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V M Sanders

Publications and source records attributed to V M Sanders.

At least 37 records · Page 2Linked to original sources
PubMed1992

Beta 2-adrenoceptor stimulation increases the number of antigen-specific precursor B lymphocytes that differentiate into IgM-secreting cells without affecting burst size.

Previous studies have shown that early addition of a beta 2-adrenergic agonist to whole splenocyte cultures immunized with SRBC induced an increase in the number of cells secreting Ag-specific antibody. Because of the low frequency of Ag-specific B lymphocytes in these cultures, it has been difficult to determine the cellular mechanism by which this increase is produced. To gain insight into this cellular mechanism, the present study was designed to evaluate the responsiveness of TNP-specific B lymphocytes cultured at both high density and limiting dilution with keyhole limpet hemocyanin (KLH)-specific, IL-4-producing Th lymphocytes, TNP-KLH, and the beta 2-adrenergic agonist, terbutaline. The results showed that a maximal twofold increase in both the number of anti-TNP IgM-secreting cells and the amount of anti-TNP IgM secretion occurred in terbutaline-exposed lymphocytes after 5 days of bulk culture. This response occurred in a concentration-dependent manner and was inhibited by concomitant culture with beta-adrenoceptor antagonists. No appreciable change was measured in the level of either IgG1 secretion in terbutaline plus Ag-exposed bulk cultures or MHC class II expression on terbutaline plus Ag-exposed TNP-specific B lymphocytes as compared with Ag alone. These data raised the possibility that beta 2-adrenoceptor stimulation induced either the differentiation of a larger proportion of TNP-specific B lymphocyte precursors into anti-TNP IgM-secreting cells, or the extensive proliferation of a constant number of TNP-specific B lymphocyte precursors, or both. Limiting dilution results showed that beta 2-adrenoceptor stimulation induced a twofold increase in the number of TNP-specific B lymphocyte precursors that differentiated into anti-TNP IgM-secreting cells, without affecting the number of anti-TNP IgM-secreting cells produced by each precursor clone.

Animals↗
PubMed1991

B cell-associated LFA-1 and T cell-associated ICAM-1 transiently cluster in the area of contact between interacting cells.

TNP-specific B cells interact with carrier-specific T hybridoma cells in an antigen-specific, MHC-restricted manner. The formation of T cell/B cell conjugates is time and temperature dependent and results in the formation of a broad area of close contact between the interacting cells. In order to determine which surface molecules on the two cells cluster at the interaction site. T cell/B cell conjugates were formalin-fixed at different times following conjugation and were stained with antibodies directed against cell surface molecules. Results of these studies indicate that the alpha- and beta-subunits of LFA-1 on B cells transiently cluster in the area of cell contact. Maximum clustering of LFA-1 occurs at 45 min, after which time LFA-1 redistributes on the surface of the B cells. Several other B cell-associated molecules (MHC Class II, ICAM-1, Ig, B220, J11D, or CD23) do not cluster at the interaction site at any time point. T cell-associated LFA-1 does not cluster with any specific pattern, but ICAM-1 does. Maximum clustering of ICAM-1 occurs 60 to 90 min after intercellular contact. After this time, ICAM-1 redistributes on the surface of the T cells. Although both the alpha- and beta-subunits of LFA-1 cluster at the interaction site on B cells, antibodies recognizing these subunits differ in their ability to affect conjugation. One antibody recognizing the alpha chain of LFA-1 (M17/4.2) inhibits T-cell/B cell conjugation, whereas another antibody that also recognizes the alpha chain-(G-48) enhances conjugation. In contrast, an antibody that recognizes LFA-1 beta (M18/2.a.8) has no effect. An antibody that recognizes ICAM-1 (YN/1.7), the ligand for LFA-1, inhibits conjugation. These data show that, during T cell/B cell interaction. LFA-1 on B cells and ICAM-1 on T cells transiently cluster with similar, albeit not identical, kinetics to the site of cell-cell contact.

Animals↗
PubMed1991

Immune-associated toxicities induced by in vivo and in vitro exposure to interferon-alpha alone or in combination with nucleoside analogs.

The present studies examine whether immune-associated toxicities develop in rodents exposed to recombinant human interferon-alpha A/D (rHuIFN-alpha) alone or in combination with anti-retroviral nucleoside analogs. Four findings have emerged from these studies: (1) lymphocyte cell number and functional activity are suppressed after subchronic (1, 8 or 10 day) in vivo exposure to therapeutic doses of rHuIFN-alpha; (2) lymphocyte-associated toxicities lessen as in vivo exposure time to rHuIFN-alpha is extended; (3) T-cell-dependent antibody production is decreased after in vitro exposure of both antigen-specific T- and B-cells to rHuIFN-alpha; and (4) in vivo-induced leukocyte toxicities associated with either rHuIFN-alpha or the nucleoside analogs alone do not synergize when the therapies are combined. These data suggest that certain key immune parameters should be monitored carefully in the early stages of IFN-alpha therapy.

