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Biomedical subjects

E B Bell

Publications and source records attributed to E B Bell.

At least 55 records · Page 3Linked to original sources
PubMed1991

T-cell receptor-bearing cells from athymic nude rats respond to alloantigen in vitro but are defective in vivo.

T-like cells from congenitally athymic nude rats of the PVG (RT1c) strain were characterized both phenotypically and functionally. There was an age-dependent increase in the number of alpha beta TcR+CD3+ cells in the lymph nodes, spleen and thoracic duct of nude rats. These cells, which comprised up to 25% of lymph node cells in animals of 8-12 months in age, were also CD3+CD5+Thy-1.1-. The expression of CD4 and CD8 on T-like cells was mutually exclusive. Approximately 30% of the CD4+ cells expressed CD45RB and 50% of the TcR+ cells expressed RT6. B-cell-depleted TcR+ cells from nude animals gave proliferative responses to mitogenic lectins or immobilized anti-CD3 antibody. T-like cells showed comparable alloreactivity to their euthymic counterparts in mixed lymphocyte reactions (MLR) against three different MHC haplotypes and to lymphocytes of a congenic strain differing only in MHC-encoded products. Monoclonal antibodies (mAb) to CD4, MHC class II, alpha beta TcR and CD3 blocked the MLR. However, T-like cells failed to induce rejection of skin allografts of the same MHC haplotypes when adoptively transferred to athymic nude hosts and were unable to mount a normal graft-versus-host (GVH) response. These results indicate that lymphocytes may rearrange and express a functional TcR in the absence of a thymus, but that the thymic microenvironment is essential for T cells to acquire full in vivo function.

Aging↗
PubMed1990

Interconversion of CD45R subsets of CD4 T cells in vivo.

T lymphocytes express multiple forms of the leukocyte common antigen CD45, transcribed by alternative usage of leukocyte-common antigen exons 4-6. Species-specific monoclonal antibodies against restricted epitopes (CD45R) of the antigen subdivide CD4 T cells into reciprocal subsets expressing either the high molecular weight isoforms CD45RA or RB or a molecule in which exons 4-6 have been spliced out (CD45R0). CD45R+ or RB+ CD4 T cells are potent in graft-versus-host reactions, and interleukin-2 related activities, whereas the CD45R0+ subset responds in vitro to recall antigens and provides help for antibody synthesis. It is unclear whether CD45R subsets derive from separate lineages, or are products of unidirectional or reversible differentiation. We show by transferring CD45R+ or CD45R- allotype-marked CD4 T cells into athymic nude rats that both subsets routinely generate cells of the opposite phenotype with a function that follows phenotype, not parentage. The recent equation of CD45R subsets as maturation stages representing 'naive' and 'memory' T cells is difficult to reconcile with this finding.

Animals↗
PubMed1990

Renal allograft rejection in CD4+ T cell-reconstituted athymic nude rats. The origin of CD4+ and CD8+ graft-infiltrating cells.

PVG-rnu/rnu nude rats reject a fully allogeneic DA renal allograft after the adoptive transfer of naive CD4+ T cells alone, but rejection is accompanied by the accumulation of many CD8+ leukocytes within the graft. In order to clearly establish the provenance of these CD8+ cells infiltrating rejecting kidney allografts, nude recipients (PVG-RT7a) were injected with CD4+ T cells from the PVG-RT7b congenic strain bearing an allotypic variant of the leukocyte-common antigen. Dual fluorescence and immunohistochemistry demonstrated that approximately 75% of the total infiltrate was host-derived; the donor-derived RT7b population was almost entirely (92-99%) CD4+, CD5+, CD3+, and alpha beta TCR+. At least 97% of the CD8+ cells were of nude origin. There was no evidence of donor-derived CD8+ cells or of a CD4+8+ double-staining population. Unexpectedly, nearly half of the alpha beta TCR+ cells from the grafts were of nude origin.

Animals↗
PubMed1990

Allograft rejection in athymic nude rats by transferred T cell subsets. II. The response of naive CD4+ and CD8+ thoracic duct lymphocytes to an isolated MHC class I disparity.

