The Experts below are selected from a list of 102 Experts worldwide ranked by ideXlab platform
Michael J H Ratcliffe - One of the best experts on this subject based on the ideXlab platform.
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b Cells the bursa of fabricius and the generation of antibody repertoires
Avian Immunology (Second Edition), 2014Co-Authors: Michael J H Ratcliffe, Sonja HartleAbstract:Birds have a unique organ for primary B lymphopoiesis, the bursa of Fabricius. Thus, avian B Cell development can be classified into pre-bursal, bursal and post-bursal stages. During embryonic development, pre-bursal B Cell precursors migrate in a single wave into the bursal mesenchyme; Cells which express Cell Surface Immunoglobulin as a consequence of productive gene rearrangement subsequently colonize the follicle anlagen. B Cells then proliferate rapidly in bursal follicles and diversify their receptor repertoire by means of gene conversion. After hatch, the formerly homogenous follicles separate into two compartments: an outer cortex and a central medulla. Starting around the time of hatch, B Cells emigrate from the bursa, predominantly from the follicle cortex, to colonize peripheral lymphoid tissues. In the periphery, naive B Cells encounter antigen, undergo a germinal center reaction and differentiate into antibody-secreting plasma Cells. Many aspects of these processes are regulated by cytokines. While the function of BAFF and CD40L on peripheral B Cells is largely conserved between birds and mammals, both of these TNF family members play unique roles in the bursa of Fabricius.
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antibodies Immunoglobulin genes and the bursa of fabricius in chicken b Cell development
Developmental and Comparative Immunology, 2006Co-Authors: Michael J H RatcliffeAbstract:The bursa of Fabricius is critical for the normal development of B lymphocytes in birds. It is productively colonized during embryonic life by a limited number of B Cell precursors that have undergone the Immunoglobulin gene rearrangements required for expression of Cell Surface Immunoglobulin. Immunoglobulin gene rearrangement occurs in the absence of terminal deoxynucleotidyl transferase and generates minimal antibody diversity. In addition, observations that Immunoglobulin heavy and light chain variable gene rearrangement occur at the same time and that allelic exclusion of Immunoglobulin expression is regulated at the level of variable region gene rearrangement provide a striking contrast to rodent and primate models of Immunoglobulin gene assembly. Following productive colonization of the bursa, developing B Cells undergo rapid proliferation and the Immunoglobulin V region genes that generate the specificity of the B Cell Surface Immunoglobulin receptor undergo diversification. Immunoglobulin diversity in birds is generated by somatic gene conversion events in which sequences derived from upstream families of pseudogenes replace homologous sequences in unique and functionally rearranged Immunoglobulin heavy and light chain variable region genes. This mechanism is distinct from and much more efficient than mechanisms of antibody diversification seen in rodents and primates. While the bursal microenvironment is not required for Immunoglobulin gene rearrangement and expression, it is essential for the generation of antibody diversity by gene conversion. Following hatch, gut derived antigens are taken up by the bursa. While bursal development prior to hatch occurs in the absence of exogenous antigen, chicken B Cell development after hatch may therefore be influenced by the presence of environmental antigen. This review focuses on the differences between B Cell development in the chicken as compared to rodent and primate models.
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Cell Surface Immunoglobulin regulated checkpoints in chicken b Cell development
Veterinary Immunology and Immunopathology, 2005Co-Authors: Parinaz Aliahmad, Michael J H Ratcliffe, Kelly A PikeAbstract:Abstract The bursa of Fabricius is critical for the normal development of B lymphocytes in avian species. Productive colonization of bursal follicles by B Cell precursors requires Surface Immunoglobulin expression. We have shown using retroviral gene transfer that expression of chimeric receptors containing the extraCellular and transmembrane domains of murine CD8α and CD8β fused to the cytoplasmic domains of chicken Igα and Igβ can support productive bursal colonization in the chicken embryo in bursal Cells lacking the expression of endogenous sIgM. We show here that chimeric receptor expression does not support continued bursal Cell development after hatch. However intrabursal administration of anti-CD8 antibodies that ligate the CD8α:Igα chimeric receptor results in maintained numbers of bursal Cells that express the chimeric receptor in the absence of endogenous sIgM. These results support a model in which sIgM receptor expression is required for productive bursal colonization in the chick embryo but sIgM receptor ligation is required to support later B Cell development after hatch.
