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C C Goodnow

Publications and source records attributed to C C Goodnow.

At least 19 recordsLinked to original sources
PubMed2000

Entry of B cell receptor into signaling domains is inhibited in tolerant B cells.

Signal transduction through the B cell antigen receptor (BCR) is altered in B cells that express a receptor that recognizes self-antigen. To understand the molecular basis for the change in signaling in autoreactive B cells, a transgenic model was used to isolate a homogeneous population of tolerant B lymphocytes. These cells were compared with a similar population of naive B lymphocytes. We show that the BCR from naive B cells enters a detergent-insoluble domain of the cell within 6 s after antigen binding, before a detectable increase in BCR phosphorylation. This fraction appears to be important for signaling because it is enriched for lyn kinase but lacks CD45 tyrosine phosphatase and because the BCR that moves into this domain becomes more highly phosphorylated. Partitioning of the BCR into this fraction is unaffected by src family kinase inhibition. Tolerant B cells do not efficiently partition the BCR into the detergent-insoluble domain, providing an explanation for their reduced tyrosine kinase activation and calcium flux in response to antigen. These results identify an early, regulated step in antigen receptor signaling and self-tolerance.

Animals↗
PubMed2000

Gene dose-dependent maturation and receptor editing of B cells expressing immunoglobulin (Ig)G1 or IgM/IgG1 tail antigen receptors.

Conserved differences between the transmembrane and cytoplasmic domains of membrane immunoglobulin (Ig)M and IgG may alter the function of antigen receptors on naive versus memory B cells. Here, we compare the ability of these domains to signal B cell allelic exclusion and maturation in transgenic mice. A lysozyme-binding antibody was expressed in parallel sets of mice as IgM, IgG1, or a chimeric receptor with IgM extracellular domains and transmembrane/cytoplasmic domains of IgG1. Like IgM, the IgG1 or chimeric IgM/G receptors triggered heavy chain allelic exclusion and supported development of mature CD21(+) B cells. Many of the IgG or IgM/G B cells became CD21(high) and downregulated their IgG and IgM/G receptors spontaneously, resembling memory B cells and B cells with mutations that exaggerate B cell antigen receptor signaling. Unlike IgM-transgenic mice, "edited" B cells that carry non-hen egg lysozyme binding receptors preferentially accumulated in IgG and IgM/G mice. This was most extreme in lines with the highest transgene copy number and diminished in variant offspring with fewer copies. The sensitivity of B cell maturation to transgene copy number conferred by the IgG transmembrane and cytoplasmic domains may explain the diverse phenotypes found in other IgG-transgenic mouse strains and may reflect exaggerated signaling.

Animals↗
PubMed2000

Role of Syk in B-cell development and antigen-receptor signaling.

Antigen receptors (BCRs) on developing B lymphocytes play two opposing roles-promoting survival of cells that may later bind a foreign antigen and inhibiting survival of cells that bind too strongly to self-antigens. It is not known how these opposing outcomes are signaled by BCRs on immature B cells. Here we analyze the effect of a null mutation in the Syk tyrosine kinase on maturing B cells displaying a transgene-encoded BCR that binds hen egg lysozyme (HEL). In the absence of HEL antigen, HEL-specific BCRs are expressed normally on the surface of Syk-deficient immature B-lineage cells, but this fails to promote maturation beyond the earliest stages of B-lineage commitment. Binding of HEL antigen, nevertheless, triggers phosphorylation of CD79alpha/beta BCR subunits and modulation of receptors from the surface in Syk-deficient cells, but it cannot induce an intracellular calcium response. Continuous binding of low- or high-avidity forms of HEL, expressed as self-antigens, fails to restore the signal needed for maturation. Compared with the effects in the same system of null mutations in other BCR signaling elements, such as CD45 and Lyn kinase, these results indicate that Syk is essential for transmitting a signal that initiates the program of B-lymphocyte maturation.

Animals↗
PubMed2000

How self-tolerance and the immunosuppressive drug FK506 prevent B-cell mitogenesis.

