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D H Lynch

Publications and source records attributed to D H Lynch.

At least 91 records · Page 5Linked to original sources
PubMed1990

The use of transfected fibroblasts and transgenic mice establishes that stimulation of T cells by the Mycoplasma arthritidis mitogen is mediated by E alpha.

Mycoplasma arthritidis produces a soluble protein which is active for murine and human lymphocytes when presented by Ia-bearing accessory cells. By using fibroblasts transfected in vitro with various class II Ag, we demonstrated that presentation of the M. arthritidis mitogen (MAM) to T cells was mediated by E alpha-containing molecules. We also showed that splenocytes from transgenic mice expressing E alpha heterozygously (B10.TRG E alpha+) or homozygously (B10.E alpha TG +/+) underwent a similar proliferation in response to MAM as compared with the failure of control B10.TRG E alpha- splenocytes to respond to MAM. Although splenocytes from inbred C3H and CBA mice exhibited much higher proliferative responses to MAM than did those from B10.TRG.E alpha+ or B10.E alpha TG +/+ mice, flow cytometry showed similar levels of E alpha expression. Furthermore, gamma-irradiated splenocytes from B10.TRG E alpha + mice presented MAM to T hybridoma cells with a similar efficacy as did splenocytes from C3H mice. The lesser response to MAM of lymphocytes from the E alpha transgenic mice as compared with those from C3H and B10.K mice was likewise not due to differential expression of their V beta TCR. We conclude that presentation of MAM to T cells is accomplished by E alpha-containing molecules. The studies also suggest that the conserved, nonpolymorphic regions of class II molecules may play an important role in host immune response to microbial products.

Animals↗
PubMed1989

Systemic immunosuppression induced by photodynamic therapy (PDT) is adoptively transferred by macrophages.

Some derivatives of hematoporphyrins are strongly retained by tumor tissue as compared to normal tissue, and exposure of these photosensitizers to radiation in the visible spectrum can cause serious biological damage. These properties have been exploited in the development of a new treatment for cancer termed photodynamic therapy (PDT). However, recent studies have also demonstrated that PDT can also induce a state of systemic immunosuppression. The purpose of this study was to determine whether PDT-induced suppression of contact hypersensitivity (CHS) responses was an active phenomenon that could be adoptively transferred by viable splenocytes from PDT-treated mice. Although induction of adoptively transferable suppressor cells in PDT-treated mice required exposure to antigen, the suppressor cells were found to be antigen nonspecific in their function. Furthermore, splenocytes from PDT-treated mice were capable of generating levels of allospecific cytotoxic T lymphocyte (CTL) activity which were comparable to those generated by normal control mice, but the ability of irradiated spleen cells from PDT-treated mice to stimulate a mixed lymphocyte response (MLR) was dramatically impaired. Finally, chromatographic separation of T cells, B cells and macrophages showed that the cell type which mediates adoptively transferable suppression of CHS responsiveness is in the macrophage lineage.

Animals↗
PubMed1988

Effect of Mlsa on antigen presentation to class II-restricted T cells.

The nature of the gene products encoded or regulated by the minor lymphocyte-stimulating (Mls) loci remains enigmatic despite extensive experimental evaluation. This work tested the hypothesis that the Mlsa genotype, when compared to the Mlsb genotype, facilitates Ag presentation to class II-restricted T cells. Titrated numbers of H-2-identical, Mls-disparate APC were used to stimulate proliferation of autoreactive, alloreactive, or Ag-specific class II-restricted T cell clones or lines. Apparent preferential presentation by Mlsa vs Mlsb APC obtained from H-2-identical strains was seen infrequently, and when observed, analysis with the use of APC from recombinant inbred lines revealed that preferential presentation did not correlate with the Mls genotype of the APC. These studies show that the Mlsa genotype does not influence overall Ag presentation to class II-restricted T cells.

Animals↗
PubMed1988

Systemic immunosuppression induced by peritoneal photodynamic therapy.

