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BMC Immunology (1)
The Journal of Experimental Medicine (1)
Bakkour, Sonia (2)
Allman, David (1)
Aster, Jon C. (1)
Karnell, Fredrick G. (1)
Koretzky, Gary A. (1)
Larimore, Kevin (1)
Liang, Linda (1)
Myung, Peggy (1)
Pear, Warren S. (1)
Pui, John C. (1)
Punt, Jennifer A. (1)
Sha, William C (1)
Xu, Lanwei (1)
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B7h-expressing dendritic cells and plasma B cells mediate distinct outcomes of ICOS costimulation in T cell-dependent antibody responses
Sha, William C
The ICOS-B7h costimulatory receptor-ligand pair is required for germinal center formation, the production of isotype-switched antibodies, and antibody affinity maturation in response to T cell-dependent antigens. However, the potentially distinct roles of regulated B7h expression on B cells and dendritic cells in T cell-dependent antibody responses have not been defined.
We generated transgenic mice with lineage-restricted B7h expression to assess the cell-type specific roles of B7h expression on B cells and dendritic cells in regulating T cell-dependent antibody responses. Our results show that endogenous B7h expression is reduced on B cells after activation in vitro and is also reduced in vivo on antibody-secreting plasma B cells in comparison to both naïve and germinal center B cells from which they are derived. Increasing the level of B7h expression on activated and plasma B cells in B-B7hTg mice led to an increase in the number of antibody-secreting plasma cells generated after immunization and a corresponding increase in the concentration of antigen-specific high affinity serum IgG antibodies of all isotypes, without affecting the number of responding germinal center B cells. In contrast, ICOS costimulation mediated by dendritic cells in DC-B7hTg mice contributed to germinal center formation and selectively increased IgG2a production without affecting the overall magnitude of antibody responses.
Using transgenic mice with lineage-restricted B7h expression, we have revealed distinct roles of ICOS costimulation mediated by dendritic cells and B cells in the regulation of T cell-dependent antibody responses.
ICOS; B7h; Costimulation; Antibody; Germinal center; Plasma cell; Dendritic cell
Separation of Notch1 Promoted Lineage Commitment and Expansion/Transformation in Developing T Cells
Karnell, Fredrick G.
Punt, Jennifer A.
Koretzky, Gary A.
Pui, John C.
Aster, Jon C.
Pear, Warren S.
The Journal of Experimental Medicine
Notch1 signaling is required for T cell development. We have previously demonstrated that expression of a dominant active Notch1 (ICN1) transgene in hematopoietic stem cells (HSCs) leads to thymic-independent development of CD4+CD8+ double-positive (DP) T cells in the bone marrow (BM). To understand the function of Notch1 in early stages of T cell development, we assessed the ability of ICN1 to induce extrathymic T lineage commitment in BM progenitors from mice that varied in their capacity to form a functional pre-T cell receptor (TCR). Whereas mice repopulated with ICN1 transduced HSCs from either recombinase deficient (Rag-2−/−) or Src homology 2 domain–containing leukocyte protein of 76 kD (SLP-76)−/− mice failed to develop DP BM cells, recipients of ICN1-transduced Rag-2−/− progenitors contained two novel BM cell populations indicative of pre-DP T cell development. These novel BM populations are characterized by their expression of CD3ε and pre-Tα mRNA and the surface proteins CD44 and CD25. In contrast, complementation of Rag-2−/− mice with a TCRβ transgene restored ICN1-induced DP development in the BM within 3 wk after BM transfer (BMT). At later time points, this population selectively and consistently gave rise to T cell leukemia. These findings demonstrate that Notch signaling directs T lineage commitment from multipotent progenitor cells; however, both expansion and leukemic transformation of this population are dependent on T cell–specific signals associated with development of DP thymocytes.
leukemia; development; hematopoiesis; lymphocyte; stem cells
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