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Cell Surface Immunoglobulin regulated checkpoints in chicken B Cell development.
Veterinary immunology and immunopathology, 2005Co-Authors: Parinaz Aliahmad, Kelly A Pike, Michael J H RatcliffeAbstract:The bursa of Fabricius is critical for the normal development of B lymphocytes in avian species. Productive colonization of bursal follicles by B Cell precursors requires Surface Immunoglobulin expression. We have shown using retroviral gene transfer that expression of chimeric receptors containing the extraCellular and transmembrane domains of murine CD8alpha and CD8beta fused to the cytoplasmic domains of chicken Igalpha and Igbeta can support productive bursal colonization in the chicken embryo in bursal Cells lacking the expression of endogenous sIgM. We show here that chimeric receptor expression does not support continued bursal Cell development after hatch. However intrabursal administration of anti-CD8 antibodies that ligate the CD8alpha:Igalpha chimeric receptor results in maintained numbers of bursal Cells that express the chimeric receptor in the absence of endogenous sIgM. These results support a model in which sIgM receptor expression is required for productive bursal colonization in the chick embryo but sIgM receptor ligation is required to support later B Cell development after hatch.
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Cell Surface Immunoglobulin receptors in b Cell development
Seminars in Immunology, 2002Co-Authors: Kelly A Pike, Michael J H RatcliffeAbstract:Abstract Expression of Surface Immunoglobulin (sIg) related receptors has been conserved in phylogenetically distinct species as a critical checkpoint in B Cell development. The sIg receptor comprises extraCellular IgM heavy and light chains, with the potential for ligand binding, complexed to the Igα/Igβ heterodimer that is responsible for signal transduction through sIg. Experimental systems, from both avian and murine models of B Cell development, have been designed to identify the function of individual receptor components in B Cell development. In this review, we assess the regulatory functions of different components of the sIg receptor complex during early development in experimental systems from evolutionarily distinct species.
Rose G Mage - One of the best experts on this subject based on the ideXlab platform.
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cd5 is a potential selecting ligand for b Cell Surface Immunoglobulin a possible role in maintenance and selective expansion of normal and malignant b Cells
Leukemia & Lymphoma, 2000Co-Authors: R Pospisil, Gregg J Silverman, Gerald E Marti, Alejandro Aruffo, Michael A Bowen, Rose G MageAbstract:Although the function of CD5 on B Cells is unknown, previous studies suggested that CD5 interaction with VH framework regions of Surface Immunoglobulins (Igs) may contribute to survival and expansion of B Cells. Here we used B-chronic lymphocytic leukemia (B-CLL) Cells and transformed B-Cell lines from normal and B-CLL patients to study CD5-Ig interactions. Immobilized Ig binds and permits isolation of CD5 from lysates of CD5-expressing Cell lines. Immunoglobulins or Fab fragments of different VH families varied in their effectiveness as inhibitors of anti-CD5 staining of CLL Cells, appendix and tonsil tissue sections. Human Ig also binds to purified recombinant CD5. We show here for the first time that the unconventional Ig-CD5 interaction maps to the extraCellular CD5-D2 domain whereas conventional epitopes recognized by anti-CD5 antibodies are localized in the Dl domain of CD5. We propose that interactions of VH framework regions with CD5 as a ligand may maintain, select or expand normal, autoimmune or...