Although photodynamic therapy is being used increasingly for the diagnosis and treatment of human cancer, its effect on immune responses has received little attention. This aspect was examined in a murine model. Mice given peritoneal photodynamic therapy had markedly decreased contact hypersensitivity responsiveness, not observed with cutaneous photodynamic therapy. The immunosuppression was systemic, because contact hypersensitivity was depressed at distal, unirradiated sites. Photodynamic therapy induced adoptively transferable cells that inhibited contact hypersensitivity responses in naive mice. The immunosuppression was reversible, but persisted for 3 weeks after photodynamic therapy. An acute-phase response characterized by leukocytosis and elevated serum amyloid P levels was observed in mice given photodynamic therapy but not in mice treated with either laser or dye alone. These data suggest a link between the acute-phase response and immunosuppression. Thus, although photodynamic therapy shows promise in cancer treatment, the induction of decreased systemic immunoresponsiveness is an important observation with potentially detrimental consequences.

Acute-Phase Reaction↗
PubMed1987

Different specificities of cloned T cells assessed by in vitro proliferation assays and by the ability to mediate skin graft rejection in vivo.

The experiments presented here have compared the specificities of T cell clones as determined by in vitro proliferative responses and their specificities as reflected by their ability to mediate skin graft rejection in vivo. Two proliferative T cell clones with distinct in vitro specificities were evaluated for their ability to mediate rejection of skin grafts from C57BL/10 Scn nu/nu mice. Clone 14.11 (L3T4+, Lyt2-) was specifically stimulated to proliferate in vitro by I-Ad determinants, while clone 3.3.10 (also L3T4+, Lyt2-) recognized M1sa products in the context of MHC-encoded cell surface determinants. The results demonstrate that both clone 14.11 and clone 3.3.10 T cells are capable of mediating rejection of DBA/2 (H-2d, M1sa) skin grafts from B10 nu/nu mice. Surprisingly, neither clone 3.3.10 T cells nor clone 14.11 T cells were found to be effective at rejecting skin grafts from the D1.C congenic donor strain of mice (also H-2d, M1sa) from B10 nu/nu mice. Further, clone 14.11 T cells were also found to be ineffective at rejecting B10.D2 (H-2d, M1sb) skin grafts from B10 nu/nu mice. These data indicate the existence of a striking dichotomy between the specificity of alloreactive T cell clones as determined by in vitro proliferation studies and their functional capabilities in vivo.

Animals↗
PubMed1987

Oncogenes and cancer.

Early studies designed to investigate the molecular basis of oncogenesis indicated the existence of discrete genes which could cause neoplastic transformation of normal cells in vitro. These genes (which became known as oncogenes) were originally thought to be derived from oncogenic retroviruses and neoplastic transformation was believed to be the result of infection of normal cells by an oncogenic retrovirus. However, recent studies have demonstrated that normal eukaryotic cells contain gene sequences which are highly homologous to oncogenes but which do not cause neoplastic transformation. These genes (termed proto-oncogenes) have been found to code for proteins which are intimately involved in the regulation of mitosis. These include growth factors, receptors for growth factors, proteins (such as protein kineses and GTP binding proteins) which transduce exogenous signals through the plasma membrane, and nuclear binding proteins. Thus, if the function or control of a proto-oncogene (or its product) is altered by mutation, gene rearrangement, or translocation, its effects on the cell will also change. This, in turn, can lead to the loss of normal mitotic control. The tumorigenic process is, of course, much more complicated that just unchecked cell growth. However, the insights into the molecular basis of cellular regulation have suggested new approaches to the early diagnosis of cancer and may ultimately lead to the development of more effective treatment protocols.

Animals↗
PubMed1986

Cell-mediated immune responses to syngeneic tumors. I. Identification of two distinct CTL effector pathways which differ in antigen specificity, genetic regulation, and cell surface phenotype.

