Biomedical subjects

W E Klinkert

Publications and source records attributed to W E Klinkert.

At least 19 recordsLinked to original sources

PubMed2001

Anti-inflammatory activity of nerve growth factor in experimental autoimmune encephalomyelitis: inhibition of monocyte transendothelial migration.

In order to analyze a putative immunomodulatory effect of NGF in experimental autoimmune encephalomyelitis (EAE) of the Lewis rat, we transduced myelin basic protein (MBP)-specific CD4(+) T cells with a recombinant retrovirus encoding NGF. These T(MBP)NGF cells secreted high levels of NGF, along with an unaltered Th1-like cytokine pattern. Transfer studies showed that T(MBP)NGF cells were unable to mediate clinical EAE, when transferred alone, and, more important, they efficiently suppressed induction of clinical EAE by non-transduced MBP-specific T cells (T(MBP )cells). In contrast, NGF transduced ovalbumin-specific T cells, which secreted high NGF levels, did not affect EAE induction. Suppression of clinical EAE by T(MBP)NGF cells was associated with a general reduction of inflammatory CNS infiltrates, with a most pronounced decrease of the monocyte/macrophage component. Using a culture model of the endothelial blood-brain barrier (BBB), we found that NGF directly acts on blood-derived monocytes via the p75 NGF receptor, thus interfering with monocyte migration through the activated BBB endothelium. Our data establish NGF as an anti-inflammatory mediator interfering with T cell mediated autoimmune disease in the CNS. They further point to monocyte migration through blood vascular endothelium as one possible mechanism of NGF action.

Animals↗

PubMed2001

Bidirectional effects of corticosterone on splenic T-cell activation: critical role of cell density and culture time.

Glucocorticoids inhibit stimulus-induced T-cell proliferation, an early and essential parameter of cellular immunity. It was recently found however that physiological concentrations of glucocorticoids can also accelerate, not only inhibit, rat T-cell mitogenesis. We investigated mechanism(s) underlying mitogenic actions of glucocorticoids on anti-T-cell receptor (TCR)- and concanavalin A (Con A)-induced T-cell proliferation. Surprisingly, the ability of the glucocorticoid corticosterone (CORT) to either enhance or inhibit T-cell proliferation was found to depend primarily on the cell density and the timing of the cultures. At cell densities up to 1 x 10(5) cells/well (i.e. 'low' density), CORT inhibited T-cell proliferation irrespective of the culture time. In contrast, at cell densities of 2 x 10(5) cells/well and higher ('high' density), CORT potently stimulated T-cell mitogenesis during the first 2-3 culture days, but subsequently inhibited the proliferative response after 5-7 days. The glucocorticoid receptor antagonist RU486 completely abolished the effects of CORT. However, production of the main T cell growth factor interleukin (IL)-2 was inhibited by CORT at both 'low' and 'high' cell densities. In addition, irrespective of cell density, T-cell mitogenesis under either control conditions or in presence of CORT was completely blocked by an anti-IL-2-receptor-alpha-chain (IL-2Ralpha) antibody, indicating that T-cell proliferation was dependent on the IL-2 pathway. Immunofluorescence staining of IL-2Ralpha on CD4+ cells after 2-3 days in culture was increased by CORT, but only on cells cultured at 'high' density. Thus, glucocorticoids increase T-cell responsiveness to IL-2 under conditions of 'high' cell density only. We conclude that glucocorticoids may contribute to a more efficient early stage of cellular immune responses under conditions of intimate cell-to-cell contact (i.e. 'high' cell density), a situation likely to be present in vivo, for instance in lymph nodes. Thus, these findings are relevant to our understanding of the glucocorticoid control of immune function.

Animals↗

PubMed2000

Glucocorticoids regulate TCR-induced elevation of CD4: functional implications.