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cd5 is a potential selecting ligand for b Cell Surface Immunoglobulin framework region sequences
Journal of Experimental Medicine, 1996Co-Authors: R Pospisil, M G Fitts, Rose G MageAbstract:In rabbits nearly all B lymphocytes express the glycoprotein CD5, in contrast to mice and humans, where only a small proportion of B Cells express this molecule (Raman, C., and K.L. Knight. 1992. J. Immunol. 149:3858-3864). CD5+ B Cells appear to develop early in ontogeny and be maintained throughout life by self-renewal. The function of CD5 on B Cells is still unknown. We showed earlier that "positive" selection occurs during B lymphocyte development in the rabbit appendix. This selection favors B Cell expressing Surface Immunoglobulins with VHa2 structures in the first and third framework regions (Pospisil, R., G.O. Young-Cooper, and R.G. Mage. 1995. Proc. Natl. Acad. Sci. USA. 92:6961-6965). Here we report that F(ab')2 fragments, especially those bearing VHa2 framework region determinants, specifically interact with the B Cell-Surface glycoprotein CD5. This interaction can be inhibited by anti-CD5 antibodies. Furthermore, immobilized F(ab')2 fragments selectively bind CD5 molecules in appendix Cell lysates. Interactions of VH framework region structures with CD5 may affect maintenance and selective expansion of particular B Cells and thus contribute to autostimulatory growth of autoimmune or transformed Cells.
Daniel H Conrad - One of the best experts on this subject based on the ideXlab platform.
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co crosslinking fcerii cd23 and b Cell Surface Immunoglobulin modulates b Cell activation
European Journal of Immunology, 1992Co-Authors: Kim A Campbell, Andrew Lees, Fred D Finkelman, Daniel H ConradAbstract:: Previous studies have shown that a highly multivalent from of anti-IgD or anti-IgM, prepared by conjugating the respective antibodies to dextran, causes extensive B Cell proliferation with ng/ml concentrations of the anti-Immunoglobulin (Ig). A modification of this system has been exploited to investigate the effect of co-crosslinking the Fc epsilon RII and Surface Ig by binding DNP to the dextran backbone (DNP-dextran) and employing a DNP-specific monoclonal IgE of either rat or mouse origin. Addition of anti-IgD-(H delta a/1)[DNP-dextran] or anti-IgM-[DNP-dextran] to purified, resting murine B Cells resulted in B Cell proliferation over a broad dose (0.03-30 micrograms/ml). Addition of DNP-specific rat or mouse IgE dramatically modulated the proliferative response. Proliferation in response to doses greater than 0.3 microgram/ml H delta a/1-[DNP-dextran] was consistently reduced in a dose-dependent manner in the presence of increasing amounts of IgE while proliferation to lower concentrations of H delta a/1-[DNP-dextran] was slightly enhanced or not influenced at all by the IgE anti-DNP. Interleukin-4 (IL-4) significantly increased the IgE effect, in line with its known enhancing effects on Fc epsilon RII levels. Experiments measuring Ig production rather than proliferation demonstrated that in the presence of IgE anti-DNP, B Cells produced lower amounts of Immunoglobulin (IgG1 or IgM) in response to an anti-Ig signal. Control experiments demonstrated that the IgE effect on proliferation was blocked by monoclonal anti-Fc epsilon RII, but not anti-Fc gamma RII, thus demonstrating the necessity for IgE/Fc epsilon RII interaction. In addition, the necessity for co-crosslinking was shown by the inability of IgE anti-DNP to affect the proliferative response to H delta a/1-dextran even in the presence of various doses of DNP-dextran. These results demonstrate that co-crosslinking of sIg and the Fc epsilon RII results in an altered B Cell response to anti-Ig mediated activation. IL-4 does not ablate this inhibition, in contrast to the effect of co-crosslinking Fc gamma RII and Surface Ig, suggesting a model whereby IgE can modulate its own production.