Athymic PVG-rnu/rnu (RT1c) rats were grafted with skin bearing isolated MHC disparities 7-14 days in advance of cell transfer. The ability of naive CD4+ or CD8+ thoracic duct lymphocytes to induce rejection was assessed by adoptive transfer of one or both T cell subsets into nude recipients bearing congenic PVG.r1 (MHC class I-only disparity, Aa) or PVG.r19 (class I and II-only disparity, Aa B/Da) skin grafts. Recipients of purified CD4+ TDL always rejected r19 allografts, whereas CD8+ TDL were ineffective against this class I + II difference. Neither the injection of CD4+ TDL nor CD8+ TDL alone resulted in destruction of r1 skin grafts. However, rejection of r1 tissue was observed in 63% of cases (19/30) when both CD4+ and CD8+ TDL were present in the nude recipients. Rejection of r1 skin was also induced in some recipients when CD8+ TDL were transferred 8 weeks in advance of CD4+ TDL. In contrast, sequential transfer in the reverse order apparently induced tolerance in the CD4+ population--i.e., surviving r1 skin grafts on 8 week CD4+ T cell-reconstituted nude recipients were not rejected following the subsequent transfer of CD8+ TDL. We conclude that CD4+ T cells were required for rejection of both class I and class II differences. In the presence of a class II difference, CD4+ T cells function autonomously to initiate both the inducer and effector stages of rejection. When the disparity is confined to class I, CD8+ T cells are required (probably at the effector stage) but are dependent on CD4+ T cells for help. There was no evidence of CD4+ effector T cells that could recognize class I directly within the graft.

Animals↗
PubMed1990

Allograft rejection in athymic nude rats by transferred T-cell subsets. I. The response of naive CD4+ and CD8+ thoracic duct lymphocytes to complete allogeneic incompatibilities.

PVG.rnu/rnu nude rats were pre-grafted with two allogeneic skin grafts, AO(RTlu) and BN(RTln), 6-14 days in advance of cell transfer. Cellular requirements for rejection were established by transferring graded numbers of B cell-depleted (Ig-) thoracic duct lymphocytes (TDL) or purified W3/25+ (CD4+) or OX8+ (CD8+) TDL subsets. Allografts were rejected by 10(5) to 5 x 10(6) Ig- TDL in a dose-dependent fashion. A similar dose-response relationship was found by transferring 5 x 10(5) to 5 x 10(6) Ig- OX8- TDL (purified by depletion of B cells and OX8+ cells). Larger numbers of Ig- OX8- TDL (10-30 x 10(6)) did not significantly accelerate rejection. W3/25+ TDL alone (10(5)), highly purified by fluorescence-activated cell sorting (FACS), were sufficient to induce allograft rejection in this athymic nude rat model. In contrast, 10 times more FACS purified OX8+ TDL (10(6)) were unable to initiate skin graft rejection despite the complete class I and class II MHC incompatibilities. Furthermore, the addition of 10(6) OX8+ cells did not accelerate or retard the rejection induced by 10(5) W3/25+ cells alone. Pre-grafted nude recipients, irradiated (500 R) 2 hr before W3/25+ TDL injection, in order to eliminate putative nude T cells, rejected allografts on the same day as unirradiated controls. We conclude that when confronted with complete MHC disparities, CD4+ T cells are necessary and sufficient to induce skin allograft rejection whereas CD8+ T cells do not appear to contribute.

Animals↗
PubMed1989

Fidelity of the repertoire in T cell reconstituted athymic nude rats. Preservation of a deficit in alloresponsiveness over one year.

A single intravenous injection of a relatively small number of T cells contained in the population of rat thoracic duct lymphocytes (TDL) is sufficient to restore to normal the peripheral T cell pool of athymic PVG.rnu/rnu nude rats. The donor T cells expand greater than 10-15-fold, self-renew, and restore immunocompetency to nude recipients permanently (greater than 2 yr). We asked whether the T cell repertoire was affected by the expansion and self-renewal process. Nude recipients were injected with syngeneic PVG TDL that had been allospecifically depleted (negatively selected) by consecutive passage from blood to thoracic duct lymph through two irradiated (DAxPVG)F1 intermediate rats. Negatively selected TDL were tested before transfer by the P----F1 popliteal LN GVH assay and showed a greater than 90% depletion of specific reactivity to DA alloantigens. Surviving cells or their progeny were recovered from LN or TDL of nude recipients 8 and 12 mo after transfer. The deficit in GVH reactivity to the DA haplotype persisted, but normal GVH activity was demonstrated against a third party (AOxPVG)F1 alloantigen. The "hole" in the repertoire could not be attributed to tolerance induced by the co-transfer of contaminating irradiated F1 TDL. PVG TDL passaged consecutively through (AOxPVG)F1 and (DAxPVG)F1 intermediates and devoid of (AOxPVG)F1 cells remained specifically depleted to both AO and DA haplotypes when recovered from nude recipients 4 and 13 mo later, but displayed GVH activity to a third-party (BNxPVG)F1 alloantigen. Thus the exact specificity of the T cell repertoire of the original inoculum was faithfully maintained in nude recipients throughout the initial phase of rapid expansion and the continued self-renewal of the mature peripheral T cell pool.

