scholarly journals OVERLAP STIMULATION OF PRIMARY AND SECONDARY B CELLS BY CROSS-REACTING DETERMINANTS

1973 ◽  
Vol 138 (5) ◽  
pp. 1276-1281 ◽  
Author(s):  
N. R. Klinman ◽  
J. L Press ◽  
G. P. Segal
Keyword(s):  
B Cells ◽  
B Cell ◽  
Antigen Receptors ◽  
Cell Stimulation ◽  
Stimulation Of

Experiments were carried out to test the validity of the hypothesis that postulated differences in the nature of the antigen receptors of primary and secondary B cells should be reflected in a greater specificity in primary B-cell stimulation (2). Enumeration of clonal precursors stimulated by either DNP-Hy, TNP-Hy, or a mixture of both antigens confirmed this hypothesis. Since the sum of primary B cells stimulated by DNP-Hy and TNP-Hy is approximately equal to the number stimulated by a mixture of both, overlap stimulation of primary B cells by these antigens could be considered negligible. In contrast, the stimulation of B cells from mice previously immunized with DNP-Hy showed extensive overlap of stimulation by DNP-Hy and TNP-Hy. Thus secondary B cells appear less fastidious in their affinity requirements for stimulation than primary B cells.

scholarly journals Ras Mediates Effector Pathways Responsible for Pre-B Cell Survival, Which Is Essential for the Developmental Progression to the Late Pre-B Cell Stage

2000 ◽  
Vol 192 (2) ◽  
pp. 171-182 ◽  
Author(s):  
Hitoshi Nagaoka ◽  
Yoshimasa Takahashi ◽  
Reiko Hayashi ◽  
Tohru Nakamura ◽  
Kumiko Ishii ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Survival ◽  
Chain Gene ◽  
B Cell Differentiation ◽  
Antigen Receptors ◽  
Cell Stage ◽  
Light Chain Gene ◽  
B Cell Survival ◽  
Effector Pathways

Ras is essential for the transition from early B cell precursors to the pro-B stage, and is considered to be involved in the signal cascade mediated by pre-B cell antigen receptors. To examine the role of p21ras in the late stage of B cell differentiation, we established transgenic mice (TG) expressing a dominant-inhibitory mutant of Ha-ras (Asn-17 Ha-ras) in B lineage cells at high levels after the early B cell precursor stage. Expression of p21Asn-17 Ha-ras was associated with a prominent reduction in the number of late pre-B cells, but had little effect on proliferation of early pre-B cells. Inhibition of p21ras activity markedly reduced the life span of pre-B cells, due, at least in part, to downregulation of the expression of an antiapoptotic protein, Bcl-xL. Thus, the apparent role for p21ras activity in pre-B cell survival may explain the decreased numbers of late pre-B cells in Asn-17 Ha-ras TG. Consistent with this possibility, overexpression of Bcl-2 in Asn-17 Ha-ras TG reversed the reduction in the number of late pre-B cells undergoing immunoglobulin light chain gene (IgL) rearrangement and progressing to immature B cells. These results suggest that p21ras mediates effector pathways responsible for pre-B cell survival, which is essential for progression to the late pre-B and immature B stages.

scholarly journals Gene Dose–Dependent Maturation and Receptor Editing of B Cells Expressing Immunoglobulin (Ig)g1 or Igm/Igg1 Tail Antigen Receptors

2000 ◽  
Vol 191 (6) ◽  
pp. 1031-1044 ◽  
Author(s):  
Sarah L. Pogue ◽  
Christopher C. Goodnow
Keyword(s):  
B Cells ◽  
Transgenic Mice ◽  
B Cell ◽  
Copy Number ◽  
Memory B Cells ◽  
Mouse Strains ◽  
Allelic Exclusion ◽  
Antigen Receptors ◽  
Cytoplasmic Domains ◽  
Transgene Copy Number

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 CD21high 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.

scholarly journals In vitro tolerance induction of neonatal murine B cells.

1976 ◽  
Vol 143 (6) ◽  
pp. 1327-1340 ◽  
Author(s):  
E S Metcalf ◽  
N R Klinman
Keyword(s):  
B Cells ◽  
B Cell ◽  
B Lymphocytes ◽  
Specific Interaction ◽  
Tolerance Induction ◽  
Antigen Receptors ◽  
Spleen Cells ◽  
Protein Conjugates ◽  
Immature B Cells