CD4 serves as a coreceptor during Ag recognition by the TCR. This interaction results in a marked increase in the sensitivity of a T cell to Ag presented by MHC class II molecules. Here we report that activation of T cells either by plate-bound mAb (anti-TCR, anti-CD3) or soluble activators (staphylococcal enterotoxin A, Con A) is associated with an (up to 3-fold) increase in CD4 cell surface expression on CD25+ cells, which was maximal after 72-96 h. Incubation with the glucocorticoid hormone corticosterone (CORT) shifted the enhancement of CD4 expression to a point about 24 h earlier than that observed in control cultures. In parallel, the proliferative response of these CORT-treated cells was profoundly enhanced. An involvement of increased CD4 expression in this enhanced proliferative response was evidenced by the observation that T cell proliferation in CORT-treated cultures was much less sensitive to inhibition by an inhibitory, nondepleting anti-CD4 mAb than that in control cultures. TCR down-regulation was, however, not affected by CORT. Thus, based on this study and previous reports we propose that both TCR-mediated signals and glucocorticoids are important physiological regulators of CD4 expression. In addition, these findings may be of significance for the sensitivity of CD4+ cells to HIV infection upon T cell activation, as the efficacy of primary patient HIV entry depends on the level of surface CD4.

Adjuvants, Immunologic↗

PubMed1999

Activated human T cells, B cells, and monocytes produce brain-derived neurotrophic factor in vitro and in inflammatory brain lesions: a neuroprotective role of inflammation?

Brain-derived neurotrophic factor (BDNF) has potent effects on neuronal survival and plasticity during development and after injury. In the nervous system, neurons are considered the major cellular source of BDNF. We demonstrate here that in addition, activated human T cells, B cells, and monocytes secrete bioactive BDNF in vitro. Notably, in T helper (Th)1- and Th2-type CD4(+) T cell lines specific for myelin autoantigens such as myelin basic protein or myelin oligodendrocyte glycoprotein, BDNF production is increased upon antigen stimulation. The BDNF secreted by immune cells is bioactive, as it supports neuronal survival in vitro. Using anti-BDNF monoclonal antibody and polyclonal antiserum, BDNF immunoreactivity is demonstrable in inflammatory infiltrates in the brain of patients with acute disseminated encephalitis and multiple sclerosis. The results raise the possibility that in the nervous system, inflammatory infiltrates have a neuroprotective effect, which may limit the success of nonselective immunotherapies.

Autoantigens↗

PubMed1999

A new antioxidative vitamin B6 analogue modulates pathophysiological cell proliferation and damage.

The new large scale synthesis of the yellow colored vitamin B6 analogue 5'-O-phosphono-pyridoxylidenerhodanine (2) (B6PR) leads to oligohydrates of its monosodium salt (4). The light-red hemiheptadecahydrate (8 1/2 hydrate) (4a) was crystallized and its three-dimensional structure determined by X-ray crystallography. Special nucleotide and protein interaction properties together with scavenging antioxidative function are combined in this simple water-soluble vitamin B6 analogues B6PR. High (mM) concentrations were untoxic to 'healthy' not affected cells and primary tissues. Complexation of ions (e.g. Ca2+, Fe2+, and Zn2+), modulation of nitric oxide synthases (NOS I-III), nitric oxide (NO) metabolism, and reactive oxygen species (ROS) was found. Special cytoprotecting, immunomodulating, stimulating and inhibiting activities were observed in vitro, not in comparison with some natural and synthetic pyridoxines. Low B6PR suppressed proliferation, high induced selective cell death of some cancer cell lines. Low B6PR protected HIV-1-infected CD4+ HUT 78 cells against HIV-1-mediated destruction (complete inhibition of HIV-1-induced syncytia formation and cell death) and reduced p24 level. Autoreactive S100beta-specific T cells of Lewis rat, a model of multiple sclerosis, could be influenced. Oxidative damage and age, acquired and inherited disease related pathophysiological disorders can be treated by this new cytopathology-selective versatile acting B6PR.

