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Query: UNIPROT:Q00604 (X-linked)
 16,883 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have analysed the ability of B cells isolated from the Peyer's patches of normal mice to respond to two different B-cell stimulatory factors. Peyer's patch B cells respond in vitro to co-stimulation by either interleukin-4 (IL-4) plus anti-IgM or B-cell growth factor II (BCGF-II) plus dextran sulphate (DXS). We have consistently observed that splenic B cells proliferate more than Peyer's patch B cells when co-stimulated by BCGF-II plus DXS. This is not due to a diminished proliferation capacity of the Peyer's patch B-cell preparations, because the Peyer's patch B cells often proliferate more than splenic B cells when co-stimulated with IL-4 plus anti-IgM. These differences are not a result of altered response kinetics or differences in relative amounts of surface IgM on the two types of B cells. We have also analysed B cells from the LPS hypo-responsive strain C3H/HeJ, and its LPS responsive partner strain C3H/OuJ, from the X-linked immunodeficient strain (xid), CBA/N, and from germ-free (GF) mice. B cells from spleens and Peyer's patches of GF mice are responsive to co-stimulation by IL-4 plus anti-IgM and to co-stimulation by BCGF-II plus DXS. Peyer's patch B cells from C3H/HeJ mice proliferate as well as Peyer's patch B cells from C3H/OuJ cells to both co-stimulation protocols. Among the types of B cells studied here, only cells from spleens and Peyer's patches of mice that bear the xid defect fail to respond to the signals delivered by lymphokine co-stimulation. Our results suggest that while Peyer's patch B cells are stimulated by these two lymphokines, Peyer's patches contain cells that react differently from spleen cells to either the lymphokines IL-4 and BCGF-II, or the co-stimulators anti-IgM or dextran sulphate.
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PMID:Stimulation of gut-associated lymphoid cells by IL-4 and B-cell growth factor II. 245 84

Interleukin-5 (IL-5) regulates the production and function of B cells, eosinophils and basophils. In particular, IL-5 plays a critical role in the development of CD5-positive B (B-1) cells. The pleiotropic activity of IL-5 on target cells is directly dependent on the initial binding to IL-5 specific cell-surface receptor (IL-5R). The IL-5 signals are mediated through the high affinity IL-5R which is composed of two different polypeptide chains, alpha and beta. The alpha chain is a membrane-penetrated glycoprotein that specifically binds IL-5 and retains features common to the cytokine receptor superfamily. The beta chain by itself does not bind IL-5, but it can convert the low affinity IL-5R into the high affinity IL-5R and in indispensable for IL-5 signal transduction. The beta chain is shared among receptors for IL-5, IL-3 and GM-CSF and is called beta c. The cytoplasmic comains of both IL-5R alpha and beta c are essential for signal transduction. The membrane proximal proline-rich sequence of the cytoplasmic domain of IL-5R alpha was found to be essential for the IL-5-induced proliferative response, expression of nuclear proto-oncogenes such as c-jun, c-fos and c-myc, and activation of Bruton's tyrosine and JAK2 kinases. Furthermore, JAK2 activation correlates with proline residues in Pro-Pro-X-Pro motif in the cytoplasmic domain of IL-5R alpha. These results indicate that activation of JAK2 and its substrate is critical to coupling IL-5-induced tyrosine phosphorylation and ultimately mitogenesis. I will discuss about molecular mechanisms of IL-5 signaling and B cell defect in X-linked immunodeficient mice in relation to IL-5 signaling.
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PMID:[Structure and function of IL-5 receptor]. 747 55

Bruton's tyrosine kinase (BTK) is a nonreceptor tyrosine kinase critical for B cell development and function. Mutations in BTK result in X-linked agammaglobulinemia (XLA) in humans and X-linked immunodeficiency (xid) in mice. Using a random mutagenesis scheme, we isolated a gain-of-function mutant called BTK* whose expression drives growth of NIH 3T3 cells in soft agar. BTK* results from a single point mutation in the pleckstrin homology (PH) domain, where a Glu is replaced by Lys at residue 41. BTK* shows an increase in phosphorylation on tyrosine residues and an increase in membrane targeting. Transforming activity requires kinase activity, a putative autophosphorylation site, and a functional PH domain. Mutation of the SH2 or SH3 domains did not affect the activity of BTK*. Expression of BTK* could also relieve IL-5 dependence of a B lineage cell line. These results show that transformation activation and regulation of BTK are critically dependent on the PH domain.
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PMID:Activation of Bruton's tyrosine kinase (BTK) by a point mutation in its pleckstrin homology (PH) domain. 753 39

