Anti-inflammatory effect of spontaneous lymphoma in SJL/J mice.

Histiocytic lymphomas develop spontaneously in about 80% of SJL/J mice between the ages of 8 and 14 months. These animals were used for the determination of whether spontaneously arising cancers compromise monocyte function similar to the monocyte defects described during growth of transplanted tumors. SJL/J mice with tumors accumulated significantly fewer macrophages than did age-matched animals without tumors either on sc implanted filters or in peritoneal exudates induced by phytohemagglutinin. There was no corresponding defect in polymorphonuclear neutrophil responses. Whereas no apparent correlation existed between tumor size and degree of inhibition, animals without demonstrable tumors had no inflammatory defects. Aging did not alter the inflammatory response to implanted filters but increased both the resident peritoneal macrophage population and the total macrophage yield to phytohemagglutinin provocation. When given transplants of histiocytic lymphomas, young SJL/J mice developed similar inflammatory defects. This study represents the first demonstration that spontaneous tumors, in addition to transplanted tumors, produce abnormalities in monocyte inflammatory responses.     

Effects on syngeneic tumors of F1 lymphocytes sensitized in vitro by parental stimulator cells

F1 lymphocytes stimulated in vitro by parental cells were evaluated for cytotoxicity against semisyngeneic tumors and lymphoblasts. B6AF1 (H-2a,b) spleen cells were placed in culture with C57BL/6 (H-2b) or B10.A (H-2a) cells and 6 days later were assayed for cell-mediated cytotoxicity in vitro; also subcutaneous, intraperitoneal, and intrapulmonary tumor neutralization experiments were performed. F1 lymphocytes sensitized by parental cells showed high levels of cytotoxicity to the tumor cells of the parental haplotype but no lysis of parental blastoid cells. Tumor cells from irrelevant haplotypes were also lysed. The cells mediating in this type of killing were characterized phenotypically as Thy-1.2- and Lyt-2.2-positive. In a subcutaneous tumor neutralization test (Winn assay), marked suppression of EL-4 lymphoma (H-2b) and B16 melanoma (H-2b) was observed. Likewise, tumor control was seen in an intraperitoneal tumor model. These studies show that F1 versus parental sensitization can be used to lyse tumor in vitro and in vivo and should be explored as an immunotherapeutic tool.     

Interleukin-12-induced cytotoxicity against syngeneic B cell lymphomas of SJL/J mice

The B cell lymphomas (RCS) that develop spontaneously in 90% of aging SJL/J mice stimulate syngeneic CD4+ Vbeta16+ Th2 cells to produce cytokines, such as IL-4 and IL-5, which promote lymphoma growth. Although RCS cells express a unique superantigen (vSAg) encoded by an endogenous MMTV (Mtv-29) provirus that also elicits IFN-gamma production from na?ve syngeneic lymphoid cells, there is no development of RCS-specific cytotoxicity. However, addition of IL-12 to co-cultures of SJL spleen and irradiated (gamma-)RCS cells resulted in the appearance of effector cells that killed RCS and NK-susceptible target cells. Antibody depletion studies revealed at least two types of RCS/IL-12-induced cytotoxic cells: (1) NK cells (Asialo GM1+) and (2) CD8+ CTL. Despite high titers of IFN-gamma in the SN of co-culture of SJL spleen and gamma-RCS cells, cytotoxicity only developed if IL-12 was also included in the co-cultures. The results of RNAse protection assays and multi-parameter FACS analysis demonstrated an upregulation of IFN-gamma and decrease in IL-4 by activated Th cells in co-cultures with IL-12. These results indicate that inclusion of IL-12 in primary co-cultures of SJL spleen and gamma-RCS cells influences the qualitative nature of the response to favor use of RCS-responsive Th1 rather than Th2 cells to facilitate the production of cytotoxic effector cells. Results of in vivo experiments support this hypothesis, as judged by tumor growth assays and FACS analysis of the tumor cell content of lymphoid tissues. Inhibition of lymphoma growth was observed in mice given gamma-RCS/IL-12-induced effector cells prior to injection of viable RCS cells. These results demonstrate that IL-12 can be used to alter the host immune response leading to induction of cytotoxic effector cells that inhibit the development and/or progressive growth of otherwise resistant B cell lymphomas in SJL/J mice.     