Animals↗

PubMed1998

A novel rat CC chemokine, identified by targeted differential display, is upregulated in brain inflammation.

A novel rat chemokine, termed ST38, was identified through its upregulation in ischemic brain tissue using a biased differential display technique targeting mRNAs with regulatory AUUUA-motifs typically found in transcripts of cytokine and immediate early genes. ST38 transcripts were transiently induced in ischemic cortex between 4 and 24 h after middle cerebral artery occlusion. ST38 is a member of the CC chemokine family, closely related to human Exodus-1. The gene of the mouse ST38 homologue was mapped to the central region of chromosome 1. In experimental autoimmune panencephalomyelitis ST38 expression correlated with the onset of inflammation and was significantly reduced by TNF-neutralization in vivo. Inflammatory stimuli induce ST38 transcription in astrocyte, microglia and macrophage cultures. These findings suggest a role of ST38 in the control of neuroinflammatory tissue responses.

Amino Acid Sequence↗

PubMed1997

TNF-alpha receptor fusion protein prevents experimental auto-immune encephalomyelitis and demyelination in Lewis rats: an overview.

To explore the therapeutic use of TNF-alpha inhibitors in human inflammatory demyelinating diseases we examined the effect of a recombinant TNFRp55 protein constructed by fusing TNFRp55 extracellular domain cDNA to a human IgG1 heavy gene fragment containing the hinge and constant domains CH2 and CH3 (TNFRp55-IgG1) in diverse experimental model systems representing inflammation and inflammatory demyelination of encephalitogenic T cells in vivo. In EAE actively induced by immunization of Lewis rats with MBP, a single dose of TNFRp55-IgG1 protected the recipient animals from clinical signs. Interestingly, the treatment neither prevented the formation CNS infiltrations, nor did it alter the cellular composition of the infiltrates. In EAE transferred by MBP specific activated T line cells, a model of inflammatory (not demyelinating) brain disease, the inhibitor's therapeutic effect on clinical disease was also striking achieving almost complete protection even after repeated transfers of encephalitogenic T cells. Finally, the recombinant inhibitor was also protective in Lewis rats with demyelinating experimental autoimmune panencephalitis produced by combined transfer of panencephalitogenic T cells and demyelinating monoclonal antibody specific for MOG. In this system, the T cells are of low encephalitogenic activity, but open the blood-brain barrier for the demyelinating immunoglobulins. The fusion protein treatment, however, prevented the formation of inflammatory lesions and demyelination. The strong therapeutic effect of the recombinant chimeric TNF-alpha inhibitor in three models of myelin specific autoimmunity raises hopes as to TNF-alpha directed therapy of human diseases like MS.

Animals↗

PubMed1995

Glucocorticoids accelerate anti-T cell receptor-induced T cell growth.

To study steroid regulation of cell-mediated immunity, we used anti-TCR-stimulated rat splenic lymphocyte mitogenesis as our experimental paradigm. Surprisingly, we found that the principal glucocorticoid of the rat, corticosterone (CORT), potently enhanced anti-TCR-induced lymphocyte proliferation after 2 to 3 days in culture, followed by inhibited cell growth after 5 to 7 days. Thus, glucocorticoids appeared to accelerate anti-TCR-induced lymphocyte mitogenesis. This effect occurred at physiologic concentrations (50-1000 nM), which are known to be released in vivo after an immune challenge. Kinetic experiments showed that CORT had to be present within 60 min after the initiation of TCR activation to produce maximal enhancing effects; a delay of 2 h or more left CORT ineffective. The lymphocytes incubated with CORT may have an increased sensitivity to IL-2 because 1) CORT suppressed IL-2 production throughout the culture period, and 2) an anti-IL-2R mAb completely blocked both control and CORT-treated anti-TCR-induced lymphocyte proliferation. Although the IL-2R alpha- and beta-chain mRNA concentrations were not altered in CORT-treated splenocyte cultures, we observed by FACS analysis an increased expression of the IL-2R alpha-chain on CORT-treated TCR alpha beta + and CD4+ T cells after 48 to 72 h of culture, suggesting an increased sensitivity of these T cells to IL-2 during the phase of enhanced proliferation. These results demonstrate a clear distinction between the enhancing effects of glucocorticoids on anti-TCR-induced lymphocyte proliferation and their well known inhibitory actions. Thus, the present study expands the regulatory role of glucocorticoids in cellular immunity, adding a novel effective stimulatory component to their inhibitory properties.

