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Biomedical subjects

M Fukuzawa

Publications and source records attributed to M Fukuzawa.

At least 127 records · Page 7Linked to original sources
PubMed1989

Effect of cyclosporin A on T cell immunity. I. Dose-dependent suppression of different murine T helper cell pathways.

Cyclosporin A (CsA) is used as a clinical immunosuppressive agent. Despite its immunosuppressive potential, some studies involving in vivo administration of cyclosporin have failed to verify the immunosuppressive activity of this agent. The present study investigates the effect of different concentrations of CsA added in vitro, or of different doses of CsA administered in vivo, on the ability of murine spleen cells to produce interleukin 2 and to generate cytotoxic T lymphocytes in vitro when stimulated with TNP-self or H-2 alloantigens. The results indicate that self Ia-restricted T helper (Th) cells are more sensitive to lower doses of CsA than Th cells that are allorestricted. Thus, doses of CsA were found (15-30 mg/kg) that inactivated self Ia-restricted Th function, but not other Th or effector function. This Th cell defect could be partially corrected in vitro by addition of Th cell factors to the sensitization cultures. A higher dose (75 mg/kg) of CsA inactivated all detectable T cell responses, and this defect was not corrected by addition of Th cell factors. T cell function returned to normal levels within two weeks of cessation of CsA at all three doses of CsA tested. The selective loss of L3T4 Th function at the lower doses of CsA was associated with a radiosensitive, Ly-2 suppressor T cell that was selective in its action on self Ia-restricted Th cell function. Loss of all T cell function at the higher dose of CsA was associated with a radioresistant non-T suppressor cell that inactivated all T cell function tested. These results are discussed with respect to the selective dose-dependent effects of CsA on Th subsets, on the activation of suppressor cells with similar selectivity, and the implications of these findings on the use of CsA to prevent rejection of tissue allografts.

Animals↗
PubMed1989

Effect of cyclosporin A on T cell immunity. II. Defective thymic education of CD4 T helper cell function in cyclosporin A-treated mice.

Cyclosporin A (CsA) is an immunosuppressive agent that is widely used in transplantation. Recent animal studies indicate that CsA can affect the development of immunity so that autoreactive T lymphocytes are generated. In this study, mice were treated with CsA prior to irradiation and transplantation of syngeneic bone marrow to determine whether CsA pretreatment would affect the ability of the bone marrow recipients to develop normal T cell function. Our results indicate that (a) thymuses of CsA-treated mice do not contain single-positive thymocytes (i.e. L3T4+Ly-2- or L3T4-Ly-2+) during i.p. treatment with 15 mg/kg/day of CsA; (b) both populations of single-positive thymocytes reappear within 2 weeks of termination of CsA and (c) irradiation and bone marrow reconstitution of these CsA-treated mice results in reconstitution of normal numbers of L3T4+ and Ly-2+ cells, but the L3T4+ T cells to not provide T helper function, as determined by interleukin 2 production and cytotoxic T lymphocytes generation. These findings indicate that CsA can affect thymic microenvironment and may be important as a model for investigating intrathymic T cell maturation. Our results may also have clinical implications for T lymphocyte development in transplant patients receiving CsA.

Animals↗
PubMed1988

Defective thymic education of L3T4+ T helper cell function in graft-vs-host mice.

Our study investigates the effect of a prior graft-vs-host (GVH) reaction on the subsequent ability of irradiated, bone marrow-re-populated mice to develop T cell function. The results indicate that such GVH-bone marrow transplanted (BMT) mice do not generate CTL responses to trinitrophenyl-modified syngeneic cells (TNP-self), but do generate strong CTL activity to H-2 alloantigens. This selective deficiency in TNP-self CTL response potential appeared as early as 10 days after GVH, and required both L3T4+ and Lyt-2+ donor T cells. The in vitro addition of either soluble Th factors or L3T4-enriched spleen cells from normal mice circumvented the defect in the TNP-self response in GVH-BMT mice. These results indicate that T effector function was not defective, and instead suggest a Th defect. Cell depletion and antibody-blocking, as well as IL-2 production experiments, indicate that the Th defect was selective for L3T4+ Th population and not for Lyt-2+ Th population. This defect in L3T4 Th function is not accounted for by the approximate twofold reduction in L3T4 cell numbers in GVH-BMT mice, because IL-2 production and CTL generation to L3T4-dependent Ag were at least eightfold below control levels. Rather, defective L3T4 Th function appears to be the consequence of a GVH-induced defect in thymic maturation because the defect was corrected in vivo by a neonatal parental thymus graft before irradiation and bone marrow transplantation. This system may be useful for elucidating the role of the thymus in the maturation of Th cells. Our findings raise the possibility that impaired development of T cell function occurring in marrow grafted patients who have undergone a GVH reaction could be partly due to a GVH-induced thymic defect.

Animals↗
PubMed1988

Monoclonal antibodies against discoidin I and discoidin II of the cellular slime mold, Dictyostelium discoideum.