Animals↗
PubMed1989

In vivo administration of Fab' fragments of anti-L3T4 (GK1.5) antibody inhibits the T helper cell function of murine lymph node cells.

The effect of intravenous injection of Fab' fragments of anti-L3T4 antibody (GK1.5 monoclonal antibody) into mice was studied. This treatment depleted L3T4+ cells from the popliteal lymph nodes of keyhole-limpet hemocyanin-primed mice. The T cells that remained were unable to provide help to antigen-specific B cells in vitro. The results obtained using Fab' fragments were comparable with those using intact anti-L3T4 antibody and demonstrate that either form of GK1.5 is a potentially useful immunosuppressive agent in mice.

Animals↗
PubMed1989

Interactions between receptors for interleukin 2 and interleukin 4 on lines of helper T cells (HT-2) and B lymphoma cells (BCL1).

IL-2 and IL-4 induce a synergistic proliferative response in HT-2 cells, suggesting that IL-2Rs and IL-4Rs may interact. The purpose of this study was to examine the effect of IL-4 on the expression and function of IL-2Rs. Preincubation of HT-2 and BCL1-3B3 cells with IL-4 for 60 min at 4 degrees C or 37 degrees C resulted in a partial decrease in the number, but not the affinity of high affinity IL-2Rs as evidenced by Scatchard analysis of binding data. The decrease in the number of high affinity receptors correlated with decreased internalization of IL-2. After preincubation with IL-4, crosslinking of 125I-IL-2 to high affinity IL-2Rs also demonstrated a approximately 50% reduction in the number of high affinity IL-2Rs. Another lymphokine, IL-1, which acts on HT-2 cells, had no measurable effect on the affinity or number of IL-2Rs. Taken together, these results indicate that IL-4 downregulates the expression of high affinity IL-2Rs on some cells. It is not known whether this occurs by a direct ligand-mediated receptor interaction, by the sharing of a common receptor subunit, or by interaction of the two receptors with another membrane molecule or cytoskeletal component.

B-Lymphocytes↗
PubMed1988

Lymphokine-mediated regulation of the proliferative response of clones of T helper 1 and T helper 2 cells.

Murine Th1 and Th2 subsets differ not only in the lymphokines they produce, but also functionally. It is not clear what factors influence the preferential activation of one subset versus the other and what regulatory interactions exist between them. The purpose of this study was to examine the effect of lymphokines produced by clones of Th1 cells (IL-2 and IFN-gamma), Th2 cells (IL-4), and APC (IL-1) on the proliferative response of Th1 and Th2 cells after antigenic stimulation. Activation of both types of clones in the presence of antigen and APC resulted in the acquisition of responsiveness to the proliferative effects of both IL-2 and IL-4, although Th2 cells were more responsive to IL-4 than Th1 cells. Responsiveness of Th1 and Th2 cells to both lymphokines decreased with time after initial antigenic activation; Th1 cells lost their responsiveness to IL-4 more rapidly and to IL-2 more slowly than Th2 cells. IFN-gamma partially inhibited the IL-2 and IL-4-mediated proliferation of Th2, but not Th1 cells. Although the presence of IL-1 was not required for the response of Th1 or Th2 cells to IL-4, its presence resulted in a synergistic effect with IL-2 or IL-4 in Th2 but not in Th1 cells. Both subsets responded to a mixture of IL-2 and IL-4 in synergistic fashion. Delayed addition and wash-out experiments indicated that both IL-2 and IL-4 had to be present simultaneously in order for synergy to occur. These results suggest that Th cell subsets might regulate each other via the lymphokines that they secrete and that the pathways of IL-2 and IL-4 mediated proliferation are interrelated.

Animals↗
PubMed1988

Regulation of antibody isotype secretion by subsets of antigen-specific helper T cells.

