Invariant Natural Killer T cell (iNK Tcell) have an innate immunity-like rapidity of response and the capacity to modulate effector functions of other cells. We show that the BTB-ZF transcriptional regulator, PLZF, is specifically expressed in iNKT cells. iNKT cells develop in the absence of PLZF, but lack many innate T cell features. PLZF deficient iNKT cells accumulate in the lymph nodes rather than in the liver and do not have an activated phenotype or express NK markers. PLZF deficient iNKT cells do not secrete high levels of IL-4 and IFNγ upon activation, however some cells produce either IL-4 or IFNγ, but not both. PLZF, therefore, is an iNKT cell specific transcription factor that is necessary for full functionality.Nearly all hematopoietic cells mature in the bone marrow. In contrast, multipotent progenitor T cells leave the bone marrow and home to the thymus, where signals from stromal cells are required for commitment to the T lineage 1 . Once directed into the T lineage, the cells undergo a rigorous selection process that eliminates more than 95% of the candidate T cells. Full maturation requires the expression of a T cell receptor (TCR) that binds self-peptide:self-MHC complexes with sufficient avidity. At some point during development, T cells are directed into one of several distinct T cell lineages such as CD4 single positive "helper" cells, CD8 single positive "killer" cells or CD4 + CD25 + regulatory cells. Commitment to these various lineages defines the specialized functions of the cell, which is critical since each cell type plays an essential and distinct role for host defense. The genes responsible for directing multipotent T cell progenitors into the various lineages are largely unknown 2 .Correspondence and requests for materials should be addressed to D.B.S (Email: santangd@mskcc.org). NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptAmong the various lineages of T cells, invariant Natural Killer T cells (iNKT cells) have several unique phenotypic traits such as the expression of receptors typically associated with Natural Killer cells (NK cells), the constitutive expression of activation markers and extremely restricted TCR diversity 3 . iNKT cells express an identical TCRα chain and most use a TCRβ chain that utilizes the Vβ8.2 gene segment. This TCR confers specificity to the non-MHC encoded self-molecule, CD1d, which binds and presents glycolipids rather than the typical peptide cargo presented by conventional MHC molecules.iNKT cells are also functionally distinct. Of particular interest is their ability to secrete large quantities of a variety of cytokines only minutes after activation via the TCR 3 . The rapid response of these cells, the conserved nature of the TCR and their indirect ability to modulate the function of many different cell types of the immune system has led to the appreciation that iNKT cells lay at a functional cusp between the innate and adaptive immune systems 4 . The broad range of cytokines released by iNKT cells results in th...

In the infarcted myocardium, activation of the inflammatory cascade clears the wound from dead cells, while stimulating matrix degradation and chamber dilation, thus contributing to the development of heart failure. IL-1 is critically involved in the post-infarction inflammatory reaction and mediates adverse dilative remodeling. We hypothesized that IL-1 may regulate post-infarction repair and remodeling through cell-specific actions on leukocytes and fibroblasts. Flow cytometry demonstrated that in mouse infarcts, early recruitment of pro-inflammatory Ly6Chi cells expressing IL-1R1, the signaling receptor for IL-1, was followed by infiltration with cells expressing the decoy receptor, IL-1R2. Increased expression of IL-1R2 may serve to terminate IL-1-driven inflammation following infarction. Loss of IL-1 signaling in IL-1R1 null mice globally attenuated leukocyte recruitment, reducing the number of infiltrating Ly6Chi and Ly6Clo cells. Non-myeloid CD11b-negative cells harvested during the inflammatory phase of cardiac repair exhibited marked upregulation of chemokines and cytokines; their inflammatory activation was IL-1R1-dependent. Moreover, IL-1β attenuated TGF-β-induced contractile activity of fibroblasts populating collagen pads, attenuated α-smooth muscle actin expression and stimulated matrix metalloproteinase synthesis in an IL-1R1-dependent manner. The effects of IL-1 on TGF-β responses in cardiac fibroblasts were not due to direct effects on Smad activation, but were associated with endoglin suppression and accentuated expression of BAMBI, a negative regulator of TGF-β signaling. IL-1 may orchestrate fibroblast responses in the infarct; early stimulation of fibroblast IL-1R1 signaling during the inflammatory phase may prevent premature activation of a matrix-synthetic contractile phenotype until the wound is cleared, and the infarct microenvironment can support mesenchymal cell growth.

The broad complex, tramtrack, bric-a-brac–zinc finger (BTB-ZF) transcription factor promyelocytic leukemia zinc finger (PLZF) is required for development of the characteristic innate/effector functions of NKT cells. In this study, we report the characterization and functional analysis of transgenic mouse T cells with forced expression of PLZF. PLZF expression was sufficient to provide some memory/effector functions to T cells without the need for Ag stimulation or proliferation. The acquisition of this phenotype did not require the proliferation typically associated with T cell activation. Furthermore, PLZF transgenic cells maintained a diverse TCR repertoire, indicating that there was no preferential expansion of specific clones. Functionally, PLZF transgenic CD4 and CD8 lymphocytes were similar to wild type memory cells, in that they had similar requirements for costimulation and exhibited a similar pattern of cytokine secretion, with the notable exception that transgenic T cells produced significantly increased levels of IL-17. Whereas transgene-mediated PLZF expression was not sufficient to rescue NKT cell development in Fyn- or signaling lymphocytic activation-associated protein (SAP)-deficient mice, the acquisition of memory/effector functions induced by PLZF in conventional T cells was independent of Fyn and SAP. These data show that PLZF is sufficient to promote T cell effector functions and that PLZF acts independently of SAP- and Fyn-mediated signaling pathways.

The promyelocytic leukaemia zinc finger (PLZF) protein is a member of the BTB/POZ zinc finger family of transcription factors. This family of transcription factors also include Th-Pok, BCL-6 and MAZR which are known to play important roles in the immune system. Here we demonstrate that PLZF deficient mice have a severe impairment in iNKT cell lineage development leading to a lack of iNKT cells in the thymus and periphery. Real-time PCR showed that PLZF mRNA is highly expressed in iNKT cells. This correlates with flow cytometry analysis which revealed exclusive expression of PLZF protein in iNKT cells within the immune system. Radiation chimeras showed that PLZF is required for iNKT cell development in a cell intrinsic manner. These results identify PLZF as a key factor in iNKT development. They also underline the BTB/POZ family of transcription factors as important factors in the immune system.