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J C Leclerc

Publications and source records attributed to J C Leclerc.

At least 19 recordsLinked to original sources
PubMed1982

Immunogenic variants obtained by mutagenesis of mouse Lewis lung carcinoma. Recognition of variant-specific antigens by cytolytic T lymphocytes.

By mutagenesis of a cell line derived from Lewis lung carcinoma (3LL), it is possible to obtain at high frequency stable tumor cell variants (tum-) that are rejected by syngeneic mice. The possibility of obtaining a cytolytic T cell (CTL) response directed specifically against these tum- variants was examined. With the four variants that were analysed, a significant cytolytic activity was obtained with peritoneal cells from immune mice collected shortly after an intraperitoneal boost and also with spleen cells after a secondary stimulation in vitro. The CTL populations preferentially lysed the immunizing tum- variant, while also showing a cross-reactive lysis against the other variants and the original 3LL cells. Highly active CTL clones could be isolated from limiting dilution microcultures of these CTL populations. The clonal analysis clearly showed the existence of two distinct CTL populations, one directed exclusively against the immunizing variant and another that lysed all 3LL targets equally. This CTL specificity analysis therefore demonstrates directly the presence of new antigens on the 3LL tum- cell variants.

Animals↗
PubMed1981

T cell-mediated immunity to oncornavirus-induced tumors. III. Specific and nonspecific suppression in tumor-bearing mice.

A strong cell-mediated immune response against Friend, Moloney, Rauscher virus-induced (FMR) cell surface antigens has been demonstrated previously in mice which reject oncornavirus-induced tumors. In order to identify an eventual suppressor mechanism in animals with progressively growing tumors, experiments were initiated in C57BL/6 mice bearing either a murine sarcoma virus (MSV) tumor or Moloney virus-induced lymphoma (MBL2). Progressive tumor growth was induced (a) in viremic animals first infected with Moloney murine leukemia virus (M.Mu LV), then inoculated as adult with MSV; (b) in nonviremic animals injected with MBL2 lymphoma cells. In the absence of tumor cells, viremia induces specific tolerance for which there is no evidence for suppressor cells. In tumor-bearing mice, specific suppressor T cells are detected which are able to inhibit the generation of anti-FMR cytolytic T lymphocytes in vitro and enhance the tumor growth in vivo. In addition to the specific suppressor T cells, a nonspecific suppressive activity mediated by metastatic T lymphoma cells is demonstrated in the spleens of lymphoma-bearing animals. The respective role of the virus and tumor cells in the induction of tolerance to M.MuLV-induced antigens, and their relationship to other components of the specific cell-mediated immune response is discussed.

Animals↗
PubMed1981

T cell-mediated immunity to oncornavirus-induced tumors. IV. Preliminary evidence for a specific suppression of anti-Moloney cell-mediated immune response by autoimmune T cells.

Previous reports have demonstrated that adult C57BL/6 mice infected with murine sarcoma virus (MSV) develop a strong cell-mediated immune response against Friend, Moloney, Rauscher virus-induced type-specific (FMR) antigens and reject their tumors. To demonstrate a possible role for auto-anti-MSV T blasts, syngeneic C57BL/6 mice were immunized with highly enriched anti-FMR cytolytic T cells. One of 3 pools of these autoimmune T cells prepared from 12 surviving immunized mice (a) inhibited specifically the in vitro anti-MSV cytolysis generation and (b) enhanced drastically the MSV tumor growth in vivo. The possibility for such an immunization procedure to induce anti-idiotype T cells, the repeatability of this effect and the relationship of the suppressor cells with antigen-specific suppressor cells and other components of the anti-MSV immune response are discussed.

Animals↗
PubMed1981

Typing of murine cell-surface antigens by cellular radioimmunoassay.

A cellular radioimmunoassay utilizing 125I-labelled Protein A was used for detecting antigen-antibody complexes on glutaraldehyde fixed cells attached to microtiter plates. This method is rapid, sensitive and specific for revealing H-2 private and public specificities as well as Ia and Lyt antigens. As plates may be kept for months, several reactivities can be tested in one step on a large panel rendering a regular supply of animals unnecessary.

Animals↗
PubMed1980

T cell-mediated immunity to oncornavirus-induced tumors. I. Ly phenotype of precursor and effector cytolytic T lymphocytes.