Animals↗
PubMed1989

A survey of nonatopic and atopic children and adults for the presence of anti-IgE autoantibodies.

The prevalence of naturally occurring anti-IgE autoantibodies was assessed by surveying 387 sera from atopic, nonatopic, and autoimmune patients. A significant number of children (28.5%) and adults (20%) with no history of allergy had high levels of autoanti-IgE. The level of autoantibodies to IgE in children with clinical asthma or atopic eczema was not significantly elevated over normal. Similarly, adults with atopic asthma, allergic rhinitis, or urticaria or sera from individuals with rheumatoid arthritis or systemic lupus erythromatosis showed no significant elevation of auto-anti-IgE. In contrast, 82% of adults with eczema had medium to high levels of auto-anti-IgE and the mean concentration in sera was significantly (P less than 0.01) raised. The relevance of auto-anti-IgE in atopic eczema is discussed.

Adolescent↗
PubMed1989

The toxicity, distribution and excretion of ricin holotoxin in rats.

The distribution and excretion of the plant toxin ricin were studied in rats after intravenous injection. 125I-labelled ricin was equal in toxicity to native ricin. Following injection, the liver was the major organ of localisation - 46% of injected dose at 0.5 h. The spleen and muscle were next with 9.9% and 13%, respectively, at 0.5 h. Ricin was relatively concentrated in the spleen (33% of injected dose/g of tissue) compared with the liver (7.4%/g) and the bone marrow (5.5%/g). The concentration in the lymph nodes was very low (1.2%/g). Ricin was quickly cleared from the animal; only 11% of the initial radioactivity remained 24 h later with 70% excreted in the urine. Excretion into the intestine via the bile duct was less than 5% by 24 h, 10-12% of the radioactivity was found in the intestinal contents or intestinal wall between 3 h and 12 h, and much of this was reabsorbed since less than 2% was recovered in faeces.

Animals↗
PubMed1989

The origin of T cells in permanently reconstituted old athymic nude rats. Analysis using chromosome or allotype markers.

Athymic PVG-rnu/rnu rats receiving a single intravenous injection of syngeneic euthymic thoracic duct lymphocytes (TDL) develop normal levels of CD4+ T lymphocytes and survive for more than 2 years in a conventional animal house. We investigated the origin of the T cells (and B cells) in reconstituted nude recipients by transferring TDL carrying either the 3T chromosome marker or the RT6b + Igk-1b allotype or the RT7b (leucocyte-common) allotype markers. Karyotype analysis of spleen and lymph node (LN) cells from 1- to 2-year-old PVG-3T/3T-reconstituted nude recipients, stimulated in vitro with phytohaemagglutinin (PHA), unexpectedly revealed that a majority (79-97%) of dividing cells were of nude origin. However, extensive nude cell division was also recorded in PHA-stimulated cultures using mixtures of euthymic (PVG-3T/3T) and unreconstituted nude spleen cells; the assumption that only T cells divide in PHA-stimulated cultures thus appears to be erroneous. In contrast to the karyotype analysis, sIg- RT6b+ LN cells obtained from nude recipients reconstituted 2 years earlier with PVG-RT6b allotype-marked TDL, were all of donor origin with no indication of a nude-derived sIg- RT6a+ population. Igk-1b+ donor B cells were not found in these same recipients. Dual fluorescence analysis of TDL from 18- to 20-month RT7b-reconstituted nudes showed that 91-100% of CD4+ cells were donor-derived. When tested functionally, sIg- RT7b+ (donor) cells, but not sIg- RT7b- (nude-derived) cells, were able to reject skin allografts and induce local graft-versus-host (GVH) responses. Donor T cells, in contrast to CD4+ cells of nude origin, divided extensively in nude recipients; FACS-purified RT7b+ (donor) TDL retransferred from 17-month primary reconstituted nude rats, expanded further (60-100-fold) in secondary nude recipients. In conclusion, only the donor-derived CD4+ cells in reconstituted nude rats displayed T-cell function; evidence to the contrary from karyotype analysis was flawed. At no stage in their life did uninjected or T-cell reconstituted nude rats develop endogenous cells that in any way resembled CD4+ products of the thymus.

Animals↗
PubMed1989

Induction of an auto-anti-IgE response in rats. III. Inhibition of a specific IgE response.