Immunosuppression associated with SJL/J murine lymphoma. I. Suppression of cell-mediated immune responses after tumor transplantation

The proliferative responses of peripheral blood lymphocytes of inbred SJL/J mice to the mitogens phytohemagglutinin and concanavalin A were evaluated serially in individual animals before and after induction of lymphomas by transplantation. Tumor-bearing mice exhibited marked suppression of mitogen responsiveness. Proliferative responses in mixed lymphocyte-tumor cell culture and mixed lymphocyte culture were also suppressed. Suppression of responses was tumor related, and responsiveness was restored in animals whose tumors regressed. There was no deficiency of responder T-cells in the peripheral blood of tumor-bearing animals, and suppressor cell activity was not demonstrable in a number of in vitro assays. However, plasma from tumor-bearing animals exhibited potent immunosuppressive activity. The presence of plasma suppressive activity was similarly tumor related. Thus this study demonstrates nonspecific suppression of cell-mediated immune responses following tumor induction, apparently mediated by a plasma suppressor factor.     

Restoration of depressed immune responses by PSK in C3H/He mice bearing the syngeneic X5563 tumor

PSK is a protein-bound polysaccharide prepared from cultured mycelium of Coriolus versicolor. The effects of PSK on immunologic responsiveness were investigated in C3H/He mice bearing syngeneic X5563 tumor. The results were as follows. elayed foot pad reaction and antibody-forming capacity to sheep erythrocytes were depressed in tumor bearing mice, and such depression was prevented by oral or intraperitoneal administration of PSK. In vitro cytotoxic activity of splenic lymphocytes against the tumor was augmented by PSK administration. Antitumor effect was augmented by combination of PSK and X-irradiation. Delayed foot pad reaction to sheep erythrocytes was suppressed in normal C3H/He mice given immunosuppressive substance obtained from tumor-bearing mice, and the depressed reaction recovered to the normal level following PSK administration. These results show that PSK is effective in the syngeneic murine tumor system.     

Activation of suppressor cells by syngeneic tumor transplants in mice.

Spleen cells from mice with syngeneic tumor transplants are hyporesponsive in mixed-lymphocyte culture. The hyporesponsiveness is due to the activation of suppressor cells. Spleen from tumor-bearing mice, treated with mitomycin and added to normal mixed lymphocyte culture (with responding cells syngeneic to the added cells), inhibits proliferation of the responding cells. Suppressor activity in the spleen cells can be detected as early as 5 days after s.c. transplantation of P-815 mastocytoma into DBA/2 mice. Tumor cells placed in cell-impermeable i.p. diffusion chambers can also activate splenic suppressor cells. Suppressor cells can be activated in syngeneic mice by (DBA/2) P-815 cells, by (C3H) L25-cells, or by recent (C57BL/6) methylcholanthrene-induced tumors. The latter tumors retain their ability to activate suppressor cells after passaging in syngeneic mice. Only one tumor, induced with methylcholanthrene in DBA/2 mice, failed to activate suppressor cells. Suppressor activity in the spleen cells from mice with 20-day s.c. tumor transplants is not reduced after removal of glass-adherent cells. Suppressor activity is significantly decreased after removal of thymus-derived cells with anti-theta treatment and complement.     

