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Biomedical subjects

D Gray

Publications and source records attributed to D Gray.

At least 19 recordsLinked to original sources
PubMed1992

CD45RA and CD45RBhigh expression induced by thymic selection events.

CD45 is a protein tyrosine phosphatase involved in T and B cell signaling. While peripheral T cells switch CD45 isoforms upon activation, events leading to exon switching during T cell development in the thymus have not been determined. The expression of high molecular weight isoforms of CD45 was examined on thymocytes from nontransgenic and T cell receptor (TCR) transgenic mice. All thymocytes from nontransgenic mice were CD45RB+ as assessed by staining with MB23G2, an anti-CD45RB-specific monoclonal antibody. Interestingly, there was a small population (1-3%) of thymocytes that displayed a higher intensity of staining with MB23G2, CD45RBhigh. CD45RBhigh thymocytes were found in all subsets defined by CD4 and CD8 expression and were also present within the TCR-alpha/beta high population. To analyze whether or not CD45 expression correlated with thymic selection events, expression of CD45RBhigh and a second isoform, CD45RA, was examined on thymocytes from H-Y and 2C TCR transgenic mice and found to correlate with positive and negative selection events but did not occur in nonselecting backgrounds. CD45RA and CD45RBhigh upregulation was also not observed in transgenic mice backcrossed into CD8-deficient mice, a scenario in which there is no positive selection of transgene-expressing thymocytes. These data suggest that modulation of CD45 isoform expression may be involved in thymic selection events.

Animals↗
PubMed1992

Less mortality but more relapses in experimental allergic encephalomyelitis in CD8-/- mice.

Mice lacking in CD8 were generated from homologous recombination in embryonal stem cells at the CD8 locus and bred with the experimental allergic encephalomyelitis (EAE)-susceptible PL/JH-2u through four backcross generations to investigate the role of CD8+ T cells in this model of multiple sclerosis. The disease onset and susceptibility were similar to those of wild-type mice. However, the mutant mice had a milder acute EAE, reflected by fewer deaths, but more chronic EAE, reflected by a higher frequency of relapse. This suggests that CD8+ T lymphocytes may participate as both effectors and regulators in this animal model.

Animals↗
PubMed1992

Follicular dendritic cell-dependent adhesion and proliferation of B cells in vitro.

In response to an antigenic challenge, B cells proliferate in germinal centers within secondary lymphoid tissue. Specialized accessory cells, follicular dendritic cells (FDC), and T cells are necessary to drive this reaction. Indirect evidence suggests that FDC provide signals which not only induce B cell proliferation but can rescue B cells programmed to die by apoptosis. An in vitro system was developed to: 1) define the role of FDC and 2) identify molecules involved in this response. Activated, low density B cells and T cells were coisolated with FDC from immune mouse lymph nodes. Upon culturing, large cellular aggregates formed, composed of 1 to 3 FDC interdigitating between 30 to 90 B cells and 1 to 5 T cells. Many of these B cells were undergoing DNA synthesis. Depleting FDC or T cells from the cultures immediately stopped cluster formation and proliferation. Separating clustered vs nonclustered cells revealed that the FDC-associated population remained viable, whereas cells in suspension became apoptotic. The adhesion/activation molecules ICAM-1, LFA-1, and CD44 supported both cluster formation and proliferation. In addition, anti-class II and anti-kappa L chain mAb interfered dramatically with DNA synthesis. This model mimics many of the features of a germinal center and can be used to further study B cell activation, proliferation, and differentiation in vitro.

Animals↗
PubMed1992

Netwhat?

The hallmark of an antibody response is considered to be its specificity for the immunogen. Nonetheless, most antibody elicited by an immunogen has been reported to be unreactive with it. We have evaluated specificity by characterizing the primary antibody response of mice to heat-aggregated human gamma-globulin with four approaches: (a) quantification of antibody-producing cells; (b) hybridoma analysis; (c) in situ antigen binding and (d) analysis of secreted antibody. The results show that the nonspecific component of this response is negligible. These observations suggest that such a component is not a basic feature of the antibody response and it is discussed that nonantigen-specific antibody may arise from a variety of causes many of which are artifactual.

Animals↗
PubMed1992

Activated human T cells express a ligand for the human B cell-associated antigen CD40 which participates in T cell-dependent activation of B lymphocytes.

To identify the ligand for the B cell-associated antigen CD40, we constructed a chimeric immunoglobulin molecule where the extracellular portion of the CD40 protein replaced the normal immunoglobulin variable region. No binding was detected on resting peripheral blood T cells. However, following T cell activation with phorbol esters and ionomycin, the chimeric protein bound specifically to activated human T cells and precipitated a 35-kDa protein from such cells. The induction of the CD40 ligand was detectable on the cell surface after 1 h, with maximal expression after 8 h of stimulation. The T cells expressing CD40 ligand were predominantly CD4 positive, although a proportion of CD8-positive cells also expressed the protein. There was no particular correlation with CD45 phenotype. Finally, we found that soluble CD40 inhibited T-dependent B cell proliferation. The results are discussed in the context of cognate interactions between B and T cells.

