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C C Goodnow

Publications and source records attributed to C C Goodnow.

At least 73 records · Page 4Linked to original sources
PubMed1995

Antigen-induced exclusion from follicles and anergy are separate and complementary processes that influence peripheral B cell fate.

Anergic self-reactive B cells competing within a polyclonal B cell repertoire fail to migrate into primary follicles and die after 1-3 days residence in T cell zones. Transfer of anergic HEL-specific B cells to recipients lacking HEL autoantigen and continuous bromodeoxyuridine labeling in mixed bone marrow chimeras confirms that follicular exclusion and cell death in 1-3 days is not an intrinsic characteristic of anergic cells but results from competition with B cells bearing other specificities together with continued binding of autoantigen. When naive (nontolerant) HEL-specific B cells were transferred into mice expressing HEL autoantigen, they were also excluded from follicles and their lifespan was dramatically shortened, although they became activated to express CD86 (B7-2/B70). In the presence of helper T cells, activated B cells but not anergic B cells were rescued from death and formed large extrafollicular foci to autoantibody-secreting cells. Antigen-induced exclusion from follicles is therefore an independent process from anergy that prevents self-reactive B cells from recirculating in the long-lived repertoire and may foster interactions with T cells during immune responses. By contrast, anergy prevents self-reactive B cells from collaborating with helper T cells and secreting autoantibody while trapped in the T zone.

Animals↗
PubMed1995

Protein tyrosine phosphatase 1C negatively regulates antigen receptor signaling in B lymphocytes and determines thresholds for negative selection.

Motheaten viable (mev) mice are deficient in the cytosolic protein tyrosine phosphatase, PTP1C, and exhibit severe B cell immunodeficiency and autoantibody production. The role of PTP1C in B cell selection and function was analyzed by breeding immunoglobulin transgenes specific for a defined antigen, hen egg lysozyme, into mev mice. Antigen triggered a greater and more rapid elevation of intracellular calcium in PTP1C-deficient B cells, indicating that this phosphatase negatively regulates immunoglobulin signaling. Elimination of self-reactive B cells carrying this signal-enhancing mutation was triggered during their development by binding a lower valency form of self-antigen than is normally required. These findings establish that activation of distinct repertoire-censoring mechanisms depends on quantitative differences in antigen receptor signaling, whose thresholds are determined by negative regulation through PTP1C.

Animals↗
PubMed1994

Competition for follicular niches excludes self-reactive cells from the recirculating B-cell repertoire.

Two different approaches to follow clones of B lymphocytes in a diverse preimmune repertoire reveal a new process for eliminating self-reactive cells in the periphery which depends on competition between cells with different specificities. A key feature of this censoring mechanism is the selective exclusion of self-antigen-binding B cells from the normal migration route into lymphoid follicles, resulting in their premature death. This is a striking example of homeostasis by cellular competition for limiting niches and may explain the paradoxical association between immunodeficiency and autoimmunity.

Animals↗
PubMed1994

Effects of the lpr mutation on elimination and inactivation of self-reactive B cells.

Mice homozygous for the lymphoproliferation (lpr) mutation, which disrupts expression of the Fas cell surface molecule, develop an autoimmune syndrome with a spectrum of autoantibodies resembling human SLE. It is not known how the loss of Fas leads to autoantibody production. To study the fate of autoreactive B cells in lpr/lpr mice, C57BL/6 (B6) strain transgenic mice expressing hen egg lysozyme (HEL) as a model autoantigen in soluble or membrane-bound forms and carrying HEL-specific Ig (Ig) transgenes were mated onto the congenic B6-lpr/lpr background. Despite the absence of Fas, elimination of self-reactive lpr/lpr B cells recognizing membrane-bound autoantigen occurred as efficiently as in autoreactive B cells bearing the wild-type (+/+) Fas gene. Functional inactivation of autoreactive B cells binding soluble HEL also occurred normally in most young lpr/lpr animals. Nevertheless, breakdown of B cell tolerance to soluble lysozyme occurred in one of eight young lpr/lpr animals and in four of seven old animals with lymphadenopathy. Interestingly, the presence of the rearranged Ig transgenes markedly delayed the onset of lymphadenopathy. These results demonstrate that Fas is not an essential molecule in the biochemical pathways mediating autoreactive B cell elimination or inactivation. The breakdown of tolerance observed in a considerable fraction of older animals nevertheless confirms that autoantibody production in this model of SLE involves a defect in active censoring of autoreactive B cells. The possible basis for that defect is discussed.