Therapy for transplant rejection, autoimmune disease and allergy must target mature lymphocytes that have escaped censoring during their development. FK506 and cyclosporin are immunosuppressants which block three antigen-receptor signalling pathways (NFAT, NFkappaB and JNK), through inhibition of calcineurin, and inhibit mature lymphocyte proliferation to antigen. Neither drug induces long-lived tolerance in vivo, however, necessitating chronic use with adverse side effects. Physiological mechanisms of peripheral tolerance to self-antigens provide an opportunity to emulate these processes pharmacologically. Here we use gene-expression arrays to provide a molecular explanation for the loss of mitogenic response in peripheral B-cell anergy, one aspect of immunological tolerance. Self-antigen induces a set of genes that includes negative regulators of signalling and transcription but not genes that promote proliferation. FK506 interferes with calcium-dependent components of the tolerance response and blocks an unexpectedly small fraction of the activation response. Many genes that were not previously connected to self-tolerance are revealed, and our findings provide a molecular fingerprint for the development of improved immunosuppressants that prevent lymphocyte activation without blocking peripheral tolerance.

Animals↗
PubMed2000

Genomic-scale gene expression analysis of lymphocyte growth, tolerance and malignancy.

Immunologists are already comfortable with the need for monitoring many different gene products simultaneously. It is a common challenge to remember what CD-one-hundred-and-something is, and an ever-increasing number of colours are required for identification on the flow cytometer. Gene expression arrays now offer the possibility of extending this approach beyond the cell surface and expanding it dramatically to survey the entire catalogue of gene transcripts in a lymphoid cell.

Algorithms↗
PubMed1999

Growing up on the streets: why B-cell development differs from T-cell development.

B-cell development differs significantly from T-cell development in that negative selection of autoreactive B cells can occur in the same microenvironment in which productive immune responses begin. Here, Sarah Townsend and colleagues discuss how this 'growing up on the streets' might provide a mechanism that fills holes in the B-cell repertoire, much as major histocompatibility complex polymorphism fills holes in the T-cell repertoire.

Animals↗
PubMed1998

Regulation of mouse CD72 gene expression during B lymphocyte development.

CD72 is a 45-kDa transmembrane glycoprotein that is predominantly expressed on cells of the B lineage except plasma cells. Previously, we identified the 255-bp minimal mouse CD72 promoter capable of tissue-specific and developmental stage-specific expression. DNase I footprinting analysis of the 255-bp CD72 promoter revealed three protected elements, footprint (FP) I, FP II, and FP III. FP II, which extends from nucleotide -189 to -169 of the mouse CD72 promoter, exhibited both tissue-specific and developmental stage-specific activity that was reflective of the activity of the CD72 gene in vivo. In this report, we show that FP II is specifically recognized by the transcription factor B cell-specific activator protein (BSAP). Mutations eliminating the binding of BSAP in reporter constructs also eliminated the increase of reporter activity in B cells. In addition, cotransfections with reporter constructs plus different amounts of expression plasmids for BSAP showed that CD72 promoter activity was up-regulated by BSAP in plasmacytoma cells and T cells in a dose-dependent manner. Moreover, the expression level of CD72 decreased 10-fold on normal plasma cells. Compared with the presence of BSAP binding in mature B cells, the binding of BSAP was undetectable in those plasma cells. This study strongly suggests that BSAP-FP II interaction plays a critical role in determining the cell-type specificity of the CD72 promoter. The absence of positive factors such as BSAP accounts for at least part of the loss of mouse CD72 expression in plasma cells and thus might be common for the down-regulation of many molecules at the plasma cell stage.

Animals↗
PubMed1998

Repression of B7.2 on self-reactive B cells is essential to prevent proliferation and allow Fas-mediated deletion by CD4(+) T cells.

Peripheral tolerance mechanisms normally prevent delivery of T cell help to anergic self-reactive B cells that accumulate in the T zones of spleen and lymph nodes. Chronic exposure to self-antigens desensitizes B cell antigen receptor (BCR) signaling on anergic B cells so that they are not stimulated into clonal expansion by CD4(+) T cells but instead are eliminated by Fas (CD95)-induced apoptosis. Because a range of BCR-induced signals and responses are repressed in anergic B cells, it is not known which of these are critical to regulate for Fas-mediated peripheral tolerance. Display of the costimulatory molecule, B7.2 (CD86), represents a potentially important early response to acute BCR engagement that is poorly induced by antigen on anergic B cells. We show here that restoring B7.2 expression on tolerant B cells using a constitutively expressed B7.2 transgene is sufficient to prevent Fas-mediated deletion and to trigger extensive T cell-dependent clonal expansion and autoantibody secretion in the presence of specific T cells. Dysregulated expression of B7.2 on tolerant B cells caused a more extreme reversal of peripheral tolerance than that caused by defects in Fas or Fas ligand, and resulted in T cell-dependent clonal expansion and antibody secretion comparable in magnitude to that made by foreign antigen-specific B cells. These findings demonstrate that repression of B7.2 is critical to eliminate autoreactive B cells by Fas in B cell-T cell interactions. The possible role of B7.2 dysregulation in systemic autoimmune diseases is discussed.