Animals↗

PubMed1993

Specific immune complexes augment in vitro acetylcholine receptor-specific T-cell proliferation.

We investigated the interaction between acetylcholine receptor (AChR)-specific T-helper cells from patients with myasthenia gravis and murine monoclonal anti-AChR antibodies. At optimal antigen concentration, anti-AChR antibodies neither enhanced nor impaired T-cell responses. However, at substimulatory antigen concentration, addition of anti-AChR antibodies substantially enhanced the proliferation of AChR-specific T cells. In spite of low amounts of antigen, immune complex formation allowed highly efficient capture and uptake of antigen via Fc receptors on antigen-presenting cells, which could be inhibited by an antibody to Fc receptors. Immune complex-mediated stimulation of sensitized AChR-specific T lymphocytes in vivo may contribute to the exacerbation of the disease, and demonstrates the interaction between T and B lymphocytes in myasthenia gravis.

Adjuvants, Immunologic↗

PubMed1992

Interaction between oligodendroglia and immune cells: mitogenic effect of an oligodendrocyte precursor cell line on syngeneic T lymphocytes.

We analyzed cellular interactions between T lymphocytes and a recently established immortal glial line, L3 that retains several properties of immature oligodendrocytes (Aloisi et al., J Neurosci Res 27:16-24, 1990). L3 oligodendrocytes (L3-OL) cannot be induced to express class II antigens, nor do they specifically present antigen to syngeneic specific T lymphocyte. However, L3-OL strongly enhance the proliferation of freshly activated, interleukin-2(IL-2)-dependent T-line lymphocytes and concanavalin A (ConA)-activated lymphoblasts, irrespective of their antigen specificity or surface phenotype (CD4+ or CD8+). Resting and some activated T cells were susceptible to the mitogenic effect of L3-OL only in the presence of exogenous IL-2, not of other cytokines. The mitogenic effect of L3-OL did not depend on cell viability. It was observed in paraformaldehyde-fixed L3-OL cells and in membrane preparations, but not in culture supernatant. Neither intact L3-OL cells nor membrane preparations had direct IL-2 activity. The conclusion that the mitogenic effect of L3-OL cells is exerted by membrane structures acting as a costimulatory factor(s) of IL-2 is supported by the finding that it is largely blocked by a monoclonal anti-IL-2 receptor antibody. The effect is distinct from membrane-bound IL-1, membrane-bound tumor necrosis factor-alpha (TNF-alpha), IL-3, or IL-6 and cannot be reconstituted by these cytokines.

Animals↗

PubMed1991

The thymus in myasthenia gravis. Changes typical for the human disease are absent in experimental autoimmune myasthenia gravis of the Lewis rat.