Animals↗
PubMed1994

Differential up-regulation of the B7-1 and B7-2 costimulatory molecules after Ig receptor engagement by antigen.

Ag-pulsed B cells are potent APCs, in part, because of the ability of the Ig receptor to mediate rapid and specific Ag uptake. However, it is also known that full T cell activation requires signals delivered by costimulatory molecules, which naive B cells seem to lack. This study examines the effect Ig receptor engagement has on the expression and function of a new CD28 counter-receptor, B7-2. Unlike B7-1 (B7), B7-2 was rapidly induced on the cell surface of B cells after engagement of the Ig receptor by either anti-Ig mAbs or hen egg lysozyme (HEL) on normal and HEL-specific B cell receptor transgenic B cells, respectively. Furthermore, B7-2 expression was up-regulated on tolerant B cells isolated from HEL/anti-HEL double transgenic mice after Ag stimulation, although at lower levels than on nontolerant transgenic B cells. No significant cell surface levels of B7-1(B7) were observed under these conditions. Finally, the B7-2 molecules induced by Ig cross-linking costimulated T cell proliferation in a CD28-dependent manner, independent of B7-1(B7) expression. Thus, the effectiveness of Ag-specific B cells as APCs depends on both their enhanced Ag uptake, mediated by the B cell receptor, and immediate up-regulation of a potent costimulatory molecule, B7-2.

Animals↗
PubMed1994

Resting and anergic B cells are defective in CD28-dependent costimulation of naive CD4+ T cells.

Successful antibody production in vivo depends on a number of cellular events, one of the most important of these being cognate B cell-T cell interaction. To examine this phenomenon in vitro, homogeneous populations of hen egg lysozyme (HEL)-specific small resting B cells and naive CD4+ HEL-specific T cells (derived from immunoglobulin [Ig] and T cell receptor transgenic mice, respectively) were cultured together. On addition of intact HEL protein. HEL-specific B cells increase their expression of activation molecules, including a B7-related protein and CD44, and enlarge into blast cells. Within the same cultures, HEL-specific CD4+ T cells also increase expression of the activation markers CD69 and CD44, enlarge, secrete lymphokines, and proliferate. This response is radiation sensitive, supporting the conclusion that HEL-specific B cells present antigen to and activate the naive T cells. By contrast, when a synthetic peptide fragment of HEL is used to bypass B cell antigen-receptor engagement, the naive T cells enlarge and display activation antigens, but fail to produce lymphokines, proliferate, or promote B cell blastogenesis. Presentation of HEL by tolerant B cells, which are no longer able to signal effectively through their antigen receptors, results in an identical pattern of incomplete T cell activation. Addition of a stimulating anti-CD28 antibody and blocking of CD28 signals with CTLA4/Ig fusion protein both show that complete activation of naive CD4+ T cells depends on the initial induction of B7 and related costimulatory molecules after HEL binding to nontolerant HEL-specific B cells. Thus, in the absence of adequate constimulation from the B cell, naive CD4+ T cells undergo a form of "partial activation" in which they upregulate surface expression of certain T cell activation antigens, but fail to efficiently produce lymphokine and proliferate. This may explain the different conclusions that have been reached regarding the consequences of B cell antigen presentation to T cells, in that the ability of B cells to activate naive CD4+ T cells depends both on their specificity and their activation state.

Amino Acid Sequence↗
PubMed1994

Ig heavy chain extracellular spacer confers unique glycosylation of the Mb-1 component of the B cell antigen receptor complex.

A unique functional role for the B cell Ag receptor, IgD, has not yet been identified. A number of properties of IgD, such as distinct intron-exon organization and a conserved pattern of developmental expression, suggest a selective evolutionary advantage for this receptor isotype. To explore structural features of IgD that may confer unique functions, chimeric Ag receptors were generated in which small segments of the IgD heavy chain membrane proximal regions were substituted for corresponding segments of the IgM heavy chain. Polypeptides that associate with the Ig receptors were analyzed. Mb-1/Ig-alpha, a signal transduction molecule, is known to be glycosylated in a distinct manner when associated with IgD compared to when associated with other isotypes. We report that this differential glycosylation results because one N-linked carbohydrate on Mb-1 fails to be processed into an Endo-H-resistant form when associated with IgM or IgG, whereas both N-linked carbohydrates are processed on Mb-1 associated with IgD. By preparing chimeric IgM-IgD heavy chains, substitution of the IgD extracellular spacer segment alone was found to be necessary and sufficient to confer an IgD-type glycosylation pattern on the Mb-1 molecule. This altered glycosylation pattern, however, did not confer a detectable difference in calcium mobilization or in protein tyrosine phosphorylation upon receptor stimulation. Interestingly, a similar altered glycosylation pattern has been reported for the T cell Ag receptor complex in which carbohydrates on the CD3 delta-chain are fully processed in gamma delta-T cell receptors but only partially processed in alpha beta-T cell receptors.