It has been demonstrated previously that draining lymph nodes (DLN) from tumor-immunized mice contain a population of lymphoid cells that are capable of differentiating into functional antitumor cytotoxic T lymphocytes (CTL) during in vitro culture. In the present studies, it was observed that DLN cells from either C57BL/10 (B10) or C3H mice that had been footpad-immunized with syngeneic tumor cells differentiated into CTL during a 4-day in vitro culture in the absence of added antigen. The specificity patterns of the CTL thus generated, however, were quite different in the two strains. DLN from B10 mice immunized with ultraviolet light-induced fibrosarcoma cells of B10 origin differentiated into CTL which were only capable of lysing target cells from the tumor used for immunization. Thus, the antitumor CTL which differentiate from B10 DLN appeared to be specific for the tumor-specific antigen (TSA) expressed by these tumor cells. In contrast, DLN from C3H mice immunized with a syngeneic ultraviolet light-induced fibrosarcoma differentiated into CTL which effectively lysed not only target cells from the immunizing tumor, but several other fibrosarcomas of both B10 and C3H origin, and which did not lyse normal nontumor targets. These C3H effectors thus appeared to be specific for a tumor-associated antigen (TAA) which is widely shared by a number of tumors. Cold target-blocking studies demonstrated that the CTL generated by C3H DLN cells contained a subpopulation of TSA-specific cells in addition to cross-reactive TAA-specific effectors. (B6 X C3H)F1 (B6C3F1) mice generated cross-reactive TAA-specific CTL in response to in vivo challenge with either B10 or C3H tumors, indicating that the ability to generate a TAA-specific CTL response behaves as a dominant trait of the responding mouse strain and not as a function of the tumor used for immunization. TSA-specific CTL and cross-reactive TAA-specific CTL were distinguishable on the basis of their cell surface phenotypes, because the TSA-specific CTL generated by B10 DLN cells were Thy-1.2+ Lyt-2.2+, whereas TAA-specific B6C3F1 CTL were Thy-1.2+ Lyt-2.2-; alloantigen-specific CTL generated from the same B6C3F1 lymph nodes were Thy-1.2+ Lyt-2.2+.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

Cross-reactive recognition by antigen-specific, major histocompatibility complex-restricted T cells of a mitogen derived from Mycoplasma arthritidis is clonally expressed and I-E restricted.

In order to determine whether or not the major histocompatibility complex (MHC)-encoded restriction element used by a T cell in the recognition of its primary antigen affected its ability to be cross-reactively stimulated by MAS (a soluble product of Mycoplasma arthritidis), a panel of cloned, soluble antigen-specific I-A- and I-E-restricted T cells were tested for their ability to cross-reactively recognize and respond to MAS. Initial studies indicated that all of the cloned T cells tested were capable of responding to MAS in the presence of genetically E alpha E beta-expressing (I-E+), but not E alpha E beta-non-expressing (I-E-) accessory cells (AC). However, subsequent studies demonstrated that the ability of most of these T cell clones to mount proliferative responses to MAS in the presence of I-E+ AC was dependent upon the presence of Lyt-1+2- T cells in the irradiated spleen cells which were used as AC sources. When T cell-depleted, I-E+ populations of spleen cells or an I-E+ antigen-presenting line (WEHI-5) were used as AC sources, only 6 of the 34 clones tested were found to be directly responsive to MAS. Subsequent to stimulation by MAS plus I-E product, these MAS-reactive T cell clones were capable of "recruiting" bystander T cells to proliferate. Finally, the ability of a given T cell clone to respond to MAS plus I-E product did not appear to be influenced by the restriction element used by that clone in its response to other antigens since both I-A-restricted and I-E-restricted T cell clones were responsive to MAS plus I-E in equivalent proportions. Thus, the data presented indicated that I-E-restricted T cell reactivity to MAS is a clonally expressed property of T cells that is independent of their conventional antigen specificities and MHC restriction patterns.

Animals↗
PubMed1985

T cell responses to Mls determinants are restricted by cross-reactive MHC determinants.