Murine (m) IL-5 induces proliferation and differentiation of both Ly-1+ B cells and activated conventional B cells. X-linked immunodeficient (XID) mice do not respond to thymus-independent type II antigens, and have an abnormal response to a variety of activation signals through Ig receptors, CD40 and cytokine receptors. Furthermore, XID mice show a B cell specific defect, reflected in decreased numbers of IL-5R alpha+ B cells and reduced responsiveness of IL-5R alpha+ B cells to mIL-5. We generated IL-5R alpha transgenic (5R alpha-Tg) mice in which B cells expressed recombinant IL-5R alpha. We crossed male 5R alpha-Tg mice with female XID mice and used their offspring to determine the IL-5 responsiveness of these B cells. All B cells of F1 male mice carrying the xid gene together with the transgene expressed the recombinant IL-5R alpha. However, those mice lacked Ly-1 B cells and their B cells acquired responsiveness to mIL-5. Interestingly, XID-5R alpha-Tg B cells, but not XID B cells, acquired mIL-5 proliferative and Ig-secretory responsiveness only in the presence of suboptimal doses of lipopolysaccharide. Stimulation of these B cells with mIL-5 plus phorbol myristate acetate induced proliferation, but not Ig secretion. These results indicate that the impaired mIL-5 responsiveness of B cells in XID mice is due to an abnormality of IL-5R-mediated signaling which may correlate with the xid gene mutation, alteration of a single amino acid of Bruton's tyrosine kinase.
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PMID:Defective IL-5-receptor-mediated signaling in B cells of X-linked immunodeficient mice. 771 12

Mouse IL-5 (mIL-5) acts on B cells and eosinophils to induce growth and differentiation through the mIL-5 specific receptor (mIL-5R). The functional high-affinity mIL-5R is a heterodimer composed of alpha and beta chains. We investigated the expression of mIL-5R and the responsiveness of B cells and eosinophils to mIL-5 in X-linked immunodeficient (xid) mice. mIL-5R expression analyzed by using mAbs specific for alpha and beta chains revealed that xid B cells had fewer mIL-5R alpha +mIL-5R beta + than BALB/c B cells. In particular, a decrease in the number of peritoneal mIL-5R+ B cells among Ly-1 B cells (known as B-1 cells) was remarkable. Furthermore, the frequency of precursors of mIL-5 responsive B cells in xid mice was approximately 100-fold lower than that of BALB/c mice. Interestingly, sorted mIL-5R+ peritoneal B cells from xid mice displayed a low response to mIL-5. Intraperitoneal injection of mIL-5 into BALB/c mice induced polyclonal IgM production and an increase in the number of eosinophils. The same regimen failed to induce an increase in the same parameters in xid mice. However, xid mice showed mIL-5-induced eosinophilia in peripheral blood to a similar extent as BALB/c mice. Eosinophils from mIL-5-injected xid mice expressed both alpha and beta chains of mIL-5, and responded to mIL-5 with prolonged in vitro survival.
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PMID:IL-5 receptor positive B cells, but not eosinophils, are functionally and numerically influenced in mice carrying the X-linked immune defect. 824 Oct 57

Loss of function of Bruton's tyrosine kinase (Btk) results in X-linked immunodeficiencies characterized by a broad spectrum of signaling defects, including those dependent on Src family kinase-linked cell surface receptors. A gain-of-function mutant, Btk*, induces the growth of fibroblasts in soft agar and relieves the interleukin-5 dependence of a pre-B-cell line. To genetically define Btk signaling pathways, we used a strategy to either activate or inactivate Src family kinases in fibroblasts that express Btk*. The transformation potential of Btk* was dramatically increased by coexpression with a partly activated c-Src mutant (E-378 --> G). This synergy was further potentiated by deletion of the Btk Src homology 3 domain. Downregulation of Src family kinases by the C-terminal Src kinase (Csk) suppressed Btk* activation and biological potency. In contrast, kinase-inactive Csk (K-222 --> R), which functioned as a dominant negative molecule, synergized with Btk* in biological transformation. Activation of Btk* correlated with increased phosphotyrosine on transphosphorylation and autophosphorylation sites. These findings suggest that the Src and Btk kinase families form specific signaling units in tissues in which both are expressed.
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PMID:Regulation of Btk by Src family tyrosine kinases. 866 62

