Cell-mediated immunity to moloney sarcoma virus in mice. I. Analysis of antigens responsible for lymphocyte stimulation in regressor mice

Effect of recombinant human interleukin 2 on the growth of a BALB/c sarcoma induced by Moloney murine sarcoma virus

The effect of in vivo administration of recombinant interleukin 2 (rIL2) on the growth of a primary female BALB/c sarcoma induced by Moloney murine sarcoma virus (M-MSV) was studied. Although low-dose administration of (6,000 JU/mouse x 14 days) rIL2 had no effect on the growth of the tumors, high-dose (15,000-80,000 JU/mouse x 14 days) intraperitoneal inoculation of rIL2 induced tumor regression, dose-dependently. Tumors in mice which received 80,000 JU/mouse/day of rIL2 regressed completely 2 weeks after the initiation of treatment. The survival rates of the treated groups were significantly higher than those of the control group. A time course experiment disclosed that the effect of rIL2 was restricted only to the group in which rIL2 treatment started 8 days after the inoculation of M-MSV. The cytotoxic activity of regional lymph node lymphocytes from rIL2-treated mice was demonstrated against primary culture of M-MSV-induced sarcoma but not against syngeneic tumor induced by methylcholanthrene (Meth A). The effect of rIL2 was partially blocked by the administration of anti-IL2 receptor antibody. Immunohistochemical examination revealed that infiltration of Thy1.2+Lyt1+2- (helper/inducer subset) lymphocytes into the tumor tissue was prominent in mice which received high-dose rIL2. The results indicated that IL2 induced regression of M-MSV-induced sarcoma mainly through activation of IL2-receptor-positive helper T cells in the tumor tissues and of killer cells in the draining lymph nodes.

Adoptive T cell immunotherapy of MSV-induced tumours in nude mice. Part I. Biology of tumour regression and recurrence

The induction of immunity to progressively growing murine sarcoma virus (MSV) tumours in nude (nu/nu) mice by reconstitution with immune T cells from syngeneic (+/+) donors has been studied. Whole spleen cell preparations served as the source of immune T cells. Transfer of immune, but not of normal, spleen cells resulted in partial or apparently complete regression of primary tumours and a related moderate to considerable extension of survival time. The dose, the time in days between immunization and transfer, as well as timing of the spleen cells in relation to tumour cell challenge, were all factors which influenced the effectiveness of the protective inocula. An unexpected consequence of even the very effective primary immunotherapy regimens, was secondary tumour development after varying tumour-free intervals. This was most frequently manifest as tumour recurrences at the original injection site either on their own or in combination with distant metastases. Such a relatively high frequency of tumour reappearance and metastatic spread contrasts markedly with the rare instances of secondary regrowth in normal immunocompetent mice. The present reconstitution system may therefore provide a new model for studying the inhibitory or stimulatory properties of T cells with respect to tumour regression and dissemination.

Induction and specificity of syngeneic antiserum against Rauscher murine leukemia virus-induced leukemia, RBL-5

Plasma membranes purified from RBL-5 leukemia cells and solubilized with Na deoxycholate were fractionated on an Ultrogel AcA34 column. Fractions containing most of the tumor-rejection activity but low amounts of gp70 and p30 were consolidated and used to hyperimmunize semisyngeneic, CBF1, hybrid mice. Using the complement-dependent cytotoxicity assay, we determined the antibody titers against RBL-5 and several other leukemic cells. Only RBL-5 and EL-4 tumor cells were lysed. Similar results were obtained when the same tumor cells were used to absorb the syngeneic antiserum and the residual cytotoxic titer determined on RBL-5 target cells. Coupling of the gamma-globulins from this antiserum to Sepharose 4B facilitated the isolation of an antigen which inhibited the C'-dependent lysis of RBL-5 tumor cells and, when used for immunization, protected the recipient mice against a subcutaneous challenge of RBL-5 leukemia cells. By means of disc gel electrophoresis, in the presence of SDS and 2-mercaptoethanol, two polypeptide chains with molecular weights of 46,000 and 21,000 were resolved. The binding of the antigen to a lens culinaris lentil lectin column and its subsequent elution with alpha-methyl mannoside suggests that the specific tumor antigen is a glycoprotein.

Rauscher leukemia virus-induced tumor antigens: complete separation from gp70, p30 and H-2

The possibility that some or all of the viral proteins, gp70, p30, and the histocompatibility antigen, H-2, function as the tumor-specific transplantation antigen (TSTA) of the R-MuLV-induced leukemia, RBL-5, and also in the secondary in vitro induction of cytotoxic T lymphocytes (CTL), was investigated. The antigen was obtained by isolating the plasma membranes of RBL-5 cells and solubilizing with sodium deoxycholate (DOC) followed by gel filtration chromatography. A fraction containing excellent tumor-rejection activity but low amounts of gp70, p30 and H-2 was chromatographed on goat anti-gp 70 goat anti-p 30 and sheep anti-H-2b immunoaffinity columns. The data obtained indicate that gp 70, p 30 or H-2 do not function as TSTA of RBL-5 leukemia, individually or as a complex. Similarly, the antigen responsible for the specific secondary induction of CTL in vitro is distinct from these three proteins.