An auto-anti-IgE response was induced in conventional (PVG-RT1U and high IgE-producing (BN) rat strains by immunization with a highly purified rat IgE myeloma IR2. Earlier work established that total serum IgE levels were decreased by this procedure (Marshall & Bell, 1985) but only in the PVG-RT1U strain. IR2-immunized rats were tested for their ability to produce a specific IgE response to ovalbumin (OVA). The primary anti-OVA IgE response was inhibited by 60-75% in both rat strains, regardless of whether the total serum levels of IgE were reduced. The secondary IgE response to OVA was also inhibited in anti-IgE-producing animals but not in rats primed with OVA before anti-IgE induction. The inhibition of the anti-OVA response was isotype specific; the IgG response to OVA was unaffected. These studies may help elucidate the regulatory role played by naturally occurring anti-IgE antibodies found particularly in atopic individuals.

Animals↗
PubMed1987

The stable and permanent expansion of functional T lymphocytes in athymic nude rats after a single injection of mature T cells.

Athymic nude rats (PVG.rnu/rnu) were injected at 6 to 10 wk of age with 1 to 200 million thoracic duct lymphocytes (TDL) containing 40 to 60% mature T cells. Thereafter TDL-injected nude recipients were monitored for evidence of T cell function for up to 2 yr. W3/25+ T helper (Th) cells in lymph nodes (LN) increased from 7% at 2 wk to 30% at 8 wk after TDL transfer. The percent of W3/25+ cells remained elevated for the life of the recipient (up to 2 yr), approximating normal levels. The total size of the recirculating pool expanded in TDL-injected nude rats to reach 2/3 the level of euthymic controls by 16 wk, an increase of 10-fold to 15-fold in W3/25+ cells. The expansion of the W3/25+ population was independent of initial TDL dose. With time spleen and LN acquired a normal histological appearance including the development of germinal centres and a marked increase in cellularity in T cell traffic areas. TDL-injected nude rats rejected skin allografts with near normal kinetics. In addition graft vs host (GVH) responsiveness, assessed by the popliteal LN assay, progressively increased reaching a level 9 mo to 1 yr after replacement that resembled the GVH activity in euthymic controls.

Animals↗
PubMed1987

Induction of an auto-anti-IgE response in rats. II. Effects on mast cell populations.

Immunization of rats with purified rat IgE myeloma (IR2) induces an IgG class autoantibody directed specifically against the IgE isotype. This has variable stimulatory effects on the serum IgE concentration in high IgE-producing BN rats but significantly decreases the serum IgE concentration in the conventional PVG.RT1u strain. We have examined the effects of inducing such an auto-anti-epsilon response on mast cell populations, as defined by their staining characteristics in BN rats. A persistent anti-epsilon response changed the proportions of mast cell types. Those containing highly sulfated, Safranin-positive granules which equate with cells described as connective tissue mast cells (CTMC) were reduced in number in skin, tongue and bone marrow, whereas the less highly sulfated, Alcian Blue-positive mast cells were increased in number in these tissues as well as in the gut, a site rich in the so-called mucosal mast cell. The overall number of mast cells in nonmucosal sites was not significantly changed in anti-IgE-producing rats. The direct effects of anti-epsilon antiserum on mast cells in vivo were investigated using an immediate skin response (ISR) technique. The IgG component of serum from IR2-immunized rats, fractionated by high performance liquid chromatography or eluted from Sepharose 4B-coupled IR2, gave positive ISR in naive rats. The ISR was inhibited by prior incubation of immuno-purified rat anti-IR2 with solid-phase IR2 or with two unrelated IgE myeloma proteins but not with rat IgG. Histological examination confirmed that degranulation of CTMC had occurred at the ISR sites.

Alcian Blue↗
PubMed1987

Formalin sensitivity and differential staining of mast cells in human dermis.

The characteristics of the human dermal mast cell population with respect to formalin fixation sensitivity, toluidine blue staining and alcian blue/safranin staining were studied. Thirty-seven specimens of normal human skin were bisected. One half was fixed in 10% neutral buffered formalin and the other in Carnoy's fixative. Sections were cut and stained with either toluidine blue or alcian blue/safranin. Significantly more mast cells were visualized with alcian blue/safranin than with toluidine blue. With both stains, only approximately 50% of the mast cells observed in the Carnoy's fixed tissue could be visualized in the formalin-fixed tissue. Alcian blue/safranin staining revealed three patterns of mast cell granule staining: mast cells containing only alcian blue-positive granules, mast cells containing only safranin-positive granules, and mast cells containing a mixture of alcian blue-positive granules and safranin-positive granules. Mast cells containing only alcian blue-positive granules constituted the majority of the dermal mast cell population and 73% of these mast cells were formalin-sensitive. Mast cells containing only safranin-positive granules and those containing a mixture of alcian blue-positive granules and safranin-positive granules showed no evidence of formalin sensitivity. The human dermal mast cell population, therefore, displays heterogeneity with respect to formalin fixation sensitivity and alcian blue/safranin staining. Dermal mast cells were visualized in significantly greater numbers in skin from the head compared with that from the body or limbs.