The preparation and properties of monoclonal antibodies against carbohydrate-binding proteins (discoidin I and discoidin II) in the cellular slime mold, Dictyostelium discoideum are described. Monoclonal antibody (mAb) ndI,II-1 bound both discoidins I and II specifically. mAb nI-1 and mAb dI-1 bound only discoidin I but their binding specificities were different: nI-1 recognized the native form and dI-1 the denatured form. mAb dII-1 bound only denatured discoidin II. In preliminary work mAbs dII-1 and nI-1 were found to be useful for localizing discoidins I and II immunohistochemically.

Antibodies, Monoclonal↗
PubMed1987

Studies on the recovery from tolerance to tumor antigens. I. Bone marrow cells from tolerant hosts are not rendered tolerant, but provide potential to reconstitute tumor-specific effector T cell clones.

The present study investigates the potential of bone marrow cells from mice tolerant to tumor antigens to repopulate tumor-specific effector T cells. C3H/He mice were inoculated i.v. with 10(6) 10,000 R X-irradiated syngeneic X5563 plasmacytoma tumor cells three times at 4-day intervals. This regimen abrogated the ability of spleen cells from these mice to develop anti-X5563 cytotoxic and in vivo protective (tumor-neutralizing) T cell-mediated immunity as induced by i.d. inoculation of viable X5563 cells followed by surgical resection of the tumor. Since such suppression was induced in a tumor-specific way, this represented a state of antitumor tolerance. When bone marrow cells from normal or X5563-tolerant mice were transferred i.v. into 950 R X-irradiated syngeneic C3H/He mice, both groups of recipient mice generated anti-X5563 tumor immunity over a similar time course and to almost the same degree. Anti-X5563 tumor immunity induced in (C3H/He X C57BL/6) F1 mice which had been transferred with bone marrow cells from normal or X5563-tolerant C3H/He mice were mediated by T cells expressing the Ly phenotype of C3H/He, but not of C57BL/6, excluding the possibility that the antitumor effector cells were derived from recipient mice. It was also demonstrated that C3H/He mice which had been reconstituted with normal marrow were rendered tolerant when the tolerance regimen was started 7 weeks, but not 1 week after the bone marrow reconstitution. These results indicate that bone marrow cells from antitumor tolerant mice are not rendered tolerant to the tumor but can provide the potential to repopulate antitumor CTL and in vivo protective effector T cells.

Animals↗
PubMed1986

The augmentation of tumor-specific immunity by virus help. III. Enhanced generation of tumor-specific Lyt-1+2- T cells is responsible for augmented tumor immunity in vivo.

The role of vaccinia virus-reactive helper T cells (Th) in augmenting in vivo generation of antitumor protective immunity and the Ly phenotype mediating the enhanced in vivo tumor immunity were investigated. C3H/HeN mice were inoculated i.p. with viable vaccinia virus to generate vaccinia virus-reactive Th activity. The mice were subsequently immunized i.p. with virus-infected syngeneic X5563 and MH134 tumor cells, and spleen cells from these mice were tested for in vivo tumor neutralizing activity. Immunization of virus-primed mice with virus-uninfected tumor cells and of virus-unprimed mice with virus-infected tumor cells failed to result in in vivo protective immunity. In contrast, spleen cells from mice immunized with virus-infected tumor cells subsequent to virus-priming exhibited potent tumor-specific neutralizing activities. Such an augmented generation of in vivo protective immunity was accompanied by enhanced induction of tumor-specific cytotoxic T lymphocyte (CTL) and antibody activities in X5563 and MH134 tumor systems, respectively. However, analysis of the effector cell type responsible for in vivo tumor neutralization revealed that enhanced in vivo immunity was mediated by Lyt-1+2- T cells in both tumor systems. Moreover, the Lyt-1+2- T cells exerted their function in vivo under conditions in which anti-X5563 tumor-specific CTL or anti-MH134 tumor-specific antibody activity was not detected in recipient mice. These results indicate that augmenting the generation of a tumor-specific Lyt-1+2- T cell population is essential for enhanced tumor-specific immunity in vivo.

Animals↗
PubMed1985

The mechanism of tolerance induction of tumor-specific delayed-type hypersensitivity responses by intravenous inoculation of tumor cells.

C3H/HeN mice were inoculated intravenously (iv) with 10(6) 10000-R X-irradiated syngeneic MCH-1-A1 fibrosarcoma cells 3 times at 4-day intervals (pretreatment). Spleen cells from these pretreated or normal mice were sensitized in vitro to MCH-1-A1 tumor cells and effector cells generated after 5 days of culture were assayed for delayed-type hypersensitivity (DTH) responses by an adoptive transfer into footpads of syngeneic recipient mice together with MCH-1-A1 cells. Normal spleen cells stimulated with MCH-1-A1 tumor cells generated appreciable anti-MCH-1-A1 DTH responses, whereas spleen cells from the above pretreated mice failed to induce anti-MCH-1-A1 DTH responses. These pretreated spleen cells did not inhibit the generation of DTH responses when co-cultured with normal spleen cells as responding cells. Since vaccinia virus-reactive helper T cells are capable of enhancing DTH responses against antigens co-expressed on vaccinia-infected cells, their ability to augment anti-MCH-1-A1 DTH responses from the pretreated spleen cells upon stimulation with vaccinia-infected MCH-1-A1 cells was investigated. The results demonstrate that under conditions in which enhanced anti-MCH-1-A1 DTH responses were obtained by supplementing vaccinia helper T cells, these vaccinia-helpers were not able to generate any significant DTH responses from the pretreated spleen cells. These results indicate that iv inoculation of tumor cells suppresses the generation of tumor-specific DTH responses not by inducing suppressor cell activity, but rather by inhibiting DTH effector clones themselves.

