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Biomedical subjects

F W Fitch

Publications and source records attributed to F W Fitch.

At least 145 records · Page 8Linked to original sources
PubMed1980

Monoclonal anti-acetylcholine receptor antibodies can cause experimental myasthenia.

Myasthenia gravis (MG) is a disease which occurs as a consequence of an autoimmune response directed against the nicotinic acetylcholine receptor (AChR) of the myoneural junction. Antisera raised against complex antigens such as AChR comprise a mixture of antibodies reactive with various determinants on the antigen molecule. The antibodies against any single determinant may be of several immunoglobulin classes and idiotypes. Antibodies produced by cloned lymphocyte-myeloma hybridoma cell lines have provided a way of analysing the diverse components making up a polyclonal antiserum and assessing the relative contribution made by each to the overall immune reaction in vivo. We have applied this technique to the investigation of the autoimmune response in MG. We demonstrate here that certain monoclonal anti-Torpedo AChR antibodies, when injected intravenously into normal rats, induce an acute myasthenic syndrome. Thus binding of a single molecular species of antibody reactive with a single antigenic determinant can result in all of the manifestations of an autoimmune disease.

Acetylcholine↗
PubMed1980

Monoclonal rat anti-major histocompatibility complex antibodies display specificity for rat, mouse, and human target cells.

24 monoclonal rat antibodies are described that are reactive with determinants encoded by the major histocompatibility complex (MHC) of the rat. These hybridoma antibodies were derived by fusing mutant mouse myeloma cells to spleen cells from Lewis rats immunized with allogeneic Brown Norway cells. All 24 antibodies are cytotoxic for both Brown Norway target cells and target cells from the appropriate MHC congenic rats. Pattern of cytotoxicity and hemagglutination strongly suggest reactivity against class I (K or D equivalent) rat MHC determinants. Cytotoxic cross-reactivity patterns were generated for each monoclonal antibody on a panel of rat and mouse lymphoid cells and human peripheral T lymphocytes. A high degree of interspecies cross-reactivity was noted with approximately one-half of the antibodies positive on human and/or mouse target cells. 11 antibodies recognized polymorphic determinants in the mouse, and, by using target cells from MHC congenic mouse strains, it was shown that these determinants are encoded by genes within the H-2 complex. Finally, by considering the overall reactivity patterns of these monclonal antibodies on all target cells, one can show that these 24 antibodies represent a minimum of 14 antibody specificities.

Animals↗
PubMed1980

Alloreactive cloned T cell lines. I. Interactions between cloned amplifier and cytolytic T cell lines.

Several T cell clones have been derived by limiting dilution of secondary mixed leukocyte culture cells stimulated by H-2- and M locus (Mls)-disparate spleen cells. When examined for the expression of cytolytic activity and the ability to proliferate, these cell clones can be classified into two major categories. One type of cell is noncytolytic; when cultured with irradiated spleen cells, such clones proliferate in response to Mls determinants. Some, but not all, of these clones express Lyt-1 alloantigens. The other type of cell is cytolytic; these clones do not proliferate when cultured with irradiated allogeneic spleen cells unless supernatant fluid (SF) is added. These cytolytic clones express Lyt-2 alloantigens. Some cytolytic clones are specific for H-2Kd and others for H-2Dd alloantigens. Still other cytolytic cell clones exhibit cross-reactive lysis of different H-2-bearing tumor and Con A blast target cells. Noncytolytic T cell clones, when stimulated by Mls antigens, were examined for their ability to promote proliferation of cytolytic T cell clones. All of the noncytolytic cell clones tested were able to promote proliferation of cytolytic cell clones with the concomitant expression of cytolytic activity directed toward the original stimulating alloantigen (H-2d). Amplification of cytolytic activity was dependent upon stimulation of the noncytolytic amplifier T cell clones by Mls antigens. Specific alloantigen (signal 1), however, was not required for proliferation of the cytolytic cell clones; the amplifying signal (signal 2), delivered by the amplifier cell clones, was sufficient alone to promote proliferation of the cytolytic cell clones. Whereas proliferation of the amplifier cells was radiosensitive, the generation of the soluble amplifying signal was radioresistant. Amplification of cytolytic activity was observed when either amplifier cells were physically separated from responding cytolytic cells in Marbrook cultures or when cytolytic cells were cultured with SF collected from amplifier cell cultures. The amplifying factors were neither antigen specific nor strain specific and could be produced by Lyt-1- cells. The availability of cloned T cell lines that retain specific biologic function offers unique opportunities to characterize cell surface proteins and cell-cell interactions.

Animals↗
PubMed1980

Monoclonal antibodies to estrophilin: probes for the study of estrogen receptors.

