulation but show increased B cell activity measured by Staphylococcus aureus protein A plaque-forming activity. Spleen cells from such GVH mice profoundly suppress the mitogenic responses of normal BALB/c or B10.D2 spleen cells to Con A and LPS. The degree of impairment of the mitogenic response and the ability to suppress normal cells is proportional to the dose of cells used to induce GVH reactions. Both the inability to respond to mitogens and the capacity to suppress are also related to the dose of irradiation given to the recipients. In addition, immunosuppression across minor histocompatibility antigens shows an unevenhandedness. If we inject parental B10.D2 or BALB/c cells into F1 recipients (P----F1), there is greater inhibition of mitogenic responses when B10.D2 parental cells are given than when BALB/c cells are given to the irradiated F1 recipients. These experiments show that significant immunosuppression occurs during GVH reactions across minor histocompatibility barriers. The degree of suppression varies according to the dose of cells used to induce GVH, the dose of irradiation to the recipient and the "strength" of the GVH recognition system. Such experiments provide models for GVH disease seen in humans who receive treatment for leukemia or other diseases that involves recipient irradiation and infusion of HLA-identical bone marrow.     

Studies of thymopoietin pentapeptide (TP5) on experimental tumors: I. TP5 relieves immunosuppression in tumor-bearing mice

The allogeneic and syngeneic immune responses of tumor-bearing mice (C57BL/6 mice bearing 3LL and DBA mice bearing P815) were evaluated by the cytotoxic lymphocyte precursor unit (CLP-U) and MLC. In general, tumor-bearing mice showed slightly enhanced immune responses 4 days after tumor inoculation. This enhanced immune response rapidly declined and about 7–10 days after tumor inoculation, both allogeneic and syngeneic responses were markedly lower than normal. Mice treated with TP5, starting 2 weeks before tumor inoculation, retained normal or enhanced allogeneic and syngeneic responses up to 3 weeks after tumor inoculation. When this tumor-induced suppressive effect was studied in cell transfer experiments, spleen cells from tumor-bearing mice enhanced the growth of tumors in syngeneic recipients whereas spleen cells from TP5-treated mice inhibited the growth of tumors in syngeneic recipients. Moreover, the spleen cells from TP5-treated mice also showed enhanced cytotoxic activity against tumor cells in vitro. These findings suggest that the tumors, after a transient stimulatory phase, induced immune suppressive mechanisms in the hosts' immune defenses. Treatment with TP5 prevented the development of these immune suppressive effects and spleen cells from TP5-treated tumor-bearing mice inhibited tumor growth in freshly tumor-inoculated recipients.     

Effect of tumor immunity on the distribution of labeled lymphoid cells in tumor-challenged mice

The distribution of ⁵¹Cr-labeled lymphoid cells from normal mice and mice immunized against a tumor were compared after intravenous inoculation of the labeled cells into normal syngeneic recipients. Spleen cell preparations from immune donors contained increased percentages of spleen and bone marrow-seeking cells, thus suggesting expansion of these cell populations when immunity to a tumor exists. Homing of labeled normal cells in tumor cell-injected normal animals was somewhat different from that seen in tumor cell-inoculated mice that were immunized against the tumor. In the latter case, accumulations of lymph node and spleen cells in recipient lymph nodes and bone marrow were consistently lower. In contrast, lymphoid cells from animals immunized against the tumor were found to accumulate in virtually the same percentages in lymphoid organs of normal and immune recipients. The behavior of lymphoid cell populations from thymus or bone marrow that consist mainly of precursor cells was unaffected by presence of malignancy and/or tumor immunity.     

Induction of tumor immunity by intact irradiated leukemic B cells (BCL1) bearing a tumor-associated cell-surface idiotype and the costimulatory B7 molecule