Animals↗
PubMed1985

[The augmentation of tumor-specific immunity by T-T cell interaction].

The present study establishes a tumor-specific immunotherapy model based on the principle of T-T cell interaction mechanism responsible for augmenting the induction of anti-tumor-specific effector T cells. In this model, high incidence of tumor regression was observed in hosts bearing transplantable or autochthonous tumors when these hosts, in which hapten-reactive helper T cells had been generated, received an injection of haptenic solution into the growing tumor mass. This indicated a role of hapten-reactive helper T cells in regressing the tumor. In consideration clinical application of this tumor-specific immunotherapy model, we have also tried to investigate the use of more appropriate haptenic compounds and have succeeded in synthesizing a noble haptenic compound cross-reactive with BCG, a haptenic muramyl dipeptide (MDP) derivative. The results demonstrated that prepriming of BCG and subsequent immunization with syngeneic tumor cells (mitomycin C-treated) modified with the haptenic MDP derivative resulted in the enhanced induction of tumor-specific immunity. Further investigation is in progress to establish a new tumor-specific immunotherapy model by utilizing this haptenic MDP derivative.

Animals↗
PubMed1984

The role of tumor-specific Lyt-1+2- T cells in eradicating tumor cells in vivo. I. Lyt-1+2- T cells do not necessarily require recruitment of host's cytotoxic T cell precursors for implementation of in vivo immunity.

The present study determines the Ly phenotype of T cells mediating tumor cell rejection in vivo and investigates some of cellular mechanisms involved in the in vivo protective immunity. C3H/HeN mice were immunized to syngeneic X5563 plasmacytoma by intradermal (i.d.) inoculation of viable X5563 tumor cells, followed by the surgical resection of the tumor. Spleen cells from these immune mice were fractionated by treatment with anti-Lyt antibodies plus complement, and each Lyt subpopulation was tested for the reconstituting potential of in vivo protective immunity in syngeneic T cell-depleted mice (B cell mice). When C3H/HeN B cell mice were adoptively transferred with Lyt-1-2+ T cells from the above tumor-immunized mice, these B cell mice exhibited an appreciable cytotoxic T lymphocyte (CTL) response to the X5563 tumor, whereas they failed to resist the i.d. challenge of X5563 tumor cells. In contrast, the adoptive transfer of Lyt-1+2- anti-X5563 immune T cells into B cell mice produced complete protection against the subsequent tumor cell challenge. Although no CTL or antibody response against X5563 tumors was detected in the above tumor-resistant B cell mice, these mice were able to retain Lyt-1+2- T cell-mediated delayed-type hypersensitivity (DTH) responses to the X5563 tumor. These results indicate that Lyt-1+2- T cells depleted of the Lyt-2+ T cell subpopulation containing CTL or CTL precursors are effective in in vivo protective immunity, and that these Lyt-1+2- T cells implement their in vivo anti-tumor activity without inducing CTL or antibody responses. The mechanism(s) by which Lyt-1+2- T cells function in vivo for the implementation of tumor-specific immunity is discussed in the context of DTH responses to the tumor-associated antigens and its related Lyt-1+2- T cell-mediated lymphokine production.

Animals↗
PubMed1984

Effector cell analysis of tumor cell rejection in vivo in two syngeneic tumor systems exhibiting distinct in vitro cytotoxic mechanisms.

The nature of the in vivo anti-tumor effector cells was investigated in two different tumor system, MH134 hepatoma and X5563 plasmacytoma, in which tumor-specific antibodies and cytotoxic T lymphocytes (CTL), respectively, mediate in vitro tumor cell lyses. Winn assays utilizing MH134- and X5563-immune spleen cells revealed that in both tumor systems, tumor neutralization was produced exclusively by a tumor-specific immune Lyt-1 T cell subpopulation which was depleted of antibody-producing B cells or T cell subset(s) capable of generating CTL responses. These Lyt-1 T cells could exert their in vivo tumor-protective function under conditions in which MH134 tumor-specific antibody was not detected or in T cell-depleted recipient mice (B cell mice) in which CTL precursors were not recruited, indicating that their activities do not depend on the induction of antibody or CTL response. These results are discussed in the context of the relationships (1) between effector systems detected in in vitro cytotoxicity tests and effector mechanisms responsible for in vivo tumor protection, and (2) between epitopes or molecules required for triggering in vitro and in vivo effectors against the tumor.

Animals↗