The susceptibility of neonatal and adult B lymphocytes to tolerance induction was analyzed by a modification of the in vitro splenic focus technique. This technique permits stimulation of individual hapten-specific clonal precursor cells from both neonatal and adult donors. Neonatal or adult BALB/c spleen cells were adoptively transferred into irradiated, syngeneic, adult recipients which had been carrier-primed to hemocyanin (Hy), thus maximizing stimulation to the hapten 2,4-dinitrophenyl coupled by Hy (DNP-Hy). Cultures were initially treated with DNP on several heterologous (non-Hy) carriers and subsequently stimulated with DNP-Hy. Whereas the responsiveness of adult B cells was not diminished by pretreatment with any DNP conjugate, the majority of the neonatal B-cell response was abolished by in vitro culture with all of the DNP-protein conjugates. During the 1st wk of life, the ability to tolerize neonatal splenic B cells progressively decreased. Thus, tolerance in this system is: (a) restricted to B cells early in development; (b) established by both tolerogens and immunogens; (c) achieved at low (10(-9) M determinant) antigen concentrations; and (d) highly specific, discriminating between DNP- and TNP-specific B cells. We conclude that: (a) B lymphocytes, during their development, mature through a stage in which they are extremely susceptible to tolerogenesis; (b) the specific interaction of B-cell antigen receptors with multivalent antigens, while irrelevant to mature B cells, is tolerogenic to neonatal (immature) B cells unless antigen is concomitantly recognized by primed T cells; and (c) differences in the susceptibility of immature and mature B lymphocytes to tolerance induction suggest intrinsic differences between neonatal and adult B cells and may provide a physiologically relevant model for the study of tolerance to self-antigens.

Concomitant, T-Independent TLR9-Mediated and BCR-Mediated Activation Provides Signals For Optimal Telomerase Induction In Chronic Lymphocytic Leukemia Cells Regardless Of IGHV Mutation Status

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 4142-4142
Author(s):  
Rajendra N Damle ◽  
Sonal Temburni ◽  
Ryon M. Andersen ◽  
Jacqueline C. Barrientos ◽  
Jonathan E. Kolitz ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Cell Activation ◽  
Telomerase Activity ◽  
Lymphocytic Leukemia ◽  
Tlr9 Activation ◽  
Cells Cultured ◽  
Stimulation Of

Abstract Chronic lymphocytic leukemia (CLL) is characterized by the clonal amplification of CD5-expressing B cells that appear to develop and evolve based on signals from the microenvironment. In vitro and in vivo evidence suggests that the B-cell antigen receptor (BCR) and Toll-like receptors (TLRs) may be keys to this stimulation. Because clonal turnover can lead to the release of naked nuclear material into the cellular microenvironment, these remnants of dying/dead cells may contribute to disease progression by repeated low level T-independent activation of CLL cells through the combination of the BCR and TLRs. To test this hypothesis, we assessed TLR9-driven or BCR + TLR9-driven CLL B-cell activation, focusing on its impact on telomerase activation in CLL cells, which is known to be important in the disease and which we have shown to be selectively activated by BCR stimulation in Ig V-unmutated (U-CLL) clones but not in Ig V-mutated (M-CLL) clones. B cells, isolated by negative selection from peripheral blood of IgM+ CLL patients and cryopreserved until use, were cultured for 16 hr without/ with TLR9 agonist, ODN 2006, alone and were assayed for apoptosis using Annexin V and flow cytometry. To study the relative contribution of simultaneous TLR9 activation and BCR activation, B cells were exposed to ODN2006 alone or HB57dex (monoclonal anti IgM Ab conjugated onto dextran) alone or a combination of the two reagents. Extracts from cells cultured for a period of 3 days were assayed for functional telomerase activity using TRAP. Parallel cultures of B cells exposed to the same stimuli were harvested at day 3 and assayed for cell activation and proliferation, which was assessed by 3H thymidine incorporation. CLL cells cultured with ODN2006 exhibited significant apoptosis within 16 hours in 6/12 cases. However at day 3, the same stimulus elicited significant increases in percentages of CD69-expressing cells and densities of HLA-DR in all CLL cases studied. As compared to BCR activation, which upregulates telomerase activity in U-CLL only, TLR9-mediated activation of CLL induced telomerase activation in all CLL cases. Furthermore, ODN2006 elicited significantly higher induction of telomerase activity in M-CLL cases compared to U-CLL cases (p=0.01). In addition, in M-CLL cases, simultaneous activation via TLR9 and BCR significantly upregulated the telomerase activity (p=0.05) that was induced by TLR9 activation alone. IRAK-1/4 inhibitor down modulated both TLR9 mediated and TLR9 +BCR mediated telomerase activity to a greater extent in M-CLL cases than in U-CLL cases. TLR9 activation of CLL cells induced a 3.75 + 0.8 fold (range 1.1 to 19.6; n=32) increase in cell proliferation. When segregated by Ig V mutation, U-CLL cells (n=16) responded significantly better (6.0 + 1.6 fold) compared to M-CLL cells (2.1 + 0.3 fold, n=16; p=0.03). However, co-stimulation of cells via their BCR significantly increased TLR-mediated responses only in M-CLL cases (from 2.3 + 0.4 fold to 5.4 + 1.7 fold; p=0.05). IRAK-1/4 inhibitor did not exert a significant effect on TLR9 mediated cell proliferation in either the U-CLL or M-CLL cases. Co-culture of CLL cells with human stromal cells, HS5, further upregulated the concerted TLR9 + BCR induced proliferative responses in 70% of the cases studied. Together, these results indicate that simultaneous stimulation of CLL cells via both their TLR9 and BCR molecules positively impacts on telomerase activity in all patients studied. Since telomerase is crucial in maintaining longevity of repeatedly stimulated cells, this could represent a mechanism for worse clinical outcome in CLL. These studies stress the need for devising therapeutic agents or combinations thereof to effectively target multiple pathways downstream of these signaling receptors and to ultimately eradicate newly evolving CLL cells. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Death by a B Cell Superantigen