The germinal center (GC) develops in secondary lymphoid tissues in response to thymus-dependent (TD) antigens. To investigate the molecular mechanism of B cell differentiation in GC, we enriched GC B cells from spleen of TD antigen-immunized wild-type and X-linked immunodeficient (XID) mice, and examined the differentiation of GC B cells into antigen-specific IgG1 antibody-forming cells (AFC) in response to anti-CD40 mAb and cytokines. A significant proportion of freshly purified GC B cells expressed receptors for IL-4 and IL-5. Anti-CD40 mAb sustained the viability of GC B cells and IL-4 co-operated with anti-CD40 mAb for further enhancement of the cell viability. Anti-CD40 mAb and IL-4 were essential for inducing differentiation of GC B cells into antigen-specific IgG1-AFC and IL-5 efficiently enhanced their differentiation. GC B cells with the xid mutation responded for proliferation to CD40 ligation to a lesser extent and for the IgG1-AFC response to anti-CD40 mAb together with IL-4, but they showed impaired responsiveness to IL-5, regardless of enhanced expression of IL-5R in response to anti-CD40 mAb and IL-4. These results suggest that anti-CD40 mAb, IL-4 and IL-5 play a critical role in the differentiation of mouse GC B cells. The GC B cells from XID mice show a functional defect with respect to IL-5-mediated differentiation.
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PMID:Mouse germinal center B cells with the xid mutation retain responsiveness to antimouse CD40 antibodies but diminish IL-5 responsiveness. 935 51

Interleukin-5 (IL-5) stimulates proliferation and differentiation of B cells and eosinophils. IL-5 receptor (IL-5R) comprises alpha and (beta)c chains. IL-5 specifically binds to IL-5Ralpha and induces the recruitment of (beta)c to IL-5Ralpha. JAK2 and JAK1 tyrosine kinases are constitutively associated with hIL-5Ralpha and (beta)c, respectively and activated upon IL-5 stimulation. IL-5 induces tyrosine phosphorylations of cellular proteins including (beta)c and STAT5 and activates Btk. X-linked immunodeficient mice have B-cell-specific defects due to missense mutation of the btk gene. The cytoplasmic proline-rich regions of both IL-5Ralpha and (beta)c are essential for the IL-5 signalling. IL-5 appears to play a critical role in hypereosinophilic syndromes and atopic diseases. The treatment of animals with anti-IL-5 mAb can decrease the enhanced bronchial responsiveness induced by allergen sensitization. Clinical studies provide a strong impetus for investigating the means of modulating IL-5 effects.
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PMID:Interleukin 5 and B cell differentiation. 972 Jul 54

Bruton's tyrosine kinase (Btk) is required for normal B cell development and signal transduction through cell surface molecules, and its defects lead to X-linked immune deficiency in mice and X-linked agammaglobulinemia in humans. In this report, we will describe the identification and characterization of a molecule, BAM11, which binds to the pleckstrin homology domain of Btk. A sequence homology search revealed that BAM11 has 89% homology, at the amino acid level, to human LTG19/ENL, that was originally identified as one of the fusion partners involved in chromosomal translocations of 11q23, MLL/ALL-1/HRX, in leukemia cells. Deletion mutants demonstrated that the region of BAM11 required for binding to Btk was localized between amino acid residues 240 and 256. Forced expression of a truncated form of BAM11 (amino acids 246-368) inhibited IL-5-induced proliferation by 50%, whereas forced expression of full-length BAM11 in Y16 cells did not affect the IL-5 responsiveness. We have also shown that BAM11 (amino acids 246-368) inhibited the kinase activity of Btk. These results suggest that the binding of BAM11 to Btk plays a regulatory role in the Btk signal transduction pathway. A cell fractionation study and analysis using EGFP-fused Btk protein demonstrated that a proportion of Btk is present within the nucleus.
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PMID:Identification and characterization of a molecule, BAM11, that associates with the pleckstrin homology domain of mouse Btk. 1100 57

T helper cell-driven activation of murine B cells has been shown to depend upon CD40-CD40 ligand (CD40L) interactions and a defined set of cytokines. These observations are primarily based on the use of conventional B cells obtained from the spleen. Therefore, it is presently unclear whether all mature B cell subsets found in the mouse have an equal dependence upon CD40-CD40L interactions and use the same T cell-derived cytokines. The present study tested the response of splenic follicular and marginal zone as well as peritoneal B2 and B1 B cells to Th cell stimulation. Splenic and peritoneal B cell subsets were sort purified based on CD23 expression, and cultured with rCD40L and cytokines or Th2 cells. The results demonstrate that follicular, marginal zone, and peritoneal B2 B cells require CD40-CD40L interactions and preferentially use IL-4 for optimal proliferation, differentiation, and isotype switching. In contrast, peritoneal B1 B cells use IL-5 in conjunction with CD40-CD40L interactions for maximal Th cell-dependent responses. Furthermore, B1 B cells are capable of proliferating, differentiating, and isotype switching in the absence of CD40-CD40L interactions. B1 B cells are able to respond to Th2 clones in the presence of anti-CD40L mAb as well as to Th2 clones derived from CD40L(-/-) mice. The CD40-CD40L-independent response of B1 B cells is attributable to the presence of both IL-4 and IL-5, and may explain the residual Ab response to T cell-dependent Ags in CD40L- or CD40-deficient mice, and in X-linked hyper-IgM (X-HIM) patients.
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PMID:Murine B1 B cells require IL-5 for optimal T cell-dependent activation. 1116 Jan 93


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