IL-2 receptor α chain (CD25JAC) expression defines a crucial stage in pre-B cell development

The analysis of the expression of the a chain of the IL-2 receptor (CD25.TAC) on the surface of B lineage cells In mouse bone marrow reveals that it is a useful marker to distinguish pre-B-I from pre-B-II cells. CD25 Is not expressed on CD45R(B220)+ c-kit+ CD43+ TdT+ λ5+ Cμ− slg− lgH chain locus DJH-rearranged pre-B-I cells of mouse bone marrow. It is expressed on large cycling CD45R(B220)+ c-kit+ CD43+ TdT+ λ5+ Cμ− sig− and on small resting CD45R(B220)+ c-kit+ CD43− TdT+ λ5+ Cμ− sig− sig- IgH chain locus VHDJH-rearranged pre-B-II cells. Therefore, the transition from pre-B-I to large pre-B-II cells is marked by the downregulation of c-kit and terminal deoxynucleotldyl transferase (TdT), and by the upregulatton of CD25. SCID, RAG-2T, μMT and γ6T mutant mice do have normal, If not elevated numbers of pre-B-I cells but lack all CD25+ pre-B-II cells in their bone marrow. The expression of a transgenic H chain under control of the μH chain enhancer in RAG-2T bone marrow B lineage precursors allows the development of large and small CD25+ pre-B-II cells. The results suggest that the differentiation of pre-B-I to pre-B-II cells in mouse bone marrow requires the expression of μH chains and surrogate L chains in membranes, probably on the surface of precursor B cell

Fc receptor gamma-chain, a constitutive component of the IL-3 receptor, is required for IL-3-induced IL-4 production in basophils

ArticleNATURE IMMUNOLOGY. 10(2):214-222 (2009)journal articl

Evidence That γδ versus αβ T Cell Fate Determination Is Initiated Independently of T Cell Receptor Signaling

Two types of T cells, αβ and γδ, develop in vertebrates. How these two T cell lineages arise from a common thymic T progenitor is poorly understood. Differentiation of αβ lineage T cells requires the surrogate α chain (pTα), which associates with the T cell receptor (TCR) β chain to form the pre-TCR. γδ lineage development does not appear to involve an obligatory surrogate chain, but instead requires productive rearrangement and expression of both TCR γ and δ genes. It has been proposed that the quality of signals transmitted by the pre-TCR and γδ TCR are distinct and that these “instructive” signals determine the lineage fate of an uncommitted progenitor cell. Here we show that the thymic T progenitor cells (CD25+CD44+c-kit+CD3−CD4−CD8− thymocytes, termed pro-T cells) from young adult mice that have yet to express TCRs can be subdivided based on interleukin 7 receptor (IL-7R) expression. These subsets exhibit differential potential to develop into γδ versus αβ lineage (CD4+CD8+ cells) in the thymus. Upon intrathymic injection, IL-7Rneg-lo pro-T cells generated a 13-fold higher ratio of αβ lineage to γδ lineage cells than did IL-7R+ pro-T cells. Much of this difference was due to a fivefold greater potential of IL-7R+ pro-T cells to develop into TCR-γδ T cells. Evidence indicates that this biased developmental potential is not a result of enhanced TCR-γ gene rearrangement/expression in IL-7R+ pro-T cells. These results indicate that the pro-T cells are heterogeneous in developmental potential before TCR gene rearrangement and suggest that in some precursor cells the initial lineage commitment is independent of TCR-mediated signals

Diclofenac Hypersensitivity: Antibody Responses to the Parent Drug and Relevant Metabolites

Background: Hypersensitivity reactions against nonsteroidal antiinflammatory drugs (NSAIDs) like diclofenac (DF) can manifest as Type I-like allergic reactions including systemic anaphylaxis. However, except for isolated case studies experimental evidence for an IgE-mediated pathomechanism of DF hypersensitivity is lacking. In this study we aimed to investigate the possible involvement of drug-and/or metabolite-specific antibodies in selective DF hypersensitivity. Methodology/Principal Findings: DF, an organochemically synthesized linkage variant, and five major Phase I metabolites were covalently coupled to carrier proteins. Drug conjugates were analyzed for coupling degree and capacity to crosslink receptor-bound IgE antibodies from drug-sensitized mice. With these conjugates, the presence of hapten-specific IgE antibodies was investigated in patients' samples by ELISA, mediator release assay, and basophil activation test. Production of sulfidoleukotrienes by drug conjugates was determined in PBMCs from DF-hypersensitive patients. All conjugates were shown to carry more than two haptens per carrier molecule. Immunization of mice with drug conjugates induced drug-specific IgE antibodies capable of triggering mediator release. Therefore, the conjugates are suitable tools for detection of drug-specific antibodies and for determination of their anaphylactic activity. Fifty-nine patients were enrolled and categorized as hypersensitive either selectively to DF or to multiple NSAIDs. In none of the patients' samples evidence for drug/metabolite-specific IgE in serum or bound to allergic effector cells was found. In contrast, a small group of patients (8/59, 14%) displayed drug/metabolite-specific IgG. Conclusions/Significance: We found no evidence for an IgE-mediated effector mechanism based on haptenation of protein carriers in DF-hypersensitive patients. Furthermore, a potential involvement of the most relevant metabolites in DF hypersensitivity reactions could be excluded