Animals↗
PubMed1998

Abortive proliferation of rare T cells induced by direct or indirect antigen presentation by rare B cells in vivo.

Antigen-specific B cells are implicated as antigen-presenting cells in memory and tolerance responses because they capture antigens efficiently and localize to T cell zones after antigen capture. It has not been possible, however, to visualize the effect of specific B cells on specific CD4+ helper T cells under physiological conditions. We demonstrate here that rare T cells are activated in vivo by minute quantities of antigen captured by antigen-specific B cells. Antigen-activated B cells are helped under these conditions, whereas antigen-tolerant B cells are killed. The T cells proliferate and then disappear regardless of whether the B cells are activated or tolerant. We show genetically that T cell activation, proliferation, and disappearance can be mediated either by transfer of antigen from antigen-specific B cells to endogenous antigen-presenting cells or by direct B-T cell interactions. These results identify a novel antigen presentation route, and demonstrate that B cell presentation of antigen has profound effects on T cell fate that could not be predicted from in vitro studies.

Animals↗
PubMed1998

Dependence of germinal center B cells on expression of CD21/CD35 for survival.

Affinity-driven selection of B lymphocytes within germinal centers is critical for the development of high-affinity memory cells and host protection. To investigate the role of the CD21/CD35 coreceptor in B cell competition for follicular retention and survival within the germinal center, either Cr2+ or Cr2null lysozyme-specific transgenic B cells were adoptively transferred into normal mice immunized with duck (DEL) or turkey (TEL) lysozyme, which bind with different affinities. In mice injected with high-affinity turkey lysozyme, Cr2null B cells responded by follicular retention; however, they could not survive within germinal centers. This suggests that CD21 provides a signal independent of antigen that is required for survival of B cells in the germinal center.

Adoptive Transfer↗
PubMed1998

Spontaneous follicular exclusion of SHP1-deficient B cells is conditional on the presence of competitor wild-type B cells.

Engagement of antigen receptors on mature B lymphocytes is known to block cell entry into lymphoid follicles and promote accumulation in T cell zones, yet the molecular basis for this change in cell distribution is not understood. Previous studies have shown that follicular exclusion requires a threshold level of antigen receptor engagement combined with occupancy of follicles by B cells without equivalent receptor engagement. The possibility has been raised that follicular composition affects B cell positioning by altering the amount of available antigen and the degree of receptor occupancy. Here we show that follicular composition affects migration of mature B cells under conditions that are independent of antigen receptor occupancy. B cells deficient in the negative regulatory protein tyrosine phosphatase, SHP1, which have elevated intracellular signaling by the B cell receptor, are shown to accumulate in the T zone in the absence of their specific antigen. Follicular exclusion of SHP1-deficient B cells was found to be conditional on the presence of excess B cells that lack elevated intracellular signaling, and was not due to a failure of SHP-1-deficient cells to mature and express the follicle-homing chemokine receptor Burkitt's lymphoma receptor 1. These findings strongly suggest that signals that are negatively regulated by SHP1 promote B cell localization in T cell zones by reducing competitiveness for follicular entry, and provide further evidence that follicular composition influences the positioning of antigen-engaged B cells.

Animals↗
PubMed1998

Quantitative and qualitative control of antigen receptor signalling in tolerant B lymphocytes.

Lymphocyte antigen receptors, such as the B cell antigen receptor (BCR), have the ability to promote or inhibit immune responses. This functional plasticity is exemplified by BCR-induced mitosis in naïve but not tolerant B cells and is correlated with biochemical differences in the signals triggered by foreign and self antigens. Acute stimulation of naïve B cells with foreign antigen induces a biphasic Ca2+ flux, and activates nuclear signalling through NF-AT, NF-kappa B, JNK and ERK. In tolerant B lymphocytes, by contrast, self antigen triggers only a low Ca2+ plateau, NF-AT and ERK. After removal from self antigen, the BCRs on tolerant B cells reacquire the ability to stimulate a biphasic Ca2+ flux and to promote proliferation. The differences in nuclear signalling between naïve and tolerant cells is brought about in part by differences in the magnitude of the Ca2+ signal. A low, sustained Ca2+ signal, such as that seen in tolerant B cells, activates NF-AT, whereas, a high but transient Ca2+ spike, which resembles that triggered in naïve B cells, activates NF-kappa B and JNK. These findings demonstrate that the quantitative differences in Ca2+ signalling between naïve and tolerant B cells are reversible and contribute to the differential triggering of nuclear signals. The activation of selected transcription factors may in turn account for the different functional responses triggered in naïve and tolerant lymphocytes.

