Type 2 innate lymphoid cells (ILC2) share cytokine and transcription factor expression with CD4+ Th2 cells, but functional diversity of the ILC2 lineage has yet to be fully explored. Here, we show induction of a molecularly distinct subset of activated lung ILC2, termed ILC210. These cells produce IL-10 and downregulate some pro-inflammatory genes. Signals that generate ILC210 are distinct from those that induce IL-13 production, and gene expression data indicate that an alternative activation pathway leads to the generation of ILC210. In vivo, IL-2 enhances ILC210 generation and is associated with decreased eosinophil recruitment to the lung. Unlike most activated ILC2, the ILC210 population contracts after cessation of stimulation in vivo, with maintenance of a subset that can be recalled by restimulation, analogous to T-cell effector cell and memory cell generation. These data demonstrate the generation of a previously unappreciated IL-10 producing ILC2 effector cell population.

The factors that regulate thymic development of the CD4+ T cell gene program remain poorly defined. The transcriptional regulator ThPOK is a dominant factor in CD4+ T cell development, which functions primarily to repress the CD8 lineage fate. Previously, we showed that nuclear protein TOX is also required for murine CD4+ T cell development. Here we sought to investigate if the requirement for TOX was solely due to a role in ThPOK induction. In apparent support of this proposition, ThPOK upregulation and CD8 lineage repression were compromised in the absence of TOX, and enforced ThPOK expression could restore some CD4 development. However, these “rescued” CD4 cells were defective in many aspects of the CD4+ T cell gene program, including expression of Id2, Foxo1, and endogenous Thpok, among others. Thus, TOX is necessary to establish the CD4+ T cell lineage gene program, independent of its influence on ThPOK expression.

Background: A breast cancer susceptibility locus has been mapped to the gene encoding TOX3. Little is known regarding the expression pattern or biological role of TOX3 in breast cancer or in the mammary gland. Here we analyzed TOX3 expression in murine and human mammary glands and in molecular subtypes of breast cancer, and assessed its ability to alter the biology of breast cancer cells.

3089 Poster Board III-26 Novel treatment strategies for pediatric acute lymphoblastic leukemia (ALL) have turned a rapidly deadly diagnosis into a highly treatable entity, but we are still failing 25% of our pediatric ALL patients who die of recurrent ALL. Definitive studies have demonstrated that adhesion of leukemia and lymphoma cells to extracellular matrices or stromal cells protects them against the toxicity of cytoreductive chemotherapy drugs. In this context, a specific role for CD49d, a dominant adhesion molecule for normal lymphocytes, was demonstrated for acute myeloid leukemia (AML) and other malignant hematopoietic cells. The finding that CD49d blockade sensitizes AML cells to chemotoxicity may be of therapeutic potential, as is suggested by recent findings for AML cells engrafted in NOD/SCID mice. CD49d is and is similarly expressed on acute lymphoblastic leukemia (ALL) cells, but our knowledge about CD49d adhesion-mediated chemoprotection of B-ALL is limited. We hypothesized whether similar to primary AML blasts, xenografted ALL cells resistant to chemotherapy can be sensitized to chemotherapy by disrupting their CD49d-mediated adhesive interaction with stroma. To test our hypothesis we used as a CD49d inhibitor the humanized anti-human CD49d antibody natalizumab, or Tysabri®, which is in clinical use for the treatment of relapsing or refractory Multiple Sclerosis. To determine the potential of Tysabri as a single agent to decrease leukemia progression, we engrafted 5-7 weeks old NOD/SCID mice with primary drug resistant B-ALL labeled with lentiviral luciferase to allow monitoring of leukemia using noninvasive bioluminescent imaging. Tysabri administered upon detection of engraftment on Day15 post-injection of leukemia in the dose of either 1 mg (n=3) or 6 mg (n=3) led to remarkably slower leukemia progression regardless of the dose compared to the control group treated with saline only (n=2). Additional administration of Tysabri on day 29 and day 37 did not result in further containment of leukemogenesis but still showed a marked reduction in progression compared to the saline treated control group. In addition, we determined in vivo that a weekly administration of Tysabri in the dose of 5mg/kg/d resulted in prolonged survival compared to the treated control (p<0.05). Next, we assessed the effect of adjuvant anti-CD49d antibody-mediated dislodgement of ALL cells of drug resistant patients in combination with chemotherapy. The group treated for 4 weeks with chemotherapy including Vincristine, Dexamethasone and L-Asparaginase (VDL) in combination with Tysabri (5mg/kg/d) admistered once weekly showed decreased progression of leukemia and significantly prolonged survival (p<0.05) compared to the VDL only treated control group. No toxicity of Tysabri treatment was observed. Taken together, our data indicates the potential of Tysabri as a novel adjuvant therapy for treatment of drug resistant B-ALL. Given the availability of clinical-grade CD49d blocking antibody, clinical studies can follow immediately, should our hypothesis be confirmed in further in vitro an in vivo studies. Disclosures No relevant conflicts of interest to declare.