Solubilized TSTA and the major viral structural proteins, gp70 and p30, in the immune response to murine leukemias induced by Friend and Rauscher virus

Antigens present in gp70 and p30 purified from Rauscher virus, were tested for immunogenicity in various assays measuring the anti-tumor immune response against lymphocytic leukemias of Friend (FBL-3) or Rauscher (RBL-5) virus origin. p30 had no effect on in vitro cytotoxicity against tumor cell targets mediated by either an anti RBL-5 serum or lymphocytes from animals immunized with FBL-3 cells. gp70 had had no effect on serum-mediated cytotoxicity but used at high concentrations it inhibited cell-mediated cytotoxicity. When used to immunize mice directly against subsequent challenge with the RBL-5 and FBL-3 leukemias, p30 had no discernible effect, while gp70 afforded partial protection against RBL-5 but only at high concentrations. Cell-free preparations of tumor membranes containing negligible amounts of gp70 were antigenically superior to gp70 in both the in vitro and in vivo assays. It is concluded that antigens on these purified proteins that are also expressed on tumor cells are not major targets of the anti-tumor immune response in this system.

Gross-virus-induced lymphoma in the rat. IV. Cytotoxic cells in normal rats

Lymphoid cells from normal W/Fu rats are cytotoxic in vitro for syngeneic Gross-virus-induced lymphoma cells in a 4 1/2 h 51Cr release test, and protect against tumour growth in vivo when adoptively transferred to syngeneic recipient rats. Cytotoxicity by normal lymphoid cells was greater with in vitro rather than in vivo passaged target cells, and was increased by preincubation of the lymphoid cells at 37 degrees C for 3 h in vitro before their addition to the target cells. Cytotoxic activity, which was localized predominantly in the spleen, was absent at birth but increased until adulthood with some decline in older age. Histocompatibility at the major Ag-B locus was not required for the killer cell--target cell interaction; normal spleen cells of many Ag-B genotypes were cytotoxic for W/FuG-1 target cells, although BDIX and (BDIX X W/Fu)F1 were less active and BN were inactive. The specificity of cytotoxicity was studied by the techniques of direct lysis, competitive inhibition or adsorption to cellular monolayers, using a variety of cell lines. Selectively of lysis or binding was observed and was restricted to rat target cells releasing exogenous or endogenous C-type viruses.

Studies on a gross-virus-induced lymphoma in the rat. III. Optimisation, specificity and applications of the in vitro immune response

Conditions are described for optimal stimulation in vitro of lymphocytes from rats primed in vivo with syngeneic MuLV-G leukaemia cells. Cultures generate effector cells which show high cytotoxic activity against leukaemic cells. Specific stimulation can be obtained with leukaemic cells and with disrupted MuLV. Leukaemic cells, normal spleen cells and the viron internal protein p30 competitively inhibit effector cells, but purified virus exerts non-specific inhibition. These findings are interpreted as supporting the hypothesis that virion antigens constitute a major target of anti-tumour cytotoxic immunity.

Studies of lymphocyte stimulation by intact tumor-cell and solubilized tumor antigen

BALB/c mice were rendered immune to syngeneic SV40-induced sarcoma by subcutaneous injection of mKSA-TU5 tissue-culture adapted cells. Spleen cells from immune mice were examined for tumor-cell neutralization in the Winn assay as well as in in vitro lymphocyte stimulation assays. A microculture (200 mul) lymphocyte stimulation (LS) assay utilizing immune spleen cells was employed with mixed lymphocyte/tumor-cell cultures (MLTC) and the papain crude soluble (CS) extracts from mKSA-TU5 cells. Specificity in the LS assay was determined using spleen cells from mice immune to other syngeneic tumors and by soluble antigenic preparation of normal BALB/c spleen cells. The Winn assay studies demonstrated that spleen cells from mKSA-sensitized mice neutralized mKSA tumor cells and this was corroborated by their resistance to direct tumor challenge. Positive lymphocyte transformation responses in MLTC were observed when mKSA-TU5-sensitized spleen cells were mixed with mitocycin-C-treated intact tumor cells or when papain-solubilized antigens of mKSA cells were employed, but not with non-immune spleen cells or with a soluble antigen from normal cells. Papain-solubilized antigen preparations employed in in vitro assays also immunized against challenge with mKSA tumor cells. Specificity of these lymphocyte transformation reactions was demonstrated with non-sensitized lymphoid cells or lymphoid cells from mice sensitized with a syngeneic Kirsten virus-induced respond. Thus, mKSA tumor surface antigens were recognized on intact tumor cells or with microgram quantities of papain-solubilized extracts from these tumor cells. We believe the lymphocyte stimulation assay affords a method for demonstrating the presence of tumor-specific antigen and for monitoring further purification procedures.

Studies on a gross-virus-induced lymphoma in the rat. II. The role of cell-membrane-associated and serum P30 antigen in the antibody and cell-mediated response

The internal viral protein, p30-1, has been identified by cytotoxicity tests using xenogeneic sera, on MuLV-G-induced rat lymphoma cells. In this system internal virion antigens, and in particular p30, are cytotoxic target antigens for syngeneic antibody and cell-mediated cytotoxicity; p30 is also present in the serum of rats with progressively growing lymphomas, and is the principal antigen responsible for the inhibition of cell-mediated cytotoxicity produced by these sera.