The idioptypic (Id) determinant of immunoglobulin expressed on the cell surface of malignant B cells represents a prototypical tumor-associated antigen (TAA), which has been used in a purified soluble form for active immunization in experimental tumor models and human hematological malignancies. Using a spontaneous transplantable murine model of B cell leukemia/lymphoma (BCL1), we have demonstrated the expression of the B7 costimulatory molecules in addition to the previously described Id determinant and class II major histocompatibility antigens. Intact irradiated BCL1 cells bearing these distinct determinants induced long lasting antitumor immunity in naive syngeneic mice. Induction was dose-dependent and most effective when three doses of 30×10⁶ intact irradiated BCL 1 cells were given at intervals of 7–10 days. The induced immunity protected 96% of 28 mice inoculated with a lethal dose of 10⁵–10⁶ nonirradiated BCL1 cells and 85% of 27 mice given a second challenge, whereas control mice died on day 20 after inoculation with 10⁶ BCL1 cells. Adoptive transfer of splenocytes derived from immune mice did not induce leukemia in syngeneic recipients. Such splenocytes, harvested more than 365 days following immunization and administered together with fresh BCL1 cells to adoptive recipients, were able to confer protection for 90 days, even following a second challenge given 104 days after the first one. BCL1 immune splenocytes transferred into BCL1-bearing mice exerted a therapeutic effect, preventing leukemia onset for at least 180 days. Our results demonstrate the ability of tumor cells to trigger effective anti-tumor immunity. These findings could ultimately be applied to the prevention of tumor relapse in treatment of hematological and other malignancies expressing TAA, class II MHC antigen and costimulatory molecules.These studies were supported by grant 942010-B from the Israel Cancer Association     

Effect of graft-versus-host disease on anti-tumor immunity

BCL1, a spontaneous B cell leukemia of BALB/c origin, is rejected by C.B-20 (Ighb, H-40b) but not BALB/c (Igha, H-40a) mice. Adoptive transfer of C.B-20 anti-BCL1 effector cells specific for the minor histocompatibility Ag H-40a protects irradiated C.B-20 but not BALB/c recipients. Because C.B-20 donor cells could potentially generate graft-vs-host disease (GVHD) in BALB/c recipients, we investigated the possibility that GVHD prevents the anti-tumor effect. GVHD was induced in (C.B-20 X B10.D2)F1 [H-2d, H-40b X H-2d,H-40b] recipients after injection of B10.D2-primed C.B-20 donor cells. GVHD was indicated by the histologic appearance of tissue sections from C.B-20----F1 livers, target organs of GVHD, which showed a marked mononuclear cell infiltrate around the portal tracts and central veins. In addition, splenic lymphocytes from these mice had altered CD4/CD8 ratios and were unable to respond to the polyclonal activators Con A and LPS. The mitogen unresponsiveness was at least partially due to the presence of a suppressor cell, because proliferation of normal spleen cells to Con A and LPS was suppressed upon addition of C.B-20----F1 spleen cells. Further immune dysfunction was evident by the inability of T cells from mice with GVHD to generate a CTL response to H-2 alloantigens. Addition of C.B-20----F1 spleen cells to F1 responder cells at the induction of culture did not prevent generation of CTL, indicating that a suppressor cell was not responsible for the lack of CTL activity. In this setting of GVHD, F1 recipients were able to reject BCL1 upon adoptive transfer of C.B-20 anti-BCL1 effector cells. These data indicate that GVHD-induced immune dysfunction does not inhibit the activity of antileukemia T cells.     

H-40, an antigen controlled by an Igh-linked gene and recognized by cytotoxic T lymphocytes. II. Recognition of H-40 as a tumor antigen in leukemic animals

C.B-20 (Ighb) but not (C.B-20 X BALB/c)F1 mice reject BCL1, a sIg+ tumor that spontaneously arose in an Igh congenic BALB/c (Igha) mouse. C.B-20 immune T cells from mice immunized with either BCL1 or BALB/c splenocytes adoptively transfer tumor protection to sublethally irradiated C.B-20 but not BALB/c or (BALB/c X C.B-20)F1 mice. These data suggest that BALB/c and BCL1 share an antigen, which if present in the host prevents the immune cells from eradicating the tumor. The antigen is controlled by H-40, a gene that maps to the C end of the Igh complex, telomeric to Tsu and in the region of Pre-1. The ability of H-40 to act as a tumor antigen for other BALB/c tumors inoculated into C.B-20 hosts was investigated. H-40 did not elicit rejection of P1798 (T lymphoma), Meth A (fibrosarcoma), or MOPC-315 (alpha, lambda myeloma) tumor cells. C.B-20 mice that previously rejected BCL1, however, showed partial resistance to a low challenge dose of the MOPC-104E (mu, lambda myeloma) tumor. These data suggest that H-40 has a differential degree of expression on BALB/c tumor cells. The ability of the adoptively transferred cells to confer protection against BCL1 is abrogated by pretreatment of the cells with anti-Lyt-1 or anti-Lyt-2 antibodies. However, an admixture of anti-Lyt-1- and anti-Lyt-2-treated cells provided protection. These data, together with the results detected by cytotoxic T lymphocyte (CTL) activity in vitro, indicate that H-40 can serve as a target antigen for tumor rejection by CTL in allogeneic hosts. The implications of the results for allogeneic bone marrow transplantation into leukemic individuals who benefit from a graft vs leukemia effect are discussed.     