B-Lymphocytes↗
PubMed1998

B cell antigen receptor signalling in the balance of tolerance and immunity.

The quantity and quality of signals from the B cell antigen receptor (BCR) drives the positive and negative selection of B lymphocytes and establishes the balance of tolerance and immunity. Experiments using immunoglobulin transgenic mice and mutations in key BCR signalling components have given insight into how the antigen receptor is tuned and how thresholds for qualitatively different outcomes are established and maintained. This research also describes how genetic variants can shift the balance between autoimmunity and tolerance.

Animals↗
PubMed1998

Polygenic autoimmune traits: Lyn, CD22, and SHP-1 are limiting elements of a biochemical pathway regulating BCR signaling and selection.

A B lymphocyte hyperactivity syndrome resembling systemic lupus erythematosus characterizes mice lacking the src-family kinase Lyn. Lyn is not required to initiate B cell antigen receptor (BCR) signaling but is an essential inhibitory component. lyn-/- B cells have a delayed but increased calcium flux and exaggerated negative selection responses in the presence of antigen and spontaneous hyperactivity in the absence of antigen. As in invertebrates, genetic effects of loci with only one functional allele can be used to analyze signaling networks in mice, demonstrating that negative regulation of the BCR is a complex quantitative trait in which Lyn, the coreceptor CD22, and the tyrosine phosphatase SHP-1 are each limiting elements. The biochemical basis of this complex trait involves a pathway requiring Lyn to phosphorylate CD22 and recruit SHP-1 to the CD22/BCR complex.

Animals↗
PubMed1998

Self-reactive B lymphocytes overexpressing Bcl-xL escape negative selection and are tolerized by clonal anergy and receptor editing.

Self-reactive B cells Tg for both a bcl-xL death inhibitory gene and an Ig receptor recognizing hen egg lysozyme (HEL-Ig) efficiently escaped developmental arrest and deletion in mice expressing membrane-bound self-antigen (mHEL). In response to the same antigen, Tg HEL-Ig B cells not expressing bcl-xL were deleted, while cells expressing bcl-2 were arrested at the immature B stage. Bcl-xL Tg B cells escaping negative selection were anergic in both in vitro and in vivo assays and showed some evidence for receptor editing. These studies suggest that Bcl-x may have a distinct role in controlling survival at the immature stage of B cell development and demonstrate that tolerance is preserved when self-reactive B cells escape central deletion.

Animals↗
PubMed1998

A critical role for complement in maintenance of self-tolerance.

The role of complement in the maintenance of self-tolerance has been examined in two models: an immunoglobulin transgenic model of peripheral tolerance and a lupus-like murine model of CD95 (Fas) deficiency. We find that self-reactive B lymphocytes deficient in complement receptors CD21/CD35 or transferred into mice deficient in the complement protein C4 are not anergized by soluble self-antigen. In the second model, deficiency in CD21/CD35 or C4 combined with CD95 deficiency results in high titers of anti-nuclear antibodies leading to severe lupus-like disease. These findings suggest a novel role for the complement system in B cell tolerance and provide insight into the genetic association of complement deficiency with susceptibility to systemic lupus erythematosus.

Animals↗
PubMed1998

The in vivo balance between B cell clonal expansion and elimination is regulated by CD95 both on B cells and in their micro-environment.

The expression of CD95 (Fas/APO-1) on B cells has been shown to play a direct role in their fate. B cells that chronically bind antigen due to prolonged antigen exposure, such as self-reactive B cells, are induced to express CD95 by CD40 ligand (CD40L) and are subsequently eliminated by CD95 ligand (CD95L) when they present antigen to CD4+ T cells. B cells that bind antigen acutely due to sudden antigen encounter, such as foreign antigen reactive B cells, up-regulate CD95, but are normally protected from CD95L-mediated apoptosis. Here, however, it is shown in vivo that foreign antigen-specific B cells fail to be protected from CD95-dependent elimination in a host that is CD95 deficient, regardless of antigenic challenge. These data indicate that B cell antigen receptor (BCR)-induced protection against CD95L-mediated apoptosis is not absolute but depends upon other micro-environmental factors in vivo. The normal balance between T cell-dependent humoral immunity and tolerance is thus regulated intrinsically by CD95 expression on responding B cells, and extrinsically by CD95-mediated control of CD95L or other molecules in the lymphoid micro-environment.

Animals↗