Adult↗
PubMed1992

Long saphenous vein storage after femoro-distal bypass grafting.

Segments of long saphenous vein generated during the preparation of conduits for femoro-distal bypasses can be stored in saline at 4 degrees C. Two occasions on which such stored vein segments have proved valuable in graft revision after early graft thrombosis are described.

Anastomosis, Surgical↗
PubMed1992

Signals involved in germinal center reactions.

Many of the features observed in the in vitro cultures discussed in this review coincide with characteristics described for an in vivo germinal center response. FDC and T cells are required to maintain B-cell proliferation which is confined to a finite amount of time (i.e. less than 2 wk). Large cellular aggregated form which contain many blasting cells undergoing DNA synthesis. In addition to proliferation, apoptosis is also occurring in the cultures but appears to be limited to the population which is not in contact with the FDC. The system can be driven by specific antigen, suggesting that clonal expansion is occurring. As in other immunological systems, there is an important role for adhesion molecules both for cluster formation and DNA synthesis. Antigen processing and presentation is a major event since blocking this through several mechanisms ends the stimulation. The role of T cells is essential both in vivo and in vitro; however, their exact contribution is still not well understood. It is interesting that blocking IL4 usage either by neutralizing the molecule or its receptor by monoclonal antibodies has no effect on the system. Which interleukins are important for germinal centers remains on open question. Evidence continues to accumulate on the important role of FDC and the molecules they express. Not only are the immune complexes an essential part, but it seems that molecules yet to be defined have an effect. For many practical reasons these have remained a mystery, but using our various systems we are attempting to reveal them. Two intriguing questions which remain include: 1. the molecular nature of the signalling between the FDC and B cell; and 2. how does the FDC retain the antigen in a native form for such long periods of time? An understanding of both mechanisms will provide us with a better appreciation for the events leading to a germinal center response and the immunological phenomenon referred to as memory.

Animals↗
PubMed1992

Immunohistochemical localization of basic fibroblast growth factor within the mouse uterus.

Uterine samples were either rapidly frozen in liquid nitrogen or placed in Bouin's fixative. A commercial primary polyclonal antibody made in rabbits against human recombinant basic fibroblast growth factor (bFGF) was used. Western blot analysis indicated that the antibody was specific for bFGF and did not react with acidic FGF. The primary antibody was followed by either goat anti-rabbit immunoglobulin G (IgG) conjugated to the fluorescent phycobiliprotein tracer phycoerythrin or biotinylated goat anti-rabbit IgG and a biotin-avidin-peroxidase complex. Specificity controls using adjacent sections were carried out by (i) substituting normal rabbit sera for the primary antisera, (ii) omitting the primary antisera or (iii) extracting sections with NaCl (2 mol l-1) prior to the immunochemical procedures. No binding of the antibody was observed with any of the specificity control sections. The connective tissue stroma and the basal lamina associated with uterine glandular and surface epithelial layers were positive for bFGF. Localization was not observed within surface or glandular epithelial cells. The basal lamina and endothelial cells associated with blood vessels within the uterus and the smooth muscle cells of the myometrium were positive for bFGF. There were no differences in uterine localization patterns or intensity during the oestrous cycle or after ovariectomy and steroid hormone supplementation. These studies demonstrate the specific localization of bFGF within the mouse uterus.

Animals↗
PubMed1992

The acute phase response in autologous bone marrow transplantation.

Due to the stress imposed by the process of bone marrow transplantation (BMT), we hypothesized that individuals receiving such a transplant underwent an acute phase response (APR). Circulating levels of C-reactive protein (CRP), haptoglobin (HAP), alpha-1 acid glycoprotein (AAG), ceruloplasmin (CER), zinc (Zn), copper (Cu), interleukin-6 (IL-6), albumin (ALB), and thyroxine-binding prealbumin (TBPA), were measured at baseline (Day -7), Day -4, Day 0 (Transplant Day), Day +2, +7, and weekly until day 28 in 14 adults receiving an autologous bone marrow transplant as Phase 1 treatment for various hematologic or solid tumor malignancies. Ten of 14 recipients survived, 9 of which had a significant increase in CRP (p = 0.012), HAP (p = 0.011), AAG (p = 0.002), and decrease in ALB (p = 0.002) and TBPA (p = 0.004) on Day +7, but not Day 0, after bone marrow reinfusion. These findings document the presence of an APR and suggest that the bone marrow transplant process (post reinfusion) initiates a stress response in the recipient.

