Hepatic Tissue Environment in NEMO-Deficient Mice Critically Regulates Positive Selection of Donor Cells after Hepatocyte Transplantation

Mouse NK1+ T cells constitute a subset of alpha/beta TCR+ T cells that specialize in the rapid production of cytokines, in particular IL-4, and may promote the differentiation of Th2-type CD4 T cells. Their TCRs, like those of a homologous subset of human T cells, use an invariant TCR alpha chain and were recently shown to be specific for the beta 2-microglobulin-associated, MHC class I-like CD1 molecules, which are encoded outside the MHC. In contrast to mainstream thymocytes, which recognize their positively selecting MHC ligand on thymic epithelial cells, positive selection of NK1+ T cells requires their CD1 ligand to be expressed on bone marrow-derived cells. To investigate the nature of the bone marrow-derived cell involved, chimeric mice were constructed with tissues from normal, SCID, and MHC-deficient mice, so that CD1 could be selectively expressed by different subsets of bone marrow-derived cells in the thymus. CD1 expression was also directly assessed using an anti-CD1 mAb, and a CD1-specific T cell hybridoma. The results suggest that immature (CD4+8+ double-positive) cortical thymocytes are the source of CD1 presentation for positive selection of NK1+ T cells.

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Autonomous Maturation of α/β T Lineage Cells in the Absence of Cooh-Terminal Src Kinase (Csk)

Journal of Experimental Medicine ◽

10.1084/jem.193.7.815 ◽

2001 ◽

Vol 193 (7) ◽

pp. 815-826 ◽

Cited By ~ 34

Author(s):

Christian Schmedt ◽

Alexander Tarakhovsky

Keyword(s):

T Cell ◽

Positive Selection ◽

Mhc Class I ◽

Negative Selection ◽

T Cell Development ◽

Src Kinase ◽

Cell Development ◽

Class I ◽

Deficient Mice ◽

Selection Of

The deletion of COOH-terminal Src kinase (Csk), a negative regulator of Src family protein tyrosine kinases (PTKs), in immature thymocytes results in the development of α/β T lineage cells in T cell receptor (TCR) β-deficient or recombination activating gene (rag)-1–deficient mice. The function of Csk as a repressor of Lck and Fyn activity suggests activation of these PTKs is solely responsible for the phenotype observed in csk-deficient T lineage cells. We provide genetic evidence for this notion as α/β T cell development is blocked in lck−/−fyn−/− csk-deficient mice. It remains unclear whether activation of Lck and Fyn in the absence of Csk uncouples α/β T cell development entirely from engagement of surface-expressed receptors. We show that in mice expressing the α/β TCR on csk-deficient thymocytes, positive selection is biased towards the CD4 lineage and does not require the presence of major histocompatibility complex (MHC) class I and II. Furthermore, the introduction of an MHC class I–restricted transgenic TCR into a csk-deficient background results in the development of mainly CD4 T cells carrying the transgenic TCR both in selecting and nonselecting MHC background. Thus, TCR–MHC interactions have no impact on positive selection and commitment to the CD4 lineage in the absence of Csk. However, TCR-mediated negative selection of csk-deficient, TCR transgenic cells is normal. These data suggest a differential involvement of the Csk-mediated regulation of Src family PTKs in positive and negative selection of developing thymocytes.

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