Induction of tumor-specific in vivo protective immunity by immunization with tumor antigen-pulsed antigen-presenting cells

The present study investigates the role of APC in inducing tumor-specific in vivo protective immunity. Thy-1+ cell-depleted, Mac-1+ cell-enriched fraction of normal BALB/c spleen cells were used as a source of APC. These APC were cultured in vitro with the membrane fraction isolated from CSA1M fibrosarcoma derived from BALB/c strain. The administration of such APC into naive BALB/c mice generated the capacity of these animals to reject the subsequently challenged viable CSA1M tumor cells. Although the induction of anti-CSA1M in vivo protective immunity required three consecutive immunizations with more than 10(5) APC which had been pulsed in vitro with 200 to 300 micrograms protein of CSA1M membrane fraction, the immunity was induced irrespective of whether APC were administered via s.c., i.v., or i.p. route. This immunity was tumor-specific, inasmuch as the inoculation of CSA1M or Meth A fibrosarcoma membrane component-pulsed APC resulted in the selective immunity against the challenge with homologous types of tumor cells. The CSA1M-specific in vivo protective immunity was also induced by injecting APC pulsed with solubilized CSA1M membrane components. Moreover, it was demonstrated that the efficiency for inducing anti-CSA1M immunity was much higher in the utilization of tumor Ag-pulsed APC than in the immunization with tumor Ag emulsified in CFA. These results indicate the critical role of APC in generating tumor rejection immunity in vivo and this model presents a novel approach to induce tumor-specific immunity without using tumor cells themselves.     

Effect of beta-Carotene on the development of the solid Ehrlich tumor in mice

The effect of beta-Carotene on the development of the solid Ehrlich tumor in BALB/c mice was investigated. Male mice received orally, on alternate days, three different doses of beta-Carotene (1, 3.5 or 7 mg/100 g) or corn oil as the control. This protocol started 14 days before tumor inoculation (1.75 x 10(5) cells) into mouse footpad and lasted until 10 days after. The tumor growth was evaluated by daily measurement of the footpad thickness, and the tumor mass was evaluated morphometrically. The proliferation rate of tumor was investigated by counting PCNA (proliferating cell nuclear antigen) positive nuclei in the 10th day of the tumor development. Histopathological examination of the lymphoid tissue: thymus, spleen and popliteal lymph node were also performed. beta-Carotene treatment, at dose 3.5 mg/100 g, increased the tumor growth, proliferative rate and the relative weight of popliteal lymph nodes, showing up an adverse effect only when this intermediate dose was used. No effects were obtained when the smaller (1,0 mg/100 g) or the higher (7.0 mg/100 g) doses were used. These results suggest that depending on the dose, beta-Carotene may determine an undesirable effect upon the tumor growth. This should be taken into account in chemopreventive experiments and human applications.     

Suppression and elimination of BCL1 leukemia by allogeneic bone marrow transplantation

Mice carrying the B cell leukemia (BCL1)+ were successfully treated by total lymphoid irradiation (TLI), cyclophosphamide, and allogeneic bone marrow (BM) transplantation. Long-term survivors were examined for residual BCL1 cells and for the ability to transfer adoptively graft vs. leukemia (GVL) activity. Residual BCL1 cells could not be detected in the allogeneic BM chimeras (greater than 14 to 16 months) with the use of indirect immunofluorescent staining with anti-idiotype antibody. However, residual tumor cells were present in 50% of the "cured" chimeric mice since adoptive transfer of 10(6) spleen cells from 50% of the treated chimeric mice caused leukemia in BALB/c recipients. In order to determine whether leukemia had been prevented in the "cured" chimeras by a persistent cell-mediated mechanism, BALB/c mice were injected with 10(6) spleen cells from the "cured" BM chimeras together with a dose of 10(2) or 5 x 10(5) BCL1 cells. Onset of leukemia was delayed or completely abolished in a significant proportion of recipients receiving the cell mixtures, suggesting the presence of anti-tumor immunity in the cured mice. The data suggest that a persistent active immune mechanism may be responsible, in part, for the significant antileukemic effects observed in mice tolerant to donor alloantigens.     