The regulation of the subclass of immunoglobulin secreted by B cells has been studied in vitro in polyclonal systems using mitogens, such as lipopolysaccharide (LPS), to bypass the requirement for cognate interaction between antigen-specific T and B cells. In these systems, interleukin-(IL)-4 induces the secretion of IgG1 (ref. 1) and IgE (ref. 2); IL-5 enhances the secretion of IgA, and interferon-gamma (IFN-gamma) enhances the secretion of IgG2a (ref. 5). Clones of murine TH cells can be divided into two subsets, TH1 and TH2 (ref. 6). Both subsets synthesize IL-3 and granulocyte-monocyte colony-stimulating factor (GM-CSF), but only TH1 clones produce IL-2, IFN-gamma, and lymphotoxin (LT) and TH2 clones produce IL-4 and IL-5 (ref. 7). We have examined the role of clones of antigen-specific TH1 and TH2 cells in the regulation of the subclasses of IgG antibody secreted by antigen-specific B cells. Our results show that both types of TH cells induce the secretion of IgM and IgG3, whereas clones of TH1 and TH2 cells specifically induce antigen-specific B cells to secrete IgG2a and IgG1, respectively. We also demonstrate that regulation of commitment to the secretion of a particular IgG isotype occurs in two distinct stages: cognate interaction between T and B cells and interaction between T-cell-derived lymphokines and B cells.

Animals↗
PubMed1988

A single antigen-specific B cell can conjugate to either a type 1 or a type 2 helper T cell.

Keyhole-limpet-hemocyanin-specific I-Ad-restricted T helper cells type 1 (TH1 cells) and type 2 (TH2 cells) were studied for their ability to physically conjugate to trinitrophenyl-specific antigen-binding B cells (TNP-ABCs). The same TNP-ABCs (which had already processed TNP-keyhole limpet hemocyanin) formed conjugates with one or the other T helper (TH) cell type, and conjugation was antigen-specific and major histocompatibility complex-restricted. The conjugation of a fixed number of one type of TH cell to the TNP-ABCs was inhibited by co-incubation with increasing numbers of cells of the other TH cell type. Thus, the vast majority of TNP-ABCs can conjugate to either type of TH cell. A similar pattern of inhibition of the conjugation of one TH cell type to the TNP-ABCs was seen when cells were co-incubated with increasing numbers of cells from an alloreactive T-cell clone. In all cases, conjugates contained only one T cell bound to one B cell, suggesting that interaction of an antigen-presenting B cell with one TH cell prevents the simultaneous binding of another TH cell.

Animals↗
PubMed1988

Epitopes on CD45R [T200] molecules define differentiation antigens on murine B and T lymphocytes.

In the course of isolating hybridomas from rats that had been immunized with anti-Ig activated murine B lymphoblasts, we have identified three new mAb reactive with the T200 or leukocyte common antigen family (CD45). One, MB4B4, reacts with T200 on all leukocytes, and immunoprecipitates all the molecules that are recognized by an existing mAb to this family. Two others, MB23G2 and MB15C11, react with a subset of T200 molecules that has a unique tissue and cellular distribution. By FACS analysis and by immunocytochemical labeling of tissue sections, MB23G2/15C11 bind to most, if not all, small B and T lymphocytes, but react weakly with macrophages and dendritic cells. Expression of the MB23G2/15C11 T200 epitope exhibits four distinct features on lymphocytes: 1) activation of CD4+ cells in the mixed leukocyte reaction results in a decreased expression of MB23G2/15C11, on a subset of 30-60% of the T-cell blasts; 2) of 16 T-helper clones examined, clones of the TH2 phenotype express moderate to high levels of MB23G2/15C11 (2.5-19-fold increase in median fluorescence over control) while the TH1 clones express low to moderate levels (1.2-6.4-fold increase in median fluorescence over control) of the antigen recognized by these mAb; 3) The MB23G2/15C11 mAb do not react with germinal center cells in tissue sections of spleen, lymph node, and Peyer's patches; 4) MB23G2/15C11 reacts primarily with a subset of large thymocytes localized to the medulla. Therefore, MB23G2/15C11 define a subset-restricted form of T200 (CD45R) on murine lymphocytes. The tissue distribution of this T200 associated epitope is distinct from previously defined CD45 antigens and suggests a role during several pathways of lymphocyte development.

Animals↗
PubMed1987

Interleukin 4 enhances the ability of antigen-specific B cells to form conjugates with T cells.

T cell-B cell conjugates are formed when trinitrophenyl-specific B cells are exposed to trinitrophenyl-ovalbumin and ovalbumin-specific T hybridoma cells. The proportion of conjugates was increased two- to threefold when antigen-pulsed trinitrophenyl-specific B cells, but not T cells, were pre-exposed to interleukin 4. Antigen-specific B cells pretreated with antigen and interleukin 4 and cultured in the presence of specific T helper cells also produced a larger proportion of antibody-secreting cells as compared to cells pretreated with antigen alone. The interleukin 4-induced enhancement of T/B conjugate formation occurred over a wide range of antigen concentrations, was dependent on the concentration of interleukin 4, and was inhibited by the monoclonal anti-interleukin 4 antibody, 11B11. The importance of Ia antigens in the enhancement of conjugate formation and generation of antibody-secreting cells is suggested by a) the fact that the interleukin 4-mediated increase in the density of Ia antigens on the antigen-specific B cells correlated with their enhanced ability to form T/B conjugates, b) the kinetics of the interleukin 4-mediated increase in conjugate formation and surface Ia expression were similar, c) 10- to 20-fold higher concentrations of anti-I-A antibody were required to inhibit T/B conjugate formation by 50% with interleukin 4-treated antigen-specific B cells compared with untreated antigen-specific B cells, and d) interferon-gamma, which inhibits the interleukin 4-mediated increase in Ia antigens, inhibited the interleukin 4-induced enhancement of T/B conjugate formation. These results indicate that the interleukin 4-induced increase in the expression of Ia antigens on B cells plays an important role in the enhancement of T/B cell interactions and the subsequent differentiation of antigen-specific B cells into antibody-secreting cells.