Amino Acid Sequence↗
PubMed1994

A selective defect in IgM antigen receptor synthesis and transport causes loss of cell surface IgM expression on tolerant B lymphocytes.

To explore the biochemical basis for maintaining immunological tolerance by functional inactivation of self-reactive B lymphocytes, transgenic mice carrying rearranged anti-lysozyme immunoglobulin transgenes and a lysozyme transgene were used as a source of large numbers of tolerant self-reactive B cells. Antigen receptors of the IgD isotype were expressed at normal levels on tolerant B cells, contained the heterodimeric MB1/B29 signalling component of the receptor complex and were structurally indistinguishable from IgD on nontolerant B cells. In contrast, cell surface expression of IgM receptor complexes on tolerant B cells was greatly reduced, despite normal expression of mRNA encoding the receptor components. Three-fold fewer immunoreactive mu heavy chains were detectable after a short period of biosynthetic labelling and the immunoreactive mu chains produced were paired with kappa light chains and assembled normally into intact receptor complexes containing the MB1/B29 heterodimer. Nascent IgM receptor complexes nevertheless failed to be processed into an endoglycosidase H-resistant form in the tolerant B cells and thus appeared to be selectively blocked in their transport from the endoplasmic reticulum to the medial Golgi. These findings demonstrate that intracellular trafficking of antigen receptor complexes is regulated by exposure to receptor stimuli at the cell surface causing a long-lasting decrease in surface receptor expression on tolerant B cells.

Animals↗
PubMed1994

Immunoglobulin signal transduction guides the specificity of B cell-T cell interactions and is blocked in tolerant self-reactive B cells.

The specificity of antibody (Ab) responses depends on focusing helper T (Th) lymphocyte signals to suitable B lymphocytes capable of binding foreign antigens (Ags), and away from nonspecific or self-reactive B cells. To investigate the molecular mechanisms that prevent the activation of self-reactive B lymphocytes, the activation requirements of B cells specific for the Ag hen egg lysozyme (HEL) obtained from immunoglobulin (Ig)-transgenic mice were compared with those of functionally tolerant B cells isolated from Ig-transgenic mice which also express soluble HEL. To eliminate the need for surface (s)Ig-mediated Ag uptake and presentation and allow the effects of sIg signaling to be studied in isolation, we assessed the ability of allogeneic T cells from bm12 strain mice to provide in vivo help to C57BL/6 strain-transgenic B cells. Interestingly, non-tolerant Ig-transgenic B cells required both allogeneic Th cells and binding of soluble HEL for efficient activation and Ab production. By contrast, tolerant self-reactive B cells from Ig/HEL double transgenic mice responded poorly to the same combination of allogeneic T cells and soluble HEL. The tolerant B cells were nevertheless normally responsive to stimulation with interleukin 4 and anti-CD40 Abs in vitro, suggesting that they retained the capacity to respond to mediators of T cell help. However, the tolerant B cells exhibited a proximal block in the sIg signaling pathway which prevented activation of receptor-associated tyrosine kinases in response to the binding of soluble HEL. The functional significance of this sIg signaling defect was confirmed by using a more potent membrane-bound form of HEL capable of triggering sIg signaling in tolerant B cells, which markedly restored their ability to collaborate with allogeneic Th cells and produce Ab. These findings indicate that Ag-specific B cells require two signals for mounting a T cell-dependent Ab response and identify regulation of sIg signaling as a mechanism for controlling self-reactive B cells.

Animals↗
PubMed1994

Differential regulation of early and late stages of B lymphocyte development by the mu and delta membrane heavy chains of Ig.