The studies presented here investigated the relationship between T cell recognition of MHC-encoded products and non-MHC-linked Mls determinants. The first aspect addressed whether Mls-reactive T cells recognize Mls-encoded products alone or in association with MHC-encoded determinants. Initial studies used Mlsa-specific T cell clones that were generated by repeated stimulation of C57BL/6 or B10.A(5R) spleen cells with DBA/2 lymphoid cells. These clones recognized Mlsa on cells expressing MHC products of the H-2b, H-2d, and H-2k haplotypes, but not the H-2q haplotype. Thus, these cloned T cells were found to recognize Mlsa products in association with public but demonstrably polymorphic H-2 determinants. The question of whether T cell clones that were specific for self-H-2 determinants (autoreactive) or soluble antigen plus syngeneic H-2 (antigen-specific) could also be stimulated by Mlsa determinants was also addressed. A substantial proportion of the antigen-specific or autoreactive T cell clones tested were stimulated by Mlsa determinants. Furthermore, stimulation of these clones by Mlsa was H-2 restricted. The pattern of H-2-restricted recognition of Mlsa by these clones was not distinguishable from that observed in the Mlsa-specific T cell clones, nor was it influenced by the primary specificity or H-2 restriction pattern of a given clone. Although these findings provide a means of explaining the observation that Mls-reactive T cells exist at extremely high precursor frequencies, they also raise questions regarding the nature of the receptor structures which are used by a single T cell in the recognition of two or more apparently distinct stimuli.

Animals↗
PubMed1983

Evaluation of naturally occurring cell-mediated cytotoxic activity in normal and UV-irradiated mice.

The levels of NCMC activity residing in the spleens of normal and UV-irradiated mice (subsequent to augmentation with polyinosinic.polycytidylic acid [poly I.C]) were evaluated using tumor target cells from both lymphoid and solid tumor sources. Early in the UV-irradiation protocols a low-level, transient depression in NCMC function was detected. The levels of NCMC activity in mice that had received daily UV-exposures for a period of 5-10 weeks, however, were found to be equivalent to, or greater than, those detected in normal mice. Furthermore, regressor and progressor tumor cell lines that had been cloned from individual UV-induced tumors exhibited low, but similar, levels of sensitivity to NCMC cells obtained either from normal or from UV-irradiated mice. Poly I.C treatment of normal and UV-irradiated mice was found to have no effect on the outcome of subsequently implanted UV-induced regressor tumors; normal and poly I.C pretreated normal mice rejected the tumor implants, although both untreated and poly I.C pretreated, UV-irradiated mice grew the tumors at equivalent rates.

Animals↗
PubMed1983

Abrogation of epidermal antigen-presenting cell function by ultraviolet radiation administered in vivo.

The exposure of animals to ultraviolet radiation (UVR) can result in dramatic alterations to their immunologic potential. Loss of ability to be contact-sensitized to skin-reactive chemicals applied to UVR-exposed surfaces, and an enhanced susceptibility to tumors induced by UVR represent two well-documented effects of such exposure. The skin Langerhans' cell (LC) is a cell type, having antigen presentation capabilities, which is functionally inactivated by UVR. The localized loss in the ability to induce a contact hypersensitivity (CS) response and the early events associated with the acquisition of a tumor-susceptible state have been hypothesized to involve LC inactivation by UVR. In this report we have investigated the relationship between the UVR-mediated loss of CS responsiveness and antigen-presenting cell (APC) function by LC following in vivo exposure of animals to UVR. The UVR-mediated loss of CS responsiveness was found to be both time-dependent and dosage-dependent, but the loss of epidermal APC function following the UVR exposure of dissociated epidermal cells or skin was immediate and dosage-dependent. The lack of time dependency associated with the loss of epidermal APC function may be due to the nature of the assay system being employed. Add-back experiments, using the proliferation of purified antigen-primed T-cells as a read-out system to evaluate APC function, require that the accessory cell be totally functional. Initiation of CS responses may still be possible, however, with LC that are partially UVR-inactivated. Lymph-node-associated and circulating accessory cells could be integrated into the response, providing any necessary components that the UV-inactivated LC lacks. We tested this possibility and conclude from these studies that this is indeed a viable possibility. Our results, therefore, provide a possible explanation for apparent differences in LC UVR susceptibility observed when in vitro and in vivo assays are employed.