Regression of tumor induced by murine sarcoma virus (MSV) is accompanied by the formation of specific cytolytic T lymphocytes (CTL). Selection of T-cells sets by Ly phenotype determination allows separation of T sets involved in the cytolytic reaction. After MSV inoculation we demonstrate that a) Ly123+ cells contain precursors of CTL, b) direct cytolysis is mainly mediated by Ly23 cells, 3) cytolytic memory is divisible into "early" memory, carried by Ly23 cells, and "late" memory, which reverts to an Ly123 precursor population, and d) Ly1 cells are required to induce anti-MSV antibody formation.

Animals↗
PubMed1980

T cell-mediated immunity to oncornavirus-induced tumors. II. Ability of different T cell sets to prevent tumor growth in vivo.

These studies demonstrate that two different types of protective immunologic reactions are generated in mice after inoculation with M.MSV. Type I protection, mediated by Ly1 cells, prevents MSV-induced sarcomas but has no effect on the growth of MLV+ lymphomas. This anti-MSV protection reflects induction of antivirion antibody and delayed type hypersensitivity reaction. Type II protection is mediated by Ly23 cells and prevents the growth of an MLV+ lymphoma, but has little or no protective effects against MSV-induced sarcomas. This "type II" reaction is directly related to CTL activity. The implications of these two protective reaction are discussed.

Animals↗
PubMed1979

Analysis of absorption spectra changes induced by temperature lowering on phycobilisomes, thylakoids and chlorophyll-protein complexes.

Using fourth derivative analysis, differences between room and low temperature absorption spectra were studied. The positions of most absorption bands of the water-soluble, accessory pigment complex, the phycobilisome, remained unchanged after cooling. The stability of the wavelength positions of chlorophyll a forms in vivo as a function of temperature (Gulyaev, B.A. and Litvin, F.F. (1967) Biofizika 12, 845--854) was generally confirmed. The wavelength positions of all chlorophyll a forms in the P-700 chlorophyll a protein complex were unchanged when the preparations were cooled to -196 degrees C. Likewise, with other chlorophyll-containing materials: the light-harvesting chlorophyll a/b protein complex and the thylakoids of higher plants, algae, and cyanobacteria, the wavelengths positions of most chlorophyll a forms were stable upon cooling. An exception was a 680 nm chlorophyll a band which was generally split at low temperature into two bands with the materials investigated. An interpretation of the multiplicity of chlorophyll spectral forms and the spectral changes induced by cooling for these forms is given using exciton theory and the energy-coupling variation of chlorophyll a molecules.

Chlorophyll↗
PubMed1979

Direct evidence that natural killer cells in nonimmune spleen cell populations prevent tumor growth in vivo.

Relatively large numbers of nonimmune spleen cells do not protect against the local growth of two lymphomas. However, this heterogeneous population of splenic lymphocytes contains a subset of cells that efficiently protects against in vivo tumor growth. This cell population (cell-surface phenotype Thyl.2(-)Ig(-)Ly5.1(+)) represents less than 5 percent of the spleen cell population and is responsible for in vitro NK-mediated lysis. Although these studies clearly and directly demonstrate that Ly5(+) NK cells selected from a heterogeneous lymphoid population from nonimmune mice can protect syngeneic mice against local in vivo growth of two different types of tumor cells (in contrast to other lymphocyte sets within the spleen), they do not directly bear upon the role of NK cells in immunosurveillance. They do indicate that highly enriched Ig(-)Thyl(-)Ly5(+) cells, which account for virtually all in vitro NK activity, can retard tumor growth in vivo. It is difficult to ascribe all anti-tumor surveillance activity to NK cells, because they probably do not recirculate freely throughout the various organ systems of the body. Perhaps NK ceils may play a role in prevention of neoplastic growth within discrete anatomic compartments where there is rapid differentiation of stem cells to mature progeny (e.g., bone marrow, spleen, and portions of the gastrointestinal tract)and may normally act to regulate the growth and differentiation of non-neoplastic stem cells. Long-term observation of chimeric mice repopulated with bone marrow from congenic or mutant donors expressing very low or very high NK activity may help to answer these questions.

Animals↗
PubMed1975

Immune rejection of tumor cells: in vivo significance of anti-tumor in vitro immune reactions.

The mechanism of immune tumor rejection remains poorly understood. The respective roles of antibodies, macrophages, cytolytic T cells (CTL) and that of "K" cells or any other cell which could be involved in antibody dependant cell mediated cytotoxicity are still unknown. It is probable that the CTL play some role in tumor rejection but the "in vivo" relevance of the other, "in vitro" detected phenomena, is less clear. The correlations between "in vivo" tumor rejection and "in vitro" detected reactions are very difficult to establish, specially for the following two reasons: a) the different methods used in vitro do not explore identical phenomena ; b) some of them provide both specific and non-specific reactions.

Aging↗