The broad-complex tramtrack and bric a brac-zinc finger transcriptional regulator(BTB-ZF), promyelocytic leukemia zinc finger (PLZF), was recently shown to control the development of the characteristic innate T cell phenotype and effector functions of NK T cells. Interestingly, the ectopic expression of PLZF was shown to push conventional T cells into an activated state that seems to be proinflammatory. The factors that control the normal expression of PLZF in lymphocytes are unknown. In this study, we show that PLZF expression is not restricted to NK T cells but is also expressed by a subset of γδ T cells, functionally defining distinct subsets of this innate T cell population. A second BTB-ZF gene, ThPOK, is important for the phenotype of the PLZF-expressing γδ T cells. Most importantly, TCR signal strength and expression of inhibitor of differentiation gene 3 control the frequency of PLZF-expressing γδ T cells. This study defines the factors that control the propensity of the immune system to produce potentially disease-causing T cell subsets.

Invariant natural killer T cells have a distinct developmental pathway from conventional αβ T cells. Here we demonstrate that the transcriptional repressor NKAP is required for invariant natural killer T cell but not conventional T cell development. In CD4-cre NKAP conditional knockout mice, invariant natural killer T cell development is blocked at the double-positive stage. This cell-intrinsic block is not due to decreased survival or failure to rearrange the invariant Vα14-Jα18 T cell receptor-α chain, but is rescued by overexpression of a rec-Vα14-Jα18 transgene at the double-positive stage, thus defining a role for NKAP in selection into the invariant natural killer T cell lineage. Importantly, deletion of the NKAP-associated protein histone deacetylase 3 causes a similar block in the invariant natural killer T cell development, indicating that NKAP and histone deacetylase 3 functionally interact to control invariant natural killer T cell development.

The interaction between the T cell antigen receptor (TCR) expressed by natural killer T cells (NKT cells) and the antigen-presenting molecule CD1d is distinct from interactions between the TCR and major histocompatibility complex (MHC). Our molecular modeling suggested that a hydrophobic patch created after TCRα-TCRβ pairing has a role in maintaining the conformation of the NKT cell TCR. Disruption of this patch ablated recognition of CD1d by the NKT cell TCR but not interactions of the TCR with MHC. Partial disruption of the patch, while permissive to the recognition of CD1d, significantly altered NKT cell development, which resulted in the selective accumulation of adipose-tissue-resident NKT cells. These results indicate that a key component of the TCR is essential for the development of a distinct population of NKT cells.

Enhanced cell death and deficient clearance of cellular debris are thought to contribute to increased self-antigen exposure in systemic autoimmune disease. To investigate the characteristics of early humoral autoimmune responses, six monoclonal antibodies were generated from two autoimmune prone strains of mice. All antibodies specifically bound the surface of late-stage apoptotic cells. Similar antibody reactivities were present in the sera of patients with systemic lupus erythematosus. While IgM antibodies significantly reduced the phagocytic uptake of apoptotic thymocytes, IgG antibodies enhanced uptake. Poly-reactivity was demonstrated in the recognition of ribonucleoproteins and lipids. An antibody reactive towards lysophosphatidylcholine reversed lysophosphatidylcholinemediated inhibition of LPS-induced TNF-a production and adversely affected the transmigration of phagocytes towards an apoptotic stimulus. In several instances, CDR were characterized by the accumulation of somatic mutations. Anti-idiotypic antibodies generated upon immunization bound distinct cellular moieties and self-antigens. Polyspecific, apoptotic cell-reactive autoantibodies can therefore directly impact upon the course of disease by influencing phagocytic uptake of apoptotic cells, by inducing a proinflammatory environment through neutralization of bioactive lipids, by blinding phagocytes to the presence of dying cells through the negation of lipidic chemotactic signals, and by mediating diversification of the humoral autoimmune response via the idiotypic network.

MHC class II expressing thymocytes can efficiently mediate positive selection of CD4 T cells in mice. Thymocyte selected CD4 (T-CD4) T cells have an innate-like phenotype similar to invariant NKT (iNKT) cells. To investigate the development and function of T-CD4 T cells in depth, we cloned TCR genes from T-CD4 T cells and generated transgenic mice. Remarkably, positive selection of T-CD4 TCR Transgenic (T3) thymocytes occurred more efficiently when MHC class II was expressed by thymocytes than by thymic epithelial cells. Similar to polyclonal T-CD4 T cells and also iNKT cells, T3 CD4 T cell development is controlled by SLAM/SAP signaling and the cells expressed both IL-4 and promyelocytic leukemia zinc finger (PLZF). Surprisingly, the selected T3 CD4 T cells were heterogeneous in that only half expressed IL-4 and only half expressed PLZF. IL-4 and PLZF expressing cells were first found at the double positive cell stage. Thus, the expression of IL-4 and PLZF seems to be determined by an unidentified event that occurs post-selection and is not solely dependent on TCR specificity or the selection process, per se. Together, our data show, for the first time, that the TCR specificity regulates but does not determine the development of innate CD4 T cells by thymocytes.