Regulation of B lymphocyte development by the mu-membrane (mu m) and delta-membrane (delta m) heavy chains of Ig was examined in an Ig transgenic mouse model. Mice were bred on a common C57BL/6 (B6) background, and expressed rearranged and hypermutated heavy and light chain transgenes encoding high-affinity receptors for the foreign antigen hen egg lysozyme (HEL). At no stage were they exposed to HEL. Variation of the Ig heavy chain construct yielded four different types of Ig transgenic mice in which developing B lineage cells either expressed mu m and delta m in the normal physiological sequence (mu m then mu m + delta m), or produced mu m alone, delta m alone or mu m + delta m from the onset of heavy chain expression in the bone marrow. Immature B220low, HSAhigh and mature B220high, HSAlow B cells were produced in all mice regardless of their developmental pattern of mu m and delta m expression. However, production of immature B cells was most efficient when mu m heavy chain was expressed alone during early B cell development. Thus expression of delta m during this period either in the presence or absence of mu m resulted in a 2- to 3-fold reduction in the numbers of immature B cells in the spleen as well as altered levels of surface B220 and HSA on these cells in spleen and bone marrow respectively. By contrast, normal maturationally regulated expression of delta m led to the presence of increased numbers of mature B cells in the spleen and lengthened the average lifespan of these cells as determined by in vivo incorporation of 5-bromo-2'-deoxyuridine. These results pointed to selective effects of mu m and delta m heavy chains on regulation of the early and late stages of B cell development respectively, and provided a rational basis for co-expression of mu m and delta m as well as the delayed expression of delta m during normal B cell development.

Animals↗
PubMed1994

Censoring of self-reactive B cells with a range of receptor affinities in transgenic mice expressing heavy chains for a lysozyme-specific antibody.

Transgenic mice carrying a rearranged Ig gene encoding the H chain of a lysozyme-specific antibody were used to examine the effect of antigen binding affinity on elimination of self-reactive B cells. In H chain transgenic mice, B cells expressed surface IgM and IgD composed of lysozyme-specific H chains and many different possible L chains from endogenous L chain genes. Immunofluorescent staining and flow cytometry revealed a distinct subset comprising approximately 1% of spleen B cells that bound lysozyme with a high affinity comparable with the original lysozyme-specific antibody. Additional subsets accounting for a total of 5-6% of spleen B cells bound lysozyme more weakly, with the weakest requiring 10,000-fold higher concentrations of monomeric hen egg lysozyme to attain 50% receptor saturation. When the various B cell subpopulations were allowed to develop in animals expressing lysozyme as a membrane-bound antigen on autologous cells, both low and high affinity lysozyme-binding B cells were undetectable in peripheral lymphoid organs. These findings demonstrate the efficacy with which low affinity self-reactive B cells can be eliminated in vivo, consistent with the notion that this cellular mechanism accounts for the absence of natural IgM antibodies against self antigens on the surface of blood cells. The data also illustrate the potential use of Ig transgenic mice for analyzing and selecting novel receptor-ligand interactions.

Animals↗
PubMed1993

Elimination of self-reactive B lymphocytes proceeds in two stages: arrested development and cell death.

In transgenic mice, self-reactive B lymphocytes are eliminated if they encounter membrane-bound self antigens during their development within the bone marrow. We show here that two separate and sequential events, arrested development and cell death, bring about B cell elimination. Developmental arrest is an early outcome of antigen binding in immature B cells, blocks acquisition of adhesion molecules and receptors important for B cell migration and activation, and is rapidly reversible by removal of antigen. Death of the arrested B cells occurs within 1 to 3 days and can be delayed by expression of a bcl-2 transgene, which results in escape of large numbers of self-reactive B cells from the bone marrow but fails to override the developmental arrest. These findings define a novel pathway for B cell elimination, involving an initial stage vulnerable to breakdown in autoimmune disease.

Animals↗
PubMed1992

Immunoglobulin M and D antigen receptors are both capable of mediating B lymphocyte activation, deletion, or anergy after interaction with specific antigen.

A series of immunoglobulin (Ig)-transgenic mice were generated to study the functional capabilities of the IgM and IgD classes of B lymphocyte antigen receptor in regulating both cellular development and responses to specific antigen. B cells from Ig-transgenic mice expressing either hen-egg lysozyme (HEL)-specific IgM or IgD alone were compared with B cells from mice that coexpressed IgM and IgD of the same anti-HEL specificity. In all three types of Ig-transgenic mice, conventional B cells specific for HEL exhibited exclusion of endogenous Ig expression and matured to populate the usual microenvironments in peripheral lymphoid tissues. These peripheral B cells could be stimulated by HEL through either IgM or IgD antigen receptors to generate T cell dependent antibody production in vivo or to enhance T cell independent proliferative responses to lipopolysaccharide in vitro. Conversely, when HEL was encountered in vivo as a self-antigen, B cells expressing HEL-specific IgM or IgD alone were both rendered tolerant. In each case this occurred by clonal anergy in response to soluble autologous HEL, and clonal deletion when HEL was recognized as a membrane-bound self-antigen. Taken together, these findings indicate that IgM and IgD antigen receptors expressed alone on conventional B cells can support normal differentiation, antigen-dependent activation, and induction of self-tolerance, the only overt difference lying in a greater degree of receptor downregulation for IgM relative to IgD after induction of clonal anergy by soluble HEL.