Immunotherapy with SLPI over-expressing mammary tumor cells decreases tumor growth

We have demonstrated previously that the inoculation of murine mammary tumor cells genetically modified to express high levels of secretory leukocyte protease inhibitor (2C1) do not develop tumors in immunocompetent mice and these cells are more prone to apoptosis than control cells. The aim of the present study was to evaluate the role of the adaptive immune response in the lack of tumor growth of 2C1 cells and the possibility of using these cells for immunotherapy. The s.c. administration of mock transfected F3II cells induces tumor in BALB/c and Nude mice. However, the inoculation of 2C1 cells develops tumor in Nude but not in BALB/c mice. The inoculation of mock transfected F3II cells to 2C1 immunized BALB/c mice by repeated administration of 2C1 cells (once a week for 3 weeks) developed significantly smaller tumors than those observed in non-immunized mice. Remarkably, survival of tumor-bearing immunized mice was higher than non-immunized animals. Herein, we demonstrate that an immunotherapy with SLPI over-expressing non-irradiated tumor cells which do not develop tumor in immunocompetent mice, partially restrain the tumor growth induced by F3II cells and increase the survival of the mice.     

The allogeneic effect on tumor growth. I. Inhibition of a murine plasmacytoma, MOPC 315, by the graft-vs-host reaction.

The allogeneic effect has been employed as a potent immunopotentiator in preventing the growth of a murine plasmacytoma and prolonging host survival. Parental BALB/c spleen cells were passively transferred to (BALB/c x A/H)F1 hybrid mice, who were then given a highly lethal dose of MOPC 315 plasmacytoma, a tumor of BALB/c origin. The resultant graft-vs-host reaction protected the recipient mice against growth of the tumor and significantly prolonged survival. This phenomenon was dependent upon the dose of BALB/c lymphoid cells employed, the route of administration, and the time interval between lymphoid cell transfer and tumor inoculation. A wide range of lymphoid cell doses and time intervals were effective, and repeated doses of allogeneic cells provided better protection than a single dose.     

Natural cell-mediated cytotoxicity in vitro and inhibition of tumor growth in vivo by murine lymphoid cells cultured with T cell growth factor (TCGF)

Summary Lymphoid cells obtained from the spleen, thymus, bone marrow, peripheral blood, and peritoneal exudate of normal mice (BALB/c, BALB/c nude, C57BL/6, C3H) and from spleens of mice bearing a transplantable lung carcinoma or primary mammary carcinoma were expanded in culture for 1–9 months, with an increase in cell number of 10⁵- to 10⁶-fold per month, in crude or lectin-depleted medium containing T cell growth factor (TCGF). All these cultured lymphoid cell (CLC) lines exhibited strong cytotoxic activity in vitro (assessed by ⁵¹Cr-release assays) toward a variety of freshly harvested and cultured syngeneic, allogeneic, and xenogeneic tumor target cells, both lymphoid and solid (including metastatic growths) in origin. Extensive killing was observed against tumor targets that were resistant to lysis by natural killer (NK) cells as well as to NK-sensitive tumor lines. Low levels of cytotoxic reactivity were also demonstrated against fresh and cultured normal lymphoid cells. The CLC had some characteristics of NK cells but also expressed some typical T cell markers. In local Winn-type neutralization assays, CLC delayed or completely inhibited the growth of lymphomas and carcinomas in syngeneic and allogeneic recipients. In mice with metastatic growth of a second-generation transplant of mammary carcinoma, CLC were shown to have some therapeutic effect when administered IV 1 day after cyclophosphamide. No significant beneficial action of IV administered CLC was observed in the absence of chemotherapy in mice implanted with a lung carcinoma. The possibilities of employing TCGF-propagated cytotoxic effector cells in adoptive immunotherapy of human malignancies are discussed.     

Inhibition of the growth of a syngeneic weakly immunogenic tumor in mice resulting from exposures affecting T lymphocyte activity

Adult BALB/c mice were thymectomized, lethally irradiated and reconstituted with cells of syngeneic embryonic liver (B-mice). The growth of the syngeneic low-immunogenic tumor of spontaneous origin (Acatol) was strongly inhibited in B-mice as compared to that in intact recipients. The transplantation of the tumor to adult-thymectomized hosts 3 months after operation also resulted in marked retardation of tumor growth as compared to intact or sham-operated animals. The same effect was observed in mice preimmunized with spleen cells from tumor-bearers but not from intact donors. It is inferred that BALB/c mice possess strong non-specific factors of tumor resistance. However, they are actively suppressed by the mature immune system. Apparently, tumor cells, regardless of low immunogeneity are antigenic enough for the syngeneic host and induce a series of immune reactions, bringing about activation of T suppressors. It is assumed that attempts at immunizing a tumor host with autochthonous T suppressors might lead to a promising approach to cancer immunotherapy.