Animals↗
PubMed1983

The effects of high-dose UV exposure on murine Langerhans cell function at exposed and unexposed sites as assessed using in vivo and in vitro assays.

Exposure of mice to a single large dose of UV radiation leads to a systemic inability of these mice to develop effective contact hypersensitivity (CS) responses to epicutaneously applied dinitrofluorobenzene (DNFB). Although this effect requires time to develop when unirradiated skin sites are used for CS sensitization, it is observed immediately at the site of UV exposure. Unirradiated skin sites on mice exposed to a single large dose of UV radiation 3 days previously were found to contain histochemically detectable ATPase+ cells with normal morphology and in normal densities, and yet CS responses were not induced to DNFB applied to these sites. Epidermal cells (EC) obtained from these skin sites were found to be capable of providing accessory cell (AC) function in in vitro T-cell proliferation assays that was qualitatively similar to EC obtained from unirradiated mice, thus indicating that exposure of mice to a single large dose of UV radiation does not induce a systemic AC dysfunction. Indeed, increased levels of AC activity were obtained in EC prepared from the UV-irradiated skin sites on the third day following UV exposure. This latter effect may be due to an influx of inflammatory cells into the irradiated site in response to the tissue damage caused by the UV radiation. We hypothesize that the inflammatory response induced by the cytodestructive effects of the UV treatment may play a central role in the generation of the systemic suppression of induction of CS responses, perhaps through the induction of acute-phase proteins.

Adenosine Triphosphatases↗
PubMed1983

T cell proliferative responses to a mitogen derived from Mycoplasma arthritidis are controlled by the accessory cell.

Cell-free supernatants from broth cultures of Mycoplasma arthritidis (MAS) induce vigorous proliferative responses in thymus-derived T lymphocytes from H2k or H2d strains of mice. Populations of lymphoid cells from mice of H2b, H2q, or H2s haplotypes do not respond to this stimulus. Previous studies with lymphoid cells from congenic and recombinant strains of mice indicate that the T cell proliferative response induced by MAS is controlled by a gene(s) that maps to the I-E/C subregion of the murine major histocompatibility complex (MHC). The T cell proliferative response induced by MAS is dependent upon the presence of a population of la+, radioresistant accessory cells (AC). Data presented here demonstrates that responder strain AC that have been pulsed with MAS (followed by extensive washing) induced vigorous proliferative responses in subsequently added T cell populations. Pulsing of T cells with MAS, followed by the addition of AC, however, did not result in T cell proliferation. MAS was found to stimulate (responder X nonresponder) F1 T cells to proliferate if the MAS was presented in the context of either responder or (responder X nonresponder) F1 AC; nonresponder strain AC were ineffective in this regard. Nonresponder strain T cells were found to be capable of responding to MAS if it was presented in the context of responder strain AC, even if the T cells and AC were completely allogeneic. Thus, nonresponder strain T cells mounted vigorous proliferative responses if the MAS was presented in the context of responder strain AC. Conversely, responder strain T cells did not respond to MAS presented in the context of nonresponder strain AC. In addition, lymphoid cells from a B10 leads to B6AF1 radiation bone marrow chimera were also found to be capable of responding to MAS, but only in the presence of AC that expressed cell surface determinants controlled by the I-E/C subregion. The data presented here indicate that MAS-induced T cell proliferative responses are controlled at the level of the AC by a gene(s) that maps to the I-E/C subregion of the MHC.

Animals↗
PubMed1982

Changes in antigen-presenting cell function in the spleen and lymph nodes of ultraviolet-irradiated mice.