Animals↗
PubMed1987

Inhibition of the helper function of murine T cells with Fab'-anti-L3T4 ricin A chain immunotoxin.

The ability of Fab'-anti-L3T4 A chain-containing immunotoxins to inhibit the helper function of keyhole limpet hemocyanin-specific T helper lymphocytes was evaluated. Keyhole limpet hemocyanin-specific T helper cells were prepared from the lymph nodes of primed mice and were enriched for T cells. Enriched populations of trinitrophenyl-specific B cells were prepared from spleens of normal mice. In the presence of antigen, the keyhole limpet hemocyanin-specific T helper cells were able to induce proliferation and differentiation of the trinitrophenyl-specific B cells. However, when the T helper cells were first treated with an immunotoxin composed of Fab' fragments of anti-L3T4 antibody coupled to ricin A chain (Fab'-anti-L3T4-A), they failed to induce proliferation and differentiation of the antigen-specific B cells. The concentrations of Fab'-anti-L3T4-A required to inhibit T cell help for the proliferation and differentiation of trinitrophenyl-specific B cells by 50% were 1 X 10(-9)M and 4 X 10(-10) M, respectively. Fab'-anti-L3T4 antibody alone did not inhibit T cell-induced B cell proliferation and differentiation by 50% at greater than 100-fold higher concentrations.

Animals↗
PubMed1987

Antigen-specific memory and virgin B cells differ in their requirements for conjugation to T cells.

The physical interaction between carrier-specific T hybridoma cells and long-term primed, TNP-specific memory B cells (TNP-MABC) exposed to TNP-OVA was compared to that of unprimed, TNP-specific virgin B cells (TNP-ABC). The direct conjugation of the T and B cells was visualized at the light microscopic level and the number of T/B conjugates was quantified directly. The results demonstrate that the TNP-MABC, as compared to TNP-ABC, formed T/B conjugates after a shorter exposure time to antigen and at a 10-fold lower concentration of antigen. Conjugate formation was inhibited almost completely by treating the TNP-MABC with concentrations of chloroquine that only partially inhibited the ability of the TNP-ABC to form conjugates. Exposure of the T hybridoma cells or the TNP-ABC to monoclonal antibodies directed against cell surface antigens prior to conjugation indicated that L3T4, Thy-1.2, and LFA-1 antigens on the T cells and LFA-1 and I-A antigens on the TNP-ABC are involved in conjugate formation. However, in contrast to the TNP-ABC where treatment of the B cells with anti-LFA-1 blocked T/B conjugate formation, pretreatment of the TNP-MABC with anti-LFA-1 had no effect.

Animals↗
PubMed1986

Characterization of the physical interaction between antigen-specific B and T cells.

It has been assumed that physical interaction between B cells and helper T cells in the presence of specific antigen is an early and essential step in the physiologic antibody response to thymus-dependent antigens. The present studies were designed to examine this physical interaction by employing carrier-specific T hybridoma cells that can provide help to highly enriched hapten-binding B cells. Direct conjugation of the B and T cells can be visualized at both the light and electron microscopic level and the number of conjugates can be directly quantified. Before their effective conjugation with T cells, the B cells must be incubated with specific antigen for 4 to 6 hr. After this time, the T cells form conjugates with the B cells within 5 min. Conjugate formation requires hapten specificity, carrier specificity, covalent linkage between hapten and carrier, and is MHC restricted. Two types of T-B conjugates were observed by electron microscopy: an antigen-independent attachment of B cell microvilli to small portions of the T cell surface and an antigen-dependent, intimate apposition of large areas of the plasma membranes of the T and B cells. The kinetics of development of the two modes of interaction suggest that the second type may be important for signal transduction, since the number of T and B cells showing intimate interactions increases with time. Monoclonal antibodies directed against Thy-1.2, LFA-1 alpha, L3T4, and I-A partially block conjugation of the two cell types, suggesting that these surface molecules are involved in T-B interaction.

Animals↗