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Co-crosslinking FcεRII/CD23 and B Cell Surface Immunoglobulin modulates B Cell activation
European Journal of Immunology, 1992Co-Authors: Kim A Campbell, Andrew Lees, Fred D Finkelman, Daniel H ConradAbstract:Previous studies have shown that a highly multivalent from of anti-IgD or anti-IgM, prepared by conjugating the respective antibodies to dextran, causes extensive B Cell proliferation with ng/ml concentrations of the anti-Immunoglobulin (Ig). A modification of this system has been exploited to investigate the effect of co-crosslinking the Fc epsilon RII and Surface Ig by binding DNP to the dextran backbone (DNP-dextran) and employing a DNP-specific monoclonal IgE of either rat or mouse origin. Addition of anti-IgD-(H delta a/1)[DNP-dextran] or anti-IgM-[DNP-dextran] to purified, resting murine B Cells resulted in B Cell proliferation over a broad dose (0.03-30 micrograms/ml). Addition of DNP-specific rat or mouse IgE dramatically modulated the proliferative response. Proliferation in response to doses greater than 0.3 microgram/ml H delta a/1-[DNP-dextran] was consistently reduced in a dose-dependent manner in the presence of increasing amounts of IgE while proliferation to lower concentrations of H delta a/1-[DNP-dextran] was slightly enhanced or not influenced at all by the IgE anti-DNP. Interleukin-4 (IL-4) significantly increased the IgE effect, in line with its known enhancing effects on Fc epsilon RII levels. Experiments measuring Ig production rather than proliferation demonstrated that in the presence of IgE anti-DNP, B Cells produced lower amounts of Immunoglobulin (IgG1 or IgM) in response to an anti-Ig signal. Control experiments demonstrated that the IgE effect on proliferation was blocked by monoclonal anti-Fc epsilon RII, but not anti-Fc gamma RII, thus demonstrating the necessity for IgE/Fc epsilon RII interaction. In addition, the necessity for co-crosslinking was shown by the inability of IgE anti-DNP to affect the proliferative response to H delta a/1-dextran even in the presence of various doses of DNP-dextran. These results demonstrate that co-crosslinking of sIg and the Fc epsilon RII results in an altered B Cell response to anti-Ig mediated activation. IL-4 does not ablate this inhibition, in contrast to the effect of co-crosslinking Fc gamma RII and Surface Ig, suggesting a model whereby IgE can modulate its own production.
Jack R Bennink - One of the best experts on this subject based on the ideXlab platform.
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a simple flow cytometric method measuring b Cell Surface Immunoglobulin avidity enables characterization of affinity maturation to influenza a virus
Mbio, 2015Co-Authors: Gregory M Frank, Davide Angeletti, William L Ince, James S Gibbs, Surender Khurana, Adam K Wheatley, Adrian B Mcdermott, Hana Golding, James Stevens, Jack R BenninkAbstract:ABSTRACT Antibody (Ab) affinity maturation enables an individual to maintain immunity to an increasing number of pathogens within the limits of a total Ig production threshold. A better understanding of this process is critical for designing vaccines that generate optimal Ab responses to pathogens. Our study describes a simple flow-cytometric method that enumerates virus-specific germinal center (GC) B Cells as well as their AC 50 , a measure of Ab avidity, defined as the antigen concentration required to detect 50% of specific B Cells. Using a model of mouse Ab responses to the influenza A virus hemagglutinin (IAV HA), we obtained data indicating that AC 50 decreases with time postinfection in an affinity maturation-dependent process. As proof of principle of the utility of the method, our data clearly show that relative to intranasal IAV infection, intramuscular immunization against inactivated IAV in adjuvant results in a diminished GC HA B Cell response, with increased AC 50 correlating with an increased serum Ab off-rate. Enabling simultaneous interrogation of both GC HA B Cell quantity and quality, this technique should facilitate study of affinity maturation and rational vaccine design. IMPORTANCE Though it was first described 50 years ago, little is known about how antibody affinity maturation contributes to immunity. This question is particularly relevant to developing more effective vaccines for influenza A virus (IAV) and other viruses that are difficult vaccine targets. Limitations in methods for characterizing antigen-specific B Cells have impeded progress in characterizing the quality of immune responses to vaccine and natural immunogens. In this work, we describe a simple flow cytometry-based approach that measures both the number and affinity of IAV-binding germinal center B Cells specific for the IAV HA, the major target of IAV-neutralizing antibodies. Using this method, we showed that the route and form of immunization significantly impacts the quality and quantity of B Cell antibody responses. This method provides a relatively simple yet powerful tool for better understanding the contribution of affinity maturation to viral immunity.