Animals↗
PubMed1992

Autoimmune tolerance and type 1 (insulin-dependent) diabetes mellitus.

The autoimmune process that results in Type 1 (insulin-dependent) diabetes mellitus may be viewed as a failure to develop or maintain tolerance to self-antigens expressed in the islets of Langerhans. During T-cell development in the thymus, cells that are reactive with self antigens encountered there may undergo clonal deletion or, as more recently described, clonal anergy which effectively removes these cells from the pool of mature antigen reactive T cells. For antigens not found in the thymus, tolerance to self antigens is more complex and may depend on site of antigen expression, ambient concentrations of lymphokines, and availability of antigen-presenting cells that can deliver co-stimulatory signals. Transgenic mice in which the majority of T cells express T-cell receptors against "self" antigens or in which expression of antigens is targeted to peripheral tissues have proven useful for studies of tolerance in both T- and B-cell compartments. In general, T-cell reactivity against foreign antigen expressed on Beta cells does not occur because of the failure to activate T cells reactive with the antigen, termed clonal ignorance. This may be broken with, for example, viral infection or cytokines. In one transgenic model, dendritic cells that surround the islets of Langerhans have been shown to be responsible for presentation of islet antigens to the immune system. B-cell tolerance can also involve mechanisms of clonal deletion or clonal anergy similar to that occurring with T cells. In addition, a mechanism for changing the affinity of the B-cell antigen receptor termed "receptor editing" has been described, which may play an important role in diversifying the B-cell repertoire while removing self-reactive cells. Tolerance to antigens may also be inducible. For example, monoclonal antibodies against T-cell epitopes may induce antigen-specific tolerance that is transferable to other animals, and MHC blocking peptides which can inhibit T-cell responses that are restricted by disease associated MHC molecules. In conclusion, although several possible triggers and mechanisms of autoimmune diabetes can be envisioned, none can be excluded by existing data. However, advances in understanding mechanisms of tolerance to islet and other self antigens suggest potentially useful therapeutic approaches to arresting the autoimmune response.

Animals↗
PubMed1992

B-cell tolerance.

Discrimination between self and non-self in humoral immunity is mediated in part by elimination or inactivation of self-reactive B-cell clones. This type of repertoire censoring requires that self-reactive B cells make a choice between these and alternative cellular fates. The details of this developmental decision-making and the steps where it is prone to go awry in autoimmunity have yet to be untangled, but genetic analysis appears likely to lead the way.

Animals↗
PubMed1992

Development and follicular localization of tolerant B lymphocytes in lysozyme/anti-lysozyme IgM/IgD transgenic mice.

To analyse mechanisms of immunological self-tolerance, a detailed comparison of the development and fate of lysozyme-specific B lymphocytes was carried out in transgenic mice expressing rearranged anti-lysozyme IgM/IgD Ig transgenes in the absence or presence of an additional transgene encoding lysozyme itself. In the absence of lysozyme, B cell development, localization, and differential expression of transgene-encoded IgM and IgD occurred in the normal sequence in Ig transgenic mice, establishing that these animals provide a physiological model for studies of B cell selection in vivo. By contrast, in lysozyme-expressing double-transgenic mice, tolerant lysozyme-reactive B cells persisted within the follicular mantle zones in the spleen, lymph nodes, and Peyer's patches, but were eliminated from the splenic marginal zones. It could be shown that lysozyme-binding and induction of tolerance occurred as soon as surface Ig was expressed on immature B cells in the bone marrow of the double-transgenic mice although this did not prevent maturation, emigration from the bone marrow, and localization in peripheral lymphoid follicles. These findings, together with recent examples of aborted maturation of self-reactive B cells, indicate two functionally distinct antigen receptor signalling events in immature B cells and suggest a unique role for the follicular microenvironment.

Animals↗