Adolescent↗
PubMed1987

Accelerated elimination of N. brasiliensis from the small intestine after auto-anti-IgE induction.

Immunization of rats with a purified IgE myeloma (IR2) induced an auto-anti-IgE response. Such treatment inhibited total IgE levels in the serum of conventional IgE-producing rats (Marshall & Bell, 1985) and increased the number of mucosal mast cells (MMC) in the intestine. The present study has investigated the ability of auto-anti-IgE induction to influence the course of a Nippostrongylus brasiliensis infection, to modify IgE synthesis, or to affect the number of MMC in the intestine following infection. Auto-anti-IgE induction was found to have a surprising effect on worm elimination. IR2-immunized rats were able to rid themselves of this nematode with an accelerated tempo--a small but significant effect after primary infection, but a substantial enhancement of worm loss after reinfection. Auto-anti-IgE induction was not able to prevent the typical increase in IgE that accompanies an N. brasiliensis infection, nor did it alter the helminth-induced intestinal mastocytosis. When MMC degranulation was measured by assaying the serum levels of a specific rat mast protease (RMCP II) following secondary infection, the amount of RMCP II released was less in auto-anti-IgE-producing rats. These findings have implications for the importance of IgE, MMC and other cells of inflammation in an anti-parasitic response.

Animals↗
PubMed1987

The effects of interferon on the recirculation of lymphocytes in the rat.

Lymphocytes from the thoracic duct (TDL) were incubated with interferon (IFN) prior to i.v. injection into syngeneic or allogeneic recipient rats. The effect of IFN treatment on the ability of lymphocytes to migrate was studied using 'standard' TDL collected overnight at 4 degrees or an 'optimal' collection of passaged TDL which recirculate with an accelerated tempo (Smith & Ford, 1983). Interferon treatment resulted in an increase in early (30 min) localization of both standard and optimal TDL into lymph nodes. Entry of standard IFN-treated TDL was increased by 91% and 54% in cervical and mesenteric lymph nodes, respectively; increases of 50% and 22% in the same lymph nodes were recorded for optimal IFN-treated TDL. Enhanced entry of standard TDL was contrasted with a reduced ability of IFN-treated TDL to migrate out of lymph nodes; there was a reduced output into the thoracic duct and a surplus of IFN-treated lymphocytes in cervical lymph nodes despite 24 hr continuous thoracic duct drainage. Incubation with interferon did not, however, alter the ability of optimal TDL to reach the thoracic duct rapidly after injection. Allogeneic lymphocytes, which are eliminated soon after injection by an NK-like cytotoxicity, a phenomenon termed ALC, were unaffected by incubation with interferon, thus IFN-treated allogeneic lymphocytes were killed after i.v. injection as rapidly as untreated cells.

Animals↗
PubMed1986

The carriage and delivery of substances to lymphatic tissues by recirculating lymphocytes. II. Long-term selective irradiation of the spleen and lymph nodes by deposition of indium-114m.

Recirculating lymphocytes were used to carry an isotope of indium, In-114m. The isotope has a half-life of 50 days, and emits both gamma and beta particles, properties that may be useful clinically. In-114m-labelled rat thoracic duct lymphocytes (TDL), injected intravenously, migrated to traffic areas in spleen and lymph nodes. The radioactivity was transferred selectively to a resident, radioresistant phagocytic population located within the marginal zone and red pulp of spleen, where it remained for at least 6 weeks. That the isotope was relatively concentrated in traffic areas, but not elsewhere, suggested that In-114m-TDL could be used as a means of producing total lymphoid irradiation without damaging bone marrow. Recipients of In-114m-TDL developed a profound lymphocytopenia within 2-3 weeks of injection but gained weight at a comparable rate to control rats. The effect of In-114m-TDL injection was also examined in rats injected with a rapidly growing, malignant rat leukaemia. In-114m-TDL delayed the onset of the proliferative phase of the leukaemia from 10 days to 20 days in a dose-dependent fashion. Repeated weekly injections of In-114m-TDL prevented the onset of the leukaemia until the injections ceased after 11 weeks. The potential use of In-114m-labelled lymphocytes in diagnosis (by external imaging) or in treatment (by localized lymphoid irradiation) is considered.

Animals↗