It has been previously reported that mice exposed to ultraviolet (UV) radiation exhibit a decrease in splenic antigen-presenting cell (APC) function. The results presented here confirm this observation and further demonstrate that animals exposed daily to UV for extended periods of time (5 weeks instead of 6 days) no longer exhibit this depressed capability. In spite of the depression in splenic APC activity found in 6-day UV-irradiated mice, lymph node APC function from these same animals was elevated compared with that found in the lymph nodes from normal animals. Lymph node APC activity in animals that were splenectomized prior to the UV irradiation, however, was not enhanced over controls. Treatment of animals with a chemical irritant (turpentine) also caused a depression in splenic APC function without modifying lymph node activity. Collectively, our findings suggest that the observed decrease in splenic APC activity, found after the first week of UV exposures, may be attributable to the migration of splenic APC to peripheral lymphoid tissue which drain the site of epidermal inflammation.

Animals↗
PubMed1982

Cell-mediated immune responses to syngeneic ultraviolet-induced tumours. V. Assessment of accessory and antigen-presenting cell capabilities of normal and ultraviolet-irradiated mice in the generation of anti-tumour cytotoxic effector cells in vitro.

Draining lymph nodes (DLN) from tumour immunized mice were found to contain a population of radiation resistant, Thy 1-, Ia+ antigen-presenting cells (APC) which can stimulate normal lymphocytes to differentiate into anti-tumour CTL in vitro. APC from both normal and ultraviolet (u.v.)-irradiated tumour immunized animals were compared and exhibited equivalent functional capabilities. DLN from tumour immunized u.v.-irradiated animals were also found to contain primed T cells which could differentiate into functional anti-tumour cytotoxic T lymphocytes (CTL) with the same kinetic profile as DLN cells from normal tumour immunized mice. These results indicate that u.v. irradiation does not cause a generalized depression in either the capability of APC in u.v.-irradiated mice to process and present tumour antigens, or in the ability of u.v.-exposed animals to be primed to tumour antigens. A decrease in splenic accessory cell function was detected in animals which had received 1 week of daily 30 min u.v. exposures. The decrease in splenic accessory cell function appears to be transient, however, as no decrease in this capability was found in splenic cells obtained from animals which had received daily u.v. exposures for longer periods of time (5 weeks to 5 months). Finally, the spleens of u.v.-irradiated, tumour-bearing mice were found to contain a population of cells which could impart partial protection against tumour growth in vivo. The results of the experiments presented here indicate that normal and u.v.-irradiated animals are capable of responding similarly in the afferent phases of immune responses to syngeneic tumour antigens, and suggest that u.v.-induced T-suppressor cells mediate their immunoregulatory effects at a stage late in the generation of effective anti-tumour immune responses.

Animals↗
PubMed1981

Experimental photoimmunology: immunologic ramifications of UV-induced carcinogenesis.

The use of animal model systems to investigate the sequence of events which lead to the induction and progression of skin tumors following chronic ultraviolet light (UVL) exposure has clearly shown that the direct mutagenic effects of UVL is only one of the components involved in this process. In spite of the fact that overt carcinogenesis is only one of the many effects produced by UV light, most hypotheses as to the mechanism by which UVL can cause the mutations necessary to achieve the transformed phenotype have focused on the direct effects of UVL on DNA and the generation of carcinogenic compounds. Investigations during the last 5 yr, however, have clearly demonstrated that immunologic factors are also critically important in the pathogenesis of UV-induced skin cancers. A complete understanding of UV-carcinogenesis must therefore consider the mechanisms which allow the transformed cell to evade immunologic rejection by the host in addition to those aspects which deal with conversion of a normal cell to a cancer cell. It is the object of this review to provide both a historical account of the work which established the immunologic consequences of chronic UVL exposure and the results of recent experiments designed to investigate the kinetics and mechanisms by which UVL affects the immunologic apparatus. In addition, a hypothetical model is presented to explain the sequence of events which ultimately lead to the emergence of the suppressor T-cells which regulate antitumor immune responses.

Animals↗