In human myasthenia gravis (MG) formation of autoantibodies against acetylcholine receptor (AChR) is commonly associated with thymic changes termed lymphofollicular hyperplasia (LFH). To learn whether the thymic lesions of human MG are primary changes in the autoimmune pathogenesis, or rather secondary events caused by peripheral autoimmunization, the authors compared the pathologic changes of MG thymuses with the thymuses of Lewis rats with experimental autoimmune myasthenia gravis (EAMG). EAMG was induced either actively by immunization with AChR, or transferred passively with monoclonal antibodies (mAb) binding to AChR. The clinical diagnosis of EAMG was confirmed by electromyography. Germinal centers, which are typical for human MG thymuses, were not detectable in the thymus of EAMG rats. Scattered B cells were seen as normal components of the thymic medulla. In EAMG their number was not augmented, nor were they accumulated focally. The perivascular spaces (PVS) were not distended and the amount of reticulin was not increased. Thymic myoid cells were identified in EAMG as well as in control thymuses; their cellular microenvironment was inconspicuous. Both in normal and in EAMG thymuses, a subpopulation of myoid cells expressed the main immunogenic region of the AChR. Heavily affected rats showed a severe cortical involution, but no specific changes of the medulla. The fact that none of the thymic lesions characteristic for human MG was found in EAMG is compatible with the concept that the thymic changes in MG are primary events in the autoimmune pathogenesis of this disease.

Animals↗

PubMed1990

Lymphoid dendritic accessory cells of the rat.

The expression of MHC class II antigens on potential APC is a crucial step in T-lymphocyte activation and the initiation of an immune response. The studies which are presented here were initiated to characterize the critical APC present in physiologically normal, untreated rats. Such a cell should constitutively express these antigens at high density and therefore provide the apparatus necessary to provoke both primary and secondary immune responses at any time. DAC were found to fulfill these criteria. In the absence of specific surface markers of rat DAC, the results are based on the strict combination of morphological appearance and functional activity. However, the high expression of MHC class II antigens may be regarded as semispecific markers for DAC which are distributed at strategic positions in many lymphoid and nonlymphoid tissues (Hart & Fabre 1981, Steiniger et al. 1984). The relatively low number of these cells observed in tissue sections and in in vitro isolates (0.1% of all cells) may explain their high activity as APC. This would facilitate the presentation of antigen in vivo to a sufficient number of competent T lymphocytes. DAC differentiate from a bone marrow progenitor cell pool preferentially under the influence of spleen cell-derived activities. Although the exact lineage has not yet been determined it may be fair to speculate that DAC form a new cell lineage probably related to interdigitating cells but not to macrophages which differentiate from bone marrow-derived precursors under the influence of colony-stimulating activities. However, the cooperation between DAC plus macrophages may provide the stage for T-lymphocyte activation and T-T collaboration (Mitchison 1990). There are still many open questions concerning the general role of DAC in vivo and in vitro. To further characterize rat DAC, their tissue distribution, role in the immune response and possible influence on intrathymic lymphopoiesis, with respect to T-lymphocyte subpopulations and the selection of the T-lymphocyte antigen-receptor repertoire, a panel of DAC-specific monoclonal antibodies must be generated in the future. Such antibodies will also be useful to study the mechanism by which DAC activate T lymphocytes.

Animals↗

PubMed1989

Functional heterogeneity among CD4+ encephalitogenic T cells in recruitment of CD8+ T cells in experimental autoimmune encephalomyelitis.

Inoculation of Lewis rats with live or attenuated (irradiated or paraformaldehyde-fixed) CD4+ encephalitogenic T cells (S1 line) protects the recipients from transferred experimental autoimmune encephalomyelitis (tEAE) induced by S1 cells. A CD8+ T lymphocyte population specifically activated against the EAE-inducing S1 cells can be readily isolated from the lymphoid organs of pretreated animals. We show, in the present study, that encephalitogenic T cell lines derived from Lewis rats differ in their ability to induce resistance against tEAE in vivo and to stimulate CD8+ cell proliferation in vitro. We also demonstrate that the S19 line of encephalitogenic T cells, in combination with myelin basic protein (MBP), can stimulate CD8+ cell proliferation in vitro. The CD8+ cells generated in this way strongly suppress MBP-specific T cell proliferation in vitro. This combined effect of T cells and MBP was also evident in vivo. Neither S19 cells nor MBP alone induced resistance against S19-mediated tEAE, rather coinjection of these cells and MBP was required. Our results suggest that resistance to EAE is mediated by distinct populations of encephalitogenic T cells that activate Ts cells through different mechanisms. In some instances, both autoreactive T cells and their relevant autoantigen(s) may be needed to activate Ts cells in vivo.