Acute-Phase Reaction↗
PubMed1992

Myocardial infarction in patients over 75 1982-1990.

Admissions to hospital of patients aged 75 or over with symptoms suggestive of acute myocardial infarction have increased markedly since 1982. Patients over 75 present to hospital as soon after the onset of symptoms as do younger patients; they require more treatment with diuretics and digoxin than do younger patients and their fatality rate is higher. Despite this, the chance of patients over 75, especially women, being admitted to a Coronary Care Unit, and so being treated with a thrombolytic and being monitored closely for the complications of acute infarction are much less than those for patients under 75. If we are confident that we can influence the outcome of and reduce fatality from acute myocardial infarction, we should be prepared to offer elderly patients the same opportunities for treatment that we currently afford to younger patients.

Age Factors↗
PubMed1992

The dynamics of immunological memory.

Memory has long been thought of as a stable phenomenon within the immune system: once generated it lasts for a very long time. This static view of immunological memory predicts that an established population of memory cells is independent of outside influences. Recent findings, concerning the population kinetics of the peripheral pool of lymphocytes and, more directly, concerning the influence of antigen on memory cell survival, are forcing us to reassess this idea. I present here a dynamic view of immunological memory which takes into account an immune system that appears in continual flux and whose constituent cells may rely upon recurrent signals for their survival. This view of memory also makes certain predictions and these are considered.

Animals↗
PubMed1991

T cell memory is short-lived in the absence of antigen.

Immunological memory has generally been ascribed to the development of long-lived memory cells that can persist for years in the absence of renewed antigenic encounter. In the experiments reported here, we have adoptively transferred memory T cells in the presence and absence of priming antigen and assessed their functional survival. The results indicate that, in contrast to the traditional view, the maintenance of T cell memory requires the presence of antigen, suggesting that memory, like tolerance, is an antigen-dependent process rather than an antigen-independent state.

Animals↗
PubMed1991

Mice lacking MHC class II molecules.

We have produced mice that lack major histocompatibility complex class II antigens, permitting us to evaluate the role of these molecules in diverse aspects of T and B cell differentiation. The mutant mice show near-complete elimination of CD4+ T lymphocytes from the spleen and lymph nodes; the few remaining CD4-positive cells are preferentially localized to B cell follicles. Surprisingly, substantial numbers of CD4 single-positive cells reside in the thymus; however, these are not mature thymocytes as we currently recognize them. B lymphocytes occur in normal numbers and are capable of terminal differentiation to plasma cells. Nevertheless, several aberrations in the B cell compartment are demonstrable: a lack of germinal centers, fewer IgM+IgD+ cells in certain individuals, reduced production of serum IgG1, and complete inability to respond to T-dependent antigens. In short, the class II-negative mice have confirmed some old ideas about lymphocyte differentiation, but have provided some surprises.

Animals↗
PubMed1991

Interaction of various cytokines with interleukin 2 in the generation of killer cells from human bone marrow: application in purging of leukemia.

We have shown that incubation of bone marrow (BM) with interleukin 2 (IL-2) generates activated bone marrow cells (ABM) with potent tumoricidal activity in vitro and in vivo. The present study was carried out to define the interaction of other cytokines with IL-2 in generation of ABM. Our data show that interleukin 1 (IL-1), interferon (IFN)- both gamma and alpha, and tumor necrosis factor (TNF-alpha) significantly increased the cytolytic potential of ABM. Interleukin 3, interleukin 4, transforming growth factor-beta and adherent cells were reduced, while granulocyte-macrophage colony-stimulating factor had no influence on the generation of cytolytic activity. IL-1 was enhanced while TNF-alpha depressed the BM progenitor cell activity in vitro. The IL-2-induced purging ability of BM contaminated with leukemic cells was increased by IL-1, TNF-alpha and IFN-gamma. This study shows that biomodulation of BM with combination of cytokines in vitro can be useful in purging a large leukemic burden.

Bone Marrow↗
PubMed1991

Novel pathways of antigen presentation for the maintenance of memory.

Follicular dendritic cells (FDC) store native antigen for long periods in lymphoid follicles and so provide a source of continued stimulation for specific B cells. The expression of MHC class II by FDC suggested they might act as antigen-presenting cells for MHC class II-restricted T cells. We show here, however, that the MHC class II molecules found on their surface are not synthesized by the FDC but are picked up from surrounding B cells in germinal centres. Although FDC by themselves cannot present native antigen to T cells, acquired MHC class II-peptide complexes can be recognized by T cells. The true physiological role of FDC seems to be as long-term antigen depots. We demonstrate that antigen localized onto FDC in vivo can be retrieved by antigen-specific B cells, which in turn process and present it to T cells. These presentation pathways are likely to be crucial in both the maintenance of long-term immune responses and the continued survival of memory cells.

Animals↗