2003 ◽  
Vol 197 (9) ◽  
pp. 1125-1139 ◽  
Author(s):  
Carl S. Goodyear ◽  
Gregg J. Silverman
Keyword(s):  
B Cells ◽  
B Cell ◽  
Protein A ◽  
Death Receptor ◽  
Variable Region ◽  
Microbial Pathogens ◽  
Host Immune System ◽  
Antigen Receptors ◽  
Sequence Of Events

Amongst the many ploys used by microbial pathogens to interfere with host immune responses is the production of proteins with the properties of superantigens. These properties enable superantigens to interact with conserved variable region framework subdomains of the antigen receptors of lymphocytes rather than the complementarity determining region involved in the binding of conventional antigens. To understand how a B cell superantigen affects the host immune system, we infused protein A of Staphylococcus aureus (SpA) and followed the fate of peripheral B cells expressing B cell receptors (BCRs) with VH regions capable of binding SpA. Within hours, a sequence of events was initiated in SpA-binding splenic B cells, with rapid down-regulation of BCRs and coreceptors, CD19 and CD21, the induction of an activation phenotype, and limited rounds of proliferation. Apoptosis followed through a process heralded by the dissipation of mitochondrial membrane potential, the induction of the caspase pathway, and DNA fragmentation. After exposure, B cell apoptotic bodies were deposited in the spleen, lymph nodes, and Peyer's patches. Although in vivo apoptosis did not require the Fas death receptor, B cells were protected by interleukin (IL)-4 or CD40L, or overexpression of Bcl-2. These studies define a pathway for BCR-mediated programmed cell death that is VH region targeted by a superantigen.

BCR-mediated uptake of antigen linked to TLR9 ligand stimulates B-cell proliferation and antigen-specific plasma cell formation

Blood ◽  
2009 ◽  
Vol 113 (17) ◽  
pp. 3969-3977 ◽  
Author(s):  
Julia Eckl-Dorna ◽  
Facundo D. Batista
Keyword(s):  
Cell Proliferation ◽  
B Cells ◽  
B Cell ◽  
Plasma Cells ◽  
Cell Formation ◽  
Specific Class ◽  
B Cell Differentiation ◽  
Enhanced Production ◽  
Stimulation Of

Abstract The activation of Toll-like receptor 9 (TLR9) expressed within B cells is associated with enhanced humoral immunity. However the role of TLR9 in the stimulation of B-cell responses, and more specifically in shaping the outcome of B-cell differentiation, remains unclear. Here, we observed that immunization with the TLR9 agonist CpG linked to protein antigen gave rise to enhanced production of antigen-specific class-switched antibodies in vivo. Unlike dendritic cells, B cells are unable to acquire these conjugates by macropinocytosis and instead depend on uptake through a signaling-competent B-cell receptor (BCR), provided the overall BCR-antigen avidity exceeds a defined threshold. The resultant stimulation of intrinsic TLR9 leads to enhanced antigen-specific B-cell proliferation and differentiation to form extrafollicular plasma cells. Thus, the direct conjugation of antigen and CpG reveals a mechanism that may operate during the initiation of primary immune responses, and may prove useful as a strategy for the design of adjuvants suitable for vaccinations.

scholarly journals T cell-dependent induction of NF-kappa B in B cells.

1993 ◽  
Vol 177 (4) ◽  
pp. 1215-1219 ◽  
Author(s):  
A C Lalmanach-Girard ◽  
T C Chiles ◽  
D C Parker ◽  
T L Rothstein
Keyword(s):  
T Cells ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Intracellular Signaling ◽  
Cell Interaction ◽  
Soluble Form ◽  
Nf Kappa B ◽  
Activated T Cells ◽  
Cell Stimulation

In comparison to B cell stimulation mediated by surface immunoglobulin (Ig) antigen receptor ligation, little is known about the intracellular events associated with T cell-dependent B cell responses. A model for the efferent phase of T cell-B cell interaction was used to examine the capacity of activated T cells to trigger nuclear expression of the trans-acting transcription factor, NF-kappa B, in B cells. Fixed, activated, but not fixed, resting Th2 cells were found to induce increased binding activity for a kappa B site-containing oligonucleotide in a time-dependent manner. This induction of NF-kappa B was eliminated by an antibody directed against a 39-kD cell interaction protein on activated T cells as well as by a soluble form of B cell CD40. Of particular relevance to intracellular signaling, NF-kappa B induction was not diminished by prior depletion of B cell protein kinase C (PKC) with phorbol myristate acetate. These results strongly suggest that T cell-dependent B cell stimulation is associated with NF-kappa B induction via p39-CD40 interaction and that this is brought about by non-PKC dependent signaling, in marked contrast to the previously documented requirement for PKC in sIg receptor-mediated stimulation. This suggest that NF-kappa B responds to more than one receptor-mediated intracellular signaling pathway in B cells and may be part of a "final common pathway" for B cell stimulation.

Sign in / Sign up

Export Citation Format

Share Document