Lysine Residue 185 of Rad1 Is a Topological but Not a Functional Counterpart of Lysine Residue 164 of PCNA

Monoubiquitylation of the homotrimeric DNA sliding clamp PCNA at lysine residue 164 (PCNAK164) is a highly conserved, DNA damage-inducible process that is mediated by the E2/E3 complex Rad6/Rad18. This ubiquitylation event recruits translesion synthesis (TLS) polymerases capable of replicating across damaged DNA templates. Besides PCNA, the Rad6/Rad18 complex was recently shown in yeast to ubiquitylate also 9-1-1, a heterotrimeric DNA sliding clamp composed of Rad9, Rad1, and Hus1 in a DNA damage-inducible manner. Based on the highly similar crystal structures of PCNA and 9-1-1, K185 of Rad1 (Rad1K185) was identified as the only topological equivalent of PCNAK164. To investigate a potential role of posttranslational modifications of Rad1K185 in DNA damage management, we here generated a mouse model with a conditional deletable Rad1K185R allele. The Rad1K185 residue was found to be dispensable for Chk1 activation, DNA damage survival, and class switch recombination of immunoglobulin genes as well as recruitment of TLS polymerases during somatic hypermutation of immunoglobulin genes. Our data indicate that Rad1K185 is not a functional counterpart of PCNAK164

IgE Immune Complexes Stimulate an Increase in Lung Mast Cell Progenitors in a Mouse Model of Allergic Airway Inflammation

Mast cell numbers and allergen specific IgE are increased in the lungs of patients with allergic asthma and this can be reproduced in mouse models. The increased number of mast cells is likely due to recruitment of mast cell progenitors that mature in situ. We hypothesized that formation of IgE immune complexes in the lungs of sensitized mice increase the migration of mast cell progenitors to this organ. To study this, a model of allergic airway inflammation where mice were immunized with ovalbumin (OVA) in alum twice followed by three daily intranasal challenges of either OVA coupled to trinitrophenyl (TNP) alone or as immune complexes with IgE-anti-TNP, was used. Mast cell progenitors were quantified by a limiting dilution assay. IgE immune complex challenge of sensitized mice elicited three times more mast cell progenitors per lung than challenge with the same dose of antigen alone. This dose of antigen challenge alone did not increase the levels of mast cell progenitors compared to unchallenged mice. IgE immune complex challenge of sensitized mice also enhanced the frequency of mast cell progenitors per 106 mononuclear cells by 2.1-fold. The enhancement of lung mast cell progenitors by IgE immune complex challenge was lost in FcRγ deficient mice but not in CD23 deficient mice. Our data show that IgE immune complex challenge enhances the number of mast cell progenitors in the lung through activation of an Fc receptor associated with the FcRγ chain. This most likely takes place via activation of FcεRI, although activation via FcγRIV or a combination of the two receptors cannot be excluded. IgE immune complex-mediated enhancement of lung MCp numbers is a new reason to target IgE in therapies against allergic asthma

Inhibition of the Intrinsic but Not the Extrinsic Apoptosis Pathway Accelerates and Drives Myc-Driven Tumorigenesis Towards Acute Myeloid Leukemia

Myc plays an important role in tumor development, including acute myeloid leukemia (AML). However, MYC is also a powerful inducer of apoptosis, which is one of the major failsafe programs to prevent cancer development. To clarify the relative importance of the extrinsic (death receptor-mediated) versus the intrinsic (mitochondrial) pathway of apoptosis in MYC-driven AML, we coexpressed MYC together with anti-apoptotic proteins of relevance for AML; BCL-XL/BCL-2 (inhibiting the intrinsic pathway) or FLIPL (inhibiting the extrinsic pathway), in hematopoietic stems cells (HSCs). Transplantation of HSCs expressing MYC into syngeneic recipient mice resulted in development of AML and T-cell lymphomas within 7–9 weeks as expected. Importantly, coexpression of MYC together with BCL-XL/BCL-2 resulted in strongly accelerated kinetics and favored tumor development towards aggressive AML. In contrast, coexpression of MYC and FLIPL did neither accelerate tumorigenesis nor change the ratio of AML versus T-cell lymphoma. However, a change in distribution of immature CD4+CD8+ versus mature CD4+ T-cell lymphoma was observed in MYC/FLIPL mice, possibly as a result of increased survival of the CD4+ population, but this did not significantly affect the outcome of the disease. In conclusion, our findings provide direct evidence that BCL-XL and BCL-2 but not FLIPL acts in synergy with MYC to drive AML development