Splenic lymphocytes from a Lewis rat, immunized with purified estradiol-receptor complex of calf uterine nuclei, were fused with cells of three different mouse myeloma lines (P3-X63-Ag8, P3-NSI/I-Ag4-1, and Sp2/0-Ag14) to yield hybridoma cultures, 9% of which produced antibodies to the receptor protein (estrophilin). When cloned by limiting dilution, approximately 70% of the viable cultures secreted antiestrophilin antibody. When expanded in suspension culture, three clones derived from Sp2/0-Ag14 were found to secrete rat IgG (gamma 2a class), whereas seven other clones (from all three myeloma lines) secreted IgM. Monoclonal IgG shows comparable affinity for nuclear and extranuclear receptors, whereas IgM reacts preferentially with the nuclear form. Both classes of antibody react with unoccupied as well as with occupied receptor and do not interfere with its ability to bind to estradiol. By growing IgG-secreting clones in the presence of [35S]methionine, radiolabeled monoclonal antiestrophilin has been prepared. Unlike antiestrophilin antibody previously generated in the rabbit or the goat, which crossreacts with estrogen receptors from every animal species tested, antibodies produced by the Lewis rat and by hybridomas derived from its spleen cells react specifically with estrophilin from calf tissues. These monoclonal antibodies provide reagents for the application of immunochemical techniques to study estrogen receptors in calf target tissues.

Animals↗
PubMed1980

Cell surface polypeptides of murine T-cell clones expressing cytolytic or amplifier activity.

Murine cytolytic T-cell and amplifier T-cell clones derived from secondary unidirectional mixed leukocyte cultures were labeled with 125I by the lactoperoxidase method and their polypeptide profiles were analyzed by NaDodSO4/polyacrylamide gel electrophoresis. All cytolytic T-cell clones derived from the same mouse strain yeilded similar cell surface polypeptide profiles. However, profiles obtained with three amplifier T-cell clones were strikingly different from each other as well as from those of cytolytic T-cell clones. Comparison of these profiles with those obtained from mixed leukocyte culture cells, whole spleen cells, glass wool/nylon wool-purified splenic T-cells, and thymocytes indicates that cytolytic T-cell clones have a characteristic cell surface polypeptide profile that distinguishes this type of lymphocyte from most other lymphocytes.

Antigens, Surface↗
PubMed1980

IgG or IgM monoclonal antibodies reactive with different determinants on the molecular complex bearing Lyt 2 antigen block T cell-mediated cytolysis in the absence of complement.

Five rat monoclonal antibodies have been derived that express specificities for determinants present on the molecular complex bearing the Lyt 2 antigen. SDS-polyacrylamide gel electrophoresis of 125I-labeled polypeptides precipitated by each of these antibodies reveal 3 components (150,000, 75,000, and 33,000 daltons), and 2 components (44,000 and 33,000 daltons) when analyzed under nonreducing and reducing conditions, respectively. Two of these antibodies are IgG and are specific for the Lyt 2.2 determinant; the other 3 are IgM and react with determinants other than Lyt 2.2, which are nonpolymorphic. Each of the 5 antibodies can block the cytolytic activities of 5-day MLC cells or of cloned cytolytic T cells in the absence of C. Treatment of responding spleen cells with any of these antibodies and C inhibits the generation of cytolytic activity in MLC.

Animals↗
PubMed1980

Studies on stimulation of cell-mediated cytotoxicity by skin test antigens. I. Candida antigen stimulation of cell-mediated cytotoxicity in vitro correlated with the skin test response to candida antigen in vivo.

The magnitude of the skin test response in a group of normal volunteers to intradermal Candida antigen correlated closely with the level of cytolytic activity stimulated by Candida antigen in vitro in the peripheral blood lymphocytes from those same individuals. The cytolytic activity stimulated by Candida antigen was cell mediated, and cold target inhibition studies demonstrated that Candida antigen-stimulated effector cells were capable of cross-species (i.e., nonspecific) killing. Analysis of the Candida antigen-induced effector cell population for various cell markers did not enable absolute identification of the cell responsible for the killing. The findings in this study indicate that the stimulation of cell-mediated cytolysis by Candida antigen may be related to the delayed-type hypersensitivity response produced by the same antigen.

Animals↗
PubMed1979

An estimate of the minimal frequency of cytolytic T lymphocyte effector cells generated in allogeneic reactions.

A 'micro' modification of the standard 51Cr release assay was developed. With this assay, significant cytolysis was obtained employing 100--200 51Cr-labeled target cells and fewer than 100 lymphocytes obtained from mixed leukocyte cultures. A minimal estimate as to the actual frequency of effector cells was determined for both primary (1 cell in 30) and secondary (1 cells in 8) cytolytic T lymphocyte populations.

Animals↗
PubMed1979

Accessory cell requirements for the generation of cytolytic T lymphocytes.

A system is presented that may simplify the study of accessory cell requirements for CTL generation. Cortisone resistant (CR) thymocytes containing alloreactive CTL precursors do not respond to allogeneic tumor cells unless non-T accessory cells are added to culture. In addition, splenic T cells do not respond to allogeneic tumor cells in the absence of non-T accessory cells. These accessory cells share several properties of macrophages.

Animals↗
PubMed1979

Enhancement of rat renal allografts with monoclonal antibody.

Treatment of rat allograft recipients before grafting with donor spleen cells and whole, pooled antidonor alloimmune serum results in indefinite renal allograft survival. The enhancement is immunologically specific. In these experiments a monoclonal, homogenous anti-BN antibody was produced by a hybridoma clone created by fusing the mouse-P3 myeloma with spleen cells from Lewis rats immunized with BN lymphoid cells. The hybridoma supernatent enhanced survival of LBN renal allografts in Lewis recipients as effectively as whole Lewis anti-BN antiserum. Dilution of the hybridoma supernatent by tenfold or a hundredfold abrogated the enhancement effect.

Animals↗