Fusion hybrid of dendritic cells and engineered tumor cells expressing interleukin-12 induces type 1 immune responses against tumor

AIMS AND BACKGROUND: Dendritic cell (DC)-tumor fusion hybrid vaccinees that facilitate antigen presentation represent a novel powerful strategy in cancer immunotherapy. Preclinical studies have demonstrated that IL-12 promotes specific antitumor immunity mediated by T cells in several types of tumors. In the present study, we investigated the antitumor immunity derived from vaccination of fusion hybrids between DCs and engineered J558/IL-12 myeloma cells secreting Th1 cytokine IL-12. METHODS: The expression vector pcDNA-IL-12 was generated and transfected into J558 myeloma cells and then bone marrow-derived DCs were fused with engineered J558/IL-12 cells. The antitumor immunity derived from vaccination of the fusion hybrid DC/J558/IL-12 was evaluated in vitro and in vivo. RESULTS: DC/J558/IL-12 cells secreted recombinant IL-12 (1.6 ng/mL), and inoculation of BALB/c mice with DC/J558/IL-12 hybrid induced a Th1 dominant immune response and resulted in tumor regression. Immunization of mice with engineered DC/J558/IL-12 hybrid elicited stronger J558 tumor-specific cytotoxic T lymphocyte (CTL) responses in vitro as well as more potent protective immunity against J558 tumor challenge in vivo than immunization with the mixture of DCs and J558/IL-12, J558/IL-12 and J558, respectively. Furthermore, the anti-tumor immunity mediated by DC/J558/IL-12 tumor cell vaccination in vivo appeared to be dependent on CD8+ CTL. CONCLUSIONS: These results demonstrate that the engineered fusion hybrid vaccines that combine Th1 cytokine gene-modified tumor cells with DCs may be an attractive strategy for cancer immunotherapy.     

Modification of growth of neuroblastoma cells in syngeneic mice by aldehyde-treated neuroblastoma cells.

Pretreatment of syngeneic strain A mice with aldehyde-fixed neuroblastoma cells (clone NB6R) almost completely protected the mice against challenge with viable NB6R cells. In contrast, tumor growth was enhanced in mice treated with fixed cells after challenge with viable cells.     

PD-L1表达调控机制及其对抗肿瘤免疫反应的影响

肿瘤的发生是一个多因素、多步骤的过程.肿瘤细胞通过抑制机体的抗肿瘤免疫应答,实现免疫逃逸,促进肿瘤生长.肿瘤免疫逃逸的分子机制是肿瘤免疫研究的核心问题之一.在T细胞介导的免疫反应中,程序性死亡受体-1(programmed death receptor-1,PD-1)是关键的抑制性免疫检查点.肿瘤通过表达程序性死亡配体-1(programmed death ligand-1,PD-L1),可以增强PD-1抑制信号,促进肿瘤免疫逃逸.研究肿瘤细胞如何调节PD-L1表达,有助于阐明肿瘤发生免疫逃逸的分子机制.近年来的研究发现,肿瘤细胞在基因转录、转录后调节以及蛋白翻译后修饰等多个环节对PD-L1表达进行调节,并且通过调控PD-L1的表达影响抗肿瘤免疫反应.这些研究为肿瘤免疫治疗提供了新的靶点.     

Inhibition of IA positive reticulum cell sarcoma tumor cell growth in syngeneic SJL/J mice by passive administration of monoclonal anti-IA antibody

SJL/J (H-2s) mice develop spontaneous reticulum cell sarcoma (RCS) tumors at the age of 8-11 months. The RCS tumor expresses IA antigens on the cell surface, stimulates syngeneic T-cell proliferation, and appears to depend on host cells' participation for its own growth. The present study investigates the role of passively administered monoclonal anti-IA antibody on RCS tumor growth. The administration of monoclonal anti-IAs antibody into SJL/J mice prior to tumor inoculation or at the same time as tumor transplantation resulted in a significant inhibition of tumor growth. Furthermore, pretreatment of RCS tumor with antibody prior to inoculation also resulted in tumor growth inhibition. The inhibition seen in all cases studied was tumor specific, since the use of normal ascites on antibody directed against unrelated antigens resulted in no inhibition of tumor growth. Examination of tumor cells derived from spleen and lymph nodes of antibody treated mice demonstrated that the observed inhibition of tumor growth was the result of a significant depletion of IA positive tumor cells. In contrast to other tumor systems studied to date whereby anti-IA antibody promotes tumor growth, the present findings demonstrate that passive administration of anti-IA antibodies inhibit RCS tumor growth in syngeneic mice. The possible mechanisms involved are discussed.