Animals↗

PubMed1987

Homing of antigen-specific T cells in the Lewis rat. I. Accumulation of antigen-reactive cells in the perithymic lymph nodes.

A permanent ovalbumin-specific T cell line of "helper/inducer" cell phenotype (W 3/13+, W 3/25+, OX 8-) was used to study the homing pattern in normal untreated Lewis rats. After i.v. injection, the migration of these cells was followed directly by using 51Cr- or [14C]thymidine-labeled cells. In addition, I tried to retrieve the cells from different lymphatic tissues by antigen restimulation. I found that most of the radiolabeled cells migrate to the lung, liver, kidney, and spleen. Other lymphoid tissues such as the thymus and the cervical and mesenteric lymph nodes were almost devoid of such cells with one exception: the perithymic lymph nodes (pt-LN). Twenty-four hours after the cell transfer, viable antigen-specific cells could be recovered from these organs. Within 9 days the pt-LN enlarged, the percentage of W 3/13+ and W 3/25+ T lymphocytes was enhanced, and both relatively high spontaneous and antigen-driven responses were measurable in cell cultures of these lymph nodes. All the effects were observed if viable but not irradiated antigen-specific T blasts were transferred. Moreover, after active immunization, antigen-reactive cells appeared to accumulate not only in the draining but also in the pt-LN. In both experimental situations, the adoptive transfer and the in vivo activation of antigen-specific lymphocytes, the pt-LN appear to play an important role in the homing of such cells.

Animals↗

PubMed1985

Enhanced activation of a T cell line specific for acetylcholine receptor (AChR) by using anti-AChR monoclonal antibodies plus receptors.

Immune complex-mediated regulation of the immune response has been studied by using T cell lines and monoclonal antibodies (MAb), both specific for the acetylcholine receptor (AChR). Rat T lymphocytes bearing the W3/25 phenotype and specific for AChR from Torpedo californica have been propagated in vitro for nearly 1 yr. These T cells proliferate in response to optimal concentrations of AChR presented by irradiated syngeneic thymus cells. At suboptimal concentrations of antigen there is little activation of the T cell line. We report here that the addition of small amounts of anti-AChR MAb produces dramatic stimulation of the T cell lines at suboptimal doses of AChR. Enhanced activation depends on the isotype and not the fine specificity of the MAb that are used. The observed phenomenon is antigen specific, and in fact, the immune complexes may actually suppress the proliferative response of irrelevant T cells to some extent. The MAb plus antigen are rapidly bound to the surface of the antigen-presenting cell, which we have shown is the dendritic cell.

Adjuvants, Immunologic↗

PubMed1984

Rat bone marrow precursors develop into dendritic accessory cells under the influence of a conditioned medium.

Primary in vitro immune responses require the interaction between T lymphocytes and Ia-positive antigen-presenting cells. Recently, techniques were established including discontinuous bovine serum albumin gradients, adherence, irradiation, and Fc-rosetting which led to a positive selection of rat dendritic cells and their identification as the major if not the only accessory cell for rat T lymphocytes treated with the mitogen, sodium periodate, or stimulator cells in mixed lymphocyte reactions. Rat dendritic cells which were found to be present in both lymphoid and non-lymphoid tissues have a low density, are non-adherent, radioresistant, non-specific esterase-negative, Fc-receptor negative and Ia-positive. Dendritic accessory cells were detected in cultures of low-density bone marrow cells and developed from radiosensitive precursors especially in a medium containing 10-20% of a supernatant elaborated by mitogen-preactivated syngeneic spleen cells. When compared to purified lymph node dendritic cells they were found to be identical in potency and phenotype. Adherent cells from bone marrow possessed neither accessory activity nor influenced the development of dendritic accessory cells. The mature dendritic accessory cells which could be enriched 1000-fold were no longer radiosensitive. The production of dendritic accessory cells from bone marrow precursors was influenced by the culture medium. Serum components were found to suppress their development. However, semipurified factor(s) released by mitogen-preactivated spleen cells enhanced the number of dendritic cells considerably. Activity resided in substances with a molecular weight in the range of 40,000 Daltons. This material could be separated on a Sephadex G 75 column from rat Interleukin 2 which had no effect on the formation of dendritic cells but did support proliferation of accessory cell-depleted, mitogen-treated lymph node cells.