Gregory M Frank - One of the best experts on this subject based on the ideXlab platform.
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flow cytometric method measuring b Cell Surface Immunoglobulin avidity
Methods of Molecular Biology, 2017Co-Authors: Davide Angeletti, Gregory M Frank, Jonathan W YewdellAbstract:Abstract The affinity of antibodies for their cognate antigens is a critical aspect of humoral immunity. The immune system has gone to great lengths to evolve a mechanism that enables real time increases in antibody affinity during the course of an immune response. This occurs in germinal centers (GC), which form in spleen and lymph nodes following immunization. GC B Cell competition for limiting amount of antigen drives the selection of B Cells expressing higher affinity Abs. Remarkably little is known about affinity maturation of B Cells in immune responses to all but a handful of small model antigens. It has proven challenging to measure the avidity of specific Abs in polyclonal sera to more complex antigens, including viruses. In this chapter we present a simple, flow cytometry based, method that determines the average avidity of GC B Cells for the influenza A virus hemagglutinin glycoprotein, the target antigen of traditional influenza vaccines. Flow cytometry using fluorescent hemagglutinin and B Cell marker specific Abs enables high throughput qualitative and quantitative detection of individual B Cells. By using a graded amount of antigen and gating on GC B Cells we define the AC50 the amount of antigen required to stain 50% of hemagglutinin specific B Cells. This number is in remarkable agreement with the avidity of the B Cell population. This method can be generally employed to include antibody avidity measurements basic and clinical studies of immunity to viruses and other medically relevant immunogens.
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a simple flow cytometric method measuring b Cell Surface Immunoglobulin avidity enables characterization of affinity maturation to influenza a virus
Mbio, 2015Co-Authors: Gregory M Frank, Davide Angeletti, William L Ince, James S Gibbs, Surender Khurana, Adam K Wheatley, Adrian B Mcdermott, Hana Golding, James Stevens, Jack R BenninkAbstract:ABSTRACT Antibody (Ab) affinity maturation enables an individual to maintain immunity to an increasing number of pathogens within the limits of a total Ig production threshold. A better understanding of this process is critical for designing vaccines that generate optimal Ab responses to pathogens. Our study describes a simple flow-cytometric method that enumerates virus-specific germinal center (GC) B Cells as well as their AC 50 , a measure of Ab avidity, defined as the antigen concentration required to detect 50% of specific B Cells. Using a model of mouse Ab responses to the influenza A virus hemagglutinin (IAV HA), we obtained data indicating that AC 50 decreases with time postinfection in an affinity maturation-dependent process. As proof of principle of the utility of the method, our data clearly show that relative to intranasal IAV infection, intramuscular immunization against inactivated IAV in adjuvant results in a diminished GC HA B Cell response, with increased AC 50 correlating with an increased serum Ab off-rate. Enabling simultaneous interrogation of both GC HA B Cell quantity and quality, this technique should facilitate study of affinity maturation and rational vaccine design. IMPORTANCE Though it was first described 50 years ago, little is known about how antibody affinity maturation contributes to immunity. This question is particularly relevant to developing more effective vaccines for influenza A virus (IAV) and other viruses that are difficult vaccine targets. Limitations in methods for characterizing antigen-specific B Cells have impeded progress in characterizing the quality of immune responses to vaccine and natural immunogens. In this work, we describe a simple flow cytometry-based approach that measures both the number and affinity of IAV-binding germinal center B Cells specific for the IAV HA, the major target of IAV-neutralizing antibodies. Using this method, we showed that the route and form of immunization significantly impacts the quality and quantity of B Cell antibody responses. This method provides a relatively simple yet powerful tool for better understanding the contribution of affinity maturation to viral immunity.