Animals↗

PubMed1982

Accessory and stimulating properties of dendritic cells and macrophages isolated from various rat tissues.

Single cell suspensions of rat lymphoid and nonlymphoid tissues were fractionated on discontinuous gradients of bovine serum albumin into high density and low density subfractions. In general, accessory activity required for responses of periodate-treated T lymphocytes was recovered only in a low density population containing a small percent of the total fractionated cells from lymph nodes, spleen, liver, skin, and peritoneal exudates. Further purification always led to an increase of both accessory activity and number of dendritic cells present in nonrosetting and nonadherent populations. After purification, a high recovery of the total accessory activity was found in fractions that contained a high percentage of dendritic cells resulting in a more than 1,000-fold enrichment in accessory activity per cell. No other fraction obtained during the purification contained significant accessory activity. In all cases, macrophage-enriched populations lacked accessory cell activity. With the exception of peritoneal exudate cell preparations, which contained an inhibitory cell, the level of accessory activity in a given population was always found to be a function of the number of dendritic cells present. Dendritic cells from all sources were nonadherent, nonphagocytic, radio- resistant, and nonspecific esterase negative. They expressed Ia antigens and lacked Fc receptors. Both epidermal and lymph node dendritic cells contain Birbeck granules, subcellular structures previously described only for Langerhans cells. Accessory activity requires viable dendritic cells but is unaffected by 1,000 rad of gamma-irradiation. However, ultraviolet irradiation abolished the activity of accessory cells. The cells that responded to periodate were IgG-negative T cells, whereas IgG-positive B cells could not be stimulated under the same conditions. Only periodate-treated T cells and dendritic cells were needed for responses to occur; removal of virtually all macrophages from these purified preparations had no effect. Dendritic cells were also required as stimulators in mixed leukocyte cultures, whereas macrophages, even though Ia positive, were inert.

Animals↗

PubMed1982

Immunological properties of thymus cell subpopulations: rat thymic dendritic cells are potent accessory cells and stimulators in a mixed leukocyte culture.

Rat thymus cells were fractionated by centrifugation on a discontinuous bovine serum albumin gradient into two subpopulations: one of high density that accounted for greater than 90% of the recovered cells, and a minor low-density subpopulation containing 4 to 10% of the total cells. The high-density subpopulation consisted mainly of uniform small-sized thymocytes, whereas the low-density subpopulation contained mostly larger-sized cells. High-density thymus cells did not function either as stimulators in a mixed leukocyte reaction or as accessory cells required for T-cell response to mitogens, Con A and sodium periodate, as determined by 3H-thymidine incorporation. Dense thymus cells also responded poorly to allogeneic and to mitogenic stimulation, even when accessory cells were added. In contrast, the low-density thymus cells responded well to allogeneic stimulation and to both mitogens. In addition, low-density thymus cells possessed stimulatory activity in mixed leukocyte cultures, as well as accessory activity for mitogenic responses. Both activities were found to reside in dendritic cells that were purified extensively (70-90% of the preparation) with good yield. When tested as accessory cells for T-cell responses to periodate, thymic dendritic cells were as potent as lymph node dendritic cells on a per cell basis. A small number of thymic dendritic cells was able to cause marked enhancement in T-lymphocyte proliferation in response to stimulation. By immunofluorescence thymic dendritic cells were shown to be Ia-positive, but Thy 1.1 -negative.

Animals↗